Volume 62, Issue 1

Carbon/carbon (C/C) composites have received considerable attention for one of the most promising materials in thermal-structural applications owing to their low density, excellent mechanical strength at high temperature, and superior thermal shock resistance. However, C/C composites are susceptible to destructive oxidation in atmospheric environment at high temperature. Matrix modification by adding ultra-high-temperature ceramics (UHTCs) into carbon substrate has been proved to be a favorable route to achieve the improved ablation resistance of C/C composites. In this work, the main fabrication approaches of UHTCs-modified C/C composites were summarized, including chemical vapor infiltration/deposition, precursor infiltration and pyrolysis, reactive melt infiltration, and slurry infiltration, and the advantages and drawbacks of each process were also briefly analyzed. In addition, anti-ablation properties of UHTCs-modified C/C composites under different ablation tests with different shape specimens were introduced. Finally, some likely future challenges and research directions in the development and application of these materials were presented.

This work summarizes the different natural lighting systems applied for pollutant treatment systems using photocatalysis. The principles and fundamentals of the technologies used are revisited and examples of technologies most used for treatment either at the laboratory or at the pilot plant level are disclosed. This unveils a general panorama of treatment technologies via photocatalysis, using natural sunlight as an illumination source. Aside from these concentrated solar power systems that are inviable for photocatalytic aqueous treatments, reported scientific works are shown about heliostats, parabolic troughs, Fresnel lenses, and direct illuminated systems. As a valuable result of this review, the power used in photocatalytic systems requires higher attention not only in these systems but in laboratories and prototypes. Photocatalysts and their countless configuration variants are limited due to the potential barriers in particle borders, interfaces, and surfaces to cause redox reactions in water and pollutant target molecules. These factors reduce photocatalyst efficiencies for converting light energy to useful electron pair charge carriers for water treatments. The use of solar concentration systems applied to photocatalytic treatment systems can generate enough charge carriers, improving the efficiency of the systems, and making it feasible to scale up various configurations of this treatment pathway. Subsequently, the photocatalyst material and light are both important.

Tissue engineering is an enabling technology that can be used to repair, replace, and regenerate different types of biological tissues and holds great potential in various biomedical applications. As the first line of defense for the human body, the skin has a complex structure. When skin is injured by trauma or disease, the skin tissues may regenerate under natural conditions, though often resulting in irreversible and aesthetically unpleasant scarring. The development of skin tissue engineering strategies was reviewed. Although the traditional approaches to skin tissue engineering have made good progress, they are still unable to effectively deal with large-area injuries or produce full-thickness grafts. In vitro three-dimensional (3D) skin constructs are good skin equivalent substitutes and they have promoted many major innovative discoveries in biology and medicine. 3D skin manufacturing technology can be divided into two categories: scaffold-free and scaffold-based. The representatives of traditional scaffold-free approaches are transwell/Boyden chamber approach and organotypic 3D skin culture. Because of its low cost and high repeatability, the scaffold-free 3D skin model is currently commonly used for cytotoxicity analysis, cell biochemical analysis, and high-throughput cell function. At present, many drug experiments use artificial skin developed by traditional approaches to replace animal models. 3D bioprinting technology is a scaffold-based approach. As a novel tissue manufacturing technology, it can quickly design and build a multi-functional human skin model. This technology offers new opportunities to build tissues and organs layer by layer, and it is now used in regenerative medicine to meet the increasing need for tissues and organs suitable for transplantation. 3D bioprinting can generate skin substitutes with improved quality and high complexity for wound healing and in vitro disease modeling. In this review, we analyze different types of conventional techniques to engineer skin and compare them with 3D bioprinting. We also summarized different types of equipment, bioinks, and scaffolds used in 3D skin engineering. In these skin culture techniques, we focus on 3D skin bioprinting technology. While 3D bioprinting technology is still maturing and improvements to the techniques and protocols are required, this technology holds great promise in skin-related applications.

Magnesium hybrid composites are a new class of lightweight metal matrix composites having excellent physical, mechanical, wear and corrosive properties. Hybrid magnesium matrix composites are fabricated using different combinations of reinforcements having basics properties like wear resistance and high strength of ceramics, self-lubricating of graphite, MoS 2 , CNT, and graphene, high thermal conductivity of carbon, diamond, and cubic boron nitride, and low cost of fly ash. This article presents an overview of different combinations of reinforcements used for fabrication of hybrid magnesium matrix composites and their effects on the mechanical and tribological properties of the hybrid materials. The major issues like agglomeration, interfacial phenomena, reinforcement–matrix bonding, and problems related to uniform distribution of particles are discussed in this article. Magnesium hybrid composites have the potential of satisfying the recent demands of aerospace, automobile, biomedical, defense, marine, and electronics industries. The future directions and potential research areas in the field of magnesium hybrid composites are also highlighted.

In recent years, calcium peroxide (CaO 2 ) has attracted widespread attention in the medical community due to its excellent antitumor and antibacterial properties, and has gradually become a hot research topic in the biomedical field. CaO 2 reacts with water (H 2 O) to produce calcium ion (Ca 2+ ), oxygen (O 2 ), and hydrogen peroxide (H 2 O 2 ), where Ca 2+ is suitable for calcium death caused by calcium overload, O 2 is suitable for O 2 -dependent anticancer therapy, and H 2 O 2 is suitable for H 2 O 2 -dependent anticancer therapy. In addition, H 2 O 2 can also be used in the antibacterial field to treat bacterial infections. All these make the CaO 2 to become a kind of excellent antitumor and antibacterial drug. This study mainly reviews the preparation and surface modification of CaO 2 , probes into the latest progress about CaO 2 nanoparticles in the field of tumor treatment and antimicrobial therapy. Finally, the challenges that CaO 2 still faces in the future research field are clarified, and its prospects are forecasted.

Basalt fiber (BF) is a kind of high-performance fiber rising rapidly in recent years. BF is typically used in the field of structure engineering because of its high strength and high modulus. The preparation of BF-based composites first requires surface modification of BF to improve the interfacial bonding between BF and the resin matrix. With the continuous deepening of the research on BF surface modification, researchers have found that special surface modification can obtain BF-based functionalized composites, and this field has received extensive attention in recent years. In this article, research work on BF-based functional composites in recent years are summarized and reviewed from the aspects of electromagnetic shielding, water treatment, catalytic function and fire insulation. Finally, this article summarizes the BF surface modification methods, and proposes the development trends and direction of BF-based functional composites.

The performance deterioration of steel anchors caused by steel corrosion is becoming more serious in slope anchorage applications. Therefore, the fiber reinforced plastic (FRP) composites have become a substitute material for traditional anchorage structures due to their advantages of low price, lightweight, high strength, and corrosion resistance. Numerous studies have proven that FRP anchors have better anchoring capacity than traditional steel anchors in practical engineering and are not as susceptible to environmental influences. This review mainly introduced the mechanical properties of FRP, focuses on the current research progress and innovation of FRP anchor in anchorage engineering, then provides a basis for the design of FRP anchor. In this study, the failure characteristics and problem of insufficient bonding strength of the first interface of FRP anchor anchoring slope were discussed, and the improvement was introduced. It will be conducive to the extension and application of FRP composites as structural materials in civil engineering. A detailed introduction is also given to biomaterials, which are mainly derived from nature and which will not only reduce waste disposal problems and environmental pollution but will also replace conventional applications. Finally, there will be an important reference and value for the development of green and sustainable engineering structures.

For the sustainability of the construction industry, geopolymers (GPMs) play an important role compared with Portland cement due to their improved mechanical properties, enhanced durability, and outstanding performance in alkali and acidic conditions. Most of the previous review investigations explored the general behavior of GPM developed with kaolin, silica fume (SF), rice husk ash, ground granulated blast furnace slag, fly ash, etc ., but a comprehensive review study on the industrial by-products, including granite waste powder (GWP) and bauxite residue (BR), is required to investigate their suitability in the construction industry. The current investigation aims to present a detailed review of the fresh, mechanical, durability, and microstructural behavior of the GPM paste produced using BR and GWP from the literature. The effect of different ingredients and testing conditions are evaluated for the fresh, mechanical, durability, thermal, and microstructural performance of the GPM paste. The results indicate that the pure BR having a lower ratio of SiO 2 /Al 2 O 3 reacts poorly; therefore, it should be blended with other aluminosilicates comprising a higher ratio of SiO 2 /Al 2 O 3 for better geopolymerization. Pre-activation of BR including 3 h calcination at 800°C, 1 h thermal pretreatment of alkali with solid activators at 800°C, mechanical co-grinding, and pulverization presented improved strength and microstructural properties of GPM. When mixing GWP in large quantities, heat curing is preferred for 8 h at 60–80°C for better behavior of GPM. Incorporating the nanomaterials into GWP-based GPM showed a significant impact on initial compressive and tensile strengths. Further studies on the synergistic use of GWP with aluminosilicate products and BR with silica-rich pozzolanic ingredients for GPM are required. Improved physiochemical features of BR-GPM and GWP-GPM are the potential research areas that can be addressed by incorporating raw materials for enhancing the internal matrix, such as nanoparticles, bio-additives, micro-fibers, etc ., that have been observed to be effective for the GPM pastes.

Due to their advantages such as high tensile strength, low cost of production, easy manufacturing methods, and ease of use, cementitious materials are extensively utilized in the construction industry. The applications of nanomaterials in cementitious materials have been found to enhance their properties. It allows molecular changes to improve the material behaviour and the performance of civil infrastructure structures, including buildings and highways. Owing to the high ductility of polyvinyl alcohol-engineered cementitious composites (ECCs), it was suggested to be used in steel-reinforced structural elements to enhance the strength and ductility of the components. The presence of hybrid fibres provided increased shattering resistance with decreased scabbing, spalling, destruction, and damage zone and better absorption of energy through distributed microcracking. The presence of nanomaterials in ECCs modifies its atomic macroscopic scales, enhancing its mechanical and microstructural properties. The versatile properties of nanomaterials offer immense potential to cementitious composite for structural applications.

Bioceramics are significantly contributing in repairing and reconstructing the defective areas of the musculoskeletal system. Bioactive glass is a non-crystalline bioceramic that has been widely used in regeneration due to its extensive bone-forming ability and biocompatibility. The plethora of bioactive glass research has been buried over the years in the area of bone construction in various forms. The composition of the bioactive glass with its network formers and modifier plays a vital role in bone-forming ability and prevents crystallization. The hybrid polymer and metal ion-doped bioactive glass add advantages to bone tissue repair. The development and the challenge during the preparation of bioactive glasses have been discussed in this review. Based on the orthopedic defect, their porous size, volume, and even mechanical properties can be tailored to obtain the desired scaffold combined with the therapeutic delivery of bioactive compounds. Bone tissue engineering is inevitable without the process of osteoinduction, osteoconduction, and osteointegration, and their role in bioactive glass was reported. Bioactive glass is the key contributor to the glass age, and it has been subjected to medicinal applications for tissue repair, regeneration, and therapeutic agent delivery.

Graphene oxide (GO) is a two-dimensional derivative of graphene material, with carboxy, hydroxy group functional groups at the middle of the sheets, and oxygen-containing functional groups at sheet edges. It has multiple advantages, such as high strength, hydrophilicity, and strong reactivity. With the development of construction materials, GO has been widely used as a nano-reinforced material in cement-based composites (CBCs). Based on a large amount of relevant literature, the preparation and dispersion behavior of GO-reinforced CBC are summarized. Besides, the impact of GO on the workability, volume stability, mechanical performance, and durability of CBC are discussed. Moreover, the influencing mechanism of GO on the hydration of CBC is expounded. From the findings of this review, the following conclusions can be drawn: the fluidity of CBC will be decreased when GO is evenly dispersed in the cement slurry, which results in a loss of workability of CBC. Meanwhile, the addition of GO improves the volume stability of CBC, while the tensile, compressive, and flexural strengths are all improved to varying degrees. The improvement of GO on the durability of CBC is mainly reflected in the corrosion resistance and permeability resistance. In addition, problems existing in the current research are summarized and future perspectives are put forward. The review work in this article could offer important guidance for further research and implementation of GO-doped CBC in practical engineering.

Ultra-high-performance concrete (UHPC) is a new type of concrete with improved features such as high strength, long service life, ductility, and toughness. UHPC’s energy-intensive cement and quartz sand may make it unsustainable despite its engineering expertise. Thus, a UHPC that is energy efficient and environmentally benign should use less energy-intensive components and industrial wastes. This review consolidates and critically reviews the latest global research on coal bottom ash (CBA) as a fine aggregate replacement material and nano-calcium silicate hydrate (C–S–H) as concrete additives. Based on the critical evaluation, replacing aggregate with CBA up to 60% improves strength by 23%. Since high-quality natural sand is depleting and CBA output is increasing due to coal power plants, the concrete industry can use CBA as an aggregate. However, CBA as an aggregate substitute in UHPC has been scarcely reported. Besides, nanomaterial technologies like nano-C–S–H have also been proven to increase traditional concrete’s strength by 33%. But, their impact on UHPC has yet to be fully explored. Thus, to develop UHPC with a lower carbon footprint and comparable or better performance to market-available UHPC, further research on CBA as aggregate replacement in UHPC with nano-C–S–H as an additive on mechanical durability and microstructure is needed.

In the construction industry, the incorporation of steel fibers in ultra-high-performance concrete (UHPC) is vital for improving its mechanical characteristics. In order to identify the essential factors of UHPC, the literature on the effect of steel fibers on UHPC is reviewed using scientometric methods in this work. The review contains complex processes like knowledge mapping, co-occurrence, and co-citation. In order to analyze the bibliographic data on the impact of steel fibers on UHPC, this study makes use of contemporary methodologies for data processing, mining, analysis, presentation, and visualization. The aim is to provide direction for further research in this area by summarizing the literature. In order to achieve this goal, data from the Scopus database, including publication sources, top authors, keywords, significant publications, and nations contributing the most to the subject, are retrieved and examined. According to the scientometric analysis, the most frequently used keyword is “steel fibers,” “Construction and Building Materials” is the most popular publication source in terms of citations and articles, and China is the top-ranking nation in the industry. Academic scholars can gain from this study’s graphical and quantitative portrayal of the contributing researchers and nations by making it easier to share concepts and form collaborative initiatives. This study also shows that steel fibers can improve the mechanical properties of UHPC but their widespread manufacturing and use are dependent on factors including the fiber content and geometry.

High nitrogen steel (HNS) have been widely used in many industrial fields in place of stainless steels. As we know, the welding is the main fabricating method of the HNS structural components. In this article, the recent investigations of joining methods of HNS, such as tungsten inert gas welding, melt inert-gas welding, laser welding, laser-arc hybrid welding, friction stir welding (FSW), and brazing method are summarized. First, the effect of nitrogen content in shielding gas, welding wire, and base metal on the evolution of microstructure, mechanical properties, and corrosion susceptibility of fusion welded joints are discussed systemically. Then the existing problem during FSW and brazing process of HNS are analyzed. Additionally, the key issues and future trends in the joining of HNS are proposed. The main purpose of this review is to provide a technical reference and theoretical basis for research and technological development during the welding of HNS.

A bulk volume of waste tires, an underrated global resource, is disposed of in landfills worldwide. Extracting recycled steel fibers from these tires is an evolving trend nowadays. The outcomes of concrete having steel fibers sourced from end-of-life tires are alike industrial steel fibers. Accordingly, the attention of researchers is focused nowadays on using alternative recycled steel fibers in place of industrial steel fibers in concrete. In the current study, the review focuses on waste recycle tire steel fiber (WRTSF)-reinforced concrete applications, considering different lengths and contents for finding the research gap in this research domain. The results and methods to recycle WRTSFs in existing studies are compiled and briefed. The adoption of appropriate composition and characteristics like length, diameter, content, etc. , of WRTSFs can be made by using this study to improve the mechanical properties of respective composites. Therefore, the aim of this evaluation is to encourage the application of concrete reinforced with WRTSF for different construction purposes, including but not limited to pavements, tunnel linings, bridge decks, hydraulic structures, and slope stabilization. The study seeks to provide guidance on the appropriate composition and characteristics of WRTSFs to improve the mechanical properties of the composite material.

The recent advancement in graphene-reinforced aluminium matrix composites improves wear behaviour in the production of lightweight and high-performance nanocomposites. Considerable works have been devoted to using graphene nanoparticles as solid self-lubricants to increase wear resistance, minimise friction coefficients, improve service efficiency, and extend the lifespan of related sliding components. In general, wear behaviour often depends on the homogeneous distribution of graphene in the aluminium matrix. The non-uniform distribution of reinforcement due to the tendency of graphene to agglomerate in aluminium matrix and its poor wettability becomes a challenge in developing optimum functional of composites. The wettability of graphene can be enhanced by proper processing methods and sufficient addition of magnesium that can improve the wear and frictional properties of the produced composites. Hence, this review article provides recent findings and the influence of graphene as reinforcement materials in composites, including the effects on wear behaviour and friction properties. This article also discusses new advancements in the effect of graphene in self-lubricating aluminium matrix composites and the impact of reinforcement on the wear mechanisms of the composites. The future direction of the wear properties of MMCs is also covered at the end of the review.

The aluminum (Al) alloy AA7075 is widely used in various industries due to its high strength-to-weight ratio, which is comparable and replaceable to steel in many applications. However, it has poor resistance to wear and corrosion compared to other Al alloys. The conventional pressure die coating with Cr and cadmium has led to premature failure while the load is applied. It is indeed to develop a novel coating method to improve the mechanical, wear, and corrosion properties of AA7075 Al alloy. In the present investigation, the binary and ternary metals such as zinc–nickel (Zn–Ni), zinc–cobalt (Zn–Co), and nickel–chromium–cobalt (Ni–Cr–Co) are electroplated on the substrate material (AA7075). In order to ensure optimal coating adhesion, the surface of the substrate material was pre-treated with laser surface treatment (LST). The mechanical and corrosion studies have been carried out on the uncoated and coated materials. It is observed from the findings that the ternary coating has higher wear resistance than the binary-coated material. The ternary coating has 64% higher resistance in the non-heat-treated status and 67% higher resistance in the heat-treated condition compared to the uncoated specimens. The tensile strength (MPa) of Ni–Cr–Co on AA7075 pressure die casting (PDC) is higher than the other deposits (582.24 of Ni–Cr–Co > 566.07 of Zn–Co > 560.05 of Zn–Ni > 553.64 of uncoated condition). The presence of a crystalline structure with the high alignment of Co and Ni atoms could significantly improve the corrosion resistance of Ni–Cr–Co coatings on AA 7075 PDC substrates when compared to binary coatings. The scanning electron microscopy (SEM) images, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy findings on the coated materials have been corroborated with the analyses on mechanical and corrosion properties. The XRD analysis of the Zn–Ni binary coating has reported that the diffraction peaks of γ-NiZn 3 (831), γ -Ni 2 Zn 11 (330), and 631 with 2 θ values 38, 43, and 73° are confirming the presence of Zn–Ni binary deposit on AA7075 PDC substrate. The XRD pattern of Zn–Co-coated material has revealed that the presence of three strong peaks such as Zn (110), Co (111), and CoZn (211) and two feeble peaks such as ε-CoZn 3 (220) and ε-CoZn 3 (301) are clearly visible. The XRD pattern of Ni–Cr–Co ternary coating has exhibited that the Ni–Cr–Co ternary deposit is a solid solution with a body-centered cubic structure due to the formation peaks at lattice plane such as (110), (220), and (210) with a crystal lattice constant of 2.88 A°. The SEM image for both the binary- and ternary-coated materials has exhibited that the deposited surface has displayed many shallow pits due to hitting by progressive particles. The SEM image has illustrated the presence of Zn–Ni atoms with smaller globular structure. The surface morphology of binary Zn–Co coating on the PDC AA7075 substrate has unveiled the evenly distributed dot-like structure and submerged Co particles in the galaxy of Zn atoms. To understand the effectiveness of bonding by laser texturing, cross-section SEM has been carried out which furthermore revealed the effective adhesion of Ni–Cr–Co on AA7075 PDC; this could also be the reason for the enhancement of microhardness, wear, and corrosion resistance of the said coating.

This study employed a novel approach by analyzing the self-healing asphalt literature based on scientometric analysis. The most difficult components of modern study are the mapping and analysis of knowledge, co-citations, and co-occurrences. Scopus was searched to find the necessary data for the analysis, which consisted of keywords, abstracts, citations, and bibliographic information. Throughout the data assessment process, the most prolific research locations, the most often referenced articles, and the most influential authors in the field of self-healing asphalt were analyzed, along with their correlations. The need for self-repairing asphalt was also emphasized, along with the main problems of using it. The keyword analysis showed that researchers have studied self-healing asphalt for crack repair in asphalt road pavements as a sustainable maintenance method. The literature study showed that heating and encapsulating rejuvenating chemicals are two techniques of self-healing asphalt. Encapsulation uses rejuvenating capsules, whereas the heating technique uses induction heating and microwave radiation. Researchers have also developed hybrid asphalt self-healing methods as enhanced self-healing for asphalt. Academics may benefit from the quantitative assessment of regions and researchers as well as the scientific description of these areas in order to form joint initiatives and spread new ideas and approaches.

In the face of fierce competition in the automotive market, severe environmental problems, and the consistent enhancement of consumer demands for vehicle performance, research and development for new automotive materials have increased. Fiber metal laminate (FML) is a representative hybrid composite in recent years but the application of FMLs in the automotive industry is still rare. In order to boost the strengths and applications of FMLs, a lot of effort has been put into enhancing their mechanical properties. In this review article, up-to-date information on the mechanical performance of FMLs for automotive components is presented. The mechanical testing methods, materials selection, structure design, fabrication methods, and the application of hybrid FMLs were explored. The objective of this review article is to study different factors that influence the mechanical properties of FMLs and provide some optimization directions from various aspects. From recent research, there will be great opportunities for hybrid FMLs utilizing natural fibers and bio-polymers in the automotive field in the future.

Fiber-reinforced concrete (FRC) has apparent benefits over traditional cementitious composites and possesses a great prospect in civil engineering projects. Previous studies reported that fiber admixtures could effectively enhance the mechanical properties, impermeability, and durability of cementitious composites. Nevertheless, the trade-off of the reinforcing efficiency, cost, and properties of the cementitious composites in different aspects has been a challenge in the application of FRC to practical engineering. This article summarizes a review concerning the recent development of FRC enhanced by different fibers and mainly focused on the fiber-reinforcing effects on the microstructure and the corresponding properties of cementitious composites. The addition of a small amount of fiber material has a significant change in the microstructure and related properties of cement-based materials, but the presence of fibers also causes structural damage and other problems. The direction of future development of some cutting-edge technologies such as coating and hybridization methods on fiber modification was concluded to assist further research in FRC. This review will further enhance the understanding of fiber for reinforcing cementitious composites.

Most of the stress–strain relationships of thermoplastic polymers for aeronautical composites tend to be nonlinear and sensitive to strain rate and temperature, so accurate constitutive models are urgently required. Classical and machine learning-based constitutive models for thermoplastic polymers are compared and discussed. In addition, some typical models have been recovered and compared by authors to evaluate the performance of classical and machine learning-based constitutive models, so that the advantages and shortcomings of these models can be demonstrated. By reviewing constitutive models, it was found that the equations of physical constitutive models are derived according to thermodynamical principles, so the physical constitutive models can describe the deformation mechanism at the microscopic level. The phenomenological constitutive models may combine the macroscopic phenomena and theories of physical models, and good performance and wide range of applications can be realized. In addition, phenomenological constitutive models combined with machine learning algorithms have attracted attentions of investigators, and these models perform well in predicting the stress–strain relationships. In the future, the constitutive models combining the theories of physical constitutive models, phenomenological constitutive models, and machine learning algorithms will be increasingly attractive as some challenging issues are effectively addressed.

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 has been an immense threat to global public health and has also had a negative socioeconomic impact worldwide. However, although the pandemic is now under control, it has demonstrated that society is unprepared to use analysis methods that are applicable to various types of viruses nor apply new therapies to prevent infections, considering the extensive time needed for vaccine development. The use of nanomaterial-based diagnostics and therapeutics can provide essential strategies for both virus detection and treatment. Gold nanoparticles (AuNPs) are the nanomaterials most commonly used to enhance virus detection because of their bioconjugation, high plasmon resonance, and excellent electrical, optical, and catalytic properties. The present review outlines the recent advances reported in the literature regarding using AuNPs for their antiviral activities with respiratory viruses, analysis techniques such as AuNP-assisted polymerase chain reaction, biosensors (electrochemical, piezoelectric, and optical), lateral flow analysis, nucleic acid assays, and gene and vaccine therapy. Finally, as a potential antiviral treatment, this review provides in vitro and in vivo toxicity results of AuNPs for respiratory viruses, as well as those related to their toxicity in humans, to evaluate their use as a future antiviral treatment.

Iron-based coagulants are widely used in wastewater treatment due to their high positively charged ion that effectively destabilise colloidal suspension, and thus contribute to the formation of insoluble flocs. Ferric chloride, ferrous sulphate, and poly-ferric sulphate (PFS) are examples of iron-based coagulants that are highly available, and are beneficial in producing denser flocs, thereby improving settling characteristics. This work aims to review the preparation methods of PFS and critically discuss the influence of these methods on the PFS properties and performance as a chemical coagulant for water and wastewater treatment. In polymeric form, PFS is one of the pre-hydrolysing metallic salts with the chemical formula [Fe 2 (OH) n (SO 4 ) 3− n /2 ] m (where, n  < 2, m  > 10) and has a dark brownish red colour as well as is more viscous and less corrosive. PFS has an amorphous structure with small traces of crystallinity, containing both hydroxyl and sulphate functional groups. It has been applied in many industries including water or wastewater treatment which is also discussed in this study. It has the ability to remove pollutants contained in water or wastewater, such as turbidity, colour, chemical and biological oxygen demand, phosphorus, and others. This study also provides a review on the combination of PFS with other chemical coagulants or flocculants in the coagulation/flocculation process, and also flocs formed after a more stable treatment process.

Ceramic waste (CW) has a significant negative environmental influence on the society. However, CW may benefit the environment if it is handled carefully and recycled in concrete production. Recycling CW may lessen the demand for raw materials and waste disposal, thereby preserving natural resources and lowering greenhouse gas emissions. Numerous studies discuss the possibility of CW utilization as concrete ingredients. However, data are spread, making it difficult for the reader or user to assess the benefits and drawbacks of using CW in concrete, which limits its applications. To study the benefits and drawbacks of using CW in concrete and provide the guidelines to the consumer with relevant information, a detailed review is required. Therefore, this study is carried out to collect all relevant updated information from published articles. The major topics of this article include the general history of CW, physical and chemical features, and the influence on concrete parameters including fresh, strength, elevated temperature, and cost benefits. Results indicate that CW decreased concrete flowability and strength. However, with up to 10% substitution, the results are satisfactory, and concrete can be used for a normal-strength structure. Furthermore, the review also identifies the research gaps that need to be investigated.

Aluminium alloys are a material that is increasingly used in industry. This is due to very good strength properties with low specific weight and low production costs. The disadvantage of kinematic system aluminium elements is their surface’s susceptibility to adhesive wear. One method of eliminating the adverse impact of adhesive tacks on the surfaces of cooperating aluminium components of machinery is the application of the method based on the anodic oxidation of alloys surface. The layers obtained by this method are widely used in sliding connections of kinematic machine parts. The modification of anodic oxide layers with admixtures has been an uninterrupted area of interest since the 1990s. This article is a review of selected methods of modifying the structure and properties of aluminium oxide layers on aluminium alloys.

Magnetically driven swimming microrobot is a typical one in the family of microrobots and they can achieve navigation and manipulation in low Reynolds number biomedical environments with an external magnetic drive strategy. This study reviews recent advances in material selection, structure design, fabrication techniques, drive control method, and applications for magnetically driven swimming microrobots. First, the materials used in magnetically driven swimming microrobots were introduced and the effect of material selection on performance was discussed. Second, structure design of swimming microrobots and manufacturing techniques are reviewed, followed by a discussion on the main advances in effective motion control, path planning, and path tracking. Then, the multi-applications of magnetically driven swimming microrobots including targeted drug delivery, cell manipulation, and minimally invasive surgery are summarized. Finally, the current challenges and future directions of the work on magnetically driven swimming microrobots are discussed.

Taking inspiration from many published review articles in respect of polyimide–nickel nanocomposites (PINiNCs), this article is written to highlight the significant effect of reinforcing and/or blending nickel nanoparticles (NiNPs) with the different constituents of polyimide monomers to increase various properties (mechanical, thermal, and stability) without sacrificing any of its positive properties. The design and fabrication methodologies of PINiNCs have been critically reported. The recent characterization probing techniques and applications, revealing their advantages and disadvantages are examined in depth. Their diverse applications in multidisciplinary as well as high technological fields and their corresponding properties are extensively documented and summarized in tables. The type of NiNPs and the detailed fabrication techniques of PINiNCs together with their advantages and disadvantages were documented. The combination between this reported fabrication technique and enhanced properties also inspires and broadens the reader’s view to understand the basic principle of structure properties relationship of PINiNCs. This review also screens the properties and current application of PINiNCs in the field of lithography technology, biomedical, electrode technology, membrane, dielectric materials, and light emitting diode technology. The main findings are focused on the strategies to fabricate novel PINiNCs. Various modern cutting-edge characterization technologies for PINiNCs have been emphasized. The industrial applications of PINiNCs have been thoroughly reviewed to develop a complete reference material on PINiNCs. Graphical abstract

Builders, designers, and the research community are becoming interested in incorporating timber and concrete based composite structures because they effectively integrate the structural qualities of timber and concrete. The structure’s stiffness, ductility, and load capacity are all affected by the quality of the timber connections used in construction. However, timber-concrete-based structures are limited due to a lack of design knowledge and the brittle failure behaviour of timber under shear or tensile loading. Experimental, numerical, and analytical methods have been proposed in the literature, and the key parameters influencing the performance of timber-concrete structures have been discussed. This study addresses the current challenges in designing timber-concrete connections and their failure modes and suggests simple performance-based analytical models that determine the failure mode. It looks at some of the best numerical design methods used in the past and tries to determine the best way to use timber as a possible way to use safe design principles for timber–concrete composite structures in the future.

Due to environmental and financial concerns, there is a growing demand for composite materials in a wide range of industries, including construction and automotive industries. In 2020, the market for wood plastic composites was estimated to be worth $5.4 billion. By 2030, it is expected to have grown to $12.6 billion, with a compound annual growth rate of 8.9% between 2021 and 2030. The fundamental disadvantage of reinforced composites by natural fibers is the different nature of the hydrophilic lignocellulosic and the hydrophobic thermoplastic polymers, although natural fibers would lower total costs. These composites typically fail mechanically as a result of fiber debonding, breaking, and pull-out. In a fiber-reinforced composite, the matrix’s function could be described as distributing the force to the added fibers using interfacial shear stresses. A strong connection between the polymeric matrix and the fibers is necessary for this procedure. Weak adhesion at the interface prevents the composite from being used to its maximum potential and leaves it open to attacks from the environment that could damage it and shorten its lifespan. Poor mechanical performance is caused by insufficient adhesion between hydrophobic polymers and hydrophilic fibers in natural fiber-reinforced polymer composites. Consequently, during the past 20 years, a variety of chemical, thermal, and physical methods have been employed to address these issues. These methods largely concentrated on the grafting of chemical groups that could enhance the interfacial contacts between the matrix and natural fibers. This review article aimed to give information on several types of fiber treatments and natural fiber-treated composites with a specific focus on their physical and mechanical properties.

Polylactic acid (PLA) is extensively used as a raw material in fused deposition modeling (FDM)-based three-dimensional printing (3DP), owing to its abundant resources, simple production processes, decent biodegradability, and adequate mechanical strength. However, it has disadvantages such as poor toughness and straightforward bending deformation. Given the considerable application potential of PLA materials in FDM-based 3DP technology, herein, studies conducted over the last 5 years toward the enhancement of the characteristics of PLA for FDM are summarized. In particular, modification approaches (chemical or physical methods) that have been employed to improve the mechanical and processing attributes of PLA are discussed, along with the development of PLA composites with unique functionalities. The insights provided herein can help expand the scope of application of PLA composites in FDM-based 3DP for utilization in fields such as transportation, aerospace engineering, industrial equipment fabrication, consumer/electronic product manufacturing, and biomedicine/medicine. Graphical abstract

This review is an attempt to explore the challenges that need to be addressed to fully utilize the potential of ceramic-based functionally graded cutting tools (FGCTs). The various aspects covered in the review include the most recent experimental and numerical work related to FGCTs, the current research trends and the need for these tools, the identification of potential material combinations, synthesis techniques and their limitations, and finally a presentation of the most recent work. To find general tribological performance, various wear mechanisms involved in the cutting process are explored. Some recent experimental and numerical works related to the self-lubricating phase in functionally graded structure and the need for self-lubricating ceramic tools, identifying potential high-temperature solid lubricants, and their limitations are also discussed. More recent and dominating fabrication methods are also discussed in detail along with a brief review of some promising methods. The implementation of numerical modeling and computational frameworks validated through experiments is found to lead to the design and development of cost-effective and efficient FGCTs. Finally, some research gaps are identified and future directions for innovative FGCT materials are proposed.

The modern food industry requires new analytical methods for high-demand food supplements, personalized diets, or bioactive foods development. One of the main goals of the food industry is to discover new ways of food fortification. This applies to food products or supplements for human and animal diets. In our research, we focused on the solid particles of AproTHEM (dried porcine hemoglobin), which is approved for animal feeding and as a meat product additive, and AproFER 1000 (heme iron polypeptides), which is still being investigated. The study showed the possible application of advanced techniques for the examination of iron-based food additives. We evaluated selected techniques for particle size and morphology examination such as laser diffraction, optical microscopy, as well as scanning electron microscopy, and briefly discussed their usefulness compared with other techniques. On the basis of our results, we proposed a path of microscopic analysis for the study of material homogeneity. The structure of heme iron was evaluated by X-ray diffraction, FT-IR, and Raman spectroscopy supported with thermal behavior analysis (differential scanning calorimeter). Furthermore, a portable colorimeter was applied for L * a * b * color analysis. Our study proved that for new food product development, particle size analysis as well as typically used advanced materials techniques can be successfully applied.

In this study, data mining, followed by the scientometric analysis of fiber-reinforced shotcrete (FRS), was carried out for knowledge mapping, co-citations, and co-occurrence. The information needed for the analysis was retrieved from the Scopus search engine. Important publishing sources, keyword analysis, writers with the most contribution in citations and publications, the most-cited articles, and the regions most actively engaged in FRS research were identified throughout the data review process. Moreover, the need for FRS, the major constraints associated with their usage, and their possible solutions were discussed. The analysis of the bibliographic data showed that research publications on FRS progressed inconsistently till 2015, and over the past 6 years (2016–2021), publication numbers increased steadily, which exhibited the interest of academics in fiber-reinforced materials. The analysis of keywords in the field showed that the most common FRS research keywords are shotcreting, shotcrete, steel fibers, FRS, and fiber-reinforced materials. Keyword analysis showed that FRS is typically used for tunnel rock support and lining. Based on the review of relevant literature, research gaps have been identified, and future research has been suggested.

Fossil fuels have been the most employed energy source with a consistent and growing consumption; however, they will be replaced by renewable energy sources (RESs). Massively using this type of energy will require new materials, especially metallic-based materials, because the typical materials have shown poor performance. In particular, hydrogen obtained from RESs has technological concerns like absorption/desorption cycling, kinetics, and cost. Similarly, the solar industry demands highly corrosion-resistant materials at high temperatures. As mentioned above, these could be solved using high-entropy alloys (HEAs). HEAs are barely around 15 years old and have been intensively investigated to be used for wide technological and scientific applications due to their unusual mechanical, physical, and chemical properties. Thus, this study summarizes advances in HEAs as promising materials for hydrogen and energy molten salt storage technologies and discusses the corrosion performance of current HEAs, considering both the microstructure and constituent element effect. Graphical abstract

The axial compression ratio is one of the important factors affecting the seismic performance of reinforced concrete (RC) walls. Thus, the axial compression ratio is critical in the seismic design of RC walls. In addition to the axial compression ratio, the other significant experimental parameter is the stirrup form of the boundary elements. To study the effect of the axial compression ratio and the stirrup form on the seismic behavior of ductile RC walls reinforced by prestressed concrete strands, four full-scale concrete walls were constructed and subjected to reversed cyclic lateral loading while experiencing constant axial compression, with axial load ratios set at 0.17 and 0.26. The considered stirrup forms of the boundary elements are circular and compound, respectively. All specimens exhibit significant drift-hardening capability with a small residual drift and a small crack width. The ultimate capacity, ductility, stiffness and attenuation process, hysteretic characteristics, energy dissipation capacity, residual deformation, and maximum and residual crack width of the shear walls are compared and analyzed. The experimental results and comparisons between the two groups of shear walls with different axial compression ratios and stirrup forms of concealed columns are presented. The characteristics of the envelope curve are also analyzed, and a simplified bilinear envelope curve model is proposed to better fit the test results.

Limitation in practical applications of biopolymer–fiber composite is mainly at higher temperatures. Thus, this study highlights the effects of fiber orientation on the durability of polylactic acid (PLA) reinforced with unidirectional (UD) continuous kenaf fibers at elevated temperatures. PLA and long kenaf fiber were fabricated using the hot-pressing method and stacked at fiber orientations of 0°, 45°, or 90°, relative to the tensile force. Dynamic mechanical analysis of the composites shows excellent anti-shock and temperature-resistant properties of the composite. UD PLA–kenaf composites with a 0° fiber orientation showed an ultimate tensile of ∼190 MPa and a flexural strength of ∼235 MPa, and the strength of the composite was able to retain up to 120°C temperature. The debonding behavior of the fiber from the matrix (fiber pull-out) supported by microscopy proved that interfacial failure occurs from the local strains, which initiate cracking. Interfacial failure and stress transfer have caused a remarkable reduction in composite strength when fibers were oriented at 90°. Hence, this current improvement in the performance of the UD PLA–kenaf fiber composite may potentially replace conventional synthetic fibers, especially for structural automotive applications.

The main aim of the current work is to investigate the effect of equal channel angular pressing (ECAP) processing parameters, namely, number of passes, ECAP die angle, route type, and processing temperature on the mechanical and electrical properties of pure copper (Cu). The finite element method was used to simulate the homogeneity of stress and plastic strain distribution during ECAP processing. The response surface methodology (RSM) was used to identify the optimum ECAP processing parameters by analyzing the impact of ECAP conditions on responses. A second-order regression model and analysis of variance were created to analyze the ECAP condition of optimum responses. A genetic algorithm (GA) was also applied to optimize the ECAP condition. Finally, a hybrid RSM–GA was created to improve the optimization of ECAP responses and corresponding conditions evaluated using GA. The developed models were validated and compared with the experimental findings to prove that they are reliable as predictive tools. The optimization findings revealed that route Bc was more effective in improving the hardness, yield stress, ductility, and impact energy whereas route A was more effective in improving the ultimate tensile strength and the electrical conductivity of the Cu billets. Furthermore, the optimum die angle, number of passes, and processing temperature for the mechanical and electrical properties were also identified individually.

The solidification property and mechanism of soft soil based on the industrial waste residue was studied systematically. First, the properties of soft soil solidified by single blast furnace slag, phosphogypsum and cement were carried out, and the solidification effect of Portland cement was better compared with blast furnace slag and phosphogypsum. Second, the composite solidification agent formula with excellent solidification performance was developed, and the mass ratio of Portland cement, blast furnace slag and phosphogypsum was 1:2.3:0.8. At this time, compressive strength was up to 8845.1 kPa. Finally, the composition and microstructure of the solidification soft soil was studied by X-ray diffractometer and scanning electron microscope. Calcium hydroxide formed by the hydration of Portland cement and calcium sulfate in phosphogypsum were used as activators for hydration reaction of blast furnace slag, and more hydration products under the synergistic action of Portland cement hydration and blast furnace slag hydration were formed. Hydrated calcium silicate colloid and Ettringite crystal played an important role in skeleton and filling, and the structure of soft soil solidified by composite solidification agent was the most compact.

Graphite-carbon nitride (g-C 3 N 4 ) was prepared by thermocondensation, and g-C 3 N 4 /BiVO 4 material (GCB) and g-C 3 N 4 /CNTs composite material (GCC) were prepared by doping different contents of BiVO 4 and carbon nanotubes (CNTs) with g-C 3 N 4 samples, respectively. Then, BiVO 4 , CNTs, and g-C 3 N 4 samples with different contents were doped to prepare ternary composite material (GCBC). In the performance experiment, Sulfamethoxazole (SMZ) was used as degradation material to evaluate the photocatalytic performance of the prepared samples, and the degradation reaction kinetics equation, quadric cycle stability experiment, free radical capture, and intermediates identification were studied. The intermediates of photocatalytic degradation of SMZ were analyzed by high-performance liquid chromatography-mass spectrometry. From the experimental data, it can be seen that for SMZ solution, when the reaction time T = 0 min and retention time rt = 7.53 min, there is a peak corresponding to the substance with m / z [M + H] + of 254, which is judged as SMZ. At 20, 40, and 60 min, rt was 2.00, 7.06, and 9.57 min, indicating the presence of intermediates in the photocatalytic process. Experimental analysis shows that there are three intermediates of SMZ degradation by composite sample GCBC. In this work, three kinds of composite materials were successfully prepared, and a variety of characterization, SMZ as pollutants, test the photocatalytic performance of composite materials (GCB, GCC, and GCBC) samples, and elucidated the cyclic stability of the material, active species capture, and photocatalytic degradation mechanism.

Thermal modification is an environment-friendly technology for improving various wood properties, especially the dimensional stability, decay resistance, and color homogeneity. In this work, four tropical wood species (African padauk, merbau, mahogany, and iroko) were thermally modified by the ThermoWood process. The influence of heat treatment on the color and chemical changes of wood was studied by spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, and wet chemistry methods. As the temperature increased, a decrease in lightness ( L *) and a simultaneous decrease in chromatic values ( a *, b *) were observed, indicating darkening and browning of the wood surface. As a result of the heat treatment, the relative content of hemicelluloses decreased the most in merbau and mahogany, while the thermal stability of iroko and African padauk was higher. All examined wood species showed a strong correlation between the lightness difference value (Δ L *) and the content of hemicelluloses ( r = 0.88–0.96). The FTIR spectroscopy showed that the breakdown of C═O and C═C bonds in hemicelluloses and lignin plays an important role in the formation of chromophoric structures responsible for the color changes in the wood.

The development of hybrid composite materials using honeycomb structure, typically a lightweight material, is commonly used in aircraft structures. However, the use of honeycomb with natural or synthetic composite remains unexplored in the literature. Therefore, this study aims to partially replace synthetic fiber, woven glass with a natural fiber of woven kenaf and honeycomb core. An experimental analysis investigated the mechanical strength of three different compositions using glass, kenaf, and honeycomb materials for structural application purposes. The properties of the sample were evaluated through the tensile, flexural, and impact strength, and the morphological damage was observed using scanning electron microscopy. The results showed that the composition of GKGKG laminate composite is the highest in tensile strength (147.64 MPa) and modulus (3.9 GPa), while the GKHKG composite was good in flexural strength (219.03 MPa) and modulus (11.47 GPa). In terms of impact properties, there was a slight difference in energy level (20–30 J) by GKGKG and GKHKG, showing the optimal hybrid configuration of composite for the newly developed material. In conclusion, the application of the new hybrid of GKHKG composite is promising in semi-structural and structural light-weight applications.

Ship–bridge collision is a common type of accident in bridge engineering which could cause heavy casualties and economic losses. To ensure the safety of both the ships and bridges during collision, a novel steel box-soft body combination was proposed in this work. The time history curves of the impact force of three downscaled facility specimens were obtained through the horizontal impact test. The influence of the steel box web spacing and the existence of the anti-collision facilities on the ship collision force reduction rate was investigated. The collision failure modes of ship bow and the anti-collision facilities, as well as the energy absorption behavior of the facility were analyzed. Based on ANSYS/LS-DYNA finite element (FE) analysis software, the nonlinear numerical models of the anti-collision facilities were generated. The analysis results show that the proposed anti-collision facility can not only greatly reduce the ship impact force, but the bow damage as well. The densified steel box web can improve the anti-collision performance of the whole anti-collision facilities to a certain extent. Compared with the direct impact on the steel plate, the maximum reduction rate of peak force of the proposed facility can be achieved to be 31.07%. The anti-collision facilities deformation energy absorption accounts for more than 70% of the total energy, which shows that the facility is able to absorb most of the energy and protect the bow. The FE simulation results coincide with the experimental outcomes, indicating the acceptable accuracy of the FE models. Graphical abstract

More than 2 billion people around the world still use raw earth architecture, in countries like Nepal, India, and Iran. In China, the proportion of people living in earthen structures rose to 36%, some of them in western Sichuan. Minority dwellings in western Sichuan, China, use local stone and yellow mud as building materials and have been used for thousands of years. Because yellow mud is a brittle material with poor mechanical properties, and because the region is prone to earthquakes, the walls are highly susceptible to damage under seismic action. To improve the mechanical properties of yellow mud, the yellow mud of Taoping Qiang Village in western Sichuan was studied and modified. Uniaxial compressive tests were conducted on the modified specimens, and the existing ontogenetic equations of raw soil-based materials were analyzed and optimized. Finally, we developed the constitutive models for yellow clay and modified yellow clay in the western Sichuan area, which can be used for different kinds of modified materials through the variation of parameters. The results show that the compressive strength of yellow clay is improved by adding the modified materials. The optimized constitutive model can better fit the test curves, which can provide a basis for theoretical calculations and seismic mitigation of minority residential structures in western Sichuan or similar structural systems.

State-of-the-art treatment of such orthopedic diseases as fracture and femoral head necrosis implies the installation of prosthesis or fixed equipment into patients’ injured parts using bone drilling. This study proposes an ultrasonic longitudinal torsion-assisted drilling (ULTAD) technique for biotic bone drilling. A comparative experiment was carried out between conventional drilling and ULTAD drilling in biotic bone, namely porcine femur. These tests proved that under the same drilling parameters, the ultrasonic component in bone drilling could reduce the drilling temperature and forces, improve the material removal by chip breaking, shorten the length of bone debris, and facilitate their discharge. Moreover, the proposed ULTAD technique reduced the number, length, and width of microcracks in the borehole wall, thus protecting the drilled biotic bone from internal damage.

The current study has portrayed the synthetic mixtures of Themeda quadrivalvis using gas chromatography–mass spectrometry (GCMS), the combination of green silver nanoparticles (AgNPs) formed with macrolide antimicrobials. The counter microbial effects were investigated with various concentrates of plant compounds, AgNPs, and macrolide-formed AgNPs against respiratory microorganisms. GCMS examination has shown the presence of various substances that intensifies the chloroform concentrate of T. quadrivalvis . A total of 51 mixtures were distinguished, and furthermore, the most severe zone of restraint was found in chloroform removal and against Klebsiella sp. (18 ± 4.7 mm). It has been demonstrated that the green mixture of AgNPs containing macrolide anti-toxins, such as azithromycin, erythromycin, and clarithromycin, demonstrates extensive antibacterial activities against a wide range of microorganisms. In contrast, the green union of AgNPs also demonstrates their efficacy against a wide range of respiratory microbes. The particles containing numerous relatively small fragments that were observed in the scanning electron microscopy analysis were found to be 20 nm in size. Previous studies have focused on phytochemicals and green amalgamations of AgNPs, but not much detail has been provided on T. quadrivalvis . It has been reported that the two concentrates (a plant concentrate in combination with consolidated green nanoparticle macrolide anti-toxins). The present study aims to treat respiratory microorganisms with a green methodology approach using nanotechnology; this analysis primarily focuses on offering creative approaches to make drugs against respiratory microbes.

The present work aims to carry out a feasible study of wire electro-discharge machining (WEDM) during the machining of Inconel 690 superalloy gears. Processing conditions of power-on time, power-off time, current, and spark-gap voltage are varied to evaluate the process performance in terms of material removal rate (MRR), surface roughness (SR), and wire consumption. Parametric optimization has been carried out using combined approach of response surface methodology (RSM) and artificial neural network (ANN). Results revealed that ANN predicted values are 99% in agreement with the experimental results which validates its effectiveness as compared to RSM predicted values. A viability study of noise characteristics of the processed gear is also done using a noise testing setup. Additionally, FE-SEM has been used to analyze the machined surface’s topography. Greater discharge energy brought by a longer pulse length raises the values of MRR, SR, and recast layer thickness (RLT). This study explores the capability of WEDM to produce a more precise and smooth gear profile as compared to other conventional machining methods. Additionally, RLT and microhardness of the machined surface have been critically studied to comprehend the better understanding of the process mechanism.

We report the synthesis of Ag/bentonite, ZnO/bentonite and Ag/ZnO/bentonite nanocomposites (NCs) using Hagenia abyssinica plant extract and their antibacterial study. The synthesized NCs were characterized by using many advanced techniques. The X-ray diffraction and high resolution transmission electron microscopy analysis confirmed the formation of composites with different phases. The average crystallite size ( D ) values of pure Ag nanoparticles (NPs), ZnO NPs, and activated bentonite (Na-AB) were found to be 8.14, 18.1, and 37.6 nm, respectively. The Ag/bentonite NCs, ZnO/bentonite NCs, and Ag/ZnO/bentonite NCs exhibited the D values of 7.4, 9.4, and 9.4 nm, respectively. The Fourier transform infrared spectral analysis revealed the presence of hydroxyl, carbonyl, and other functional groups on the surface of the synthesized NCs. The transmission electron microscopic analysis revealed the formation of Ag and ZnO NPs with hexagonal, rod-shaped, and spherical structures. HRTEM also revealed the presence of (102) plane of ZnO and (220) plane of Ag in Ag/ZnO/bentonite NCs. The antibacterial activities of the composites suspension were evaluated against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 by the disc diffusion and broth dilution methods. The ternary NC and Ag/ZnO/bentonite exhibited better zone of inhibition of 14.3 ± 0.3 and 17.3 ± 0.2 mm at 10 mg·mL −1 toward E . coli and S . aureus bacterial strains. The minimum inhibitory concentration and minimum bactericidal concentration values of Ag/ZnO/bentonite NCs were found to be 156.25 and 312.5 µg·mL −1 for E. coli . The investigation results revealed that the low temperature bio-synthesized Ag/ZnO/bentonite is a promising bactericide over the binary composites.

The cost of the coolant and its disposal cost are significant issues in metal machining processes. In biocompatible magnesium alloy-based medical implants and instrument manufacturing, the cost hikes are owing to the use of unconventional machining processes and computerised numerical control machines. This research aims to improve machinability performance and optimize process parameters for biocompatible magnesium implant manufacturing for biomedical applications using eco-friendly nanofluid of MoS 2 nanoparticles suspended in waste coconut oil. The nanofluid was prepared from the multiple times used waste coconut oil (waste) and was mixed with MoS 2 nanoparticles. The orthogonal array L16, Taguchi analysis, and analysis of variance were employed in experimental design and statistical optimization. The machinability performance was determined by measuring and comparing the responses like cutting force, feed force, surface roughness, cutting zone temperature, and tool wear. They were compared with machining using a nanofluid and conventional commercial coolant. The results reveal that the proposed method of machining improved machinability performance appreciably; therefore, the observations of the proposed method were used and the process parameters were optimized. Mathematical models were developed for the prediction of process parameters. The proposed method exhibited the average reduction of the cutting force by 68.23167 N, feed force requirements by 34.180 N, the cutting zone temperature by 60.435°C, the surface roughness by 0.118908 µm, and the tool wear by 039938 mg·h −1 .

This study used aluminum scraps to produce a secondary aluminum metal matrix for heat storage analyses. Silica and kaolin reinforced aluminum metal matrix composites were successfully produced via stir casting. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed for phase and microstructure characterization. XRD revealed alumina (corundum), aluminum and kyanite phases while SEM indicated pores in the composites. Density, average specific heat (from 30 to 200°C), thermal conductivity, and hardness tests were carried out. Total heat energy stored per kg, from 30 to 200°C, was obtained. The inclusion of 7.5 and 15 wt% kaolin increased the specific heat of the matrix from 474.3 to 564.57 J·kg −1 ·°C −1 and 474.3 to 679.03 J·kg −1 ·°C −1 , respectively. Likewise, adding 7.5 and 15 wt% silica sand increased the thermal conductivity of the matrix from 154.99 to 175.62 W·m −1 ·°C −1 and 154.99 W·m −1 ·°C −1 to 181.38 W·m −1 ·°C −1 , respectively. The addition of 7.5 wt% silica sand and 7.5 and 15 wt% kaolin increased the hardness value of the matrix from 72.11 to 73.11 HB, 72.11 to 81.38 HB, and 72.11 to 82 HB, respectively. Hardness of the composites reinforced with kaolin is higher than that of the composites reinforced with silica sand. This is attributed to the higher molecular weight of kaolin. Significant increase in specific heat and thermal conductivity was achieved.

Fly ash (FA) and slag could improve the performance of glazed hollow bead (GHB) thermal insulation mortar, but little research touched on how the FA and slag affect its performance and optimize its component contents. In this study, an experimental and statistical investigation is conducted to analyze the influences of FA and slag variables on the performance of GHB mortar based on the response surface methodology (RSM). The predicted model was proved statistically significant in terms of the fluidity, compressive strength, flexural strength, and thermal conductivity. Then, the validated model was used to identify the critical parameters and discuss their mechanisms of action. It can be found that (i) FA plays a significant role in fluidity and compressive and flexural strength owing to its morphological and physical filler effects; (ii) slag has an obvious influence on compressive strength and thermal conductivity due to its microaggregate effect. Finally, optimization design was conducted using the desirability approach of RSM to give the optimal component of 20.73% FA and 21.49% slag. The predicted combination was validated by confirmatory tests within an error of 1.52%. This study provides a feasible and effective solution for optimizing GHB thermal insulation mortar to achieve higher performance.

Vitamin D 3 and iron are important components of a balanced diet. Supplementing meals with these is essential to support the recovery of humankind’s malnutrition. It is necessary to develop effective delivery systems to ensure the high bioavailability of these hydrophobic components. For this purpose, emulsions were prepared based on hemp seed oil and with soap nut extract ( Sapindus mukorossi fruits) as a natural emulsifier. To characterize the differences in the properties of the emulsions depending on the content of the oil phase and the emulsifier, measurements were performed to determine the following parameters: the color characteristics, transparency of the samples, infrared spectrum, particle size distribution, polydispersity of the system, and the rheological properties of the emulsions. The results showed that the highest stability was observed in systems with a relatively low oil concentration, i.e. , 1%. These samples also had an average particle size not exceeding 200 nm. In turn, the low oil content significantly reduced the dynamic viscosity of the emulsions. At the same time, microscopic observations indicated that the presence of an oil phase was advantageous, not only because of the possibility of providing vitamin D but also because of the high hydrophobicity of the iron particles. Therefore, the realized research made it possible to identify the optimal emulsion composition. The created system can find applications in delivering dietary supplements such as vitamin D 3 and iron by providing high dispersion of components and high stability.

The current study examines thin film flow and heat transfer phenomena with some additional effects such as magnetohydrodynamic, viscous dissipation, and slip condition over unsteady radially stretching surfaces for various shapes of copper ( Cu ) \left({\rm{Cu}}) nanoparticles dispersed in ethylene glycol ( EG ) \left({\rm{EG}}) . The effective thermal conductivity of a nanofluid made of Cu nanometer-sized particles distributed in EG {\rm{EG}} is significantly higher than that of pure EG. Partial differential equations are transformed into ordinary differential equations using the proper transformations. An effective convergent technique ( i.e. , BVP4C) is used to compute the solutions of nonlinear systems. MATLAB software is used to perform the calculations. The effect of numerous emerging physical characteristics on temperature and velocity, such as unsteadiness parameter ( S ) \hspace{ 1em}\left(S) , slip parameter ( K ) \left(K) , Hartmann number ( M ) \left(M) , solid volume fraction ( ϕ ) (\phi ) , and Eckert number ( EC ) \left({\rm{EC}}) is investigated and illustrated graphically. The physical quantities, such as the skin friction coefficient and the Nusselt number, are calculated, described, and displayed in tabular form. It is observed that blade-shaped Cu nanoparticles had the lowest surface drag, highest heat transfer rate, and minimum film thickness compared to the brick and cylinder-shaped nanoparticles. According to our detailed investigation blade-shaped Cu {\rm{Cu}} nanoparticle is the most suited solution for manufacturing unsteady radially stretching modules.

The vibration and noise performance of the offshore platforms are significant factors affecting the comfort and physical and mental health of the staff, and are also important indicators for evaluating the status of platforms. Based on the principle of structural dynamics, taking the semi-submersible platform as the research object, this article systematically and comprehensively studies the vibration characteristics and transfer laws of some partial-frame structures to the overall structure by combing theoretical derivation and numerical simulation. Firstly, the coupling dynamic model of the device-plate-platform is established, and the vibration transmission from the excitation source to the platform structure through the coupling system is analyzed theoretically. Secondly, the multimodal vibration mechanism of the plate frame and cabin structure is discussed by considering the plate frame and the plate frame as one. Finally, based on the semi-submersible platform structure, the study of complex multi-modal vibration transfer law of platform structure is carried out, which contributes to the research on multimodal coupled vibration protection of offshore platform structure. Graphical abstract

The pore-structure characteristics of hybrid basalt–polypropylene fibre-reinforced concrete were investigated by using mercury intrusion porosimetry. The applicability of various fractal models in characterising the HBPRC pore structure was compared. The results show that the types and content of fibres show different influences on the cumulative pore volume and fractal characteristics of hybrid basalt-polypropylene fibre-reinforced concrete. Compared with pore-volume and solid mass, the fractal characteristics of pore surface area of hybrid basalt-polypropylene fibre-reinforced concrete is more significant. Furthermore, the pore-surface fractal model that established based on the energy conservation relationship during mercury intrusion is more accurate and effective for the characterization of fractal dimension of hybrid basalt-polypropylene fibre-reinforced concrete. The research results can provide important theoretical guidance for the study of pore structure and fractal characteristics of fibre-reinforced concrete.

In recent years, manufactured sand produced from crushed rock has been used as fine aggregate instead of natural sand in construction and industrial fields to minimize the impact of natural sand depletion in nature and society. In this research, the mechanical properties and durability of alkali-activated sustainable mortar using manufactured sand and different sodium silicate (solution) to precursor ratios (SSPR; 0.60, 0.65, 0.70, 0.75, and 0.80) by weight were investigated. Metakaolin and fly ash were used as precursor, sodium silicate (solution) and sodium hydroxide were used as alkali-activator, and manufactured sand made from broken limestone was used to completely replace river sand as fine aggregate to prepare metakaolin/fly ash (MK/FA) alkali-activated sustainable mortar to ensure sustainable development. The compressive, tensile, and flexural strengths, anti-permeability, and crack resistance of MK/FA alkali-activated sustainable mortar were tested. The impact of different SSPRs on the mechanical properties and durability of alkali-activated sustainable mortar was analyzed. Quadratic function fitting models of tensile strength to compressive strength and flexural strength to compressive strength were proposed. Furthermore, the statistical effects of each parameter were explored using analysis of variance and F -test of statistical analysis. The experimental results indicate that the SSPR has a remarkable effect on the mechanical properties and durability of MK/FA alkali-activated sustainable mortar. When the SSPR is in the range of 0.6–0.8, the compressive, tensile, and flexural strength of the alkali-activated sustainable mortar initially increased and then decreased; however, there is an opposite trend in water penetration depth and crack index. MK/FA alkali-activated sustainable mortar exhibits best compressive strength, tensile strength, flexural strength, anti-permeability, and cracking resistance of 40.2 MPa, 3.38 MPa, 4.3 MPa, 41.3 mm, and 245 mm, respectively, at SSPR of 0.7. The experimental findings of this study can provide theoretical guidance for practical engineering of alkali-activated sustainable mortars using manufactured sand.

To study the effects of macro- and micro-fiber on the concrete beams, bending resistance tests were conducted on the polypropylene fiber-reinforced concrete beams. Stepwise loaded tests were carried out to obtain the load–deflection curves for different test pieces, cracking load values of the first inclined crack, recording and depicting crack development, changes in mid-span deflection of the test pieces, load–strain relationships of concrete, etc. The crack patterns and failure modes were observed. The research findings have shown that the ultimate load of the concrete beams doped with multi-size polypropylene fiber is 58.31 and 34.08% higher than that of ordinary concrete beams and concrete beams with single macro-fiber, respectively. Notably, the ultimate anti-bending bearing capacity of the beams significantly improves following the addition of macro-fiber. Polypropylene fiber can offset the defects caused by macro-fiber, remarkably suppress the development of cracks, and control the deformation of beams due to the effects of micro-fiber of different dimensions.

In this study, composite nanofiber films for the wound dressing application were prepared with silk fibroin (SF) and polycaprolactone (PCL) by electrospinning techniques, and the SF/PCL composite nanofiber films were characterized by the combined techniques of scanning electron microscopy (SEM), the equilibrium water content, Fourier transform infrared spectrometer test, X-ray diffraction (XRD) and cell viability test. The results indicated several parameters, including the rotating roller speed, solution concentration, and SF/PCL ratio, affected SF/PCL composite nanofibers’ diameter size, distribution, and wettability. The SF/PCL composite nanofiber manifested a smaller fiber diameter and more uniform nanofibers than pure PCL nanofibers. The contact angle changed from 121 ± 2° of the neat pure PCL to full wetting of 40% SF/PCL composite nanofiber films at 2,000 rpm, indicating good hydrophilicity. Meanwhile, cells exhibit adhesion and proliferation on the composite nanofiber films. These results testified that SF/PCL composite nanofiber films may provide good wettability for cell adhesion and proliferation. It was suggested that optimized SF/PCL composite nanofiber films could be used as a potential biological dressing for skin wound healing.

The roughness of the joint surface plays a significant role in evaluating the shear strength of rock. The waviness (first-order) and unevenness (second-order) of natural joints have different effects on the characterization of joint surface roughness. To accurately quantify the influence of the two-order asperity on the joint roughness coefficient (JRC) prediction of joint surface profile curve, the optimal sampling interval of the asperity was determined through the change of the R p {R}_{{\rm{p}}} value of the joint surface profile curve. The separation of the two-order asperity of 48 joint surface profile curves was completed at the optimal sampling interval, and morphological parameters of the asperity such as i ave {i}_{{\rm{ave}}} , R max {R}_{{\rm{\max }}} , and R p {R}_{{\rm{p}}} were counted from three aspects: asperity angle of the profile curve, asperity degree, and the trace length. Based on the statistical results of the morphological parameters considering the two-order asperity, the new nonlinear prediction models were proposed. The results showed that the curve slope mutation point SI = 2 mm is the optimal separation distance of the two-order asperity of the joint surface profile curve. The refined separation method that considers the waviness and unevenness of morphological parameters can characterize the detailed morphological features of the joint surface in more dimensions. The support vector regression (SVR) and random forest (RF) models that take into account a two-order asperity separated results have higher accuracy than traditional models. The prediction accuracy has improved by 7–8% in SVR model compared with SVR(SO) and RF(SO). The SVR nonlinear model that considering separation of two-orders of joint surface roughness is more suitable for the prediction of JRC.

The purpose of this work is to predict the mechanical properties of single- to few-layered borophene (η-LB)/epoxy composites using molecular dynamics modelling. An epoxy matrix was used to hold borophene in layers, and a borophene sheet was homogeneously incorporated into the epoxy matrix to generate borophene/epoxy nanocomposites. In this work, the mechanical properties of borophene/epoxy nanocomposites have been analysed in further detail. In addition to the mechanical properties of the nanocomposites, the impacts of borophene on the density distribution of epoxy polymers in the nanocomposites led to the observation that the local density is relatively high near the borophene–β 12 interface and gradually declines to the bulk value as one advances away from the interface. The mechanical properties of the borophene-layered nanocomposites were superior to those of their substitutes, with the former having a higher Young’s modulus and a lower thermal expansion coefficient. This is due to the fact that borophene layer loading may result in a significant quantity of high-density polymer being present in the nanocomposites, which enhances the overall properties of the nanocomposites. In addition, the interaction between the three to four layers of loaded borophene layer provides the greatest reinforcement among the two nanocomposites systems. Finite element analysis analyses on the preferred results of the β 12 LB were in excellent agreement with those of the experimental simulation data, demonstrating that this computational technique may be used to reliably predict the characteristics of borophene/epoxy composites in the future.

Functional foods, drug delivery systems, and cosmetics are the main areas of application for multiphase systems, where the use of naturally derived compounds is preferred. Hence, this study aimed to assess the possibility of using natural surfactants and saponin-rich extracts to produce emulsions containing antibacterial and antioxidant cinnamon and clove essential oils (EOs). The analyses of nanoparticles using dynamic light scattering showed that the addition of plant extracts to solutions allows one to obtain stable emulsions and decreased zeta potential (< −40 mV) and droplet size (<200 nm). In all investigated emulsions, the increase of antioxidative properties was observed when both EOs and plant extracts were used. The emulsion with clove oil stabilized with Quillaja saponaria bark saponins has the highest combined antioxidative properties (3.55 ± 0.01 μg gallic acid equivalent per g). Additionally, a stronger antibacterial action against Pseudomonas bacteria was observed for clove oil with Quillaja saponaria and cinnamon oil with Glycyrrhiza glabra . In addition, plant extracts did not affect significantly the other properties of the oil emulsions, e.g. wettability, colour, and refractive index. All results show that the proposed emulsions can be helpful in the preparation of multifunctional emulsions, where the co-action of saponins and EOs is especially beneficial.

The recycling of hazardous municipal solid waste incineration fly ash (MSWIFA) is drawing more attention, in which the alkali-activation technique may provide great potential to make full use of it as sustainable acoustic materials. The present work evaluated the applicability of alkali-activated MSWIFA-based materials (AAFMs) as porous acoustic barriers. The chemical composition and microtomography of the as-prepared AAFMs were characterized by X-ray diffraction. Fourier-transform infrared spectroscopy, and scanning electron microscopy. With the incorporation of MSWIFA and foaming agents, the dry bulk density and porosity of AAFMs were subsequently examined. Moreover, the compressibility and leachability of AAFMs were also investigated to evaluate their mechanical performance and environmental safety as construction materials. A sound absorption test was eventually conducted to explore the sound absorption performance of AAFMs, considering the main factors such as aluminum addition, MSWIFA dosage, and sample thickness. The results verified the good chemical stability, leachability, and sound absorption performance of porous AAFMs. Specifically, it indicated that the aforementioned factors have a boosting effect on forming highly porous structures that improve sound absorption performance, namely sound absorption coefficient and noise reduction coefficient.

Helical carbon nanotubes (HCNTs) are chiral materials that can form an induced magnetic field when current passes through them, making them a desirable material for absorbing microwaves. However, poor electrical properties and inert surfaces limit the application of HCNTs as sole materials. In this study, we develop HCNTs@Ti 3 C 2 T x MXenes hybrid aerogel microspheres synthesized using an electrospinning-assisted ice template method. The modified surfaces of the HCNTs form hydrogen bonds with Ti 3 C 2 T x MXenes to produce hybrid aerogel microspheres. Because of the different functionalized surfaces of HCNTs (F-HCNTs), F-HCNTs@Ti 3 C 2 T x MXenes could be adjusted to obtain effective reflection loss (RL) of microwaves ranging from 2 to 18 GHz. The observed advantageous RL is attributed to the modified surface of the HCNTs, their porous structure, and the optimized impedance matching derived from the synergistic effect between HCNTs and Ti 3 C 2 T x MXenes. Successful assembly method for the 3D architectures of HCNTs@Ti 3 C 2 T x MXenes hybrid aerogel microspheres significantly widens the practical applications of HCNTs in microwave absorption.

Practitioners in the industry are developing predictive methods for assessing key parameters and responses of engineering materials. The aim of this research is to optimize the average surface roughness ( R a ), flexural strength (FS), tensile strength (TS), print time ( T ), and print energy consumption ( E ) of 3D printed Nylon 6 (PA6). Quantitative parameters for infill density (ID), layer thickness (LT), and print speed (PS) were selected. Employing the central component design (CCD)-response surface methodology (RSM) for investigational design, statistical analysis, and multi-objective optimization, a total of 20 samples were produced and analyzed to develop prediction models. The implication of the selected parameters was confirmed through variance analysis (ANOVA), and the models were validated using confirmatory trial tests. It was found that LT was essential in achieving appropriate R a and T values, while ID was a crucial factor in obtaining the necessary mechanical properties. RSM optimization led to an FS of 70.8 MPa, TS of 40.8 MPa, lowest T of 53 min, lowest possible R a of 8.30 µm, and 0.203 kW·h “ E ” at ID = 84%, LT = 0.21 mm, and PS = 75 mm·s −1 . The study also revealed weak bond strength between layers and layers debonding after bending tests, as shown in SEM micrographs. The PA6 material exhibited flexibility during tensile testing, going into plasticity before breaking. The created numerically optimized model is anticipated to benefit manufacturers and practitioners in predicting the required surface quality for various factors before conducting experiments, ultimately improving 3D printing (3DP) processes and outcomes. Despite limitations such as limited parameter selection, small sample size, and material-specific focus, this research presents valuable insights for the 3DP industry.

Using recycled aggregates to prepare geopolymer concrete plays an essential role in reducing dependence on natural resources and solving the problem of waste accumulation. However, the application of geopolymer recycled aggregate concrete (GRC) has been greatly limited due to the defects in the quality of recycled aggregates and the limitations of the brittleness of concrete materials. Therefore, the work is dedicated to improving GRC properties and exploring the mechanism of action of steel fiber (SF) and nano-Al 2 O 3 . In this study, calcined gangue, slag, fly ash, and recycled aggregate were used as raw materials, the influence of SFs (0–1.25 vol%) was first explored by single factor analysis, and on this basis, the effect of nano-Al 2 O 3 (NA) (0–2 wt%) on the GPC performance of SF was studied. The microstructure of GRC was analyzed by scanning electron microscopy. The test results showed that adding SF could significantly improve the splitting tensile and flexural strength of GRC, among which 0.75 vol% is the most excellent. However, the increase in compressive strength could be more apparent. The addition of NA can make up for the lack of SF in improving compressive performance. When NA content is 1 wt%, the version of GRC is most apparent. Adding 1% NA has the most significant advance in GRC performance. The microstructure analysis showed that the NA could promote the polymerization reaction, generate more gel, and make the contact interface between SF and matrix more compact, thus improving the strength of GRC.

Hybrid composite materials are becoming more desirable for various industrial applications to enhance sustainability and develop better environmentally friendly green products. This work aims to enhance the synergy of both bio-ceramic eggshell materials and date palm leaflet (DPL) fillers to integrate their advantages in an optimized hybridization manner to enhance their significance in producing novel biomaterials with improved desired mechanical, thermal, and morphological characteristics. Different weight percentages of hybrid green reinforcement (poultry eggshells and DPLs) were utilized in various hybridization ratios (3:7, 5:5, 7:3), (15:5, 10:10, 5:15), and (20:10, 15:15, 10:20) to fabricate 10, 20, and 30 wt% novel biomaterials. The regularly chopped DPLs were immersed in various concentrations of sodium hydroxide at different soaking times to optimize and improve their bonding with the polypropylene (PP) matrix. The mechanical, thermal, and morphological properties of the fabricated hybrid composites were investigated. The results have revealed that certain hybridization ratios could improve the tensile and flexural modulus by up to 26 and 11%, respectively. According to the thermogravimetric analysis and its derivatives, hybridization was also found to have an excellent influence on the thermal stability of the PP matrix. Regarding morphological micrographs utilizing scanning electron microscopy, DPLs exhibited good bonding, whereas eggshell fillers depicted different behaviors of bonding depending on their surface topologies. It was also found that hybridization with higher eggshells had better effects on flexural strength than date palms, regardless of their weight percentages. The 30 wt% hybridization case was found to be capable of improving the modulus of elasticity of composites to 838 MPa and the flexural modulus to 735 MPa, which are suitable for various structural applications and green products.

Recycled steel fiber comes from the waste produced by machining. Adding recycled steel fiber into concrete can significantly enhance the toughness of concrete. In order to study the impact toughness of recycled steel fiber-reinforced concrete, the drop weight repeated impact experiment method was used to study the performance of recycled steel fiber-reinforced concrete under repeated impact load. Four kinds of recycled steel fiber-reinforced concrete samples with different volume contents were designed and made, and the loading impact experiments under five working conditions were carried out. Taking the drop weight and drop height as changing parameters, the corresponding blow counts of the first crack and sample failure under the impact of the drop hammer are recorded, and the ductility coefficients of different samples are calculated. The results show that the impact resistance of the sample decreases significantly with the increase of the drop weight and drop height. With the increase of recycled steel fiber content, the impact toughness of the sample increases obviously. The impact toughness of recycled steel fiber-reinforced concrete under standard loading conditions is the best.

Al–Zn–Mg–Cu–Zr aluminum alloys have shown promise as materials for drill pipes; however, their application temperature is limited to below 120°C. This study investigates the influence of incorporating the rare earth element Nd on the microstructure and mechanical properties of Al–Zn–Mg–Cu–Zr alloys. The microstructural evolution during casting, homogenization, hot deformation, and heat treatment processes is characterized using optical microscopy and scanning electron microscopy. The composition of the rare earth phase is determined through transmission electron microscopy (TEM). Furthermore, first-principles calculations are employed to determine the formation enthalpy, cohesive energy, shear modulus, bulk modulus, Young’s modulus, and Poisson’s ratio of bulk Al 8 Cu 4 Nd. The effect of Nd addition on the mechanical properties of the alloy is investigated through hardness and tensile testing. The results indicate that the addition of Nd significantly refines the grain and dendrite sizes of the alloy and effectively suppresses recrystallization behavior during hot extrusion and solution treatment. TEM observations reveal the presence of micrometer-sized blocky Al 8 Cu 4 Nd phases and nanometer-sized Al 3 Nd phases. The Al 3 Nd phases are located near dislocations, hindering dislocation movement and thus enhancing the alloy’s mechanical properties. First-principles calculations demonstrate that the bulk Al 8 Cu 4 Nd phase exhibits superior structural stability, deformation resistance, and brittle characteristics, which negatively impact the ductility of the alloy. The alloy with Nd addition can maintain a high hardness value for an extended period at high temperature, and the tensile strength of the alloy with 0.26 wt% Nd addition reaches 396.2 MPa at 120°C. These results indicate that the rare earth element Nd can improve the high-temperature mechanical properties of the alloy.

The aim of this study is to evaluate the effect of an office bleaching agent on the color of various single-shade resin composites. Three single-shade resin composites were tested in this study. Thirty disk-shaped specimens were prepared with a diameter of 10 mm and a height of 1 mm, and they were divided into three groups ( n = 10). After color measurements, 40% hydrogen peroxide containing bleaching agent gel was applied to all the specimens. Baseline and final color measurements were performed using a clinical spectrophotometer. Statistical analyses were performed. All bleached specimens had clinically incomprehensible color changes (Δ E < 3.3). Comparisons for single-shade composites revealed no statistically significant color difference between groups. With the limitation of this study in mind, color changes in single-shade resin-composites after office bleaching were found to be clinically acceptable. It may be appropriate to use single-shade composites that shorten the in-chair clinical time by facilitating shade selection.

For low-carbon sustainability, recycled rubber particles (RPs) and recycled aggregate (RA) could be used to make rubber-modified recycled aggregate concrete (RRAC). The characteristics (compressive strength and peak strain) of RRAC with various amounts of RA and RPs after heating at various temperatures were studied in this work. The results show that high temperatures significantly decreased the uniaxial compressive strength (UCS), whereas the addition of RA ( e.g. , 50%) and RPs ( e.g. , 5%) can mitigate the negative effect caused by high temperatures. The peak strain can also be improved by increasing the replacement ratios of RA and RP. Support vector regression (SVR) models were trained using a total of 120 groups of UCS and peak strain experimental datasets, and an SVR-based multi-objective optimization model was proposed. The excellent correlation coefficients (0.9772 for UCS and 0.9412 for peak strain) found to illustrate the remarkable accuracy of the SVR models. The Pareto fronts of a tri-objective mixture optimization design (UCS, strain, and cost) were successfully generated as the decision reference at varying temperature conditions. A sensitivity analysis was performed to rank the importance of the input variables where temperature was found as the most important one. In addition, the replacement ratio of RA is more important compared with that of the RP for both the UCS and strain datasets. Among the mechanical properties of concrete, compressive strength and peak strain are two key properties. This study provides guidance for the study of RRAC constitutive models under high temperatures.

Component ratio change is considered to be the main reason leading to the deterioration of asphalt properties, but there are few studies on the aging mechanism from the perspective of modifier molecules. To reveal the aging mechanism of styrene–butadiene–styrene block copolymer (SBS)/styrene butadiene rubber (SBR) compound-modified asphalt, the micro mechanism in the aging process was studied by combining molecular dynamics (MD) and Fourier transform infrared spectroscopy (FTIR). First, MD was used to establish the micro models of SBS/SBR compound-modified asphalt at different aging stages (non-aging, short-term aging, and long-term aging) and to verify its rationality. Second, the micro characteristics of the SBS/SBR compound-modified asphalt micro model, such as solubility parameters, diffusion coefficient, interface interaction energy, and radial distribution function, were analyzed by calculation. Finally, the FTIR results proved the rationality of the simulation and explained the aging mechanism of SBS/SBR compound-modified asphalt. The results show that the cohesiveness density and solubility parameters of SBS/SBR compound-modified asphalt increase, the diffusion coefficient decreases, and the molecular interface stability increases during the aging process. And, the carbonyl index, sulfoxide index, and aromatic ring index increased in different degrees after aging. The study explains the aging mechanism of SBS/SBR compound-modified asphalt from the perspective of modifier molecules and provides a theoretical basis for the research of asphalt anti-aging.

China possesses abundant pumice resources and thereby makes the utilization of pumice in the preparation of pumice aggregate concrete (PAC) a significant strategy for environmental protection and resource conservation. To obtain the effect of pumice pore structure variation on the compressive strength of PAC, PACs with strength classes LC20, LC30, and LC40 were prepared. Moreover, the pore structure of PAC was characterized using nuclear magnetic resonance to investigate the effect of pore structure variation on the compressive strength of PAC. Results showed that the higher the coarse aggregate content of PAC, the higher the percentage of large capillary and non-capillary pore sizes of PAC, corresponding to higher porosity and lower compressive strength. The hydration products in PAC continuously fill in the pore structure, the proportion of large capillary pores and non-capillary pore size gradually decreases, the proportion of small capillary pores and medium capillary pore size gradually increases, the pumice concrete matrix gradually becomes dense, and the compressive strength increases. The prediction model of the pore structure and compressive strength is established based on gray theory, and the relative error between predicted and tested values is not significant, which can effectively predict its compressive strength. It provides effective guidance for the engineering practical application of PAC.

The aim of this study is to investigate the effect of alkaline treatment and addition of microcrystalline cellulose (MCC) on the density, tensile strength, elastic modulus, impact strength, and Poisson’s ratio of unsaturated polyester resin composites reinforced by cantala fibers (UPR-CFs). The fibers were immersed in alkaline solution of 6% NaOH for 0, 3, 6, 9, and 12 h. The composite had cantala fibers (CFs) and MCC volume fraction ( v f ) of 30 and 5%, respectively. The results showed that the alkaline treatment for 6 h resulted in the highest density, tensile strength, and elastic modulus of the composites, while the highest Poisson’s ratio was achieved in UPR-untreated CF composites. The addition of MCC filler also increased the density, tensile strength, and elastic modulus of the composite significantly. Both alkaline treatment and MCC addition did not significantly affect the impact strength. With the increase in the strength and modulus of elasticity, composites can be applied more widely to structures that bear higher loads.

The environment is a very important topic today as well as in the future. One source of air pollution that has the potential to harm health is the wear particles released by vehicle braking systems. If these wear particles come from hazardous materials, they could destroy human health and the environment. Based on these conditions, exploring more environmentally friendly materials to substitute hazardous materials as friction materials is necessary. In this study, brake linings were prepared from bamboo fiber and eggshell (ES) particles with various pre-treatment conditions. The composition of the material frictions consisted of phenolic resin, bamboo fiber, bamboo particles, ES particles, zinc, alumina, and graphite in the following: 35% phenolic resin, 10% graphite, 10% bamboo fiber, 10% alumina powder, 5% zinc powder, and 30% bamboo particles and ESs. This study focused on observing the mechanical and tribological behavior of friction materials when using ES particles as fillers. There are three stages to manufacturing friction material: a cold press, a hot press, and heat treatment. The optimization of the characteristics of ESs as organic brake linings was carried out using the Taguchi method and analyzed using data envelopment analysis-based ranking (DEAR). An interesting finding from this study was that when ES particles were calcined at 900°C for 120 min, the ES particle size was 200 mesh, and the ES volume fraction at 25% resulted in the most optimal brake lining performance. Calcination at 900°C for 120 min completely changed the CaCO 3 phase to CaO. This study also shows that calcined ES particles have the potential to be developed as friction materials for environmentally friendly two-wheeled vehicles in the future. The produced brake linings exhibited hardness, a coefficient of friction, and specific wear rates of 92.82 HR, 0.32, and 4.43 × 10 −6  mm 3 ·N −1 ·m −1 , respectively.

Cold spray is considered as an emerging technique for preparing wear-resistant metal matrix composite coatings on the surface of various kinds of metallic materials. In this work, a viable strategy of “cold spraying + hot rolling post-treatment” was successfully applied to prepare wear-resistant B 4 C/6061 Al composite coating on commercially available 6061 Al plates. The results revealed that hot rolling post-treatment results in uniform distribution of B 4 C particles in the alloy matrix, good inter-splat bonding, and sufficient plasticity in the splats through effective healing of the defects and splat boundaries in the as-sprayed deposit. As a result, the coating/substrate bonding strength in the hot rolled sample increased two-fold when compared with that of the as-sprayed sample. Moreover, hot rolling process resulted in much improved tribological properties of the coating with the wear rate ∼40% of that of the substrate. The obtained results indicated that the idea of combining cold spraying and hot rolling treatment is quite effective for improving the tribological properties of Al alloy plates. Further, this approach seems equally good for repairing/remanufacturing of unserviceable 6061 Al alloy components. Graphical abstract

A series of Li + , Na + , or K + , Tm 3+ , and Yb 3+ co-doped Bi 2 WO 6 upconversion phosphors were prepared by a high-temperature solid-phase method at 800°C for 3 h. X-ray diffraction showed that Li + , Na + , K + , Tm 3+ , and Yb 3+ doping did not affect the orthorhombic structure of the Bi 2 WO 6 matrix. Scanning electron microscopy images of the Bi 2 WO 6 :1% Tm 3+ , 6% Yb 3+ and 1% Li + , 1% Na + , or 1% K + -doped Bi 2 WO 6 :1% Tm 3+ , 6% Yb 3+ samples reveal irregular particles with a 0.5–5 µm particle size range; upon Na + or K + doping, the particle size increases and the particle surface becomes smooth. EDS analysis shows that the above ions are well incorporated into the powder particles. At 298 K, the relative temperature sensitivities are 0.00144, 0.0016, 0.0024, and 0.0018 K −1 for the 1% Tm 3+ , 6% Yb 3+ :Bi 2 WO 6 samples without alkali metal ions and doped with 1% Li + , 1% Na + , or 1% K + based on the thermally coupled energy level 3 F 3 / 3 F 2 characterization temperature. However, under the same conditions, when using the nonthermally coupled level 3 F 3 / 1 G 4 characterization temperature, the relative temperature sensitivities of these four samples are 0.0378, 0.0166, 0.046, and 0.0257 K −1 , increasing by 26.3, 10.3, 19.1, and 13.9 times, respectively. The relative temperature sensitivities of the 1% Na + , 1% Tm 3+ , and 6% Yb 3+ :Bi 2 WO 6 samples are the highest at 298 K.

Engineered cementitious composites (ECC) exhibit behaviors of multiple cracking and strain-hardening compared to ordinary concrete. However, the use of ultrafine silica sand (S) to produce ECC results in increased cost and environmental overload. This study was to develop an eco-friendly and cheaper ECC by incorporating different replacement ratios of industrial byproduct molybdenum tailings (MT). The mechanical properties of ECC with MT were evaluated. Based on industrial computer technology, nuclear magnetic resonance, and scanning electron microscope techniques, the three-dimensional spatial distribution and fluid distribution of pores and the microstructure of the ECC were investigated, respectively. The mechanical properties of stirrup-confined ECC stub columns were also investigated. Results indicated that the ECC incorporating 25% MT exhibited the best mechanical properties, in which the tensile strength ( f t ) increased by 32.16% and exhibited well strain-hardening behaviors. Under a 25% MT replacement ratio, ECC had the lowest porosity and good interfacial transition zone, and bonding interface between polyvinyl alcohol (PVA) fiber (PF) and matrix. Moreover, the stirrup-confined ECC stub column with 25% MT can ensure better both the peak stress ( f cc ) and peak strain ( ε cc ). The assessment of environmental impact and cost further indicated that the incorporation of MT to prepare ECC is a promising method.

This study investigates the seismic performance of a composite structure comprising cold-formed steel and high-strength concrete. Four short shear walls composed of cold-formed steel and high-strength concrete, namely, one specimen without diagonal bracing, one with angle-steel bracing, and two with lattice bracing, were designed for testing their low cyclic loading. The cracking load, ultimate displacement, maximum horizontal bearing capacity, failure process, hysteretic curve, and skeleton curve of the four specimens were obtained during the test. The results showed that the use of cold-formed steel-concealed bracing in the high-strength concrete short shear wall can effectively change the failure mode of the wall into bending shear failure with good ductility. An analysis of the energy dissipation of the four specimens revealed that the energy dissipation capacity and ductility of high-strength concrete short shear wall with cold-formed steel concealed bracing were improved, indicating that the use of cold-formed steel concealed bracing greatly improved the total energy dissipation capacity of high-strength concrete short shear wall. The calculated shear bearing capacity in the diagonal section of the wall with concealed bracing was compared with the measured one. Considering specifications, a formula for calculating the shear capacity in the oblique section of short shear wall with concealed bracing was proposed.

In this study, the influence of two distinct reactive aggregate dosages on the alkali–silica reaction (ASR) of concrete was investigated. The expansion ratio, axial compressive strength, splitting tensile strength, and relative dynamic elastic modulus (RDEM) of concrete were considered as the main parameters to study the failure criteria of concrete induced by ASR at 40°C. Microscopic experiments, such as scanning electron microscopy and X-ray computed microtomography, were applied to analyze the damage induced by ASR on the concrete prisms and the propagation of internal cracks of the reactive aggregates in nanospace. The results showed that the two ranges can be used as the failure criteria produced by the ASR of concrete containing 3 and 6% dosages of reactive aggregates at 40°C, respectively, when the RDEM of concrete was reduced to 70‒75% and 85‒90%. Additionally, the results of CT indicated that microcracks tended to extend from the initial defects of aggregate to the cement slurry. Meanwhile, ASR gel packed with the pores, which reduced the porosity. It was noteworthy that the adhesive force between the ASR gel and the cement matrix after filling pores could not make up for the loss of the mechanical properties of concrete.

The main focus of this study is on the effects of fly ash, basalt powder, and tungsten carbide (WC) on the mechanical (tensile strength, flexural strength, impact strength, and Shore D hardness) and tribology behavior of sisal fiber-reinforced composites. Using epoxy resin, the fillers (5–10 wt% of each) were mixed with sisal fiber and resin (30 wt%). A tensile strength of 86.3–112.2 MPa was observed with the addition of fly ash, basalt powder, and WC fillers. The tensile strength of S2 composite (basalt powder + epoxy resin) was 33.63% higher than that of composite without fillers. The flexural strength of S5 composite (basalt powder + WC) was found to be 166.4 MPa, which is nearly 19.95% higher than the composite without filler. The fly ash with WC (S4) and basalt powder (S5) composite showed similar impact strength (5.34 J·m −2 ), which was nearly 62% greater than the composites without filler. The superior hardness was noticed in S5 composite compared to all other filler-added composites. The least wear rate was noticed in S3 (WC) composites irrespective of all the loading conditions. The hybridization of fillers also enhanced the mechanical properties of sisal fiber–reinforced composites. However, single filler–reinforced composite (WC) improved the wear resistance compare to hybrid filler–reinforced composites. The inclusion of filler increases the load-carrying capability and adhesion, as determined by scanning electron microscope. The river-like pattern confirms that S2-composite failure was dominated by ductile. The least wear debris and grooved surfaces were results higher wear resistance in the hybrid filler–reinforced composites.

To clarify the effect of Hindered amine light stabilizer (HALS) on ultraviolet (UV) aging behavior of asphalt binder, the evolution history and characteristics of the UV induced micro-structure of modified asphalt were characterized. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt during UV aging. By defining the micro-structure of asphalt in aging joints induced by UV, the identification and classification of typical micro-structure are proposed. On this basis, an evaluation method based on the morphology evolution process of modified asphalt aging was proposed to quantitatively analyze the effect of HALS on the UV aging of asphalt binder. The results show that the control effect of HALS on the UV aging behavior of asphalt can be verified by SEM and AFM detection methods. At the same time, the aging interval of the asphalt modified by hindered amine was divided by the method, and it was verified that the HALS could significantly prolong the service life of the asphalt binder. The micro-morphology of asphalt binder undergoes the process of crack generation and propagation during UV aging. The micro-morphological changes of UV aged asphalt were interfered effectively by HALS, which could alleviate and control the development of UV induced micro-cracks, and promote the fusion of micro-cracks. This study provides an effective evaluation method for detecting UV aging microscopic evolution of HALS.

Vanadium dioxide (VO 2 ) has attracted extensive attention due to the specific metal-insulator phase transition as well as the wide device applications. The practical performance of VO 2 -based device strongly depends on the quality of VO 2 , since the higher quality of VO 2 film always shows much more pronounced phase transition behavior. Thus, the preparation of high quality VO 2 film is essential and highly desirable. In this work, we have prepared high-quality VO 2 film on SiC substrate by water vapor oxidation with graphene (G) buffer layer, which showed excellent phase transformation properties. Compared with the VO 2 /SiC sample without G buffer layer, the VO 2 /G/SiC films show the resistance changes up to four-orders of magnitude across the phase transition boundary and superior optoelectronic properties, which indicates the significant role of G layer in the film growth process. The current study not only provides an economical and feasible method for VO 2 /G/SiC thin film preparation with high quality, but also supply some clues for the application of G-based VO 2 devices in the future.

Recycled aggregate concrete has been widely used in practical engineering construction, and the carbonation resistance of buildings within their allowable strength range is currently urgently needed to be considered. By constructing a time prediction model for the carbonation depth of recycled concrete, the time when the complete carbonation zone reaches the depth of the steel bar inside the concrete can be determined, and then the carbonation life of the building can be determined. However, the current carbonation model for recycled aggregates (RAs) has theoretical and practical limitations. The existing semi-empirical model has not quantitatively considered the influence of particle sizes of RAs on the carbonation depth, but only qualitatively analyzed the effect of particle size on the carbonation depth. In practical applications, the existing models usually only determine the structural life under one-dimensional carbonation conditions in laboratory conditions, ignoring the fact that two-dimensional carbonation mainly occurs in actual engineering. In order to overcome these limitations, a semi-empirical model for predicting the carbonation depth of recycled concrete is proposed for life prediction of structural carbonation. Based on the replacement rate of RAs, external environmental influences, and the stress state of components, the particle size of RAs is considered in the carbonation depth prediction model, and model parameters are fitted by performing carbonation experiments on specimens with different mix ratios. The model is then validated by applying a large amount of existing experimental data to the fitted model, and the results show that the model has good applicability for the constructed components. Furthermore, the model is used to predict the carbonation life of the main components in actual engineering and considers two-dimensional carbonation. It was found that when the replacement rate of RAs was 40%, the predicted life of the main components after carbonation in actual engineering was close to the design life.

Poly(amic acid) (PAA), a precursor of polyimide (PI), is synthesized by reacting dianhydride 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride with diamine 3,3′-dihydroxybenzidine in N,N ′-dimethylacetamide. Organoclays with different alkyl chain lengths were dispersed in PAA, and the weight percentages (wt%) of the organoclays varied. The PI hybrid films were prepared over multiple steps under heat treatment conditions. Bentonite (BTN) was used as the pristine clay, and octylamine (C8) and hexadecylamine (C16) were used to chemically modify the surface of BTN to obtain the desired organoclay samples. Organoclays C8-BTN and C16-BTN were dispersed in a PI matrix, and the organoclay content varied in the range of 1–9 wt%. The thermal, morphological, and optical properties of the PI hybrid films were investigated based on the organoclay content. Although the thermal stability of the PI hybrid film improved when a small amount of organoclay was added, it decreased when the nano-filler content exceeded a certain critical content. Specifically, in the hybrid containing C8-BTN, the critical content is 5 wt%, while in the hybrid with C16-BTN, the critical content is 7 wt%. In addition, the morphology of the clay dispersed in the matrix at the critical content showed the best dispersed phase. The physical properties (thermal characteristics, dispersibility, and optical transparency) of the PI hybrid film containing C16-BTN were better than those of the hybrid film containing C8-BTN. However, the thermal expansion of the C8-BTN hybrid was lower than that of the C16-BTN film at the same content.

Porous asphalt concrete (PAC) have a typical big void-skeleton structure, and porous asphalt mixtures with large voids are more prone to freeze–thaw damage. As a result, research on the influence of freeze–thaw cycles on the micro-structure and mechanical characteristics of porous asphalt mixes offers a theoretical framework for overcoming water stability concerns in porous asphalt mixtures in practice, as well as for further popularization and application. In this study, styrene–butadiene–styrene (SBS)-modified asphalt and high viscosity modified asphalt were constructed on the basis of the original asphalt, and the mix proportions of asphalt mixes PAC-13, AC-13, and SMA-13 were designed. To begin, molecular dynamics simulations were used to look into the effects of freeze–thaw cycles on asphalt–aggregate interface adhesion and mixture micro-mechanical properties. Second, the effects of freeze–thaw cycles on the void characteristics of porous asphalt mixtures were explored utilizing digital image processing technologies. Finally, the freeze–thaw split test was utilized to evaluate the macroscopic mechanical properties of a porous asphalt mixture after freezing and thawing cycles. According to the study findings, high viscosity modified asphalt made with 4% SBS/8% TPS has the greatest performance. The application of SBS/TPS-modified asphalt can considerably improve the damage resistance of porous asphalt mixes. The micro-structure and mechanical qualities of porous asphalt mixtures are damaged by freeze–thaw cycles, and the damage gets worse as the number of cycles rises. The study’s conclusions provide a theoretical justification for the application of porous asphalt pavement.

In the present study, a new type of slightly curved arc HRB400 steel bars (SCAHSs) was proposed to solve the problem of temperature-induced stress loss in mass concrete structures without cutting off steel bars. The flexural performance of SCAHSs and straight HRB400 steel bars reinforced one-way concrete slabs were first experimentally investigated. Then, the effects of the shape and dimension of SCAHSs on the distribution and width of concrete cracks were analyzed and discussed. Subsequently, the synergistic tensile work characteristics between SCAHSs and concrete were presented. Finally, equations for the bearing capacity and allowable crack widths for SCAHSs in hydraulic massive structures were proposed. The test results indicated that after replacing the straight steel bars in the concrete slab with SCAHSs, the crack width of the concrete slabs increased, with the maximum crack width at the bottom of the concrete slabs increasing by a factor of 1.2–1.4. As the rise-span ratio of SCAHSs increased, the flexural stiffness of SCAHSs reinforced concrete slab decreased slightly, but the deflection increased. The allowable crack widths of SCAHSs reinforced concrete slabs under environment categories I, II, and III were 0.20, 0.17, and 0.12 mm, respectively.

This study examined the fresh and hardened characteristics of alkali-activated binders (AABs) based on ternary mixtures of red mud (RM), class F fly ash (FA), and ground granulated blast-furnace slag (GGBFS). The binders were prepared by dry mixing of 50% RM, 25–50% FA, and 0–25% GGBFS. The alkali activators were prepared from sodium hydroxide solution with different concentrations (6–14 mol) and sodium silicate solution. Curing at room temperature was adopted for the preparation of all samples. The flowability, setting time, and compressive and flexural strength tests were used to examine the properties of the resulting binders. To study the microstructural characterization, the scanning electron microscope, X-ray diffraction, and Fourier transformation infrared techniques were used. The results show that the flowability of the AAB decreases with higher GGBFS content, the addition of GGBFS reduces the setting time, and the incorporation of GGBFS increases the flexural and compressive strengths of the AAB. Microstructural and chemical analysis results indicate that in addition to geopolymer gel, calcium silicate hydrate (C–S–H) is formed upon adding GGBFS, producing a denser microstructure.

Graphitic carbon nitride (g-C 3 N 4 ) has attracted extensive research interest in pollutants remediation. However, the photocatalytic activity of g-C 3 N 4 was significantly limited by its small specific surface area. In this work, a green, high-energy ball milling method was used to fabricate g-C 3 N 4 nanosheets. The structure, morphology, and optical properties of the prepared g-C 3 N 4 nanosheets were characterized. The effect of ball milling parameters on the photocatalytic performance evaluated by Rhodamine B (RhB) and tetracycline (TC) was investigated systemically. Among the tested samples, the g-C 3 N 4 sample milled with a 4 mL isopropanol solution at a rotation speed of 420 rpm, ball-to-powder weight ratio of 10:1, and milling time of 24 h exhibited the highest RhB degradation efficiency of 91.4% and TC degradation efficiency of 70.2%. The enhanced photocatalytic activity after ball milling was ascribed to the increase in specific surface area and efficient separation of electron–hole pairs. The trapping experiment indicated that holes and superoxide radicals were the main active species in the degradation reaction. Moreover, the photocatalytic degradation mechanism of organic pollutants on g-C 3 N 4 nanosheets was also discussed in detail.

Based on the conventional triaxial compression test of marble, the microscopic parameters corresponding to the macroscopic mechanical properties of marble were obtained by PFC2D, and on this basis, discrete element method models were established to conduct numerical tests of triaxial compression of marble under different confining pressures and loading rates to study the effect of loading rates on the rock specimens. Under the same confining pressure, brittle damage occurs in marble when the loading rate is low, and the damage type transforms from brittle to ductile as the loading rate increases. The peak strength, cracking stress, damage stress, cohesion, and internal friction angle of marble appear to increase with the increase in the loading rate under the same confining pressure. The characteristic stresses and strength parameters are linearly related to the loading rate. The influence of the loading rate on the peak strength is the most significant. With the increase in the confining pressure, the fitting coefficient of the linear relationship between initiation stress and loading rate decreases from 18.9 to 15.4 for different confining pressures, indicating that the growth rate of initiation stress decreases with the increase in the confining pressure when the loading rate is increased, and the increase in confining pressure suppresses the growth rate of initiation stress with loading rate.

The utilization of corn husk as a renewable bio-cellulose material for producing bio-composite membranes through wet chemical and sol–gel process offers numerous advantages. It is an abundant, inexpensive, nontoxic, and readily available agricultural waste product. To enhance the properties of bio-composite membranes, various particulate ionic fillers such as titanium dioxide, calcium oxide, and eggshell (as a source of calcium carbonate) are incorporated in different weight percentages (0, 1, and 5%). These fillers act as additives to the corn husk nanofiber mixed with polyvinyl alcohol during the formation of the biomembrane. The resulting biocomposite membranes exhibit several desirable characteristics. They are lightweight, easy to shape, biodegradable, nontoxic, and possess excellent physical, mechanical, thermal, and electrical properties. Moreover, the addition of 5 wt% of eggshell powder leads to an increase in the dielectric constant and electrical conductivity, reaching approximately 3.300 ± 0.508 and 1.986 × 10 3 (Ω·m) −1 , respectively. These measurements were taken at a frequency of 500 Hz and a temperature of 27°C. Furthermore, these membranes demonstrate self-cleaning abilities due to a contact angle greater than 90°. The electrical properties of the biocomposite membrane improve with a higher percentage of inorganic filler, making them suitable for applications in smart membranes, as well as mechanical, electrical, and thermal systems. Graphical abstract

Modified multimodal (MMP) Cr 3 C 2 –NiCr coatings were fabricated by high-velocity oxy-fuel (HVOF) spraying deposited on a CuCrZr alloy substrate. However, due to the lack of its inevitable porosity, an additional laser re-melting (LRM) approach is highly required to improve the coating performance. Therefore, the LRM technique is employed in this study to improve the microstructure properties of an MMP Cr 3 C 2 –NiCr coating by HVOF. Solid-state phase transformation from Cr 3 C 2 to Cr 7 C 3 occurred during the LRM process. After the LRM process, the coating exhibits the presence of Cr 3 C 2 nanoparticles that serve as reinforcement. These nanoparticles demonstrate minimal lattice misfit and exhibit high stability throughout the LRM process. The surface of the coating undergoes modification, resulting in the formation of homogeneous nano (20–130 nm), micron (150 nm to 0.3 μm), and submicron (2–3 μm) Cr 3 C 2 structures, along with high-density microstructures, after the LRM process. Nano-Cr 3 C 2 particle reinforced with high total work function and incredibly increased corrosion rate significantly improves coating corrosion resistance. Overall, porosity decreased from 3.9% of the HVOF coating to 0.3% of the LRM. As a result, the current density of anticorrosion decreased from 33.7 to 4.35 µA·cm −2 , and the Vickers microhardness average values ranged from 1,050 to 1,300 HV 0.3 , indicating improved microstructure development and related properties. Graphical abstract

Rock masses in underground engineering are usually damaged, which are caused by rock genesis and environmental stress. Studying the constitutive relationship between rock strength and deformation under loading is crucial for the design and evaluation of such scenarios. The new damage constitutive model considering the dynamic change of joint damage was developed to describe the behavior of rocks under loading in this work. First, considering the influence of jointed rock mass structural features in their entirety, the Drucker–Prager criterion and the Hoek–Brown criterion were combined. Second, based on the idea of macro–micro coupling, the calculation formulae of damage variables were derived. Finally, the damage constitutive model of the jointed rock mass was established, and the proposed model was fitted and compared with the test data. Results show that the variation rules for damage value and peak strength are opposite, and the stress–strain is highly sensitive to changes in the parameter s of the model. Moreover, the proposed model can accurately describe the effect of joint deterioration on the entire process of rock mass compression failure, which shows that the damage constitutive models are useful for evaluating the strength characteristics of jointed rock mass in engineering practice.

In the proposed study, TiC is used in different sizes ( i.e. , 70–150 nm and 200–250 μm) and different ratios ( e.g. , 0, 10, 20, and 30 wt%) to reinforce the epoxy matrix. Micro- or nano-epoxy–TiC mixtures are poured into molds that have been prepared. The results obtained show a significant improvement in hardness, impact, creep, and tensile strength when the hard particles of nano- and micro-TiC are increased up to 20 wt%. This is due to the good dispersion of the TiC powder with minimal agglomeration and air bubbles. In addition, the results obtained show a decrease in hardness, impact, creep, and tensile strength when the ratio of the hard particles of nano- and micro-TiC is increased to 30 wt% due to agglomeration and air bubbles, which create a path for cracks to propagate. The results of the hardness, impact, creep, and tensile strength tests when 20 wt% nano-TiC composite specimens are used are 22.4, 67.55 J·m −2 , 0.0132, and 34.7 MPa, respectively. These results show higher values than other composite specimens. A pin-on-disc wear testing process with various sliding lengths is used to analyze wear behavior. The maximum wear resistance of the 10 wt% of micro-epoxy–TiC composites is found at a load of 5 N and a 100 m sliding distance. Optical microscopy shows small scratches on the 10 wt% micro-epoxy–TiC composite specimens in comparison with the 10 wt% nano-epoxy–TiC composites at a load of 5 N and a 200 m sliding distance.

As a new type of environmentally friendly building material, cemented sand and gravel (CSG) has advantages distinct from those of concrete. Compressive strength is an important mechanical property of CSG. However, his method of testing is mainly by doing experiments. For this reason, a deep learning algorithm, long short-term memory (LSTM) model, was proposed to predict the compressive strength of CSG by using four input variables, namely cement content, sand rate, water-binder ratio, and fly ash content, with a total of 114 sample data. Three metrics – coefficient ( R 2 ), root mean square error (RMSE), and mean absolute error (MAE) – were used to evaluate the model’s performance, and the predicted results were compared with the traditional machine learning algorithm, namely the random forest (RF) model. Finally, SHapley Additive exPlanations can be combined to explain the contribution degree of each input feature in the machine learning inquiry model to the prediction results. The results show that the prediction accuracy and reliability of LSTM are higher. The LSTM model has R 2 = 0.9940, RMSE = 0.1248, and MAE = 0.0960, while the RF model has R 2 = 0.9147, RMSE = 0.4809, and MAE = 0.4397. The LSTM model can accurately predict CSG compressive strength. Cement and sand rate contribute more to the predicted results than other input characteristics.

The utilization of recycled concrete can effectively solve the problems of large accumulations of construction waste and the constant consumption of natural aggregates. Slurry-wrapping modification and concrete-filled steel tubes (CFSTs) are effective approaches to enhance the utilization ratio of recycled concrete. The study involved 4 ordinary CFST columns and 16 slurry-wrapping recycled aggregate concrete-filled steel tube (SRACFST) columns. The variable parameters included the slurry-wrapping recycled aggregate replacement ratio and the section form. The result shows that the ultimate strength of the specimens reached the minimum and maximum at 25 and 100% aggregate replacement ratio. The favorable strength performance of the SRACFST columns is attributed to the dominant positive effect of the slurry-wrapping treatment in reducing matrix porosity over the negative impact of the recycled aggregate’s complex interface transition zone. Due to the hoop factor, the residual bearing ratio peaks at a 25% substitution ratio. Four design standards were used to predict the ultimate strength, with GB50936 and EC4 yielding more accurate estimations, while AISC360-10 and AIJ provided conservative estimations. This study presents the equations of the stress–strain curve for the whole axial compression process, which can be directly applied in the theoretical and numerical analysis of RACFST columns.

The space-time evolution characteristics of fractures in coal seams under external loads are of great significance for the exploration and development of coalbed methane and the safe mining of coal. In this study, the in situ industrial μCT scanning experiments of gas-bearing coal under triaxial compression conditions was carried out using a loaded coal rock industrial μCT scanning system. The computed tomography (CT) scan images of different deformation stages were obtained. The temporal characteristics and spatial evolution patterns of fractures during gas-bearing coal rupture were investigated by combining image retrieval techniques and fractal theory. The results show that (1) as the axial load increases, the maximum similarity of the CT images showed a gradually decreasing trend. (2) Under the triaxial compression conditions, the number of two-dimensional cracks in a coal-containing gas at different spatial positions exhibited a changing pattern in which it slowly decreased before rapidly increasing. (3) The patterns of change in the three-dimensional fracture rate, fracture density, and fractal dimension were quite similar, showing four stages of slow decline, slow growth, sharp growth, and slow growth again. In contrast, the Euler number exhibited the exact opposite pattern of change. (4) The coal sample space showed prominent zonal failure characteristics. The bottom of the coal sample space position (Area C) near the loading indenter had the most developed cracks and serious damage, the middle of the coal sample space position (Area B) was the second, and the upper of the coal sample space position (Area A) near the fixed indenter had slow fracture development and minimal damage.

Herein, a single-camera stereo digital image correlation (DIC) method is developed for dynamic deformation measurement, and a dual-biprism high-speed stereo camera system is proposed to capture surface images. Then, full-field displacement and strain distributions are obtained after correlation and differential calculation using the stereo-DIC algorithm. After a typical experiment is performed to verify the accuracy of the proposed system, full-field displacement and strain distributions of sandwich panels subjected to low-velocity impacts are determined. These results show that the proposed system is an efficient and convenient tool for dynamic deformation measurement.

The mechanical properties of large 2219 Al–Cu alloy rings need to be further improved with the diameter of the launch vehicle being more than 10 m. In this study, the effects of cold rolling (CR) and cold compression on microstructure evolution and the comprehensive mechanical properties of such rings were compared. The evolution of dislocation characteristics, grain structure, second phase, and the mechanical properties of the T8-aged samples were examined. Results show that compared with CR, because of deformation characteristics, cold compression deformation induces less increase in dislocation densities; however, the increase in dislocation densities on the core was higher than at other positions, resulting in a more uniform grain structure and elongation in the axial and radial direction. The cold compression deformation contributes to the uniform dissolution of the secondary phase, resulting in denser precipitates, and thus improved strength. Brittle fractures occur in fewer CR samples because of the longer moving distance of the Al matrix. In summary, both CR and cold compression can improve the mechanical properties. However, the cold-compressed sample exhibits more uniform microstructure and higher comprehensive mechanical properties (the radial elongation increased from 7.1 to 11.2%; the in-plane anisotropy decreased from 36.6 to 8.9%), without any brittle fractures, because of more uniform metal flow.

Grouting material is the core force transfer medium of grouting sealing and anchorage reinforcement methods for cracks in earthen sites; the performance of grouting slurry is the key to affecting the reinforcement effect. To solve the problems of poor flexural strength, easy shrinkage and cracking of existing grouting slurry, using Glutinous Rice Pulp, Calcined Ginger Nuts, and Loess Soil as substrates, and choosing the content and length of basalt fiber (BF) as control variables, 13 groups of specimens were designed by orthogonal test method to explore the influence of mixed fiber on the mobility, shrinkage, compressive, and flexural strength. The microstructure was analyzed by SEM to explain the strengthening mechanism from physical and chemical perspectives. The results show that the mobility decreases linearly with the increase in BF content and length; after mixing BF, the shrinkage rate is significantly reduced, but when the fiber length and content are relatively high, the surface is prone to cracking. The excellent bridging ability of BF can effectively improve the compressive and flexural strength of the specimen. When the fiber length and content are high, the specimen shows certain ductile failure characteristics, and the fracture energy increases more than 10 times.

High population density in major cities has led to compact designs of residential multi-story buildings. Consequently, it is a natural choice of the architects to suggest the location of high-voltage wires close to the ducts with contaminated air. This observation results in the motivation for this study, i.e. , the understanding of the complicated interaction of the Lorentz force (due to the current-carrying wire) with the micropolar flow in the vertical direction in the duct, with polluted air (containing dust particles) being modeled as a micropolar fluid, which is driven by some external pressure gradient. Therefore, this study focuses on an incompressible and electrically conducting micropolar fluid flow through a rectangular vertical duct, in the presence of a current-carrying wire placed outside the flow regime. The governing equations, after being translated into a dimensionless form, are solved numerically using a finite volume approach. The velocity, microrotation, and temperature fields thus obtained are examined. It has been noted that the strong magnetic force caused by the wire may distort the flow symmetry and slows down the flow. Furthermore, in the absence of wire, particles spinning in clockwise and counter-clockwise directions occupy the same amount of space in the duct, thus incorporating a sort of equilibrium in the duct. However, the imposed variable magnetic field adds to the spinning of particles in one part of the duct, while simultaneously suppressing it in the other region.

Shot peening (SP) process is a typical surface strengthening process for metal and metal matrix composites, which can significantly improve the fatigue life and strength. The traditional SP simulation model falls short as it only takes into account one or a few shots, proving insufficient for accurately simulating the entire impact process involving hundreds of shots. In this study, a random multiple shots simulation modeling methodology with hundreds of random shots is proposed to simulate the impact process of SP. In order to reduce the simulation error, the random function Rand of MATLAB is used to generate the shot distributions many times, and the shot distribution closest to the average number is selected and the three-dimension parametric explicit dynamics numerical simulation model is built using ABAQUS software. Orthogonal experiments are carried out to investigate the influences of shot diameter, incident impact velocity, and angle on the residual stress distribution, roughness, and specimen deformation. Results showed that the average relative errors of maximum residual compressive stress, roughness, and deformation of specimen between simulation model and experimental value are 30.99, 16.14, and 16.73%, respectively. The primary factors affecting residual stress and deformation is shot diameter, and the main factor affecting roughness is impact velocity.

Asphalt is a vital construction material for roads, and its properties can be enhanced by modification. In this study, a composite modified asphalt was developed using pyrolytic carbon black (PCB) and chicken feather fiber (CFF). Box–Behnken design of response surface methodology was employed to optimize the preparation parameters, and the optimal parameters were determined to be a PCB dosage of 15% (weight ratio), a CFF dosage of 0.3% (weight ratio), and a chicken feather (CF) shear time of 8.2 min. A Dynamic Shear Rheometer (MCR302) was used to analyze the high-temperature rheological properties of the modified asphalt samples, and the results showed that the addition of PCB and CFF enhanced the high temperature performance and anti-aging performance of the asphalt. The rheological properties at high temperature increased progressively with the increase in CFF dosage. The Bending Beam Rheometer (BBR) test was conducted to evaluate the low-temperature rheological property of PCB/CFF composite modified asphalt, which was observed to decrease with the increase in CFF dosage. The microscopic properties and the chemical group of 15% PCB + 0.3% CFF with 8.2 min CF shear time composite modified asphalt (0.3%PC-MA) were analyzed using Fourier Transform Infrared spectrometer and Fluorescence Microscopy, and the results indicated that PCB and CFF were physically blended with asphalt without undergoing a chemical reaction, and they were well compatible with and evenly distributed in asphalt. Finally, the high- and low-temperature performances, as well as water stability, of the base asphalt (BA), 15% PCB dosage modified asphalt (P-MA), and 15% PCB dosage modified asphalt with x % CFF dosage with a shear time of 8.2 min (PC-MA) were compared. The addition of CFF significantly enhanced the high-temperature and low-temperature performances, as well as water stability of P-MA mixtures. The aim of this study is to provide a laboratory test basis for the application of PCB/CFF composite modified asphalt.

The synthesis of an efficient adsorbent to remove chromium ions from water is challenging. Therefore, in this study, a new nanomagnet composite (Fe 3 O 4 /biochar/ZIF-8) was synthesized by a one-pot hydrothermal method using a metal–organic framework (MOF, ZIF-8) as a sacrificial template, citrus peels as a source of biochar, and iron oxide nanoparticles for magnetization. The synthesized nanocomposite showed a high efficiency toward the adsorption of Cr( vi ) ions. The adsorption study showed that the experimental data were well-described using the Langmuir isotherm model and pseudo-second-order model. According to the Langmuir model, the adsorption capacities toward Cr( vi ) adsorption were 77 and 125 mg·g −1 for Fe 3 O 4 /biochar and Fe 3 O 4 /biochar/ZIF-8, respectively, indicating the role of MOF in improving the adsorption performance. The Fe 3 O 4 /biochar/ZIF-8 showed an excellent adsorption performance in the presence of coexisting ions at a wide pH range using different eluents to study reusability up to five successive cycles. We can conclude from this study that this nanoadsorbent is a promising material for removing pollutants from environmental water samples. Graphical abstract

As this unmanned aerial vehicle (UAV) has a planned airframe that can carry a 25 kg payload, understanding its structural capabilities, such as its compressive and tensile strengths under different situations, is essential. For the purpose of comprehending the fluid–structure interaction (FSI) of the fuselage, this study designs and analyses the lightweight materials used in the airframe of a complex Gyrodyne UAV. A computer model of a composite airframe for a Gyrodyne UAV is built to examine its durability. An essential factor in the aircraft business is minimizing unnecessary weight, and this FSI study emphasizes the importance of sandwiches and their hybrid combinations in this regard. After the material finalization, around 140 material combinations are tested using an advanced computational composite platform, in which four different lightweight material families are implemented. The fluid load (pressure) is imported into ANSYS workbench 17.2, and the structural airframe is then solved according to the boundary conditions of the application domain. Also, experimental experiments using the high-speed jet facility are run to verify computational improvements. Materials for the airframe of the Gyrodyne UAV have been narrowed down to a final list of contenders. As the work focuses on the FSI analysis, not much computational fluid dynamics (CFD) results were discussed here. Only the imported pressure from the CFD analysis was imposed on to the Gyrodyne UAV to proceed for the FSI analysis.

To investigate the effects of wet–heat–salt coupling environment (WHSCE) and the content of polyvinyl alcohol (PVA) fibers on the durability of cementitious composites (CC), a series of durability tests were carried out. In this study, the salt concentration in the WHSCE was set to 5%, the temperature at 50°C, and the relative humidity at 100%. Six different contents of PVA fibers were set up in the test for exploring their effects on the durability (impermeability, chloride ion penetration resistance, freeze–thaw resistance, and chloride salt erosion resistance under dry and wet cycle conditions) of CC. The results showed that durability of CC under the WHSCE was enhanced regardless of the content of PVA fibers added. At the PVA fiber amount of 1.2%, the impermeability pressure, electric flux, mass loss rate, compressive strength loss rate, and compressive strength corrosion resistance coefficient under the WHSCE reached the optimal values. This indicated that the durability of CC was most favorable when the amount of PVA fibers was 1.2% since many engineering structures are subject to erosion by various factors in the ocean, which can inevitably affect the service life of the purchase. In this study, the effect of PVA fiber content on the durability of CC in complex environment is studied, which provides experimental data and analytical ideas for improving engineering located in the ocean, hoping to provide a theoretical basis for their subsequent application in practical engineering.

The novel structure of a basalt fiber reinforced polymer (BFRP)-confined ceramsite concrete column (BFCCC) reinforced with bamboo strips (BSs) was investigated. The characteristics of light weight, BSs and FRP reinforcement were reflected in the structure. Thirty-six BFCCCs and 18 unconfined ceramsite concrete columns were fabricated and subjected to axial compression tests, and the stress–strain curves were obtained. The research parameters included the number of BFRP layers and the volume content of BSs. Both types of specimens, with and without BFRP confinement, underwent brittle failure after reaching the ultimate bearing capacity. The increase in the number of BFRP layers had a positive effect on the bearing capacity and deformation capacity of the specimens. With the increase in the number of BFRP layers, the compressive strengths of BFCCCs were improved by 1.17–1.44 times, and the deformations were improved by 6.30–12.92 times, compared to the unconfined concrete. The addition of BSs could improve the ductility of the specimen, while the effect on the bearing capacity had an optimal value of 2.0%. The stress–strain curves of the BFCCCs showed obvious softening behavior after the peak point. Models were proposed to predict the axial stress–strain curves of BFCCCs reinforced with BSs.

As rubber is a hyperelastic material, its nonlinear deformation behavior during aging is significantly influenced by various factors, including the material characteristics, demonstrating a significant uncertainty. Most of the existing uncertain prediction methods of rubber nonlinear property degradation are based on the probability density function, which requires a large number of samples to obtain the probability distribution and requires a lot of work. Therefore, the interval model is used in this study to characterize the uncertainty. However, the traditional interval constitutive models ignore the correlation between interval variables, and the prediction results have large errors. In order to minimize prediction errors and improve prediction accuracy, an interval Mooney–Rivlin (M–R) correlation model that considers the correlation between parameters was established. To address the influence of uncertainties, an interval Arrhenius model was constructed. The M–R model requires multiple fittings of stress–strain curves to obtain the model parameters, and the prediction process is relatively complex. Therefore, combing the two proposed models, the relationship equations of rubber tensile stress with aging temperature and aging time were first established by interval Arrhenius, and then the interval M–R model was used to obtain the variation ranges of parameters C 10 {C}_{10} and C 01 {C}_{01} . By contrasting this with the measured rubber aging information, the effectiveness of the proposed model was confirmed. Compared with the prediction model based on the average value, the maximum error of prediction of this model is reduced by about 60%. Compared with the traditional interval model, the prediction region is significantly reduced, which further improves the prediction accuracy. The above results indicate that this interval aging lifetime prediction model is suitable for characterizing the nonlinear stress–strain behavior of rubber-like elastomers.

As a representative flexible piezoelectric polymer, polyvinylidene fluoride (PVDF) and its copolymers have been widely used in energy harvesters and piezoelectric sensors. In this work, hybrid nanocomposite films were prepared by adding a small amount of carbon black (CB) and Ni nanoparticles to the poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) matrix using the solution casting method, followed by stretching and poling to increase the electroactive β-phase content. The results show that the hybrid fillers consisting of 0.3 wt% CB and 0.1 wt% Ni nanoparticles exhibit the best piezoelectric performance. The maximum output voltage of the PVDF-HFP/CB/Ni films reaches 3.5 V under 1 mm micro-vibration, which is 75% higher than that of pure PVDF-HFP films. Characterization results by X-ray diffraction analysis, Fourier-transform infrared spectrometry, and differential scanning calorimeter analysis show that the hybrid fillers are more effective in promoting the phase transformation from the α-phase to the β-phase in the matrix due to synergistic effect.

Due to recycled aggregate concrete technology, sustainable resource utilization can be achieved, but the weak frost resistance of this type of concrete affects its application in cold regions. Using waste polypropylene fibers as reinforcing materials can improve the mechanical properties and durability of concrete. This study explores the influence of waste polypropylene fiber on the frost resistance durability and microstructure of recycled brick aggregate (RA) concrete. The results show that with the increase in freeze–thaw cycles, the mass of the concrete first increases and then decreases, while its relative dynamic elastic modulus and compressive strength gradually decrease. After 60 freeze–thaw cycles, the maximum mass loss, maximum relative dynamic elastic modulus loss, and maximum compressive strength loss of the RA concrete are 1.73, 45.1, and 73.7%, respectively. Waste fiber (WF) can improve the frost resistance of concrete, as demonstrated by the obvious reduction in mass loss, relative dynamic elasticity modulus loss, and compressive strength loss, which are 0.11, 33.0, and 64.0%, respectively, after 60 freeze–thaw cycles. The action mechanism of WF on the frost resistance of RA concrete is revealed, and the life prediction model of RA concrete with WF under freeze–thaw conditions is established.

This article deals with volatile organic substances (VOCs) and odours that can be released into the indoor environment from synthetic leathers that are part of upholstered furniture. The primary task of this study was to provide a detailed analysis of selected synthetic leathers and assess their emission characteristics, including odour substances. VOC emissions were determined using the test chamber method (ČSN EN ISO 16000-9) at a temperature of 23°C and a relative humidity of 50%. The emitted compounds were adsorbed by standard stainless steel tubes with Tenax TA sorbent. VOCs were analysed by thermal desorption and gas chromatography with mass spectrometry The properties of odours were tested using a Sniffer 9000 device, which was directly connected to a gas chromatograph with a flame ionization detector. The dominant substances (with the highest concentration) that were emitted by samples of tested synthetic leathers include toluene (118.2 µg·m −3 ), 1,2-propanediol (46.2 µg·m −3 ), and limonene (153.0 µg·m −3 ). Ohio synthetic leather produced the most unpleasantness hedonic tone (-4) from all evaluated materials.

In this study, the properties of seawater volcanic scoria aggregate concrete (SVAC)-filled circular stainless steel (SFCST) and glass fibre-reinforced plastic (GFRP) tubes (SFCGT) were investigated. Ten groups were considered and 30 specimens were prepared, including four different parameters: the concrete type (SVAC and ordinary concrete [OC]), outer tube type (GFRP and stainless steel tubes), concrete strength (C30 and C40), and tube thickness (0, 3, and 4 mm). The typical influences of the SVAC and outer tube on the mechanical properties of specimens were then analysed. The research findings show that the strength and ductility of the SFCGT and SFCST are significantly higher than those of plain SVAC. The peak strain and strength enhancement factor of the SFCGT and SFCST increase with an increase in the tube thickness, and the concrete strength has a detrimental impact on the toughness of the specimen. Unlike in the confined OC specimens, a sudden decrease is observed in the stress–strain curves of the SFCGT and SFCST owing to the changes in the deformability of the SVAC. Generally, the strengths of the SFCGT and SFCST specimens are 10.3% lower and 4.1% higher than those of the confined OC specimens, respectively. Finally, analytical models of the strength and stress–strain curves considering the influences of the SVAC and passive confinement were established, and numerical simulations were performed to provide a basis for the practical application of the SFCGT and SFCST.

This study introduces a three-dimensional numerical analysis of the mixing yield stress fluid inside stirred vessels. The Bingham–Papanastasiou model predicts the yield stress behavior of the working fluid. The implications of a new anchor impeller design are investigated; it involves certain modifications to a typical anchor impeller’s blade. Different curved shapes replace the straight blade of a classical anchor. The flow pattern and energy consumed inside the stirred system for various geometrical configurations, Reynolds numbers (0.1, 1, 10, and 100), and Bingham numbers (1, 10, 100, and 500) have been investigated. According to the findings, introducing this new geometrical configuration gives a significant acceleration of flow pattern and extension of the well-mixed zone, as well as decreased power consumption ( Np {\rm{Np}} ). Three configurations were introduced to the mixing system: Case 1 is a standard anchor impeller, and Cases 2 and 3 are curved anchor impellers with two shapes different. Case 3 (helical design of blade) has been found to be the less power consumption case by five times, i.e. , for Case 1 and Case 2, Np = 5 {\rm{Np}}=5 , whereas for Case 3, Np = 1 {\rm{Np}}=1 . Based on the results, it is evident that the configuration (Case 3) demonstrates a superior geometric design in enhancing mixing characteristics compared to the other configurations.

We propose a tunable all-dielectric zero-index metamaterial based on phase change material. By constructing the alternating rod structure with phase change material and silica material, the zero-refractive index characteristic is realized. In order to verify the equivalent zero-index characteristic, we calculated the electromagnetic field distribution at center frequency. Based on phase invariance, it was found that this kind of metamaterial can achieve equivalent zero refractive index characteristics. To further achieve the polarization-insensitive zero refractive index, we propose a metamaterial structure based on the fishing nets structure. Based on the S-parameter inversion algorithm, the equivalent dielectric constant, equivalent permeability, equivalent impedance, and equivalent refractive index of the metamaterial were extracted. Based on the extracted equivalent parameters and the corresponding electromagnetic field distribution, the designed all-dielectric metamaterial has the tunable equivalent zero refractive index characteristic.

The usage of biodegradable materials is gaining mounting applications owing to the environmental problems created by petroleum-based synthetic materials. Agro-waste materials are finding more scope as reinforcement materials in polymer composites, mainly because of their cost-effectiveness and availability. The main aim of this research work is to utilize agro-waste material in the form of mango seed waste (MSW) as a reinforcing material with polyvinyl alcohol (PVA) to form biocomposite. The biocomposites were fabricated using the solution casting technique. The research work focuses on the influence of varying ultrasonication periods (0–20 min at 5-min intervals, i.e. , 0, 5, 10, 15, and 20 min) on the properties of PVA/MSW biocomposites. The fabricated biocomposites were subjected to tensile test, fracture morphology, moisture absorption (MA), Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results revealed that the material with the highest tensile strength was 3.95 MPa obtained with the 20-min ultrasonication sample. This value is 49% higher than that obtained in the sample without ultrasonication. The scanning electron microscopy analysis shows that the 20-min ultrasonication sample indicated a good distribution of MSW fillers in the PVA contrasted with the rest of the samples. The thermal stability of the samples treated with ultrasonication was found to be significantly higher than that of the untreated samples, whereas the MA value decreased with increasing ultrasonication time. It can be observed from the results that biocomposites can be a potential alternative to the synthetic materials used in packaging applications.

The bed structure of high-grade large-scale CNC machine tools is crucial for maintaining their long-term service accuracy. This study focused on the key casting process of large nodular cast iron beds. AnyCasting software was employed to simulate and analyze the casting scheme, and then the mold filling and solidification processes were proposed based on the simulation results. The proposed casting scheme indicates that the designed gating system exhibited excellent filling capability. The dual sprue ceramic pipe bottom pouring technique, in conjunction with the chills, not only improved casting efficiency but also met the requirements of sequential solidification design. The castings possessed a dense microstructure characterized by uniform and stable phase composition, primarily comprising lamellar pearlite, with ≤0.5% of phosphorus eutectic and cementite. Furthermore, the microstructure of these materials displayed favorable graphite morphology with a spheroidization rate exceeding 85% and spheroidization grade of 2–3. This study has important academic and application value for the casting process of producing low-stress, high-grade CNC machine tool bed cast iron materials.

With the rapid development, microelectronic technology has put forward strict requirements for electronic packaging materials (EPMs). SiCp/Al composites with high volume fraction of SiC has become an ideal candidate for EPMs due to their superior properties including high thermal conductivity, tailorable coefficient of thermal expansion as well as low density in many fields. This study reviewed the manufacturing process of SiCp/Al composites in recent years. In addition, the interface between particle and matrix, the application, and the development trend of SiCp/Al composites has also been summarized.

The electrohydrodynamic atomization (EHDA) process is a method of forming liquid droplets or jets in a solution under an electric field. Molecular dynamics simulations were used in this study to reveal the EHDA dripping mode at a microscopic level. In this study, we investigated whether a liquid contains ions under the influence of a 1 V·nm −1 electric field that affects the dipole direction of water molecules to explore the cause of the dripping mode. It was hypothesized that the presence of ions would disrupt the local electric field distribution, causing liquid rupture. Furthermore, we observed the jetting behavior under varying ion concentrations and identified jetting instability. To solve this problem, the pre-load voltage method was used to control the distribution of ions in the solution, thus effectively increasing the ion concentration at the nanotube opening. In this study, we also investigated the movement behavior of ions in solution under different pre-load voltages, leading to a stable dripping mode under different ion concentrations. This study offers microscale mechanism research perspectives for EHDA and can be used in future studies for parameter setting and optimization.

Metal-based additive manufacturing has gained significant attention in the field of medical implants over the past decade. The application of 3D-printing technology in medical implants offers several advantages over traditional manufacturing methods, including increased design flexibility for implant customization, reduced lead time for emergency cases, and the ability to create complex geometry shapes for patient-specific implants. In this review study, the working principles and conditions of metal 3D-printing technologies such as selective laser sintering, selective laser melting, and electron beam melting, as well as their applications and advantages in the medical field, are investigated in detail. The application scenarios and research status of non-degradable metals including titanium alloy, medical stainless steel, etc., and degradable metals like magnesium alloy are introduced as printing materials. We discuss the improvement of mechanical properties and biocompatibility of implants through surface modification, porous structure design, and the optimization of molding processes. Finally, the biocompatibility issues and challenges caused by the accuracy of CT imaging, fabrication, implant placement, and other aspects are summarized.