Band 59, Heft 1

4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) was reacted with three structurally different diamines to produce poly(amic acid)s, which were then imidized to produce colorless and transparent polyimide (CPI) films through stepwise thermal cyclization. The three amines used to synthesize CPI based on BPADA are: bis(3-aminophenyl)sulfone (APS), p- xylyenediamine ( p -XDA), and bis[4-(3-aminophenoxy)-phenyl] sulfone ( m -BAPS). The obtained CPI films were almost colorless and exhibited excellent optical transparencies. The solubility of the CPI films in various solvents was investigated, and all the CPI films were found to be soluble in common solvents such as chloroform, dichloromethane, N,N’ -dimethyl acetamide, and pyridine. The thermo-optical properties and oxygen transmission rates (O 2 TRs) of the CPI films were examined for various biaxial stretching ratios in the range of 100–150%, and their properties were compared. When the stretching ratio changed from 100 to 150%, the glass transition temperature and yellow index did not show any significant change; however, the O 2 TR decreased for all CPI films.

Nano-crystalline (nc) Cu with Cr 2 O 3 dispersoid (~4 vol.%) was successfully made by reactive-milling at 210 K with a mixture of pure Cu, Cu 2 O, and Cr powder. The vacuum hot pressing (HP) was performed at 1123 K and 50 MPa for 2h to consolidate the milled powder for further analysis. TEM (Transmission Electron Microscopy) work revealed that the HPed materials were comprised with a mixture of the nc-Cu and a homogeneous distribution of Cr 2 O 3 dispersoids. The microstructure and Vickers hardness of the as-milled powder and the HPed materials were characterized by standard metallographic techniques. The grain size of the Cu was measured using Scherrer’s formula (XRD) and TEM observation; the Cr 2 O 3 dispersoid size was estimated from the HADDF (High Angle Annular Dark Field) images and element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. The formation kinetics and coarsening of the Cr 2 O 3 dispersoids in Cu matrix were discussed based on the calculations with thermodynamic parameters in comparison with those of Al 2 O 3 .

This study concerns the weldability of dissimilar Ultra high-strength steel (UHSS) and advanced high-strength steel (AHSS), which is used in the modern machine industry. The materials offered superior strength as well as relatively low weight, which reduces microstructure contamination during a live cycle. The choice of the welding process base of the base material (BM) and welding parameters is essential to improve the weld joint quality. S700MC/S960QC was welded using a gas metal arc welding (GMAW) process and overmatched filler wire, which was performed using three heat input (7, 10, and 15 kJ/cm). The weld samples were characterized by a Vickers-hardness test, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The test reveals a decrease of softening areas in the HAZ and the formation of the stable formation of Bainite-Ferrite for S700MC and Bainite-martensite for S960QC when the heat input of 10 kJ/cm is used. It is recommended to use the GMAW process and Laser welding (Laser beam-MIG), with an optimal welding parameter, which will be achieved a high quality of manufacturing products.

A series of CuO/CeO 2 catalysts were successfully synthesized via solution combustion method (SCS) using different fuels and tested for CO oxidation. The catalysts were characterized by energy-dispersive X-ray analysis (EDXA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), N 2 adsorption-desorption isotherms and H 2 temperature-programmed reduction (H 2 -TPR). It was found that the used fuels strongly affected the characterization and the low-temperature reduction behavior of CuO/CeO 2 catalysts. The CuO/CeO 2 -urea catalyst exhibited higher catalytic activity toward CO oxidation ( t 50 =120∘C, t 100 =159∘C) than the 5 other synthesized catalysts. In addition, the CuO/CeO 2 -urea catalyst displayed high stability for CO oxidation during five cycles and water resistance. The enhanced catalytic CO oxidation of the synthesized samples can be attributed by a combination of factors, such as smaller crystallite size, higher specific surface area, larger amount of amorphous copper(II) oxide, more mesoporous and uniform spherical-like structure. These findings are worth considering in order to continue the study of the CuO/CeO 2 catalyst with low-temperature CO oxidation.

Quantitative microstructural evolution and the corresponding microhardness of electrodeposited nanostructured nickel sheet during cold rolling deformation are investigated by x-ray diffraction, transmission electron microscopy and Vicker’s microhardness testing. Particularly, to investigate the effect of stress states on deformation behavior, two series of gradient nanostructured nickel with symmetric structures and the homogeneous counterparts with three levels of grain size are compared based on macro-statistical data. In such hierarchical sandwich-like gradient samples, the layers with larger grain size, as the soft phase, indeed sustain more deformation. Deformation-induced grain rotation changes are observed in the center layers with a relatively larger grain size, accompanied by an obvious decrease in microhardness. According to the quantitative microstructural parameters including the grain size, dislocation density and stacking fault probability before and after deformation, evaluation based on Hall-Petch and Bailey-Hirsch relationships indicates the transition from strain hardening to softening can be attributed to grain orientation change.

In this paper, a three-layered cement-based wave-absorbing board is designed and prepared by mixing wave-absorbing fillers such as nano-Si 3 N 4 , multi-layer nano graphene platelets (NGPs), nano-Ni, carbon fiber (CF) and carbon black (CB) into cement slurry. The effect of the amount of wave-absorbing fillers on the mechanical properties, resistivity and wave-absorbing reflectivity of cement slurry is studies. The microstructure of NGPs, nano-Si 3 N 4 and the wave-absorbing board are characterized by TEM and SEM. Research shows that low content of NGPs and other wave-absorbing fillers can significantly reduce the resistivity of cement slurry and improve its mechanical strength, and dense massive crystals are precipitated in the cement hydration products. The reflectivity test reveals that in the frequency range of 2~18 GHz, the minimum reflectivity of the three-layered cement-based wave absorbing board reaches −18.8 dB, and the maximum bandwidth less than −10 dB reaches 15.3 GHz. This study can serve as reference for the preparation of new three-layered cement-based wave absorbing boards.

The use of liquid hydrocarbons, such as FCC naphtha, having olefin components makes an adverse impact on our environment. To deal with the problem, one could convert those lethal components, including olefin and paraffin structures, into aromatic compounds under aromatization processes. To this aim, generally zeolite catalysts, especially the ZSM-5 sample, are utilized to facilitate the aromatization processes. According to the general knowledge in this field, such parameters as the metal promoter and the amount of acidity of catalyst affect the performance of zeolite catalysts. In this paper, with the aim of getting acquainted with the conditions to form the desirable products under the best performance of the zeolites, numerous published papers were reviewed.

We have grown Cu 2 O films by different routes including self-oxidation and metal-organic deposition (MOD). The reduction efficiency of Cu 2 O films on graphene oxide (GO) synthesized by modified Hummer’s method has been studied. Surface morphology and chemical state of as-prepared Cu 2 O film and GO sheets reduced at different conditions have also been investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). Results show that self-oxidation Cu 2 O film is more effective on phtocatalytic reduction of GO than MOD-Cu 2 O film. Moreover, reduction effect of self-oxidation Cu 2 O film to GO is comparable to that of environmental-friendly reducing agent of vitamin C. The present results offer a potentially eco-friendly and low-cost approach for the manufacture of reduced graphene oxide (RGO) by photocatalytic reduction.

The microstructure and texture in pure nickel were investigated during multi-step cross cold rolling (CCR) and subsequent annealing. It was found that the deformation texture in the CCR nickel was dominated by Brass and rotated Brass about normal direction (ND) (Bs ND ) texture components, along with marginal cube textures. The resulted deformation textures had a significant effect on the recrystallization behavior. Annealing of the CCR nickel at 550°C for 1 h led to the formation of dominant <012> // ND fiber accompanied by minor rotated cube textures, rather than strong cube texture. Increasing the annealing temperature up to 800°C resulted in further enhancement of <012> // ND fiber textures. The possible reasons for recrystallization behavior in annealed CCR sample were discussed based on in-situ annealing experiments from two aspects of oriented nucleation and oriented growth theories.

In this article, we analyzed the effect of variable thermal conductivity on reflected elastic waves. The waves are propagating through a thermoelastic medium rotating with some angular frequency. The concept of micro-temperature is also been considered, in which microelements of the medium contain a high temperature. A heat conduction phenomenon is encountered by dual phase-lag heat conduction model. P (or SV)-type wave is incident on the medium with some specific angle of incidence. After reflection from the surface incident, P-wave is converted into quasi longitudinal and quasi transverse waves and propagates back into the medium. Helmholtz’s potential function along with the harmonic wave solution is used to obtain the solution of the model. Analytically, we calculated the amplitude ratios and attenuation factor for each reflected wave against the angle of incidence. The obtained results are also represented graphically for different values of rotational frequency and variable thermal conductivity for a particular material.

The application of flexible polymer nanocomposites for food packaging to inactivate microorganisms associated with foods is the demand of the present-day food industry to assure quality throughout the packaging operation. The utilization of polyvinyl alcohol (PVA) assisted zinc oxide nanocomposite for food stuff packaging has been very attractive in the recent past. Nanostructured ZnO was synthesized at optimized pH (10.5) from different ratios of zinc acetate and Moringa oleifeira leaf extract (1:7, 1:3, 1:1 and 3:1). ZnO coated polyvinyl alcohol (ZnO/PVA) nanocomposites were prepared from 5, 9, 13 and 16% by wt of ZnO and PVA using solution casting method. The thermal stability of ZnO synthesized with 1:1 ratio at pH 10.5 was investigated with TGA/DTA. The analytical techniques such as X-ray diffraction (XRD), ultra-violate visible analysis (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) were used for the characterization of the synthesized ZnO and ZnO/PVA nanocomposites (NCs). The antibacterial activity of the synthesized ZnO and ZnO/PVA NCs were evaluated against gram negative E. coli and gram positive S. aureus bacteria. The electrochemical stability of ZnO/PVA NCs was also investigated by cyclic voltammetric (CV) method. The thermogram of ZnO indicated that the oxide was found to be stable even beyond 500°C. The SEM analysis revealed rod shaped morphology for synthesized ZnO from 1:1 ratio at pH 10.5. But the nanocomposite prepared with 5% of ZnO of (1:1) at the same pH exhibited uniformly dispersed rod-shaped particle on the surface as well as in matrix of polyvinyl alcohol film. According to XRD result, ZnO synthesized with more percentage of plant extract resulted in the small size crystallites while that with low percentage of plant extract resulted in the larger crystallite size. The antibacterial inhibition efficiency of ZnO/PVA NCs was better and found to increase with increase in the amount of ZnO.

An increase in the service life of electrical products from copper and its alloys is directly related to an increase in the wear resistance of materials. Structural refinement and alloying with cadmium are known to have a positive effect on the strength characteristics and wear resistance of copper, which makes it possible, with a Cd content of 1% by weight, to increase the wear resistance of copper several times, but cadmium is considered an environmentally unsafe element. In this regard, the paper presents the results of studies of a widely used Cu-Cr-Zr alloy system in the ultrafine-grained (UFG) state, micro-alloyed with cadmium (0.2%, weight), in order to improve physical, mechanical, and operational properties, as well as environmental safety. Severe plastic deformation, providing structure refinement to ~150 nm, and microalloying with cadmium of a Cu-Cr-Zr system alloy, after a complete processing cycle, provides a tensile strength of 570±10 MPa and 67% electrical conductivity. At the same time, the abrasion resistance increases by 12 and 35% relative to the industrial systems Cu-Cd and Cu-Cr-Zr, respectively. The obtained characteristics are very promising for improving the operational properties of continuous welding tips, collector plates, and contact wires operating under conditions of intense wear.

In general, the main compositions of porcelain and bone china composed of 54-65%wt silica (SiO 2 ), 23-34% wt alumina (Al 2 O 3 ) and 0.2-0.7%wt calcium oxide (CaO) suitable for preparation high quality ceramic products such as soft-hard porcelain products for teeth and bones, bioceramics, IC substrate and magneto-optoelectroceramics. The quality of ceramic hand mold is depended on raw material and its properties (pH, ionic strength, solid-liquid surface tension, particle size distribution, specific surface area, porosity, density, microstructure, weight ratio between solid and water, drying time, and firing temperatures). The suitable firing conditions for porcelain and bone china hand-mold preparation were firing at 1270°C for 10 h which resulted in superior working molds for making latex films from natural and synthetic rubber. The obtained fired porcelain hand molds at 1270°C for 10 h provided good chemical durability (10%NaOH, 5%HCl and 10%wtNaCl), low thermal expansion coefficient (5.8570 × 10 −6 (°C −1 )), good compressive (179.40 MPa) and good flexural strength (86 MPa). While thermal expansion coefficient, compressive and flexural strength of obtained fired bone china hand molds are equal to 6.9230 × 10 −6 (°C −1 ), 128.40 and 73.70 MPa, respectively, good acid-base-salt resistance, a smooth mold surface, and easy hand mold fabrication. Both obtained porcelain and bone china hand molds are a low production cost, making them suitable for natural and synthetic rubber latex glove formation.

The present review paper focuses on the current state of the art of the alumina-silicate ceramics and surface modifications of ceramics dedicated as fillers in composites with carbon fiber. The use of aluminum-silicates in the form of a cenosphere due to their outstanding properties, i.e. , low density, high hardness, and total chemical inertness seem to be promising in biomaterial engineering applications. First of all, the possibilities of the composites application in orthopedic and prosthetic implantology. The following section discusses problems with the use of aluminum silicate ceramics and their processing. Subsequently, in the paragraphs to follow, the possibilities of modifying the surface with chemical methods are discussed, among others oxidation, chemical methods like ionic liquids etching, silanization, and physical processes i.e. , thermal treatment. In the summary, the directions of development of ceramic-carbon fiber composites and the primary deficiencies of these composites on which to focus on and solve are discussed.

Perovskite solar cells (PSCs) are one of the most promising photovoltaic technologies undergoing rapid developments. PSC efficiency has reached 25.2% in only seven years, which is close to the record efficiency of silicon solar cells. In addition, the use of PSCs in tandem solar cells either in the 4-terminal or monolithic configuration, can lead to a significant increase conversion efficiency. However, the stability and the scalability are the main issues that still hinder the commercialization of the perovskite technology. The present review focusses on the recent development in perovskite solar cells materials, cell architectures and fabrication methods and their effect on the conversion efficiency and stability of the devices. In addition, solutions proposed to overcome the main challenges and to make tandem solar cells are discussed.

Aim of the present manuscript is to provide an overview of all possible methods and light source typologies used by the different research groups for obtaining the energetic nano-materials’ photo-ignition, showing the latest progress related to such phenomenon employing, also, alternative radiation sources to the common Xe lamp. In fact, the employment of a different source typology can open new usage prospects respect to those enabled by the Xe lamp, mainly due to its technological limitations. Therefore, several studies are faced to test light sources, such as lasers and LEDs, for igniting the nano-energetic materials (as CNTs mixed with metallic catalyzers, Al / CuO nano-particles, etc); these nano-materials are usefully employed for starting, in volumetric and controlled way, the combustion of air-fuel mixtures inside internal combustion engines, leading to significant benefits to the combustion process also in terms of efficiency, reliability, and emissions of pollutants. Several research works are presented in literature concerning the ignition of liquid / gaseous fuels, without nano-particles, employing laser sources (i.e laser-based plugs in place of the common spark plugs); therefore, an innovative solution is proposed that employs multi-point laser-plugs for inducing the ignition of nano-materials dispersed into the air-fuel mixture inside the cylinder, so further improving the combustion of the fuel in an internal combustion engine.

This paper provides a critical review on the current status of graphene-reinforced metal matrix composites (GRMMCs) in an effort to guide future work on this topic. Metal matrix composites are preferred over other types of composites for their ability to meet engineering and structural demands. Graphene is considered an ideal reinforcement material for composites due to its unique structure and extraordinary physical, thermal, and electrical properties. Incorporating graphene as a reinforcement in metals is a way of harnessing its extraordinary properties, resulting in an enhanced metallic behavior for a wide variety of applications. Combining graphene with bulk metal matrices is a recent endeavor that has proven to have merit. A systematic study is needed to critically examine the efforts applied in this field, the successes achieved, and the challenges faced. This review highlights the three main pillars of GRMMCs: synthesis, structure, and properties. First, it discusses the synthesis techniques utilized for the fabrication of GRMMCs. Then, it highlights the resulting microstructures of the composites, including graphene dispersion and interfacial interactions. Finally, it summarizes the enhancements in the mechanical, electrical, thermal, and tribological properties of GRMMCs, while highlighting the effects of graphene type and content on those enhancements.

Aluminum-silicate cenospheres are the most valuable residue present in fly ashes after combusting stone coal. Cenospheres are hollow bodies with desirable engineering properties, such as hardness, low bulk density and complete chemical inertness, thanks to which they can be used in biomedical engineering. The following review presents data on obtaining and processing the material, as well as potential biomedical applications.

Graphene is a new, advanced material with many possible applications in basic and clinical medicine, electronics and automation. Graphene compounds can be successfully used as an integral part of drug delivery systems, in the construction of transistors, polar processors, touch screens, solar cells and in the production of materials for the manufacture of personal protective equipment, i.e. products and equipment intended to protect the health and life of users. The literature review presented in this paper concerns physical and mechanical properties of composites containing graphene or its structure as well as methods of obtaining polymer, metallic and ceramic composites doped with graphene structures. Data analysis of the potential use of graphene and its composites in personal protective equipment such as monitoring sensors, clothing and security equipment such as ballistic armor, helmets and protective clothing were also reviewed and summarized.

The crystal structures of various types of perovskite halide compounds were summarized and described. Atomic arrangements of these perovskite compounds can be investigated by X-ray diffraction and transmission electron microscopy. Based on the structural models of basic perovskite halides, X-ray and electron diffractions were calculated and discussed to compare with the experimental data. Other halides such as elemental substituted or cation ordered double perovskite compounds were also described. In addition to the ordinary 3-dimensional perovskites, low dimensional perovskites with 2-, 1-, or 0-dimensionalities were summarized. The structural stabilities of the perovskite halides could be investigated computing the tolerance and octahedral factors, which can be useful for the guideline of elemental substitution to improve the structures and properties, and several low toxic halides were proposed. For the device conformation, highly crystalline-orientated grains and dendritic structures can be formed and affected the photo-voltaic properties. The actual crystal structures of perovskite halides in the thin film configuration were studied by Rietveld analysis optimizing the atomic coordinates and occupancies with low residual factors. These results are useful for structure analysis of perovskite halide crystals, which are expected to be next-generation solar cell materials.

The biomedical materials that have been used in the structure of heart pumps are classified as biocompatible, and these can be metals, polymers, ceramics, and composites. Their positions in the pump vary according to the part’s function. Whereas various materials have different properties, all biomaterials chosen for cardiovascular applications should have excellent blood biocompatibility to reduce the likelihood of hemolysis and thrombosis. There are two major categories of the heart pumps; pulsatile and rotary blood pumps (axial and centrifugal) and the features of some of these materials allow them to be used in both. Rotary and pulsatile blood pump devices have to be fabricated from materials that do not result in adverse biological responses. The purpose of this review is to study the available biocompatible materials for the pulsatile and rotary blood pumps as clinically-approved materials and prototype heart pump materials. The current state of bio-compatible materials of rotary and pulsatile blood pump construction is presented. Some recent applications of surface amendment technology on the materials for heart assist devices were also reviewed for better understanding. The limitations of heart assist devices, and the future direction of artificial heart elements have been considered. This review will be considered as a comprehensive reference to rapidly understanding the necessary research in the field of biocompatible materials of pulsatile and blood rotary pumps.

Ni-based alloy coatings prepared by laser cladding has high bonding strength, excellent wear resistance and corrosion resistance. The mechanical properties of coatings can be further improved by changing the composition of alloy powders. This paper reviewed the improved microstructure and mechanical properties of Ni-based composite coatings by hard particles, single element and rare earth elements. The problems that need to be solved for the particle-reinforced nickel-based alloy coatings are pointed out. The prospects of the research are also discussed.

Grain refinement is the most universal and effective method of strengthening metallic materials, which is known as the “Hall-Petch” relationship. However, when grain size is refined to sub-micro regime (Ultrafine Grain, UFG) or even nano regime (Nano Grain, NG), the plasticity of metallic materials becomes poor. Massive studies indicate that the low strain hardening ability resulted from the enhanced dynamic recovery and lack of dislocation accumulation in fine grains is the main reason for low ductility in UFG/NG metals. To resolve this “strength-ductility” conflict, different strategies have been taken, like bimodal/multimodal structure, nanotwins, gradient structure and intragranular nano dispersoids. Among them, the introduction of nano dispersoids into the fine grains attracted lots of attention due to its wide applicability and great success in simultaneously increasing the strength and ductility of the UFG/NG metal. In addition to the enhanced mechanical performance, the introduced second-phase particle may also bring some extraordinary functional properties into the metallic material. In this paper, a brief view of the strategies to improve ductility of the UFG/NG metals and the relevant toughening mechanisms are revealed. Special attentions are paid to the utilization of intragranular nano dispersoids in Aluminum alloys.

Thermoelectric materials have long been proven to be effective in converting heat energy into electricity and vice versa. Since semiconductors have been used in the thermoelectric field, much work has been done to improve their efficiency. The interrelation between their thermoelectric physical parameters (Seebeck coefficient, electrical conductivity, and thermal conductivity) required special tailoring in order to get the maximum improvement in their performance. Various approaches have been reported in the research for developing thermoelectric performance, including doping and alloying, nanostructuring, and nanocompositing. Among different types of thermoelectric materials, layered chalcogenide materials are unique materials with distinctive properties. They have low self-thermal conductivity, and their layered structure allows them to be modified easily to improve their thermoelectric performance. In this review, basic knowledge of thermoelectric concepts and challenges for enhancing the figure of merit is provided. It discusses briefly different groups of layered chalcogenide thermoelectric materials with their structure and thermoelectric properties. It also reports different approaches in the literature for improving their performance and the recent progress done in this field. It highlights graphene as a promising nano additive to layered chalcogenide materials’ matrix and shows its effect on enhancing their figure of merit.

In the last years, electrospinning has become a technique of intense research to design and fabricate drug delivery systems (DDS), during this time a vast variety of DDS with mainly electrospun polymers and many different active ingredient(s) have been developed, many intrinsic and extrinsic factor have influence in the final system, there are those that can be attributed to the equipment set up and that to the physical-chemical properties of the used materials in the fabrication of DDS. After all, this intense research has generated a great amount of DDS loaded with one or more drugs. In this manuscript a review with the highlights of different kind of systems for drug delivery systems is presented, it includes the basic concepts of electrospinning, types of equipment set up, polymer/drug systems, limitations and challenges that need to be overcome for clinical applications.

Recent outbreak of the COVID-19 pandemic has changed the world dramatically, posing profound challenges to our healthcare infrastructure, economic systems, social and cultural life but also to our freedom. What this pandemic made us realize so far, is that, despite the tremendous advances in medicine and pharmacy, in the initial moments, which are crucial in the containment of spreading of any pandemic, the key role is played by the non-pharmaceutical measures. These measures are the ones that bridge the time between pandemic outbreaks and the development of drugs or vaccines and are crucial for the number of human lives spared. Smart textiles and novel materials as part of the personal protective equipment (PPE) and telemedicine are crucial factors in the healthcare system. Here, we present an overview on the use of textiles in the fight against pandemics, in the past and current COVID-19, we analyze the morphology of the commonly used face masks, made of cotton and typically used polypropylene (PP). We also present the perspective that smart textiles, wearable technologies and novel materials are offering in the fight against future pandemics, mainly as part of the personal protective equipment and telemedicine.

For engineering applications, hardness must be complimented with high toughness for applications where high contact loads are there. A good combination of hardness, toughness and low coefficient of friction can be achieved, by suitable tailoring of microstructures of coating in hard nanocomposite coatings. Tribologocal applications require hard coatings with tailored functionalities for different applications; hard nanocomposite coatings are potential materials for such applications. Ti and amorphous carbon based systems have shown more promising material. The present review discusses the nanocomposite hard coatings, mechanism of enhancement of toughness, multilayer hard nanocomposite coatings. Here, mainly Ti and Si based nanocomposite has been discussed as carbon based reviews are available in plenty in literature and well documented. Ti-B-N, Ti-Si-B-C, Ti-Si-B-C-N, Si-C-N, Ti-Al-N, Ti-Al-Si-N, Al-Si-N, Ti-Cr-Al-N, Zr-Si-N and some other similar system nanocomposite hard coatings are important where the gradual and intelligent additions of different elements in hard single component phase provides the combination of hardness, toughness and low coefficient of friction. Some of these systems are discussed. In the end, the future directions of research, Technology„ which are required to achieve tough nanocomposite hard coatings for actual applications are also highlighted.

Iron phosphates have rich chemical structures with various morphologies and sizes. Since they are environment friendly with good biocompatibility, they have good performances in the fields of catalysis and battery electrode material rising in recent years, as well as in the traditional fields like agriculture and steel. They also have important applications in adsorption, separation and concentration due to their unique structural characteristics. In this paper, iron phosphates are classified based on their common characteristics such as structure, morphology and size, and their application in the past two decades is reviewed, with emphasis on their application in adsorption, separation and concentration of different species. Further, their application in adsorption, separation and concentration of heavy metals is prospected.

High-voltage direct current (HVDC) transmission is known as green-energy transfer technology and has recently become an attractive alternative of high-voltage alternating current (HVAC) due to its high-power transmission capability and lower power loss. Use of composite insulators on direct current (DC) transmission lines experienced rapid growth in recent years due to their high hydrophobicity and better performance in contaminated environment than conventional ceramic insulators. During their service operation on DC lines, insulators are prone to more accumulation of contaminants due to unidirectional electric field. The contaminants under wet conditions allow leakage current to flow on the insulator surface. Being organic in nature, polymeric insulators have a tendency to age under the combined effects of electrical and environmental stresses. To fully understand the long-term aging performance of DC composite insulators, a detailed survey was considered necessary. Towards that end, this paper critically summarizes worldwide experience of aging performance of composite insulators in the field as well as in laboratory conditions.

Perovskites BaTiO 3 , La 0.1 Ba 0.9 TiO 3 and BaFeO 3 were prepared by different methods and utilized as photo-catalytic material for the degradation of the AO7 dye, with visible light. The toxicity of the treated solutions and the toxicity of perovskite powders that remained in suspension after centrifuged was assessed. Different catalytic properties were found by changing synthesis methods, annealing conditions, temperature of assay, initial concentration of pollutant and amount of perovskite in suspension. BaTiO 3 was prepared by ceramic or complex polymerization methods. This perovskite presents cubic structure, and the preparation method do not seem to have any influence on the unit cell parameter. On the other hand, annealing temperature has a marked influence on the time needed to attain good crystallinity. In the case of BaFeO 3 prepared by the ceramic method, for low annealing temperature there is the formation of tetragonal phase, which changes to hexagonal with the increase in annealing temperature, being a Ba 2 Fe 2 O 5 monoclinic phase involved in this phase transition. Regarding AO7 photocatalytic degradation, the best results, with almost complete colour removal, were obtained with BaFeO 3 (97%), prepared by ceramic method, and with BaTiO 3 (78%), prepared by polymer complex method. Toxicity assays towards Daphnia magna were performed with AO7 25 ppm aqueous solution samples, collected in the centrifuged suspensions of the photocatalytic assays, performed with different perovskites, and samples collected in centrifuged suspensions of perovskite powders. In general, there is no increase in toxicity when compared to the toxicity of an AO7 25 ppm aqueous solution. Only in the photodegradation assay with BaFeO 3 a clear increase in toxicity was observed, indicating that toxic by-products are being formed.

Disadvantages in the use of polylactic acid (PLA) as a base material for Tissue Engineering applications include the low osteoconductivity of this biomaterial, its acidic degradation and the deficient cellular adhesion on its surface. In order to counteract these drawbacks, calcium carbonate (CaCO 3 ) and β -tricalcium phosphate (Ca 3 (PO4) 2 , β -TCP) were proposed in this work as additives of PLA-based support structures. Composite scaffolds (PLA:CaCO 3 : β -TCP 95:2.5:2.5) manufactured by fused deposition modeling (FDM) were tested under enzymatic degradation using proteinase K enzymes to assess the modification of their properties in comparison with neat PLA scaffolds. The samples were characterized before and after the degradation test by optical microscopy, scanning electron microscopy, compression testing and thermogravimetric and calorimetric analysis. According to the results, the combination of the PLA matrix with the proposed additives increases the degradation rate of the 3D printed scaffolds, which is an advantage for the application of the composite scaffold in the field of Tissue Engineering. The higher degradation rate of the composite scaffolds could be explained by the release of the additive particles and the statistically higher microporosity of these samples compared to the neat PLA ones.

In the present work, we study the rotations of the polarization of light propagating in right and left-handed films and layered structures. Through the use of complex values representing the rotations we analyze the transmission (Faraday effect) and reflections (Kerr effect) of light. It is shown that the real and imaginary parts of the complex angle of Faraday and Kerr rotations are odd and even functions for the refractive index n , respectively. In the thin film case with left-handed materials there are large resonant enhancements of the reflected Kerr angle that could be obtained experimentally. In the magnetic clock approach, used in the tunneling time problem, two characteristic time components are related to the real and imaginary portions of the complex Faraday rotation angle . The complex angle at the different propagation regimes through a finite stack of alternating right and left-handed materials is analyzed in detail. We found that, in spite of the fact that Re(θ) in the forbidden gap is almost zero, the Im(θ) changes drastically in both value and sign.

The research is devoted to the problem of designing materials with an adjustable property of permeability. The obtained tool for property regulation allows achieving hyper-selectivity in relation to separation of helium isotope mixtures, as well as some other gas mixtures. The reasearch is theoretical in nature; however, it suggests a clear direction of activity for experimenters. The result obtained is valid for ultrathin barriers of any form. As a result, a new exact solution of the Schrödinger equation of wave dynamics, which is valid for the case of two-barrier systems, is found. This solution allows for comprehensive consideration of the process of wave passage through a barrier and identification of the causes leading to super-permeability of individual components.

Investigation on current conduction mechanism through Tb and Mn codoped Bismuth Ferrite grafted polyvinyl alcohol (BTFMO-PVA) nanocomposite film above room temperature (300 K – 415 K) is reported here in detail. A detailed study on dielectric properties of the sample is done over a wide temperature range in a frequency range of 20 Hz - 2MHz. The conduction is attributed to correlated barrier hopping model. Bipolaron hopping dominates over single-polaron hopping in this system. Complex electric modulus spectra and complex modulus spectra are well explained by suitable models to understand the effective dielectric response. The sample responds to the externally applied magnetic field exhibiting negative magnetocapacitance at room temperature.

The paper presents the morphological, structural and compositional properties of the sonochemically prepared ZnO-1.4wt% Graphene (Z-G) nanocomposites as a function of pH value of suspension varying from 8.5 to 14 and thermal annealing at 450°C in nitrogen or air ambient. The SEM analysis of the Z-G hybrids dried at 150°C in air has shown a nano-flower like nanostructure for a pH value of 14. The XRD analysis of dried Z-G hybrids revealed a crystallite size increase from 3.5 nm to 18.4 nm with pH increase, and this result was explained in terms of colloids zeta potential evolution with pH value. The Raman and EDS spectroscopy have shown a split of the G band (1575 cm −1 ) of graphene into two bands (1575 cm −1 and 1605 cm −1 ), an increased height of D (1323 cm −1 ) band, and an additional amount of carbon due to CO 2 absorption from the air, respectively. The carbon incorporation increased with the decrease of pH, and was associated with a hydrozincite phase, Zn 5 (CO 3 ) 2 (OH) 6 . The formation of dried Z-G nanocomposite was clearly demonstrated only at a pH value equal to 14, where two ZnO Raman active bands at 314.9 cm −1 and 428.2 cm −1 appeared. This result may indicate the sensitivity of the Raman spectroscopy to the nanoflower-like nanostructure of dried Z-G hybrids prepared at pH=14. The thermal treatment of Z-G hybrids in N 2 at 450 ° C has increased the number of ZnO Raman bands as a function of pH value, it has decreased the amount of additional carbon by conversion of hydrozincite to ZnO and preserved the graphene profile . The thermal treatment in air at 450 ° C has increased the crystalline symmetry and stoichiometry of the ZnO as revealed by high and narrow Raman band from 99 cm −1 specific to Zn optical phonons, but it has severely affected the graphene profile in the Z-G hybrid , due to combustion of graphene in oxygen from the ambient.

Bulk nanocrystalline graphite has been investigated as a possible candidate for piezoresistive sensors. The thin films were grown using capacitively coupled plasma enhanced chemical vapor deposition and a technological workflow for the transfer of the active material onto flexible substrates was established in order to use the material as a piezoresitive element. Preliminary electrical measurements under mechanical strain were performed in order to test the piezoresistive response of the material and promising GF values of 50 − 250 at 1% strain were obtained.

As the number of poorly soluble drugs is increasing, nanocrystals have become very interesting due to wide range of application possibilities. Curcuminwas used as a model active ingredient in this work. Even though it has many proven positive effects, due to its physicochemical issues, its possibilities have not been fully exploited. The goal of this work was to select optimal conditions for a top-down method for curcumin nanosuspension production, and to perform their comprehensive characterization applying complementary methodologies: dynamic light scattering, polarization and atomic force microscopy, thermal analysis, X-ray powder diffraction, antioxidant activity evaluation, release kinetics assessment, and screening of potential biological effects applying cell viability assays on normal human lung fibroblasts, human melanoma and human adenomacarcinoma cells. After 30 min of milling, nanosuspensions stabilized by polysorbate 80 and by its combinations with sucrose palmitate showed good stability, while curcumin crystal structure was unaltered. Obtained nanocrystals were well defined, with average diameter 120–170 nm and PDI of about 0.25, zeta potential was below −30 mV and pH~5 for all formulations. Nanodispersions exhibited high antioxidant potential and improved dissolution rate compared to the corresponding coarse dispersions. Although curcumin nanodispersions exhibited significant antiproliferative effect to each cancer cell line, the highest effect was towards adenocarcinoma cells.

In this study, Hardox 450 and HiTuf steels were boronized by pack-boriding method at 800, 900, and 1000∘C for 5 h. The phases, microstructure, hardness, and wear behavior of boride layers formed on the surface of samples were investigated using XRD, SEM, Micro-Vickers hardness testers, and a pin-on-disc tribotester, respectively. XRD analysis showed that both FeB and Fe 2 B phases were formed in the borided area of Hardox 450 steel, but only Fe 2 B phase occurred in the boride layer of the HiTuf steel. Micro-Vickers hardness results indicated that the hardness values of the boride layer decreased from the column-shaped structure to towards the matrix in both of Hardox 450 and HiTuf steels. Furthermore, the wear test results showed the coefficients of friction (COF) decreased significantly in the borided samples. The COF of the unborided Hardox 450 steel was reduced considerably from 0.29 to 0.02 by boriding treatment. Similarly, the COF of unborided HiTuf steel was significantly diminished from 0.16 to 0.04 by boriding treatment. In conclusion, the results of this study have indicated that the wear resistance of Hardox 450 and HiTuf steels can be improved by pack-boriding.

Modification of poly-ether-ether-ketone (PEEK) to adapt to the biological properties of materials is currently the key point in the research of medical materials. The tribological properties and biocompatibility of the PEEK composites modified by carbon fiber (CF), potassium titanate whisker(PTW) and nano-particles were discussed in this paper. The results show the modified PEEK composites by a certain length to diameter ratio of CF show the best using effect in vivo experiments in good blood compatibility, which is suitable for orthopaedic implant materials. A large number of experiments show that the PEEK composites would be modified with a certain ratio of CF (about 30%wt.), whisker (about 15%wt.) and HA (about 5%wt.) particle with better biological tribological properties, more important value in medical research.

Montmorillonite (MMT) was modified with cetyl trimethyl ammonium bromide (CTAB) to obtain organomontmorillonite (OMMT) by stirring and pulsed ultrasonic mixing. Polyamide 6 (PA6)/OMMT nanocomposites were then prepared via in-situ polymerization.The resulting OMMT and PA6/OMMT nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results suggested that the OMMT interlayer distance was greatly increased to 3.13 nm due to CTAB being inter-calated into the MMT galleries. The OMMT interlayer distance was further enlarged to 10-20 nm during the polymerization process. The OMMT layers were exfoliated into nanoscale layers and uniformly dispersed in the molten ∈ -caprolactam and PA6 matrix, and exfoliated structure nanocomposites were formed.

This paper studies in-situ synthesis of Fe 2 O 3 /reduced graphene oxide (rGO) anode materials by different hydrothermal process.Scanning Electron Microscopy (SEM) analysis has found that different processes can control the morphology of graphene and Fe 2 O 3 . The morphologies of Fe 2 O 3 prepared by the hydrothermal in-situ and oleic acid-assisted hydrothermal in-situ methods are mainly composed of fine spheres, while PVP assists The thermal in-situ law presents porous ellipsoids. Graphene exhibits typical folds and small lumps. X-ray diffraction analysis (XRD) analysis results show that Fe 2 O 3 /reduced graphene oxide (rGO) is generated in different ways. Also, the material has good crystallinity, and the crystal form of the iron oxide has not been changed after adding GO. It has been reduced, and a characteristic peak appears around 25°, indicating that a large amount of reduced graphene exists. The results of the electrochemical performance tests have found that the active materials prepared in different processes have different effects on the cycle performance of lithium ion batteries. By comprehensive comparison for these three processes, the electro-chemical performance of the Fe 2 O 3 /rGO prepared by the oleic acid-assisted hydrothermal method is best.

In this paper, the microstructure and wear resistance of Zr-17Nb alloy treated by high current pulsed electron beam were studied in detail. A phase change occurs after pulse treatments using X-Ray Diffraction (XRD) analysis, showing β (Nb) phase and α (Zr) phase transformed by a part of β (Zr, Nb) phase. Also, narrowing and shifting of β (Zr, Nb) diffraction peaks were found. Scanning Electron Microscope (SEM) and metallographic analysis results reveal that the microstructure of alloy surface before high current pulsed electron beam (HCPEB) treatment is composed of equiaxed crystals. But, after 15 and 30 pulse treatments, crater structures are significantly reduced. Besides, it was also found that the alloy surface has undergone eutectoid transformation after 30 pulse treatments, and the reaction of β (Zr, Nb) → αZr + β Nb had occurred. Microhardness test results show that microhardness value presents a downward trend as the number of pulses increases, which is mainly due to the coarsening of the grains and the formation of a softer β (Nb) phase after phase transformation. The wear resistance test results show that the friction coefficient increases first, then decreases and then increases with the increase of pulse number.