Band 115, Heft 11-12

The growing demand for sustainable construction has encouraged the exploration of utilizing industrial waste in cementitious materials, aiming to conserve natural resources and manage industrial waste efficiently. This study focuses on incorporating coal mine overburden (CMOB) as a substitute for natural fine aggregate in concrete mixes. The research systematically assesses concrete properties at curing ages of 28, 56, and 90 days. Laboratory tests are conducted to examine compressive strength, splitting tensile strength, flexural strength, and impact resistance of CMOB-incorporated concrete. Incorporating CMOB up to a 60 % replacement level enhances concrete strength, impact resistance, resistance to water penetrability, and microstructure. Optimal mechanical strength, enhanced impact resistance, and improved transport properties are achieved at this level, resulting in a 10–35 % increase in strength and a 13–29 % improvement in resistance to water penetrability compared to control concrete. Microstructural analysis indicates similarities in surface morphology and micro-cracks within the interfacial transition zone (ITZ) to normal concrete. Given the high water absorption of CMOB, the use of superplasticizers is advisable to maintain the desired workability. These findings support the practical utilization of CMOB in concrete applications, offering potential environmental and economic benefits.

The synthesis of polymer composites consisting of conducting polyaniline (PANI), cobalt ferrite (CoFe 2 O 4 ), and poly(vinylidene fluoride) (PVDF) is achieved by the polymerization technique. A nanocomposite consisting of polyaniline (PANI) and CoFe 2 O 4 is prepared using the interfacial chemical oxidation polymerization technique, resulting in a composition containing 50 wt.% of CoFe 2 O 4 . Nanoparticles of cobalt ferrite (CoFe 2 O 4 ) were synthesized by using the sol–gel auto-combustion process. The PANI/CoFe 2 O 4 (1:1) nanocomposites with weight percentages of 5, 10, 15, and 20 are incorporated into the PVDF matrix as fillers in order to alter the morphology and AC electrical conductivity of the PVDF/PANI/CoFe 2 O 4 composite materials. The structural and morphological properties were studied using characterization techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. At room temperature, impedance spectroscopy, dielectric measurements, and AC electrical conductivity were carried out in the frequency range of 40 Hz to 5 MHz. The dielectric permittivity has been shown to decline exponentially in low-frequency zones before remaining almost constant up to 5 MHz. When the frequency is increased up to 1 MHz, the AC conductivity of all composites remains constant; after that, it increases as the frequency increases. It was found that PANI-CoFe 2 O 4 nanocomposites modified the overall charge transport mechanism by modulating the core grain and grain boundary. The experimental Nyquist plot for different composite samples was fitted by an appropriate RC electrical model to evaluate relaxation time. The relaxation time τ 1 ( R 1 C 1 ) and τ 2 ( R 2 C 2 ) were both reduced after the reinforcement of PANI-CoFe 2 O 4 nanocomposites.

Copper is a commonly preferred dopant for cadmium telluride based solar cells. Even though it is widely used as it enhances the electrical properties, it has the tendency to diffuse into the CdTe layer as well as the CdS/CdTe junction interface which adversely affects the performance of CdTe solar cells. In this experimental study copper doping of buffer cadmium sulfide layer has been performed to analyse its effect on structural, electrical, and optical properties of CdS and CdTe layers. While from the X-ray diffraction analysis it was observed that there was reduction in peak intensities and crystallite sizes of both the CdS and CdTe layers with the increase in amount of copper dopant, from the electrical properties it was found that there were improvements in carrier concentration, mobility, and conductivity of both the layers. To mitigate the losses due to Cu doping, enhance the efficiency and stability of CdTe solar cells an extensive numerical modelling approach was undertaken to employ electron transport layers (ETL) and hole transport layers (HTL) to the copper-doped CdS/CdTe solar cells. We obtained optimum results with titanium dioxide and copper barium thiostannate as ETL and HTL respectively. Finally, CdTe-based solar cells were modelled integrating copper-doped CdS as the buffer layers, TiO 2 as ETL and CBTS as HTL respectively. The obtained experimental values of Cu-doped CdS and CdTe layers were implemented into this model. This superstrate configuration yielded impressive output parameters: open circuit voltage of 1.07 V, short-circuit current density of 29.32 mA cm −2 , fill factor of 85.08 %, and efficiency of 26.67 %.

The large bone defect is still the main challenge in bone tissue engineering which can be solved using a scaffold. In the present study, a biological composite composed of chios mastic gum and 30 wt.% papyrus vaccine pollen has been reinforced with 0.5, 1, and 1.5 wt.% of hydroxyapatite particles obtained through alkaline hydrolysis from Ariidea fish bone. The outcomes evinced that the (chios mastic gum: 30 wt.% papyrus vaccine pollen: 1 wt.% hydroxyapatite) sample exhibited a higher compressive strength in all the prepared samples which is in the range of the compressive strength of human cancellous bone. Both atomic force microscopy and scanning electron microscope morphological analyses confirmed that the papyrus vaccine pollen and hydroxyapatite particles were distributed consistently and homogeneously throughout the chios mastic gum. The prepared bone scaffold has the potential to be used for bone tissue engineering.

In the Indian context, the production of steel is increasing day by day. The huge crude steel output requires enormous amounts of raw materials from the mining industry. The availability of high-grade steel-making raw materials has decreased worldwide. There are huge challenges for the metallurgist in developing a suitable process in the steel industry, which is essential due to the possible scarcity of high-grade raw materials in the future. In this present study, an appropriate process for lean-grade iron ore and non-coking coals, along with the binders, is used as self-reducing composite pellets for iron making. These composite pellets are made in different combinations, including particle sizes, different non-coking coals, and binders. Initially, the mechanical properties of composite pellets are evaluated through the shatter and abrasion index. Then, cold-bonded self-reducing pellets are directly reduced in a standard tube furnace at varying temperatures and times. The reduced samples are further characterized using X-ray diffraction, scanning electron microscopy, and chemical analysis methods. Finally, Box–Behnken Design statistical modelling based on the extent of reduction ( EOR ) is successfully utilized for optimizing the process parameters.

Lead indium niobate holds particular attention as a functional piezoelectric material as it can transit from a disordered phase to an organized one with exposure to heat for a long time. Obtaining pure-phase perovskite lead indium niobate ceramics without any pyrochlore phase using the conventional mixed oxide method poses significant challenges. This difficulty arises from the low tolerance and electronegativity difference of lead indium niobate in comparison to other perovskite compounds. The dielectric properties of lead indium niobate can be enhanced by adding lead titanate to its composition. In this study, a binary system of lead indium niobate with lead titanate is synthesised close to the morphotropic phase boundary composition by taking 35, 40 and 45 mol.% of lead titanate by using two-step sintering method. Out of the different compositions, the lead indium niobate with 35 mol.% of lead titanate shows high piezoelectric properties and can be a suitable material for energy harvesting.

The present study provides an in-depth investigation of the exfoliation of molybdenum disulfide (MoS 2 ) using high-energy ball milling and the subsequent development of aluminum‒molybdenum disulfide (Al–MoS 2 ) nanocomposites via a powder metallurgy (PM) route. X-ray diffraction confirmed that the commercially available bulk MoS 2 did not develop new phases after intense ball milling for up to 30 h. The effects of ball milling on the thermal stability and morphological changes in MoS 2 powder have also been reported. The milling action caused a shift in the band gap of MoS 2 , from 1.2 to 1.44 eV due to quantum confinement phenomena confirmed by UV–visible absorption spectroscopy. The impacts of ball milling on the specific surface area and mean pore diameter of MoS 2 were determined by the Brunauer–Emmett–Teller surface area analysis technique. Additionally, the investigation through Fourier transform infrared spectroscopy verifies the presence of functional groups, such as hydroxyl (O–H), alkane (C–H), and ether (C–O), on the MoS 2 surface. The milling resulted in a significant reduction in particle size from an initial mean size of 1.2 µm–480 nm. Field emission scanning electron microscopy micrographs of the exfoliated MoS 2 revealed a thin, cracked, and flake-like morphology. High-resolution transmission electron microscopy images revealed that the high-energy ball milling resulted in few-layered MoS 2 nanoplatelets after 30 h of ball milling. Subsequently, the investigation extended its focus to the development of Al–MoS 2 nanocomposites using the PM route, incorporating MoS 2 into the Al matrix at different weight percentages (1, 2, 3, and 5 wt.%). Al-5 wt.% MoS 2 nanocomposite showed the highest relative density of 93.09 %, the maximum hardness of 743.6 MPa, and the best wear performance among all the Al–MoS 2 nanocomposites. The hardness of Al-5 wt.% MoS 2 nanocomposite was 109.11 % higher than that of the pure Al sample developed similarly. A maximum compressive strength ( σ max ) of 494.67 MPa was observed in Al-5 wt.% MoS 2 nanocomposite, which was 1.84 times the value of σ max obtained from sintered pure Al sample.

Conventional plastics derived from petroleum resources have dominated the packaging sector. However, the use of such plastics has resulted in environmental issues. Research on development of biodegradable plastics has gained momentum. In the present work, eco-sustainable poly (butylene adipate terephthalate) (PBAT)/poly lactic acid (PLA) blend films have been developed with beeswax as an additive. Films have been made by blending biopolymers PBAT with PLA. Beeswax, as an additive has the ability to enhance the water vapour and oxygen barrier properties films. Beeswax content has been varied in the films (0, 0.5, 1 and 2 wt.%). The prepared films have been characterized for their mechanical (tensile testing), water absorption, morphological and biodegradation behavior. Maximum tensile strength has been observed for film containing 1 wt.% of beeswax. Water absorption of the films has been lowered by addition of beeswax. Based on the obtained results, 1 wt.% of beeswax addition has been found to be suitable for PBAT/PLA blend films.

1.0 wt.% Y 2 O 3 (alloy S Y ), TiO 2 (alloy S T ), ZrO 2 (alloy S Z ), dispersed 79W–10Ni–5Nb–5Mo (in weight%) alloys have been produced by mechanical alloying with 5:1 ball to powder weight ratio (BPR) for 20 h at 300 rpm in toluene medium. The powders were consolidated by spark plasma sintering at 1,100 °C for 5 min and at 65 MPa pressure. Oxidation study of the consolidated alloys was carried out at 1,000 °C for 10 h to establish the sustainability at elevated temperature. The study shows that alloys S Y, S T exhibit compressive residual stress and alloy S Z evidences tensile residual stress in the oxidized condition. The oxidation rate is significantly lower in alloy S Y due to passive layer formation facilitated by Y 2 O 3 and Ni. The oxidation kinetic study also suggests substantial reduction in rate constant in alloy S Y . The present study also provides interesting inputs regarding development of oxidation resistant alloys for high temperature applications.

This paper highlights the synthesis and processing of alumina−calcium titanate (Al 2 O 3 –CaTiO 3 ) composite for multifunctional application in the biomedical industry. In this work, the Al 2 O 3 –CaTiO 3 composite was synthesized using sol-gel techniques. Calcium oxide, aluminum isopropoxide, titanium isopropoxide, ethanol, and nitric acid were used as precursor chemicals, solvents, stabilizers, and catalysis, respectively. The powder was calcined at a temperature of 800 °C for 1 h. The densification and sintering behavior of uniaxially pressed calcined powder was carried out using a pressureless sintering electric furnace at a temperature of 1,400 °C for 2 h. X-ray diffraction and scanning electron microscopy analysis were used to determine the phases and morphology of powders and sintered nano-composite. The impedance analysis was used to investigate the electrical properties of the sintered composite. As a result, the phases and morphology of Al 2 O 3 and CaTiO 3 were confirmed by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy analysis. Impedance analysis indicates the increasing dielectric constant and AC conductivity of the sintered sample with the function of temperature and frequency. Finally, it can be concluded that the biocompatibility of both phases could potentially be fabricated and used in biomedical industries as a functional biomaterials application.

Superhydrophobic surfaces are important in waterproof applications that withstand harsh chemical exposure, ultraviolet radiation, and heat. Surface energy modification of the surface, such as silanization or (fluoro)polymer coatings, increases the hydrophobicity of the nanostructure. The present study follows a bilayer architecture that turns hydrophilic silicon into a superhydrophobic one. The first step creates a unique silicon–graphene hybrid structure on the silicon surface by coating graphene on the P-type silicon substrate. In the second step, low surface energy material (a combination of hexadecyltrimethoxysilane and hexamethyldisilazane) is coated by the dip coating process. This study investigates the durability of superhydrophobicity under severe mechanical, thermal, and chemical conditions. High-temperature tolerance and water jet tests are also performed. The present work also involves the study of coating regeneration. This approach can be applied to all shapes and sizes of silicon–graphene surfaces and is proven to be excellent in the semiconductor industry.

The research investigates the effect of variable notch-width ratios on mechanical and electromagnetic radiation (EMR) parameters during the tensile fracture of silicon steel. The primary purpose is to comprehend the plastic deformation and crack propagation at an atomic level. The mechanical and EMR parameters chosen for analysis were correlated. The EMR energy release rate correlated well with the elastic strain energy release rate. The good fit between the EMR parameters and the plastic zone radius is a novel method to determine the crack growth behaviour of metals. A theoretical model of dislocation predicted the nature of EMR signals at fracture. A reasonable agreement between cross-slip energy with maximum stress at crack instability, the elastic strain energy release rate, and the EMR energy release rate will help assess the dislocation dynamics of metals. The EMR amplitude was sensitive to varying strain rates.

The study investigates joining AA6061-T6 and AA5083-H12 aluminum alloys, each 6 mm thick, in a butt joint. It aims to analyze the impact of varying input parameters on the microstructural and mechanical properties of the joints. Three tool rotation speeds (900, 1,120, 1,400 rpm) and welding speeds (40, 63, 80 mm min −1 ) are examined. Temperature in the weld zone correlates with tool rotation speed positively and welding speed inversely. Initially, the average grain size in the stir zone decreases with increasing tool rotation (900–1,120 rpm) and welding speed (40–63 mm min −1 ), then increases with further increments (1,400 rpm, 80 mm min −1 ). Tensile strength increases by 7 % from 900 to 1,120 rpm but decreases by 19 % at 1,400 rpm. Similarly, it rises by 14 % from 40 to 63 mm min −1 , then decreases by 6 % at 80 mm min −1 . Optimal mechanical properties occur at 1,120 rpm and 63 mm min −1 , with ductile mode failure identified in joints with higher efficiency.

The present research reports the effect of binder addition on the physical and mechanical properties of green and fired mill scale pellets. A mixture of mill scale powder and varying weight percentage of bentonite (1, 1.5 and 2 wt.%) and molasses (2.5, 5 and 7.5 wt.%) binders were used separately to prepare green mill scale pellets by hand rolling to form spherical balls of diameter around 10 mm and then fired at 1,100 °C for 1 h. It was observed that the moisture content in pellets made with the addition of bentonite was found in the range of (6.16–6.70 wt.%) which was higher compared to those made with the addition of molasses (2.40–4.18 wt.%). A drop number in the range of (1.33–5.33) and (20.33–47.67) were observed for bentonite and molasses bonded pellets respectively. The compressive strength for bentonite bonded pellets varied from (633–780) N cm −2 and molasses bonded pellets it ranged from (179–213) N cm −2 . X-ray diffraction study revealed the formation of only hematite phase after sintering at 1,100 °C.

Geopolymer concrete, which utilizes aluminosilicate precursor materials such as metakaolin, volcanic ash, industrial solid waste including fly ash and ground granulated blast furnace slag as a binder, is an eco-friendly alternative to Portland cement concrete. Although geopolymer concrete does not use cement, it still has shortcomings in terms of environmental friendliness because the aggregates (fine and coarse) used to prepare geopolymer concrete are natural resources and their excessive use in concrete manufacturing leads to natural resource depletion. In view of this, several researchers have tried to replace natural aggregates with various waste materials, which not only conserves natural resources but also helps in waste management. In the present study, the potential of steel slag and coal mine rock waste as a substitute for coarse and fine aggregates in geopolymer concrete to make it truly green is experimentally evaluated. The use of steel slag and coal mine rock waste as coarse and fine aggregates in geopolymer concrete was observed to significantly improve its strength and durability properties compared to fly ash based geopolymer concrete.

The current study uses three engineered fibres: white flax, brown flax, and jute fibres to form plain intra-woven fabrics. The fabrics were alkali treated with a 5 % NaOH solution and mechanical, physical, and thermal tests were conducted to characterize the individual fabrics. It was observed that treated woven fabrics significantly enhanced the overall mechanical strength compared to untreated fabrics. White and brown flax interlaced fabrics increased the tensile strength by 157 % and 574 %, Young’s modulus by 36 % and 26 %, and breaking strain by 58 % and 89 % than jute interlaced brown and white flax, respectively. Thermo-gravimetric analysis revealed that the fabric containing white flax fibre exhibited a maximum degradation temperature of 364.45 °C and after treatment, each fabric revealed a higher degradation temperature. The change in chemical composition of the green fibres after treatment was studied through Fourier transform infrared spectroscopy analysis.

The mechanism of copper electrodeposition with varying potential investigated by using electrochemical impedance spectroscopy (EIS) has been reported in this current study. The bath of the deposit has limited and unlimited supply of copper ions to the substrate by using two counter electrodes i.e., platinum (Pt) and copper (Cu) respectively. The electrodeposition of copper on graphite electrodes was investigated by utilizing cyclic voltammetry (CV), potentiostatic and EIS methods. On the Nyquist plots, copper ion charge transfer is represented by a single capacitive constant at high frequencies while copper ion diffusion from the solution to the electrode surface is represented by a Warburg-type contribution at low frequencies. The corresponding Bode plots represent a decent matching between the experimental and fitting data. The effect of potential on double-layer capacitance, diffusion coefficient, and diffusion layer thickness along the interface of electrode and electrolyte has been discussed extensively. The morphologies of the copper particles depositing on the surface of the electrode were also studied and it shows a transition from spherical to dendritic structure as a function of deposition potential.

The problem of fracture in quasi-brittle materials is strongly linked with a zone of micro-cracking known as the fracture process zone (FPZ). For monotonic loading, the material length scale parameter D 0 is used in strength scaling law to describe the transition from strength criteria to linear elastic fracture mechanics criteria. The Paris Law approach to quasi-brittle materials for cyclic loading introduces another length scale parameter, D 0c . Experimental testing of concrete, rock, and sandstone showed two contradictory results. A few experiments showed that the parameter D 0c is higher than D 0 , and the cyclic FPZ is larger than monotonic FPZ. Another set of experiments showed that D 0c is smaller than D 0 , and the cyclic FPZ is smaller than monotonic FPZ. This interesting contradiction is named the Bažant-Le-Kirane Paradox (B-L-K Paradox) after the scientists involved in the experimentation. The B-L-K Paradox is the holy grail of fatigue fracture mechanics, and solving this problem will allow for the rational design of concrete structures.

Laser transmission welding efficiently welds polymers by precisely applying concentrated heat with a laser beam, making it a widely used, non-contact, contamination-free, automated, and fast polymer joining method in automotive, medical, and electrical industries. This study presents a three-dimensional finite element model simulating the laser transmission welding of polypropylene, a widely utilized engineering thermoplastic with superior mechanical properties and exceptional chemical resistance. The primary objectives are to analyze thermal phenomena, predict parameters such as weld temperature and weld pool size, and conduct a thorough parametric analysis. The finite element model incorporates a volumetric heat source within COMSOL ® Multiphysics, incorporating a radiative beam in an absorbing media interface, while considering key thermal factors such as conduction, convection, and radiation. Experimental tests are conducted to validate the developed thermal model. The paper deepens comprehension of the mechanics behind laser transmission welding of polypropylene, providing insights into the impact of process parameters on the thermal field and weld pool size.

Wire arc additive manufacturing (WAAM) has emerged as a versatile and cost-effective technique for fabricating complex, large-scale components with enhanced material flexibility. The bead profile, like width, height, and penetration, is critical in WAAM fabrication, influencing the quality and performance of the final component. Consistent and precise profiles are essential for accurate layering and material deposition in complex 3D structures. Various parameters, such as current, voltage, deposition rate, interpass temperature, and welding mode, impact deposit quality in WAAM. This study focuses on implementing a controlled heat input deposition approach, utilizing various welding modes: Control Weld (classic MIG/MAG), Speed Weld (voltage-controlled pulsed arc), Vari Weld (current-controlled pulsed arc), Rapid Weld (high-capacity spray arc), Root Weld (energy-reduced short arc), and Fine Weld (energy-reduced, current-controlled short arc). The study scrutinizes the impact of altering the welding mode on bead profile, bead quality, macroscopic morphology, microstructure, and mechanical properties in single-bead WAAM structures.

The increasing adoption of lithium-ion battery packs in electric vehicles has sparked considerable interest in choosing the appropriate busbar material and obtaining suitable mechanical, electrical, and thermal properties of the welded joints. This study comprehensively employs ultrasonic metal welding to create tab-to-busbar connections utilizing 0.3 mm nickel-coated copper and 0.5 mm aluminum sheets. Joint mechanical performance, microstructural characterization, and welding mechanism at different weld energies and clamping pressures are studied to understand the material flow, inter-atomic mixing, and newer grain formation phenomena. The correlation between the dynamic characteristics of electrical contact resistance and the resulting temperature is also revealed under various welding conditions by applying current through the joints. The micro-hardness analysis disclosed the different weld zones of distinctive values where the material has been mixed. Further, the nickel coating on the copper surfaces facilitates metallurgical bonding to a significant extent. The results revealed that the inter-atomic diffusion, wave-like bonding area, and micro-bond development on the weld cross-sectional surface are the foremost reasons for satisfactory welds.