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Researchers are interested in the production of metal oxide-carbon core-shell nanostructures due to their superior performance, stability as well as optical and electrical properties. However, their synthesis approaches are quite lengthy and also excessive chemicals use hampered performance adversely. This study proposed a novel method for producing core-shell NPs (GO@ZnO), i.e. ZnO nanostructures wrapped in graphene oxide (GO). The Core-shell NPs are produced using electrochemical (EC) and electrical discharge (ED) hybrid processes. A two-step approach is used, in which at first ZnO colloidal solution is prepared using zinc electrode as the core, and then the graphite electrode produces the shell. For zinc and graphite electrodes, experimental settings include 2 M electrolyte concentration, 120 V voltage, 10% and 20% duty cycles. The core-shell structures are confirmed through TEM images. The best electrochemical activity of core-shell (GO@ZnO at NaOH medium) was observed, with a high specific capacitance of 1042 F/g at 2 A/g current density. At 5000 cycles, 91.21% specific capacitance retention was reported, indicating excellent cyclic stability. In addition to this, the capacitance retention of the device was 83.5% after 5000 cycles, This study established the conversion of waste to efficient supercapacitor electrodes via eco-friendly, low-cost, two, simple process. [Display omitted] • First-time hybrid discharge (Electrochemical and electro discharge) approach used to produced core-shell nanoparticles. • This article focused on using e-waste, as spent Zn–C batteries (Zinc and graphite) used to produce GO@ZnO core-shell nanoparticles. • The size distribution, morphology, and optical characterization have been demonstrated in detail. • The supercapacitor performance of core-shell nanoparticles shows high specific capacitance of 1042 F/g at 2 A/g current density. • 83.5% retention of specific capacitance also exhibited over 5000 cycles for the device. [ABSTRACT FROM AUTHOR]

This work reports the growth and characterization of nanocrystalline Zinc magnesium sulphide thin films fabricated on glass substrates using the chemical bath deposition technique. X-ray diffraction studies revealed that the as-prepared films are nanocrystalline in nature and possess a cubic phase with a preferred orientation along the (111) plane. The crystallite size increases from 18.3 to 29 nm with deposition time. The field emission scanning electron microscope micrographs showed uniform nanostructures on the film surface. The grain sizes increased from 215 to 310 nm with deposition time. EDX spectra displayed the presence of elements Zn, Mg, and S. The absorbance peak increased with deposition time and all the films had a transmittance of over 80 %. From the absorption measurements, the band gap showed an increase from 3.848 eV to 3.945 eV with deposition time. The fabricated ZnMgS thin films exhibit crucial characteristics suitable for optoelectronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Wire Arc Additive Manufacturing (WAAM) is an advanced technique for producing medium-to-large-sized components, offering high deposition rates and low equipment costs. Path planning strategies are critical in determining grain growth direction and achieving isotropic properties in the components. This study introduces a novel path planning strategy, the switchback mode, to mitigate unidirectional grain growth and enhance the mechanical properties of WAAM-deposited components. ER-4043 aluminium alloy walls were deposited using the switchback mode and compared with the conventional bi-directional path planning strategy. The findings reveal that different path planning strategies result in variations in layer size, surface morphology, microstructure, residual stress, microhardness, wear resistance, and tensile properties. Notably, the switchback mode demonstrated superior mechanical strength compared to the bi-directional mode, with yield strength (YS) increasing from 90.2 MPa to 113.9 MPa, ultimate tensile strength (UTS) from 148.8 MPa to 178.7 MPa, and elongation percentages from 18.4 % to 21.3 %. Furthermore, the residual stress changed from tensile to compressive when switching from bi-directional to switchback mode. • WAAM is efficient for large components with high deposition rates and low costs. • Path planning affects grain direction and isotropic properties in components. • Path planning impacts microstructure, residual stress, surface roughness, and mechanical properties. • Switchback path planning offers better mechanical strength than bi-directional. [ABSTRACT FROM AUTHOR]

In the present study, a metal matrix composite of nitride, boride, and oxide layer over the Ti6Al4V substrate has been formed by using high-quality reinforcement like cBN, TiO 2, and Ti6Al4V. Response surface methodology (RSM) has been successfully implemented to investigate the effect of process parameters (laser power, scanning speed, and shielding gas flow rate) on the responses like clad layer thickness and micro-hardness value of the cladded part. Statistical analysis shows that laser power and scanning speed significantly influence layer thickness and microhardness. Further considering the optimal combination of process parameters, cladded surfaces with different percentage compositions of reinforcement are characterized. The clad shows different microstructures like needles, cylindrical rods, and short-length dendritic. These confirm the formation of a metal matrix composites of nitrides and borides (TiN, TiAlN, AlN, and TiB 2) as the main constructive phase of the clad. Further analyzing the binding energy of these phases through XPS, the formation of the compounds exhibits higher intensity. These enhance the hardness as well as wear resistance properties of the clad. The coefficient of friction in the cladded surfaces is less than the base material due to anti-wear chemical compounds like boride and nitride. However, spalling craters and wear debris are found in cladded samples. [Display omitted] • Laser surface deposition on Ti6Al4V substrate. • Study of the combining effect of laser power, scanning speed and shielding gas flow rate on the clad properties. • Compound formation of Hard phases-TiN, TiAlN, AlN, TiB 2. • Binding energy distribution analysis of the compounds formed. • Observation of Short-length dendritic and needle type microstructure. [ABSTRACT FROM AUTHOR]

The present work explores the potential applications of sustainable micro-electrical discharge coating (μ-EDC) process for surface modification of micro-components using solid lubricating powder mixed in bio-oil (Jatropha and Neem oil) as a dielectric medium. The surface modification was carried out on Ti-alloy work piece by setting the voltage and duty factor at different levels. Different characterization technique was followed to evaluate the micro-hardness, surface roughness, and coating layer thickness of the modified surfaces. The analysis of results are presented for the individual oil and powder mixed oil. For Jatropha, the maximum micro-hardness obtained is 642.43 HV 0.1 (128%, 274.02 HV 0.1 for base material), average surface roughness (R a) ranges from 0.54 μm to 1.83 μm; whereas for neem oil, the maximum obtained micro-hardness 592.90 HV 0.1 , R a range: 0.78 μm–1.64 μm. When the above oils were mixed with MoS 2 powder, the obtained results were further enhanced. The maximum micro-hardness obtained were 543.75 HV 0.1 and 712.43 HV 0.1 , and R a ranges from 0.47 μm to 1.39 μm, and 0.43 μm–1.35 μm, for Jatropha+MoS 2 and neem+MoS 2 , respectively. The transfer of tool and dielectric materials is affirmed through EDX plots. [Display omitted] • Novel environment friendly and sustainable coating method for solid lubrication in miniature components. • Conversion of bio-oils (Neem and Jatropha) to bio-dielectrics which can be used for micro-electrical discharge coating. • Among all bio-dielectrics, Neem + MoS 2 produces the best hardness (712.43 HV) and minimum roughness profiles (0.43 μm). • Replacement of conventional synthetic dielectric by proposed bio-dielectrics without disturbing the ecological balance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Arc-based post-processing significantly smoothens the surface of WAAM components. • Arc-based surface smoothening technique doesn't require additional equipment. • Arc-based surface smoothening utilizes the same WAAM setup for the process. • Surface under electric arc melts and redistributes material, smoothing undulations. • The arc-based surface smoothening is suitable for aluminium WAAM components. The components fabricated through the wire arc additive manufacturing (WAAM) process exhibit poor surface topology and often require post-processing steps like milling, shot-peening, and laser remelting. The current study investigates a technique to enhance the surface topology of WAAM components by employing the same WAAM setup. The electric arc, generated by the gas tungsten arc welding (GTAW) setup, is selectively scanned over the fabricated WAAM component. The surface, under the influence of the electric arc, melts the material and redistributes it, eliminating excessive peaks and valleys. This surface smoothening operation produces a surface typically with a ∼45 % reduction in the average roughness (Sa) of the top surface and a ∼70 % reduction in Sa for the side surface of the WAAM component. [ABSTRACT FROM AUTHOR]

Laser cladding is a unique process for adding one material to the surface of another base material by utilizing high energy and coherent laser beam. For the present investigation, h-BN (hexagonal boron nitride) + SS316 composite coating was applied on SS316 substrate surface by fiber laser cladding operations. Under the influence of various input process parameters, the surface morphology, microstructure, X-ray diffraction, clad layer thickness, micro-hardness, and tribological behaviour of the composite coating were examined. The result showed good metallurgical bonding between the clad powder and substrate surface. Surface morphology did not show any pores and cracks on the clad surface. From FESEM analysis, the clad surface was found to be smooth and free from any crack propagation during laser processing. X-ray diffraction analysis showed formation of Fe 3 N, Cr 2 N, CrB, B 2 C 5 N 2 , γ- (Ni, Fe), h-BN phases which are responsible for enhancing mechanical and tribological properties of the clad layer. During the study, the micro-hardness of the clad layer was found to increase with an increase in % v/v of h-BN by 2–2.5 times compared (525 HV 0.3) to parent material (220 HV 0.3). Further, dry sliding wear test was carried out with Pin-On-Disc which showed that the coefficient of friction value decreased significantly from 0.560 (parent surface) to 0.251 (clad surface). [ABSTRACT FROM AUTHOR]

In the present study, hard, wear, and corrosion resistance coating is deposited on titanium alloy with hexagonal boron nitride powder (avg. size 70 nm) suspended in deionized water by micro-electro discharge coating process. The influence of input process parameters on surface integrity, wear properties, and corrosion resistance is studied. XRD analysis of coating surface shows the presence of phases such as BN, Al 2 O 3 , TiN, TiAlN, TiO, and CuO. Micro-hardness of the coating surface increases by five times as compared to titanium alloy (parent material). At the parameter settings of 60 V, 0.7 duty factor, and 12 g/l, the maximum deposition rate of 5.65 ± 0.1 × 10−4 g/min and recast layer thickness of 13.1 μm is obtained. Pin on disk wear test results reveal the reduction of wear rate of the coated surface to one-fourth of that of the base material. The average coefficient of friction (COF) for the deposited BN surfaces reduces to 0.26 from 0.4 (substrate material). Corrosion resistance of the coated surface is found to be 1.24 μm/year in flowing water conditions and 1.07 μm/year in stagnant water whereas for the parent material it is 5.92 μm/year in flowing water condition and 4.89 μm/year for stagnant water condition. • hBN powder mixed micro-electrical discharge coating was successfully carried out on the titanium alloy. • Phase analysis results indicate the presence of BN, TiN, TiAlN for improving the wear and corrosion resistance properties. • Wear and friction test results indicate significant improvement as compared to the parent material. • The maximum corrosion rate was observed for the base material is 5.92 μm/year and for the coated sample is 2.83 μm/year. [ABSTRACT FROM AUTHOR]

This work highlights evaluation of suitable process parameters to result significantly higher hardness, fracture toughness and wear resistance in metal matrix composites (MMC) developed with different proportions of reinforcements, namely, TiB 2 , TiN, and SiC in steel (AISI 304). The composites are developed through powder metallurgical route and are subsequently laser surface glazed. Thorough characterizations of composites' mechanical and tribological behaviors before and after laser surface treatment and application of response surface methodology (RSM) for modeling and analysis of its behavioral responses towards variations in process parameters are performed. [ABSTRACT FROM AUTHOR]

In the present research, direct metal laser sintering (DMLS) method was chosen to fabricate titanium nitride (TiN) reinforced Ti6Al4V alloy based metal matrix composites (MMCs) under an argon atmosphere using continuous wave (CW) fiber laser having a capacity of 400 W. Laser sintering process parameters, such as layer thickness (0.4 mm), laser beam spot diameter (0.4 mm), and hatching gap (0.2 mm) were kept constant throughout the experiments. Effects of input variable process parameters, such as laser power (50-65 W), scanning speed (3500-4500 mm/min), and volume % of TiN (5-15% v/v) on density, microhardness, and coefficient of friction of the fabricated MMCs were analyzed. The obtained results show the improvement in the physical properties of the fabricated MMCs and FESEM images evidently confirm the presence of TiN particulates and also revealed the uniform distribution of the TiN reinforcement in Ti6Al4V matrix. It was found that the microhardness measured by Vickers test was improved from 388 to 590 HV0.2 with an increase in the volume percentage of TiN. The results showed the coefficient of friction for fabricated samples were in the range of 0.33-0.42. The density (3.40-4.10 g/cm3) of the MMCs was found to increase with increasing the volume percentage of TiN reinforcement in the powder mixture. X-ray diffraction (XRD) analysis of the fabricated MMC confirmed the presence of different in-situ phases, such as Ti, TiN, TiO2, VN, AlV, Ti3Al2N2, and V6N2.7 as a consequence of a series of a chemical reaction between TiN and different elements of Ti6Al4V in the argon atmosphere. [ABSTRACT FROM AUTHOR]

The purpose of this study is to make a boron carbide (B 4 C) and cubic boron nitride (cBN) reinforced Ti6Al4V metal matrix composites (MMC's) by direct metal laser sintering (DMLS) technique using the continuous wave (CW) SPI fiber laser and to check the feasibility of the formation of three dimensional objects by this process. For this study, the process parameters like laser power density (3.528–5.172 W/cm 2 (×10 4 ), scanning speed (3500–4500 mm/min), composition of the reinforced materials B 4 C (5–25% by volume) and cBN (3% by volume) were taken as input variables and hatching gap (0.2 mm), spot diameter (0.4 mm), layer thickness (0.4 mm) were taken as constant. It was analyzed that surface characteristic, density and the mechanical properties of sintered samples were greatly influenced by varying the input process parameters. Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) and X-Ray diffraction (XRD) were performed for microstructural analysis, elemental analysis, and recognition of intermetallic compounds respectively. Mechanical properties like micro-hardness & wear rate were examined by Vickers micro-hardness tester & pin on disc arrangement respectively. From hardness tests, it was observed that hardness property of the sintered specimens was increased as compared to the parent material. The XRD results show that there is a good affinity between Ti6Al4V-B 4 C-cBN to produce various intermetallic compounds which themselves enhance the mechanical properties of the samples. From FESEM analysis, we can conclude that there is a uniform distribution of reinforcements in the titanium alloy matrix. Furthermore, the coefficient of friction (COF) was characterized by the irregular pattern and it tends to decrease with an increase in the volume % of reinforcement. The results obtained in this work may be useful in preparing the MMC's with improved mechanical properties and overall characteristics. [ABSTRACT FROM AUTHOR]

Numerous solution-based methods are used to prepare zinc oxide (ZnO) and graphene oxide (GO) nanocomposite (ZnO-GO NCs) such as sol-gel, hydrothermal, and precipitation. These methods require lots of reagents and involve many stages. In this study, a novel one-step solution-based discharge method is used to prepare ZnO-GO NCs through an electrochemical discharge process (ECDP) without the use of any catalyst or toxic chemical reagent. This study focused on analyzing the effects of input parameters on the production rate of ZnO-GO NCs. The experiment was performed by using Taguchi L9 orthogonal array. Materials removal rate (MRR) is considered as output response. The results reveal that voltage is the most significant factor, followed by temperature and duty cycle for obtaining higher MRR. The optimum parameters obtained from the Minitab software for higher MRR are 40 V, 30%, and 45 °C. Further, the morphology of the nanoparticles (NCs) produced at optimum parameters is analyzed which shows flower shape NCs with multilayer graphene oxide, confirmed by the FESEM and TEM images. The XRD peak at 11.27° and Raman spectroscopy peak of G and D bands reveal GO formation. The prepared ZnO-GO NCs tested as supercapacitor activity in the KOH solution. At the optimum parameter, the specific capacitance is observed to be 523.4 F/g at 2A/g current density. The NCs electrode shows good cyclic stability, with 86% retention of specific capacitance after 5000 cycles. This study shows a promising future of converting the e-waste product into valuable nanomaterials such as GO and ZnO from used dry cell batteries. • · Hybrid discharge generates ZnO-GO nanocomposite without hazardous chemicals. • · MRR was obtained using Taguchi L9 orthogonal array. • · Size distribution, morphology, and optical characterization have been demonstrated. • · 86% specific capacitance retention after 5000 GCD cycles. [ABSTRACT FROM AUTHOR]

Solid lubricant coatings play a critical role in enhancing the tribological properties of engineering materials, particularly in aerospace and biomedical applications. Ti6Al4V is widely used in aerospace and defense industries due to its excellent mechanical properties and high strength-to-weight ratio. In this regard, a solid lubricant metal matrix composite (MMC) clad was successfully fabricated over Ti6Al4V. A full factorial (L16) was successfully implemented to investigate the interaction of process parameters for laser power and scanning speed with response outputs, such as the clad layer thickness and microhardness. The microstructural study of the clad confirmed the presence of dark and bright phases of the microstructure with cylindrical, elliptical, and lamellar structures. This showed the presence of molybdenum and sulfide phases (MoS 2 , TiS, CuS) and the presence of a nickel phase (TiNi, NiS, CuNi), confirmed through X-ray diffraction (XRD) analysis and energy-dispersive X-ray (EDX) spectroscopy; these phases bestowed hardness as well as solid lubricating properties on the clad. The microhardness of the clad was found to be 2-3 times that of the substrate material. The wear behavior of the clad was studied in the load range of 5-15 N; the coefficient of friction (0.33 for clad and 0.5 for base), wear track depth profile, and wear mechanism revealed that the cladded sample has higher wear resistance as compared to the substrate material. The worn morphology showed that microcutting and microplowing are the major phenomena of wear occurrence. Further, X-ray photoelectron spectroscopy (XPS) analysis was performed to determine the binding energy of the compound formed at the clad zone, which can predict the most significant phase for the alteration of the mechanical behavior of the solid lubrication clad.

Wire arc additive manufacturing (WAAM) was employed to fabricate 4043 aluminum alloy walls. To investigate the effects of sinusoidal, triangular, and rectangular waveforms of alternating current (AC) and their transients on the wall geometry, microstructure evolution, hardness, and wear properties were evaluated. The root mean square (RMS) current value was maximum for the rectangular and minimum for the triangular waveform. The section produced by the triangular waveform had the highest height-to-width ratio, indicating that this waveform can be a favorable choice for creating components using WAAM. The optical micrographs of the transverse cross-section of the printed sections revealed the grain structure produced with this waveform to be heterogeneous, having a columnar dendritic structure at the bottom and equiaxed at the top portion. The waveforms also had an impact on the hardness and wear characteristics of all the walls, which were attributed to their cooling rate.