Reverse micro-EDM is the most suitable method for fabricating circular cross-section array microelectrodes. This work presents an experimental investigation into the effect of process parameters such as capacitance, voltage, and feed on the geometrical characteristics (diameter, length, and taper) of tungsten carbide (WC) array microelectrodes. Using a ø2 mm × 35 mm length rod of tungsten carbide, a 3 × 3 array of microelectrodes was fabricated with a 230 μm diameter hole in a copper sheet, providing a depth of 1.5 mm. Increasing the process parameters from 10 nF capacitance, 90 V voltage, and 0.3 mm min⁻¹ feed to 100 nF capacitance, 130 V voltage, and 0.9 mm min⁻¹ feed decreased the diameter by 6.75% and increased the taper of the electrodes by 3%. The ANOVA analysis indicates that capacitance, voltage, and feed significantly affect the geometrical characteristics of array microelectrodes. Using the multi-objective optimization technique grey relational analysis (GRA), it was found that at a capacitance of 10 nF, a voltage of 130 V, and a feed rate of 0.3 mm min⁻¹ achieved the minimum deviation in the geometrical characteristics of WC array microelectrodes. This paper will help determine the hole size required to achieve the specific dimensions on the array microelectrodes and select optimal process parameters.

This work reports the development of a sustainable Al7075 metal matrix composite reinforced with bio-derived activated carbon (AC) obtained from rice hull agricultural waste. Unlike conventional reinforcements such as SiC and Al₂O₃, rice hull-derived AC provides an eco-friendly, lightweight, and cost-effective alternative. The composites were fabricated using ultrasonic stir casting with varying AC contents (2–8 wt%). Microstructural characterization (OM, FESEM-EDS, and XRD) confirmed uniform dispersion of AC and the absence of detrimental Al₄C₃ formation. Mechanical testing revealed that 2 wt% AC yielded the optimum properties, improving hardness (by 21%) and tensile strength (by 23%) compared to unreinforced Al7075. Abrasive wear studies showed enhanced wear resistance and reduced coefficient of friction at the same reinforcement level. Beyond mechanical and tribological assessment, this work introduces a predictive framework using machine learning models (Gradient Boosted Trees, Gaussian Process Regression), which achieved near-perfect accuracy (R² > 0.99 for wear, R² > 0.96 for COF). These findings establish rice hull–derived activated carbon as a viable reinforcement for Al7075 composites and highlight the potential of data-driven approaches in predicting tribological performance, thereby advancing sustainable and intelligent material design.

The escalating global energy demand and environmental degradation driven by fossil fuel consumption necessitate urgent transitions to sustainable alternatives. This comprehensive review examines biodiesel production via the transesterification route, emphasizing feedstock diversity, catalyst efficacy, and the physicochemical properties of biodiesel that influence diesel engine performance and emissions. First- to fourth-generation biofuels are critically analyzed, emphasizing the advantages of non-edible feedstocks such as Jatropha and algae, along with the use of efficient heterogeneous catalysts like CaO and KF/CaO. These catalysts enable high biodiesel yields, achieving up to 82.3% from Jatropha carcass oil and 69.3% from Karanja oil, while simultaneously minimizing food-security concerns. The basic properties of biodiesel such as viscosity, density, cetane number, and iodine value have a direct bearing on combustion efficiency, emission rates, and low temperature performance. Engine test result indicated that biodiesel blends are more environmentally friendly than fossil diesel as they significantly reduce carbon dioxide and hydrocarbon emissions. Although the higher oxygen content of biodiesel contributes to more complete combustion, it can also result in a moderate increase in nitrogen oxide (NOx) emissions. Among various feedstocks, rapeseed and algal biodiesels demonstrate an optimal balance between emission reduction and thermal efficiency, making them promising candidates for practical applications. In contrast, biodiesels derived from feedstocks with elevated cloud points, such as mustard oil, exhibit poor low-temperature flow properties, which can limit their suitability in colder climates. Overall, this study reaffirms the potential of transesterification-derived biodiesel as a sustainable and efficient alternative to conventional diesel, provided that feedstock selection, catalyst formulation, and emission mitigation strategies are effectively integrated within regional energy and environmental policy frameworks.