This research delves into the tribological performance of hybrid aluminum metal matrix composites (HAMMCs) incorporating zirconium diboride (ZrB₂) particles and fly ash as reinforcing agents. The study employs a linear reciprocating wear test to investigate the impact of dry sliding wear on these HAMMCs under ambient and elevated temperatures. Wear mechanisms are discerned through field emission scanning electron microscopy. Optimization of wear test parameters, coefficient of friction (COF), and wear rate is achieved using the genetic algorithm. Additionally, artificial neural network (ANN) and multiple linear regression analysis are employed to formulate a predictive model for wear, estimating specific wear rate and COF under various testing conditions. The ANN predictions exhibit a deviation ranging from 0% to 1.39% from the experimental values, indicating the model's effectiveness in understanding and predicting wear behavior in the study of HAMMC.

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.