This study aims to assess the impact of the water ratio and nanoparticle concentration of neat diesel fuel on the performance characteristics of and exhaust gas emissions from diesel engines. The experimental tests were conducted in two stages. In the first stage, the effects of adding water to neat diesel fuel in ratios of 2.5% and 5% on engine performance and emissions characteristics were examined and compared to those of neat diesel at a constant engine speed of 3000 rpm under three different engine loads. A response surface methodology (RSM) based on a central composite design (CCD) was utilized to simulate the design of the experiment. According to the test results, adding water to neat diesel fuel increased the brake-specific fuel consumption and reduced the brake thermal efficiency compared to neat diesel fuel. In the examination of exhaust emissions, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in the tested fuel containing 2.5% of water were decreased in comparison to pure diesel fuel by 16.62%, 21.56%, and 60.18%, respectively, on average, through engine loading. In the second stage, due to the trade-off between emissions and performance, the emulsion fuel containing 2.5% of water is chosen as the best emulsion from the previous stage and mixed with aluminum oxide nanoparticles at two dose levels (50 and 100 ppm). With the same engine conditions, the emulsion fuel mixed with 50 ppm of aluminum oxide nanoparticles exhibited the best performance and the lowest emissions compared to the other evaluated fuels. The outcomes of the investigations showed that a low concentration of 50 ppm with a small amount of 11 nm of aluminum oxide nanoparticles combined with a water diesel emulsion is a successful method for improving diesel engine performance while lowering emissions. Additionally, it was found that the mathematical model could accurately predict engine performance parameters and pollution characteristics.

The development of sustainable, high-performance friction composites is critical for the automotive industry, given the environmental and health concerns associated with conventional brake pad materials such as asbestos and copper. This study investigates the effect of incorporating micro- and nano-sized Al₂O₃, SiC, and carbon nanotubes (CNTs) into a novel, eco-friendly, asbestos-free, and copper-free brake pad formulation. Six composite samples were fabricated via a cold-pressing and hot-molding process: five formulations containing a single, size-controlled micro-/nano-sized reinforcement (Al₂O₃, SiC, and CNTs), and one reference formulation (CBP# Reference) containing an unrefined, commercial-grade combination of Al₂O₃ and SiC in place of the size-controlled additive. All formulations were rigorously characterized for their physical, mechanical, and tribological properties. The nano-Al₂O₃ formulation exhibited the highest density (2.197 g/cm³) and compressive strength (249.7 MPa), while the micro-SiC formulation achieved superior wear resistance, recording the lowest weight loss (0.0053 g) and the highest hardness (90 HV). The nano-SiC formulation offered the most balanced overall performance, combining high hardness (86.2 HV) with the highest average friction force (33.65 N) and the most stable friction-time response among all samples. The CNT-reinforced formulation produced the highest maximum friction force (42.07 N) but showed only moderate improvement in density, hardness, and compressive strength relative to the ceramic-reinforced samples. Compared with the CBP# reference, all five developed formulations exhibited higher hardness and coefficient of friction alongside lower weight loss, confirming their potential as durable, sustainable alternatives for automotive brake friction applications.