Maharshi Dey

The poor tribological and mechanical performance of Al alloys hinders their use in practical applications where low COF and high durability are required. This study examined and evaluated a novel laser-sintered Ni-Cr coating to improve the load-carrying capacity and tribological performance of an Al alloy (Al 6061) substrate. The authors demonstrate that laser sintering cycle count is a decisive process variable governing coating dispersion, microstructural consolidation, and tribological performance in Ni-Cr coatings fabricated via Selective Laser Sintering (SLS). Increasing the laser cycle count progressively refined the surface morphology, improved coating dispersion, and strengthened interparticle bonding. As a result, the average durability after three cycles was seven times that after one laser cycle, accompanied by markedly improved COF. To further improve durability and load-carrying capacity, Ti₃SiC₂ was introduced into the Ni-Cr coating. The coating containing 10 wt% Ti₃SiC₂ exhibited a 20-fold increase in durability, extending the time to failure to approximately 70,000 s (700 m) while maintaining a low coefficient of friction (~0.48) compared with the coating containing no Ti₃SiC₂. The greater durability of the Ni-Cr-10wt%Ti₃SiC₂ coating in this novel study was attributed to improved adhesion to the substrate, better particle distribution during sintering, and greater load-carrying capacity. While further process changes do not yield feasible samples, this study showed that surface properties can be improved within the available small-process regime. Overall, laser sintering of a Ni-Cr-10wt%Ti₃SiC₂ coating shows promise as a means to improve the tribological and mechanical performance of Al 6061. This study should aid researchers and other stakeholders in fabricating well-adhering, durable, and tribotactic composite coatings on Al6061 and similar material systems.

The major challenges in designing a Hybrid Renewable Energy System (HRES) include selecting appropriate renewable energy sources and storage systems, accurately sizing each component, and defining suitable optimization criteria. This study addresses these challenges by employing Particle Swarm Optimization (PSO) within a multi-criteria optimization framework to design an HRES in Kern County, USA. The proposed system integrates wind turbines (WTS), photovoltaic (PV) panels, Biomass Gasifiers (BMGs), batteries, electrolyzers (ELs), and fuel cells (FCs), aiming to minimize Annual System Cost (ASC), minimize Loss of Power Supply Probability (LPSP), and maximize renewable energy fraction (REF). Results demonstrate that the PSO-optimized system achieves an ASC of USD6,336,303, an LPSP of 0.01%, and a REF of 90.01%, all of which are reached after 25 iterations. When compared to the Genetic Algorithm (GA) and hybrid GA-PSO, PSO improved cost-effectiveness by 3.4% over GA and reduced ASC by 1.09% compared to GAPSO. In terms of REF, PSO outperformed GA by 1.22% and GAPSO by 0.99%. The PSO-optimized configuration includes WT (4669 kW), solar PV (10,623 kW), BMG (2174 kW), battery (8000 kWh), FC (2305 kW), and EL (6806 kW). Sensitivity analysis highlights the flexibility of the optimization framework under varying weight distributions. These results highlight the dependability, cost-effectiveness, and sustainability for the proposed system, offering valuable insights for policymakers and practitioners transitioning to renewable energy systems.

In this study, the dry sliding characteristics of a Ti₃SiC₂/Ti₅Si₃ matrix reinforced with different TiC contents against a 100Cr6 steel ball were investigated. The composites were fabricated using the spark plasma sintering method with Ti, SiC, and C powders. SEM revealed that the composites possessed damage tolerance behavior, where grain pull-out, buckling, delamination, and diffuse microcracking were observed. In comparison, the unreinforced composite showed severe adhesive wear and tribo-oxidative wear mechanisms. The integration of the TiC phase in the Ti₃SiC₂/Ti₅Si₃ matrix enhanced the wear resistance by at least one order of magnitude. A new wear regime was observed in the TiC-reinforced composites, classified as mild wear, where tribo-oxidation and third-body abrasion were dominant, with ferrous deposits on the sliding surfaces.

In this paper, we report the synthesis of Cr ₂ AlC by using biochars derived from lignin, Distiller's dried grains with solubles (DDGS), and hemp fibers. Initially, the powders were pyrolyzed at 1350°C for 4 h in Ar atmosphere to form biochars. The ball‐milled and sieved biochar powders were then mixed with Cr and Al powders in different stoichiometric ratios according to the C‐content of the biochars. The mixed powders were reacted at 1350°C for 4 h in Ar atmosphere. Detailed scanning electron microscopy and X‐ray diffraction analysis showed the powders derived from hemp and DDGS biochars were > 90% pure as compared to powders derived from lignin biochar which was 76% pure. It is expected that ternary ceramics derived from biochars can be an addition avenue for carbon‐storage.

In this paper, we report the synthesis and characterization of composites of bioplastics (Poly‐lactic Acid (PLA), Polyhydroxyalkaonate (PHA), and PLA‐PHA blends) filled with dried grains with solubles (DDGS) and hydroxyapatite (HAP) by using a solvent casting process. Detailed microstructural, thermal, and mechanical characterization is presented in the text. At low concentrations of HAP (5–10 vol%) and DDGS (5–31 vol%) additions, the bioplastic films had mechanical integrity, but the ultimate tensile strength (UTS) decreased after the addition of DDGS and HAP reinforcements due to poor adhesion between the bioplastics and fillers. In the intermediate concentration, pre‐pregnated chips of DDGS (31–51 vol%)‐bioplastics and HAP (30–50 vol%)‐bioplastics with dichloromethane (DCM) were partially dried and then hot‐pressed to produce bulk samples (HPC‐process). The addition of bioplastics improved the plasticity of DDGS‐bioplastics composites. The HAP‐bioplastics composites showed polymer dependent response, for example the ultimate compressive strength (UCS) of 50%HAP‐PLA, and 30%HAP‐PLA were 77.6 ± 10.2 and 97.7 ± 5.9 MPa, respectively which are comparable to bone. The DDGS additions increased the hydrophilicity of PLA, PHA, and PLA‐PHA blend. For comparison, HAP increased the hydrophilicity of PHA and PLA‐PHA blends. At higher concentration (bioplastics with 70 vol% HAP additions), the films converted into microencapsulated HAP particles with bioplastics by a simple milling process thus eliminating the need for emulsions and/or surfactants during the microencapsulation process.

In this paper, we report the synthesis and characterization of pyrolyzed lignin compacts reinforced with 50 wt % wheat straw (WS) or sugar beet pulp (SBP) fibers. The compacts were pyrolyzed at 300, 500, 700, and 900 °C in an Ar atmosphere. Detailed thermogravimetric analysis (TGA), thermomechanical analysis (TMA), Fourier transform infrared (FTIR) spectroscopy, and microstructure analysis were performed on these samples. FTIR analysis showed that pyrolysis of lignin–WS and lignin–SBP resulted in aromatic char. Scanning electron microscope (SEM) studies showed that foams obtained by pyrolyzing both lignin–50 wt % SBP and lignin–50 wt % WS composites have a cellular structure. X-ray tomography and energy-dispersive spectrometry (EDS) studies showed that pyrolysis of wheat straw caused the formation of mineral-rich nodules in the pyrolyzed lignin matrix, which was responsible for the denser and uniform microstructure of the lignin–WS composites. Due to this reason, the lignin–WS composites were denser and had a better mechanical strength as compared to the lignin–SBP composites. Both the compositions also showed temperature-dependent wettability behavior.