Annamalai University

Plasma Arc Welding (PAW) is an advanced fusion welding technique extensively employed for manufacturing components intended for high-temperature and corrosive service environments, such as aerospace expansion joints, metallic bellows, and exhaust system components. Among its variants, Melt-in-Mode Plasma Arc Welding (MIM-PAW) is particularly suitable for joining thin sheets with thicknesses ranging from 1 to 2.4 mm. It is recognized as highly effective for welding Inconel 625, an austenitic nickel-based superalloy known for its excellent mechanical strength, oxidation resistance, and thermal stability. Owing to these characteristics, Inconel 625 is widely used in liquid rocket engine components, gas turbine engines, and other high-temperature engineering applications. Although the alloy can be welded using several fusion welding processes, including gas tungsten arc welding, electron beam welding, and laser beam welding, MIM-PAW offers tremendous control and produces high-quality joints in medium-thickness sheets. The present study examines the influence of welding current on the metallurgical and mechanical behaviour of 2.4 mm thick Inconel 625 butt joints produced by MIM-PAW. Defect-free welds were fabricated using optimized parameters of 70 A welding current, 130 mm/min travel speed, 1 L/min plasma gas flow rate, and 4.5 mm arc length. The optimized joint exhibited a bead width of 5.748 mm, HAZ width of 0.1266 mm, fusion zone area of 7.915 mm², and HAZ area of 1.796 mm². The joint achieved an ultimate tensile strength of 872 MPa, yield strength of 566 MPa, elongation of 36%, notch strength of 918 MPa, notch strength ratio of 1.05, and joint efficiency of 92.96% at a heat input of 351 J/mm. Microstructural observations revealed that lower welding currents produced finer, equiaxed grains, whereas higher currents promoted grain coarsening and elongated grain morphology.

Dengue and chikungunya are arboviral diseases mainly vectored by the mosquito Aedes aegypti. Presently, there is no treatment for these viral diseases and their prevention is still based on vector control measures. Nanopesticides fabricated using herbal extracts as reducing and capping agents currently represent an excellent platform for pest control. In this scenario, the present study assessed the acute toxicity of seven plants employed in ethno-veterinary medicine of southern India, as well as the green synthesis of zinc oxide nanoparticles, on third-instar larvae of A. aegypti. Larvae were exposed to extracts of the seven plants obtained with solvents of different polarity (acetone, ethanol, petroleum ether, and water) for 24 h. Maximum efficacy was observed for Lobelia leschenaultiana leaf extracts prepared using all the four solvent extracts (LC50 = 22.83, 28.12, 32.61, and 36.85 mg/L, respectively). Therefore, this plant species was used for the synthesis and stabilization of ZnO nanoparticles based on its maximum efficacy against third-instar larvae of A. aegypti. L. leschenaultiana-encapsulated ZnO nanoparticles showed 100% mortality when tested at 10 mg/L, the LC50 was extremely low,  1.57 mg/L. Zinc acetate achieved only 65.33% when tested at 60 mg/L, with a LC50 of 51.62 mg/L. Additionally, ZnO nanoparticles inhibited growth of Pseudomonas aeruginosa, Proteus vulgaris, Shigella sonnei, and Vibrio parahaemolyticus and also inhibited biofilm formation on selected microbila pathogens, showing impact on EPS production and hydrophobicity. Overall, our results suggest that L. leschenaultiana-fabricated ZnO nanoparticles have a significant potential to control A. aegypti mosquitoes and Gram-negative bacterial pathogens.

Exploring a cost-effective, robust electrocatalyst with long-term durability continues to be challenging for large-scale hydrogen production. Here, we present a green, electricity-free mechanochemical synthesis of a multifunctional Pd-H-Mo-/Co-N electrocatalyst, demonstrating outstanding performance for OER, HER, OWS, HzOR, MOR, UOR, and SOR in alkaline seawater with the required potentials of 1.59, 1.49, 1.55, 1.45, 1.49, 1.51, and 1.60 V @ 10 mA/cm2, respectively; it has strongly coupled metal/metal nitride synergy, which improves catalytic performance, combining high specific energy, large surface area, and improved electron transfer through energy-efficient green synthesis. The Pd-H-Mo-/Co-N, with the smallest phase angle in the Bode plot, indicated that the Pd-doped heterointerface effectively enhanced the deprotonation ability to accelerate the reaction kinetics. Pd-H-Mo-/Co-N, with a smaller activation energy of 6.40 kJ/mol, required less overpotential to overcome the barrier and efficiently drive water oxidation than H-Mo-/Co-N (11.43 kJ/mol). The higher rate constant for Pd-H-Mo-/Co-N extracted from the Trumpet plot indicated the rapid formation of O2. The solar-driven water electrolysis (1.55 V) with comprehensive environmental assessments affirms the sustainability and scalability of Pd-H-Mo-/Co-N as a robust platform for large-scale hydrogen generation. This research offered a green synthetic route for multifunctional electrocatalysts, which can assist in H2 production and degrade pollutants in wastewater simultaneously. The proposed path completely eliminates hazardous byproducts, reduces material costs, and operates under ambient conditions, providing a scalable and environmentally benign pathway for the production of green hydrogen. Also, our findings establish a new model for the design of multifunctional electrocatalysts, advancing the projections of a sustainable hydrogen economy by providing an outline for near-future energy and environmental technologies.

The organic crystal 4-nitrophenol 4-aminobenzoic acid monohydrate (4NP4ABA) was synthesized by slow evaporation at room temperature. Single-crystal and powder X-ray diffraction confirmed a monoclinic structure. Hirshfeld surface analysis with fingerprint plots provided quantitative insight into the intermolecular interactions influencing crystal packing. Surface quality was assessed using chemical etching, while FT-IR spectroscopy was used to identify functional groups. Tauc’s plot was used to determine the energy band gap, and fluorescence spectroscopy revealed strong green-yellow emission at 550 nm. Dielectric studies of 4NP4ABA showed a decrease in dielectric constant and loss with increasing frequency, whereas higher temperatures resulted in improved conductivity. The Cole–Cole impedance spectrum obtained from the crystal revealed that resistivity decreased with increasing temperature. Overall, 4NP4ABA exhibits favourable optical and electrical properties, making it a promising candidate for advanced materials applications.

Nanotechnology has introduced transformative advancements in the food industry, significantly improving food safety, quality, and sustainability. This review provides a comprehensive review of the role of nanotechnology in various aspects of food development, including packaging, processing, storage, and safety protocols. It highlights the innovative applications of nanomaterials in enhancing food bioavailability, optimizing texture, and refining taste. The synthesis of magnetic nanoparticles (MNPs) and encapsulation technologies are explored for their role in preserving and delivering bioactive ingredients and flavours. Additionally, the integration of nano sensors into smart and active packaging systems offers new opportunities for real-time monitoring of food quality and safety. The review also discusses the toxicological impacts of nanomaterials and emphasizes the need for continued research in this rapidly evolving field. Overall, nanotechnology has the potential to revolutionize food production, ensuring improved safety and sustainability while meeting the growing global demand for quality food products.