Chennai Institute of Technology

Expanded graphite (EG), a derivative of graphite with a unique worm-like porous structure, has become popular owing to its exceptional thermal, electrical, and chemical properties. EG is combined with phase-change materials (PCM) to form a composite PCM with enhanced properties, and EG serves as a functional additive. This review explores the preparation of EG, along with a detailed study of its properties and characterization. Various preparation methods for EG, including thermal, chemical, and electrochemical processes, are elaborately explained with detailed analyses of the temperature, intercalating agent, and reaction time to achieve the final material property. This review further examines the role of EG in combination with PCM for energy storage systems and building applications, highlighting the advantages and disadvantages of using EG in these fields. The current challenges faced by the addition of EG, including optimization and large-scale production, are briefly discussed. Finally, future research directions for EG are proposed, explaining the setup of the current technology. The review concludes with the importance of EG in guiding the development of new materials for the next generation, considering the balance between the performance and cost of the material.

This study examines the influence of silicon carbide (SiC) particle size on the mechanical performance of AA7075/SiC composites fabricated via microwave sintering. Composites reinforced with SiC particles of varying sizes (60.7, 10.91, 5.33, and 0.73 μm) were synthesized, and their tensile strength, compressive strength, hardness, impact energy, and relative density were systematically evaluated. Microstructural characterization, including x-ray diffraction (XRD), was performed to elucidate the mechanisms governing the observed behavior. The results reveal a progressive improvement in mechanical properties with decreasing particle size. The composite reinforced with 0.73 μm SiC exhibited the highest tensile strength ( 362 MPa) and compressive strength ( 451 MPa), while intermediate particle sizes of 5.33 and 10.91 μm showed moderate improvements compared to the coarse 60.7 μm reinforcement, which exhibited comparatively lower strength. These improvements are primarily attributed to strong interfacial bonding, reduced porosity, and the activation of multiple strengthening mechanisms, such as the Orowan strengthening, and Zener grain pinning. Microwave sintering facilitated uniform densification and microstructural homogeneity, yielding a maximum relative density of 98.26

The consistent detection of low-level carbon monoxide (CO) and methane (CH 4 ) is important for safety, environmental monitoring, and early leak identification. Semiconductor metal oxides are considered to be the most promising candidates for such applications. However, their performance is usually hindered by limited speed and less sensitivity. Herein, three heterojunction systems—ZnO/SnO 2 (Z/S) (n–n), NiO/ZnO (N/Z) (p–n), and SnO 2 /NiO (S/N) (p–n)—were synthesized through a controlled hydrothermal route. A systematic comparative study of these n–n and p–n interfaces is carried out to determine the most effective heterojunction structure for improved room-temperature CO and CH 4 sensing performance. Structural and morphological studies have proved a well-defined interface with homogenous surface features. In fact, the phase purity was well proved by X-ray diffraction, the homogeneous element distribution was identified by field emission scanning microscopy/energy dispersive X-ray spectroscopy, and the surface roughness was decreased, as determined by atomic force microscopy 2D/3D profiles with R a values of 81.547 nm (Z/S), 46.084 nm (N/Z), and 24.272 nm (S/N). Ultraviolet–visible spectroscopy confirmed the sequential bandgap narrowing: 3.2 eV for Z/S, 2.6 eV for N/Z, and 2.4 eV for S/N, indicative of enhanced electron interaction across the interfaces. J–V measurements exhibited diode-like behavior, showing a sequential decrease in cutoff voltage to 0.7, 0.6, and 0.4 V, respectively. Accordingly, electrochemical impedance spectroscopy analysis showed a decrease in charge-transfer resistance from 16.2 to 2.2 and 1.4 kΩ. Improved electron mobility has also been demonstrated from thickness measurements, which revealed that the S/N film exhibited the thinnest layer (0.4 μm) relative to Z/S (2.0 μm) and N/Z films (1.4 μm). This was further emphasized in the gas-sensing experiment, which demonstrated the clear omnipotence of the S/N heterostructure; hence, it enabled a fast response/recovery time of 15/24 s for CO and 18/42 s for CH 4 at low concentrations with high sensitivity and long-term stability in ambient conditions. The improved sensing ability could be ascribed to the strong p–n junction, smallest depletion width, and low interfacial resistance. Moreover, the sensing ability of the sensor was validated using machine learning algorithms, wherein consistently, the Random Forest (RF) algorithm appeared to have a stronger predictive power than Support Vector Machine (SVM). In fact, RF performed better than SVM by achieving higher R-Squared (R 2 ) values for each regression problem, which were generally in the range of 0.80–0.85 compared to the lower and more fluctuating performance of SVM. Likewise, a drift was noticed in the classification performance where RF achieved accuracies of 0.91/0.88 for CO and 0.93/0.89 for CH 4 under A1 and A2 scenarios, respectively, outperforming SVM in all cases. Finally, this study hereby confirms that the concept of heterojunction, specifically the S/N interface, combined with machine learning-assisted analysis, provides a promising route forward for the realization of next-generation room temperature gas sensors with high sensitivity, fast response, and accurate predictive capabilities.

Poly(3,4-ethylenedioxythiophene)–polyindole (PEDOT–PIn) is a distinguished π-conjugated conducting polymer; however, its inherent brittleness and loosely arranged molecular framework hinder its long-term operational reliability in practical devices. To address these shortcomings, a novel niobium nitride (NbN)–PEDOT–PIn hybrid nanocomposite is synthesized, featuring a mechanically stable three-dimensional network formed by embedding PEDOT–PIn nanostructures within stratified layers of NbN through a controlled oxidative polymerization strategy. This multifunctional material functions both as a high-efficiency electrode for electrochemical energy storage and as an effective catalyst for electrochemical and photocatalytic applications. The hybrid material exhibits outstanding electro catalytic sensitivity toward Fenbendazole (FNB), as assessed by differential pulse voltammetry (DPV). As an energy storage medium, the NbN–PEDOT–PIn composite enables rapid and reversible ion storage processes, as demonstrated by galvanostatic charge–discharge (GCD) testing, where the hybrid electrode delivers a high specific capacitance(SC) of 680 F g−1 at a current density of 1 A g−1. Cyclic voltammetry (CV) and log–log plot analysis confirms a capacitive contribution exceeding 97

Interest in waste-to-energy technologies, especially the co-pyrolysis of biomass, food, and plastic waste, has grown as a result of the world’s significant increases in waste production and energy demand. In this study, energy-rich biofuel and value-added chemicals were recovered from waste materials. The feedstocks used were fish waste, sugarcane bagasse, and waste plastics. The plastics included polyethylene (PE), polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE). These wastes were collected from commercial, agricultural, and residential sectors. The experiments were carried out with the motive of producing more pyrolysis liquid by blending fish waste with waste plastics (FWP) and sugarcane bagasse with waste plastics (SBP) in equal proportions in a fixed bed reactor under different operating temperatures between 350 °C and 550 °C. The maximum oil product yields for the pyrolysis of FWP were 52.0 wt