K. Jayasankar

Shear-force-dominated dual-drive planetary ball milling for the scalable production of graphene and its electrocatalytic application with Pd nanostructures

The exceptional properties of graphene-based derivatives have governed numerous research fields in recent years. The scaled up and reliable production of high-quality graphene is still a challenging task. This work presents an efficient and low-cost approach for the mass production of high-quality graphene (50 g scale batch) through the dual-drive planetary ball milling of graphite with a dicarboxylic acid. The dimensional changes of graphite were determined from the diffraction pattern of the (002) plane at different milling times and the unique signature of graphene noticed in the Raman spectra. Transmission electron microscopy clearly revealed the existence of single and bilayer graphene sheets. Non-destructive exfoliation was evidenced by the surface binding states of the C 1s core level spectra. The as-synthesized graphene was utilized as the catalytic support for formic acid fuel cell applications. Graphene supported palladium nanocomposites were prepared, and the electrocatalytic activity towards formic acid oxidation was explored. The cyclic voltammogram of the graphene–palladium nanocomposite reveals that the onset potential for formic acid oxidation is −0.1 V with a prominent oxidation peak at 0.263 V.

Statistical Modeling Studies of Iron Recovery from Red Mud Using Thermal Plasma

Optimization studies of plasma smelting of red mud were carried out. Reduction of the dried red mud fines was done in an extended arc plasma reactor to recover the pig iron. Lime grit and low ash metallurgical (LAM) coke were used as the flux and reductant, respectively. 2-level factorial design was used to study the influence of all parameters on the responses. Response surface modeling was done with the data obtained from statistically designed experiments. Metal recovery at optimum parameters was found to be 79.52%.

A novel approach for reducing toxic emissions during high temperature processing of electronic waste

A novel approach is presented to capture some of the potentially toxic elements (PTEs), other particulates and emissions during the heat treatment of e-waste using alumina adsorbents. Waste PCBs from mobile phones were mechanically crushed to sizes less than 1mm; their thermal degradation was investigated using thermo-gravimetric analysis. Observed weight loss was attributed to the degradation of polymers and the vaporization of organic constituents and volatile metals. The sample assembly containing PCB powder and adsorbent was heat treated at 600°C for times ranging between 10 and 30min with air, nitrogen and argon as carrier gases. Weight gains up to ∼17% were recorded in the adsorbent thereby indicating the capture of significant amounts of particulates. The highest level of adsorption was observed in N2 atmosphere for small particle sizes of alumina. SEM/EDS results on the adsorbent indicated the presence of Cu, Pb, Si, Mg and C. These studies were supplemented with ICP-OES analysis to determine the extent of various species captured as a function of operating parameters. This innovative, low-cost approach has the potential for utilization in the informal sector and/or developing countries, and could play a significant role in reducing toxic emissions from e-waste processing towards environmentally safe limits.

Microstructural Evolution of Nanocrystalline ZrO 2 in a Fe Matrix During High-Temperature Exposure

The current study examines the evolution of nanocrystallites of ZrO2 with time and temperature in a Fe-ZrO2 composite. The crystallite sizes were determined through X-ray peak broadening analysis by the Williamson–Hall method together with dark field transmission electron microscopy. The ZrO2 crystallites were found to be stable and retained their sizes at 973 K and 1073 K for hold durations up to 600 minutes. On the other hand, the crystallites were seen to grow at 1173 K and reached up to ~ 200 nm for a hold time of 600 minutes. The Ostwald ripening model was adopted to understand crystallite growth while a dislocation-driven pipe diffusion was adopted for understanding the kinetics of grain growth. The activation energy of grain growth was calculated as ~ 379 kJ mol−1. The modeled and experimentally calculated size evolutions with time and temperature were shown to be in good agreement with each other. A detailed discussion on the kinetics and activation energy of grain growth of ZrO2 crystallites in a Fe matrix is presented in this manuscript.