Indian Institute of Technology Kharagpur

About: Indian Institute of Technology Kharagpur is a education organization based out in Kharagpur, India. It is known for research contribution in the topics: Computer science & Dielectric. The organization has 16887 authors who have published 38658 publications receiving 714526 citations.

Thermal reduction of graphene oxide: How temperature influences purity

Abstract: Among various methods used for the reduction of graphene oxide (GO) into a purer form of graphene, the thermal reduction method provides a simpler, safer, and economic alternative, compared to other techniques. Thermal reduction of GO causes significant weight loss and volume expansion of the material. Current work investigates the onset temperature where reduction in terms of exfoliation takes place, which is determined to be 325 °C at standard atmospheric pressure. Reduction temperature plays the most crucial role as it controls the quality of reduced graphene oxide in terms of weight percentage of carbon and lattice defect. The study leads to achieving highest content with a minimum defect in the graphene lattice at the optimum temperature, which is found to be 350 °C at standard atmospheric pressure. The thermal reduction process has been analyzed with the help of Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal degradation kinetics. From thermal degradation kinetics of GO, the rate of reaction has been found to be independent of concentration and is a sole function of temperature.

Green synthesis of graphene.

Abstract: The present work reports a green route to synthesis of graphene by reduction of graphite oxide with cocos nucifera L. (coconut water) as reducing agent which is naturally available, non-toxic and environmental friendly. The graphite oxide has been prepared by oxidation of graphite with KCIO3/NaNO3/H2SO4 as reported in our earlier findings. X-ray diffraction, FTIR, UV-Visible and Raman spectroscopy confirmed the formation of graphene. SEM, TEM and AFM analyses have also been carried out to study the morphological characteristics of the obtained product. Also, TG analysis presents the thermal stability behavior of the formed product. Zeta potential measurements were also carried out to determine the surface charge characteristics.

Reliability Properties of Reversed Residual Lifetime

Abstract: If the random variable X denotes the lifetime (X ≥ 0, with probability one) of a unit, then the random variable X t = (t − X|X ≤ t), for a fixed t > 0, is known as `time since failure', which is analogous to the residual lifetime random variable used in reliability and survival analysis. The reversed hazard rate function, which is related to the random variable X t , has received the attention of many researchers in the recent past [(cf. Shaked, M., Shanthikumar, J. G., 1994). Stochastic Orders and Their Applications. New York: Academic Press]. In this paper, we define some new classes of distributions based on the random variable X t and study their interrelations. We also define a new ordering based on the mean of the random variable Xt and establish its relationship with the reversed hazard rate ordering.

Parallel-Connected Shunt Hybrid Active Power Filters Operating at Different Switching Frequencies for Improved Performance

Abstract: This paper proposes a combination of low- and high-frequency hybrid active power filter (APF) to operate in parallel for better performance. The individual hybrid APF is a series combination of L-C filter with the corresponding voltage source inverter. The dc links of both the inverters are connected in parallel, and the voltage of the dc link is maintained by the low-frequency inverter (LFI). The low- and high-frequency inverters eliminate lower order and higher order harmonics, respectively. In addition, it is possible to design the LFI such that it can also compensate the reactive power of the load. The individual L-C filter of the hybrid topology is designed to take care of specific order of harmonics that are predominant in the load. A combination of feedforward and feedback controller is designed for the proposed conditioner. The performances of the proposed topology and the controller are first examined by MATLAB/SIMULINK-based simulation. An experimental prototype is also designed to confirm the usefulness of the proposed system.