Thermal investigation of nanospheres and nanowhiskers of CuInS2

The nanospheres and nanowhiskers of ternary CuInS2 are synthesized by sonochemical and hydrothermal techniques, respectively. The energy dispersive X-rays showed the samples to be stoichiometric. The tetragonal unit cell structure of synthesized samples is characterized by X-ray diffraction. The corresponding morphology of the synthesized samples is studied by electron microscopy in scanning and transmission modes. The thermal investigation of the synthesized nanospheres and nanowhiskers is carried out by recording thermogravimetric (TG) and differential thermal analysis (DTA) curves. These simultaneous thermocurves are recorded in temperature range of ambient to 1253 K in an inert nitrogen atmosphere for three heating rates of 10, 15 and 20 K·min−1. The thermal study showed nanospheres to decompose by five steps and nanowhiskers to decompose in a single step. The kinetic parameters like activation energy, phonon frequency factor, activation enthalpy, activation entropy and Gibbs free energy change are determined for both samples. The kinetic parameters are evaluated from the thermocurves data using model-free isoconversion methods like Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO) and Friedman (FR). All the obtained outcomes are investigated in details.