Comparative thermal kinetic analysis of Nickel hydroxide nanoparticles through Chemical precipitation and Sol-gel routes

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Abstract In most of the chemical methods, the as-prepared NPs have metal hydroxide form. The calcination temperature is very important to prepare the metal oxide from metal hydroxide. On the other hand, calcinations is a commonly used treatment method to increase the crystallinity and activity of the prepared NPs. Thus, in the present work, the chemical precipitation and sol-gel routes were employed to produce the Nickel hydroxide nanoparticles and analyse their functional, structural and thermal behavior of prepared NPs using FTIR, XRD and TGA/DTG. The formation of Ni(OH)2 is confirmed by FTIR analysis including both techniques. The crystallite size values are 15.55 ± 1.65 and 4.11 ± 1.37 nm for chemical precipitation and sol-gel respectively. The kinetic factors of thermal activation energy (Ea), order of decomposition (n), and frequency factor (Z) were calculated using Sharp–Wentworth, Freeman-Carroll, MacCallum-Tanner, Coats-Redfern, Horowitz–Metzger, and Broido. The thermo dynamical factors were identified from thermal activation energy. The Phadnis–Deshpande model is employed to identify the mechanism of solid state kinetic reaction. The thermal activation energy are 10.23 KJmol− 1 for both methods. Solid state kinetic model observe a nucleation and nuclei growth (Avrami-Erofeev nuclei growth) and 2D diffusion mechanism for chemical precipitation and Sol-gel respectively. For both procedures, a temperature of 300°C is regarded the minimum appropriate temperature for further calcinations. From the kinetic parameters, we may also conclude that the decomposition of Ni(OH)2 to NiO is thermally stable, slow reaction and spontaneous process at the reported temperature.

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