T. Ganga Devi

Thermal decomposition of cubic ammonium perchlorate—the effect of barium doping

Abstract Isothermal decomposition of cubic ammonium perchlorate (AP) has been studied as a function of concentration of barium dopant by thermogravimetry in the temperature range 530–550 K. The rate of decomposition first passes through a minimum and then a maximum showing opposite effects, as the dopant concentration increases. The decomposition kinetics of both pure and doped AP was found to be best described by first order rate law with an activation energy (E) of ca. 138 kJ mol−1. The results favour an electron-transfer mechanism

Thermal decomposition kinetics of zirconyl oxalate, zirconyl oxalic acid and ammonium zirconyl oxalate

Abstract The thermal decomposition studies of zirconyl oxalate (ZO), Zirconyl oxalic acid (HZO) and ammonium zirconyl oxalate (NZO) have been earned out in air by TG, DTG and DTA techniques. The kinetic parameters (non-isothermal method) for their main oxalate decomposition step have been evaluated using the method suggested by Horowitz and Metzger. The results indicate that the values of E and A for the main oxalate decomposition step of these compounds are in the order ZO ≈ HZO

Effect of precompression on the thermal stability of solids

Abstract Thermal decompositions of precompressed and uncompressed samples of KBrO3, KMnO4 and NH4ClO4 have been studied by thermogravimetry under isothermal conditions in static air. The rate of decomposition increased with increase in the applied pressure in the case of the last two solids, but the rate dramatically decreased in the case of KBrO3. The results indicate that precompression generally sensitizes electron transfer reaction as a result of an increase in the dislocation density, whereas it desensitizes diffusion-controlled reactions as a result of the densification of solid matrix. The method of precompression is suggested as a quick and simple tool for testing whether a decomposition reaction is diffusion controlled or not.

Numerical data for the evaluation of kinetic parameters of solid state decompositions by the non-isothermal method

Abstract Determination of the kinetic parameters of the thermal decomposition of solids usually requires a knowledge of the function g (α), describing the mechanism of decomposition. An effective and fast method is described for the determination of kinetic parameters from a single non-isothermal curve. Numerical data in the form of a ready reference table are given from which the kinetic parameters can be obtained once the correct form of g (α) has been established.

Effect of Particle Size on Non-Isothermal Decomposition of Potassium Titanium Oxalate

Abstract The effect of particle size on the thermal decomposition of potassium titanium oxalate (PTO) has been studied using TG-DTA-DTG techniques in nitrogen atmosphere at different heating rates. The thermal decomposition of PTO undergoes through five stages, finally forming the stable potassium titanate. The theoretical mass loss data agree very well with experimental data for all stages of the thermal decomposition of PTO. The third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, were subjected to kinetic analyses by a model free method, which is based on the isoconversional principle. We observed that both the onset and peak temperatures in DTA and DTG and the apparent activation energy are independent of particle size. The kinetic results indicate that the third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, undergoes through a single step.