Influence of irradiation on the thermal decomposition of lithium perchlorate

Abstract

Abstract The influence of Co-60 gamma-irradiation, up to 500 Mrad, on the kinetics of the thermal decomposition of lithium perchlorate has been studied over the temperature range 400–440°C. The material (m.p. 236°C) decomposes in the molten state and the lithium chloride formed remains dissolved initially but separates out as solid after about 50% decomposition. Decomposition occurs in four stages, viz., (i) initial gas evolution, (ii) induction, (iii) acceleratory and (iv) decay. Kinetic analysis of stages (i) and (ii) could not be made with any degree of certainty. The acceleratory and decay stages analyse according to the Prout-Tompkins relationship, first order law, and the contracting volume formula with two constants in each case, one for the acceleratory and the other for the decay stage. Activation energies for these two stages calculated from the Prout-Tompkins constants are 64.1 and 33.3 kcal mole−1 respectively. Irradiation increases initial gas evolution and shortens the induction period. It also enhances the rate constants in the acceleratory and the decay stages. Moreover, whereas the activation energy for the acceleratory stage is slightly diminished that for the induction and the decay stages is unaffected. The chemical reaction occurring is the rupture of the Cl─O bond (64.3 kcal) with the ultimate formation of lithium chloride as evident from the activation energies in the induction and the acceleratory stages. After about 50% decomposition, when lithium chloride separates out as solid, further decomposition occurs at the lithium chloride-lithium perchlorate interface because of which the activation energy is much lowered.