| dc.description.abstract | The thesis embodies studies on the thermal decomposition of hydrazinium mono? and di?perchlorates. Using differential thermal analysis, thermogravimetric analysis, X?ray, constant volume pressure technique and mass spectrometry, the decomposition products, the activation energies and the decomposition mechanisms have been determined.
The perchlorates of hydrazine, namely, hydrazine monoperchlorate (HP?1) and hydrazine diperchlorate (HP?2), attract attention because they are potentially high?energy solid rocket propellant oxidizers. Although they are energetically preferable to ammonium perchlorate, they have not yet found use as propellant oxidizers because of their explosive sensitivity. One of the objectives of the present work was to control the thermal decomposition of these salts, thereby possibly controlling the explosive sensitivity of hydrazinium perchlorates and making them useful as solid rocket propellant oxidizers. A prerequisite to the control is the understanding of the mechanism of thermal decomposition.
There have been only two detailed investigations carried out so far on the thermal decomposition of hydrazinium monoperchlorate, and there is only one paper reported in literature on the thermal decomposition of hydrazinium diperchlorate.
In the case of hydrazinium monoperchlorate, a critical analysis of the previous work reveals that there are disparities in the results of different schools. There are wide differences in the reported activation energies and decomposition products. These differences may be ascribed primarily to (i) different nature of the material used by these schools; one of them used the dehydrated HP?1, while the other used the hemihydrate as such, (ii) different temperature ranges over which the investigations have been carried out, and (iii) possible effects of the gaseous products: one group of workers allowed the decomposition gases to accumulate over the solid, while the other group either allowed the gaseous products to escape or trapped the condensibles in a liquid nitrogen trap.
The present work attempts firstly to resolve the discrepancies in the results of previous workers on the thermal decomposition of HP?1 and get a better insight into the mechanism of its decomposition, and secondly to study the thermal decomposition of HP?2 in greater detail on which there is only one paper in the literature.
Studies have been carried out on the thermal decomposition of (i) pure hydrazinium monoperchlorate in the molten and solid states, (ii) doped hydrazinium monoperchlorate in the molten and solid phases, and (iii) pure and doped hydrazinium diperchlorate. Further, the effect of particle size, ageing and pre?irradiation on the thermal decomposition of hydrazinium diperchlorate has been studied.
Results of the present investigation on the thermal decomposition of hydrazinium perchlorates are summarised below:
Hydrazinium monoperchlorate decomposes both in the solid and molten states. The solid?state decomposition of HP?1 has been observed for the first time. Allovalent anion impurities have been found to accelerate the decomposition while allovalent cation impurities retard the reaction. The mechanism of thermal decomposition is speculated to involve the migration of either ClO?? or H? ions to a preferential site where proton transfer might take place.
The activation energy and decomposition products for the molten?state decomposition of HP?1 have been found to be essentially the same as reported by Jacobs and Russell?Jones. It has been proposed that the decomposition proceeds via the formation of an associated complex. Allovalent impurities, both cationic and anionic, desensitize the thermal decomposition significantly. Method of preparation of HP?1 is also seen to affect the reaction.
Hydrazinium diperchlorate has been found to decompose in two ways. Below 140°C the products formed are HP?1 and HClO?. Above 140°C the products formed are different, the residue being NH?ClO?. Doping studies suggest that decomposition might involve the diffusion of ionic species as the rate?determining step.
Ageing has been found to desensitize the reaction up to about 25 days while particle size does not seem to have any appreciable effect on the decomposition rate of HP?2. Pre?irradiation with UV light affects the decomposition only at higher ? (> 0.3) values. | |
