Thermal decomposition of alkali metal perchlorates

The effect of past mechanical history on the subsequent thermal decomposition kinetics of sodium, potassium, rubidium and caesium perchlorates, has been investigated. At low temperatures the decomposition of all these salts is significantly sensitized by pre-compression. At high temperatures, however, prior compression results in a lowered decomposition rate in the case of potassium, rubidium and caesium perchlorates and in an increase in the thermal reactivity of sodium perchlorate. The high temperature behaviour is shown to be an indirect consequence of the low temperature behaviour. The difference in behaviour between sodium perchlorate and the other alkali metal perchlorates is explained on the basis of the stability of the respective chlorates, formed during the low temperature decomposition. This is substantiated by experiments which show that the addition of sodium chlorate to sodium perchlorate brings about a sensitization while potassium perchlorate admixed with potassium chlorate results in a desensitization at high temperatures.

Influence of rapid thermal annealing (RTA) on the structural and electrical properties of SnS films

The performance of optoelectronic devices critically depends on the quality of active layer. An effective way to obtain a high quality layers is by creating excess of metal atoms through various heat treatments. Recently, rapid thermal annealing (RTA) has proved a versatile technique for the post-treatment of semiconductor materials as compared to other techniques due to its precise control over the resources. Thus, we carried out a set of experiments on SnS films to explore the influence of RTA treatment on their properties. From these experiments we noticed that the films treated at 400 °C for 1 min in N2 atmosphere have a low electrical resistivity of ~5 Ωcm with relatively high Hall mobility and carrier density of 99 cm2/Vs and 1.3 × 1016 cm−3, respectively. The observed results, therefore, emphasise that it is possible to obtain good quality SnS films through RTA treatment without disturbing their crystal structure.

Formation of Pb(Ti,Zr)O3, from thermal decomposition of oxalate precursors

Lead zir conyl oxalate hexahydrate (LZO) and lead titanyl zirconyl oxalate hydrate (LTZO) are prepared and characterized. Their thermal decompositions have been investigated by thermoanalytical and gas analysis techniques. The decomposition in air or oxygen has three steps — dehydration, decomposition of the oxalate to a carbonate and the decomposition of carbonate to PbZrO3. In non oxidising atmosphere, partial reduction of Pb(II) to Pb(0) takes place at the oxalate decomposition step. The formation of free metallic lead affects the stoichiometry of the intermediate carbonate and yields a mixture of Pb(Ti,Zr)O3 and ZrO2 as the final products. By maintaining oxidising atmosphere and low heating rate, direct preparation of stoichiometric, crystalline Pb(Ti,Zr)O3 at 550°C is possible from the corresponding oxalate precursor.

Thermal stabilization of glucose oxidase and glucoamylase by physical entrapment

Physical entrapment was used as an approach to achieve thermal stabilization of enzymes. The ti values for the thermoinactivation of glucose oxidase and glucoamylase were increased several-fold by their entrapment in polyacrylamide gels. In polyacrylate gels the individual enzymes behaved differently, probably owing to microenvironmental effects arising by the polyelectrolyte nature of the carrier.

Thermal decomposition of rare-earth trioxalatocobaltates

The thermal decomposition of rare-earth trioxalatocobaltates LnCo(C2O4)3 · x H2O, where Ln = La, Pr, Nd, has been studied in flowing atmospheres of air/oxygen, argon/ nitrogen, carbon dioxide and a vacuum. The compounds decompose through three major steps, viz. dehydration, decomposition of the oxalate to an intermediate carbonate, which further decomposes to yield rare-earth cobaltite as the final product. The formation of the final product is influenced by the surrounding gas atmosphere. Studies on the thermal decomposition of photodecomposed lanthanum trioxalatocobaltate and a mechanical mixture of lanthanum oxalate and cobalt oxalate in 1 : 2 molar ratio reveal that the decomposition behaviour of the two samples is different. The drawbacks of the decomposition scheme proposed earlier have been pointed out, and logical schemes based on results obtained by TG, DTA, DTG, supplemented by various physico-chemical techniques such as gas and chemical analyses, IR and mass spectroscopy, surface area and magnetic susceptibility measurements and X-ray powder diffraction methods, have been proposed for the decomposition in air of rare-earth trioxalatocobaltates as well as for the photoreduced lanthanum salt and a mechanical mixture of lanthanum and cobalt oxalates.

Thermal Decomposition of hydrazinium monoperchlorate in the solid state

Hydrazinium monoperchlorate (HP-1) has been shown to decompose thermally in the solid state according to the chemical equation: 5N2H5CIO4 = 4NH4CIO4+1HCI+3N2+4H2O The activation energy for the evolution of HCl as determined mass spectrometrically is 8.05 kcal mol−1 in the temperature range of 80 to 120°C. The rate of decomposition is seen to be altered by doping HP-1 with small concentrations of SO2−4, Ca2+ and Al3+.

Thermal decomposition of sulphur hexafluoride

Abstract is not available.

Thermal Decomposition Studies on Ammonium Perchlorate—Polybutadiene Composite Propellant

The thermal decomposition of ammonium perchlorate based solid composite propellant using carboxyl terminated polybutadiene as binder has been studied employing thermogravimetry and differential thermal analysis techniques. The thermal decomposition characteristics of the propellant have been found to be quite similar to those of pure ammonium perchlorate with activation energy, 32 Kcal/mole and 60 Kcal/mole respectively in the low and high temperature regions. The effect of the sample size and shape on the thermal decomposition has also been evaluated.

Thermal decomposition of titanyl oxalates II : Kinetics of decomposition of barium titanyl oxalate

Kinetics of the thermal decomposition of barium titanyl oxalate have been studied. Decomposition of the anhydrous oxalate is complex and deceleratory throughout. Kinetics of decomposition of the intermediate carbonate Ba2Ti2O5CO3 is greatly influenced by the thermal effects during its formation. The sigmoidal (α, t) curves obey a power law equation followed by first order decay. Presence of carbon in the vacuum prepared carbonate has a strong deactivating effect. Decomposition of the carbonate is accompanied by growth in particle size of the product, barium titanate.

Mossbauer effect studies of the thermal decomposition of iron(II) oxalate in hydrogen

Mössbauer-effect and X-ray studies were carried out on the product samples of the thermogravimetric analysis (TGA) and of the isothermal decomposition of iron(II) oxalate in flowing H2. Two types of sample configurations were employed for isothermal studies between 280 to 420°C for various periods of heating. Low temperature Mossbauer measurements at liquid nitrogen temperature were carried out to examine the superparamagnetic (SPM) contributions. From the spectra of samples decomposed at 340°C, in vertical experiments, the percentage SPM and percentage ferromagnetic (FM) area of Fe3O4 were estimated and an average size (˜167Å) for Fe3O4 was derived. Mossbauer measurements (at high temperatures) were carried out on Fe3C formed in horizontal experiments, for two samples decomposed at ˜320°C for 1 hr and 2 hr. An estimate of SPM and FM Fe3C was obtained by calculating KV, the anisotropy energy for the Fe3C in these two samples and values of 5.07 × 10−16 and 7.02 × 10−16 erg/sec, respectively, were obtained.

Thermal decomposition of methylammonium perchlorate

The thermal decomposition of methylammonium perchlorate (MAP) has been studied under isothermal and non-isothermal conditions. Differential thermal analysis of MAP showed, in addition to the exotherm due to decomposition, another exotherm at 408° which was observed for the first time. Chemical analysis and the infrared spectrum of the residue left behind after the decomposition proved it to contain NH4ClO4. The results have been explained on the basis of a methyl group transfer in addition to proton transfer in the decomposition process.

Thermal decomposition of sodium azide

The thermal decomposition of sodium azide has been investigated in the temperature range 240–365°C. Three values for the activation energy, 37.0, 59.0 and 14 kcal mol−1 have been obtained depending on the temperature range of study. The mechanism of decomposition seems to involve excited azide ions (through internal conversion) and excitations. The activation energy of 14 kcal mol−1 appears to be associated with the promotion of electron in the presence of sodium metal.

Thermal degradation of polystyrene

The importance of the study of thermal degradation of polymeric fuels arises from their role in the combustion of solid propellants. Estimation of the condensed-phase heat release during combustion can be facilitated by the knowledge of the enthalpy change associated with the polymer degradation process. Differential scanning calorimetry has been used to obtain enthalpy data. Kinetic studies on the polymeric degradation process have been carried out with the following objectives. The literature values of activation energies are quite diverse and differ from author to author. The present study has tried to locate possible reasons for the divergence in the reported activation energy values. A value of 30 kcal has been obtained and found to be independent of the technique employed. The present data on the kinetics support to chain-end initiation and unzipping process. The activation energies are further found to be independent of the atmosphere in which the degradation of polymer fuel is carried out. The degradation in air, N2, and O2 all yield a value of 30 kcal/mole for the activation energies.

Thermal decomposition of titanyl oxalates-I : Barium titanyl oxalate

Thermal decomposition of barium titanyl oxalate tetrahydrate (BTO) has been investigated employing TGA, DTG and DTA techniques and gas and chemical analysis. The decomposition proceeds through five steps and is not affected much by the surrounding gas atmosphere. The first step which is the dehydration of the tetrahydrate is followed by a low-temperature decomposition of the oxalate groups. In the temperature range 190–250°C half a mole of carbon monoxide is evolved with the formation of a transient intermediate containing both oxalate and carbonate groups. The oxalate groups are completely destroyed in the range 250–450°C, resulting in the formation of a carbonate which retains free carbon dioxide in the matrix. The trapped carbon dioxide is released in the temperature range of 460–600°C. The final decomposition of the carbonate takes place between 600–750°C and yields barium titanate. The i.r. spectra, surface area measurements and X-ray, powder diffraction data support entrapment of carbon dioxide in the matrix.

Combustion and thermal decomposition characteristics of composite solid propellants

The role of thermal decomposition of the binder and the oxidiser in the thermal decomposition, ageing and combustion of composite solid-propellants has been investigated. The present study shows that the burning rate and ageing of polystyrene and ammonium perchlorate propellant are related to the thermal decomposition of the propellant itself and ammonium perchlorate.