M.P. Kannan

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

Kinetics of thermal decomposition of sulphate-doped potassium metaperiodate

Abstract The effect of sulphate dopant on the thermal decomposition kinetics of potassium metaperiodate (KIO 4 ) has been studied by isothermal thermogravimetric analysis in the temperature range 580–600 K. Doping enhances the decomposition rate and the effect increases linearly with increasing dopant concentration. The decomposition process was found to the best described by the Prout-Tompkins equation. The activation energies (E) for pure and 1 × 10 −4 , 1 × 10 −3 , 1 × 10 −2 and 1 × 10 −1 mol% sulphate-doped KIO 4 are, respectively, 239.7, 229.2, 218.4, 212.5 and 209.5 kJ mol −1 . Doping did not affect the E values significantly.

THERMAL DECOMPOSITION OF DOPED AMMONIUM PERCHLORATE

Isothermal decomposition of orthorhombic ammonium perchlorate (AP) has been studied as a function of concentration of the dopants, SO42− and PO43−. In either case, the rate of decomposition passes through a maximum as the dopant concentration increases. Activation energy of the decomposition process remains unaltered by doping. The results are interpreted in terms of electron transfer mechanism.ZusammenfassungDie isotherme Zersetzung von orthorhombischen Ammoniumperchlorat (AP) wurde in Abhängigkeit von der Konzentration der Dopanten SO42− und PO43− untersucht. In jedem Falle geht die Geschwindigkeit der Zersetzung mit steigender Dopantenkonzentration durch ein Maximum. Die Aktivierungsenergie des Zersetzungsprozesses wird durch dopen nicht verändert. Die Ergebnisse werden auf einem Elektronentransfer-Mechanismus basierend interpretiert.РезюмеИзучено изотермичес кое разложение орторомбического пе рхлората аммония в зависимости от конце нтрации легирующих д обавок сульфат- и фосфат-ионо в. В каждом случае скорость разложения с увеличением концен трации легирующей добавки п роходит через максимум. Энергия акт ивации процесса разл ожения остается неизменной при легировании. Результаты объяснен ы на основе механизма электронного перено са.

Effect of Divalent ion Dopants on the Kinetics of Thermal Decomposition of Potassium Bromate

Isothermal decomposition of KBrO3 has been studied as a function of concentration of the dopants, SO42- and Ba2+ by isothermal thermogravimetry in the temperature range 668 - 683 K. The rate law and the activation energies remained unaltered by doping. The results suggest a diffusion-controlled mechanism, the diffusing species being both K+ and BrO3-.

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.

Thermal decomposition kinetics of barium zirconyl oxalate

Abstract Thermal decomposition studies of barium zirconyl oxalate were carried out in air using TG, DTG and DTA techniques. The kinetic parameters (non-isothermal method) for each step of decomposition were evaluated by means of the Coats-Redfern, modified Horowitz-Metzger and Freeman-Carroll equations, using the weighted least-squares method. The results indicate that the initial oxalate decomposition is the rate-determining step.

A comparative study of the thermal decomposition kinetics of zirconyl oxalates of calcium and strontium

Abstract The thermal decomposition kinetics of calcium and strontium zirconyl oxalates have been studied in air using TG, DTG and DTA techniques under non-isothermal conditions. The reaction order, activation energy, pre-exponential factor and entropy of activation were computed by means of the Freeman-Carroll, Coats-Redfern and Horowitz-Metzger equations, using the least squares method, for each step of decomposition. The values of A , E ∗ and Δ S ∗ obtained by the three methods agree well.

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.