Kitheri Joseph

Kinetics of thermal decomposition of Th(C2O4)2·6H2O

Abstract Thermal decomposition of thorium oxalate hexahydrate was investigated under nonisothermal and isothermal conditions in moist argon by using simultaneous thermogravimetric–differential thermal analyser. Nonisothermal experiments were carried out at various linear heating rates. Intermediates formed in each stage of the thermal decomposition of thorium oxalate hexahydrate were deduced. Kinetics of decomposition in each stage were evaluated from the dynamic TGA–DTA data by means of Coats and Redfern equation. The values of the activation energy (E) and the pre-exponential factor (A) of each stage of the thermal decomposition at various linear heating rates were calculated. These kinetic parameters were evaluated from isothermal experiments also and probable decomposition mechanism is proposed.

Studies on the kinetics of oxidation of urania-thoria solid solutions in air

The oxidation behaviour of (UyTh1ˇy)O2 powders (ya 0:15; 0:30; 0:72 and 0:77) was studied by means of thermogravimetry. The oxidation was carried out under both isothermal and non-isothermal conditions. The limits of oxygen solubility in terms of O/M ratios of (UyTh1ˇy)O2 solid solutions, derived from the thermogravimetric data, were 2.08, 2.15, 2.35 and 2.36 for ya 0:15; 0:30; 0:72 and 0:77, respectively. A single-step oxidation was observed for (UyTh1ˇy)O2 solid solutions with ya 0:15‐0:77. The activation energy for the oxidation of (UyTh1ˇy)O2 powders with ya 0:15 and 0.30 (the final product is single-phase), was found to be (48.5 a 2.5) kJ mol ˇ1 . The activation energy for the oxidation of (UyTh1ˇy)O2 powders with ya 0:72 and 0.77 (the final product is a bi-phasic mixture) was found to be

Thermoanalytical study of the reaction of potassium carbonate with ferric oxide

The reaction of potassium carbonate with ferric oxide was investigated thermogravimetrically. Both non-isothermal and isothermal conditions were used for the kinetic study of this reaction. The reaction between K2CO3 and Fe2O3 yields KFeO2 and the reaction occurs at lower temperature than the decomposition temperature of pure K2CO3. Arrhenius parameters were derived from the experimental data and a reaction mechanism for the formation of KFeO2 is proposed. # 1999 Elsevier Science B.V. All rights reserved.