Search Results

You are looking at 31 - 40 of 2,291 items for :

  • "Thermal decomposition" x
  • All content x
Clear All

Thermal decomposition kinetics of potassium iodate

Part I. The effect of particle size on the rate and kinetics of decomposition

Journal of Thermal Analysis and Calorimetry
Author: K. Muraleedharan

thermally activated solid-state reactions to obtain thermal stability parameters of solids [ 4 – 8 ]. The kinetics of the thermal decomposition of inorganic materials could be markedly affected by pre-treatments, by the shortening of the induction period

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Berta Holló, Milena Krstić, Sofija P. Sovilj, György Pokol, and Katalin Mészáros Szécsényi

general interest in the case of potential bioactive compounds [ 13 – 15 ]. Besides, the thermal decomposition pattern may help us to estimate the bond strength, redox properties, and exchangeability of the central atoms in the molecule [ 16 ], thus

Restricted access

Introduction Thermal decomposition of solids is an important field of solid state chemistry with wide technical applications and has been used to obtain thermal stability parameters of solids [ 1 – 4 ]. The thermal

Restricted access

Abstract  

Differential scanning calorimetry (DSC) measurements were performed over the temperature range 93–480 K and three enantiotropic (at 323, 409, and 461 K) and one monotropic (at 271 K) phase transitions were detected. Thus, four solid phases (three of them stable and one metastable) and one liquid phase were found. It was concluded, from the entropy change (ΔS) values of these phase transitions that two of them are stable rotational phases and two are crystalline phases (one stable and one metastable). The thermal decomposition of [Mg((CH3)2SO)6](ClO4)2, which was studied using thermogravimetry (TG) with simultaneous differential thermal analysis (SDTA), takes place in two main stages. The gaseous products of the decomposition were identified on-line by a quadruple mass spectrometer (QMS). In the first stage, which starts just above ca. 432 K, the compound loses two dimethylsulphoxide (DMSO) molecules per one formula unit. In the second stage (502–673 K) [Mg(DMSO)4](ClO4)2 decomposes explosively and Cl2, O2, H2, and MgSO4 are finally produced.

Restricted access

Abstract  

The thermal decomposition of ammonium perchlorate (AP) is considered to be the first step in the combustion of AP-based composite propellants. In this report, the effect of the specific surface area of titanium oxide (TiO2) catalysts on the thermal decomposition characteristics of AP was examined with a series of thermal analysis experiments. It was clear that the thermal decomposition temperature of AP decreased when the specific surface area of TiO2 increased. It was also possible that TiO2 influences the frequency factor of AP decomposition because there was no observable effect on the activation energy.

Restricted access

Abstract  

The size effect of silica nanoparticles (SiO2) on thermal decomposition of poly(methylmethacrylate) (PMMA) was investigated by the controlled rate thermogravimetry. Thermal degradation temperature of PMMA–SiO2 composites depended on both fraction and size of SiO2, the thermal degradation temperature of 23 nm (diameter) SiO2–PMMA (6.1 wt%) was 13.5 °C higher than that of PMMA. The thermal stabilities of 17 nm SiO2–PMMA (3.2 wt%) and 13 nm SiO2–PMMA (4.8 wt%) were 21 and 23 °C, respectively, higher than that of PMMA without SiO2. The degree of degradation improvement was increased linearly with the surface area of SiO2. The number of surface hydroxyl group in unit volume of SiO2 particle increased with increasing the specific surface area of SiO2, and the interaction between hydroxide group of SiO2 and carbonyl group of PMMA had an important role to improve the thermal stability of PMMA.

Restricted access

Abstract  

Study of runaway reaction between tri-n-butyl phosphate (TBP) and nitric acid resulting in red-oil formation (and related problems) in the process evaporators of reprocessing plants has been a major safety concern since last 50 years. Thermal decomposition of nitrated TBP results in rapid pressurization and in close-vent condition it may lead to failure of process vessel and containment. Thermal decomposition of nitrated TBP is reported in the literature but corresponding studies for alternate PUREX/UREX solvent tri-iso-amyl phosphate (TiAP) are not available. In this work, comparative study of the thermal decomposition of nitrated solvents (TBP as well as TiAP) under adiabatic conditions in a sealed autoclave is presented. Experimental results indicate much lesser pressurization in the case of TiAP as compared to TBP.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Igor Dalinger, Svyatoslav Shevelev, Vyacheslav Korolev, Dmitriy Khakimov, Tatyana Pivina, Alla Pivkina, Olga Ordzhonikidze, and Yuriy Frolov

intramolecular interactions should be responsible for the thermal stability and mechanisms of thermo decomposition of highly nitrated azoles. Kinetics of thermolysis provides a good approach for the mechanism of thermal decomposition of new compounds. We report

Restricted access

Abstract  

Formation and thermal decomposition of red-oil during unit operations of nuclear fuel cycle process flowsheets is a severe risk. In the literature, red-oil formation has been investigated thoroughly in general and in detail after Tomsk-7 incident on 6th April 1993. However there is no information on the thermal decomposition of formed red-oil. In this work, results of unique experiments on adiabatic thermal decomposition of red-oil, red-oil equilibrated with excess of 4N nitric acid and 100% TBP equilibrated with excess of 4N nitric acid have been discussed.

Restricted access

Abstract  

Ammonium niobium oxalate was prepared and characterized by elemental analysis, XRD and FTIR spectroscopy analysis, which confirmed that the molecular formula of the complex is NH4(NbO(C2O4)2(H2O)2)(H2O)3. Dynamic TG analysis under air was used to investigate the thermal decomposition process of synthetic ammonium niobium oxalate. It shows that the thermal decomposition occurs in three stages and the corresponding apparent activation energies were calculated with the Ozawa–Flynn–Wall and the Friedman methods. The most probable kinetic models of the first two steps decomposition of the complex have been estimated by Coats–Redfern integral and the Achar–Bridly–Sharp differential methods.

Restricted access