Asif S. Bhatti

The thermal decomposition of oxalates: Part 22. The preparation and thermal decomposition of some oxy tungsten(VI) oxalates

Abstract The preparation and characterization of tungsten oxalates are described. The compounds have been characterized on the basis of analytical and Fourier transform infrared (FTIR) spectral data. The thermal decomposition has been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). The tungsten oxalates prepared decompose endothermically between 100–250 °C. The products of these decompositions have been characterized by X-ray powder diffraction as WO 3 . The dehydration is usually seen as a separate degradation step distinct from the decomposition of the oxalate to the oxide. The composition of the oxalate precipitates varies with the method of preparation.

Decomposition kinetics of magnesium hydroxide using DTA

Abstract The decomposition kinetics of magnesium hydroxide to magnesium oxide have been followed using differential thermal analysis (DTA). The method of determining the ideal conditions for calculating the decomposition kinetics is described. For the decomposition the kinetic equation describing the process is found to be dα d T = (1 − α) 4 3 [(1 − α) 1 3 − 1] Values of activation energies were found to be from 229 to 88.3 kJ mol −1 .

The thermal decomposition of azodicarbonamide

Abstract The work presented here was designed to investigate various aspects of the decomposition of azodicarbonamide, an organic solid used as a chemical blowing agent in the plastics industry. The decomposition was studied by TG and DTA experiments, and the heat of reaction calculated to be 1046 kJ mol −1 also the activation energy was found be experiments to be 77 kJ mol −1 . The reaction products were analyzed by IR spectroscopy and the products identified, to postulate a reaction sequence.

The thermal decomposition of oxalates. part 21: The preparation and thermal decomposition of an oxy molybdenum(VI) oxalate

Abstract The complex oxomolybdenum(VI) oxalate having the formula MoO 2 C 2 O 4 · 2H 2 O has been prepared and characterized by chemical analysis and infrared spectra and its thermal decomposition has been studied by TG and DSC. The molybdenum oxalate prepared decomposes exothermally between 200 and 300°C in one step. The product of this decomposition is molybdenum oxide, (blue oxide); this compound has been characterized by X-ray powder diffraction and the observed d values are identical with data reported for MoO 3 .

The effects of additives on the thermal decomposition of azodicarbonamide

Abstract The thermal decomposition of azodicarbanamide containing a promotor and pigments is studied by thermal analysis. The promotor used was the “Standere” 3450 containing zinc and cadmium, the activation energies ranged from 25.1 to 38.2 kJ mol −1 with different ratios. Six pigments are studied giving a range of activation energy values from 45.3 to 156.8 kJ mol −1 .

The thermal decomposition of oxalates. Part 18. The preparation and thermal decomposition of acid barium oxalates

Abstract This study entails the preparation of various forms of barium oxalate. The main method of preparation used was the simultaneous mixing of equimolar solutions of barium chloride and oxalic acid over a range of concentrations of starting materials from 0.2 to 1.6 mol. Each compound was analysed for its percentage of barium, oxalate and water content. Thermogravimetric and differential thermal analysis data were obtained and the results verified by comparison with chemical analysis data. It is shown that varying the conditions of preparation produces forms of barium oxalate differing in chemical composition.

MODIFIED POLYSTYRENES: EFFECTS OF PENDANT FUNCTIONAL GROUPS ON THERMAL STABILITY

Linear polystyrenes modified with pendant chloromethyl, sulfide, sulfoxide, sulfone and aldehyde functional groups have been prepared and their modes of thermal decomposition studied by thermal analysis in a flowing nitrogen atmosphere. Results are interpreted in terms of the effects of functional groups on polymer stability.

The rates of hydration of sea water magnesias

Abstract The rates of hydration of various industrially available magnesium oxide samples prepared by the sea water process are reported. The rates were followed at various pressures of water vapor using an automatic balance and compared with the hydration rate of a zeolite 4A. It was found that the rate depended on the vapor pressure above the solid. The results suggest that condensation of the water occurs in the porous structure and that water in contact with the surface can form magnesium hydroxide, and a model is postulated to describe the rate of hydration, which takes into account the equilibrium condition.

The thermal decomposition of oxalates. Part 20. The decomposition kinetics of acid barium oxalates

Abstract The thermal decomposition of barium oxalate is followed using isothermal and rising temperature techniques. The results obtained from the two methods are in good agreement for both loss of oxalic acid and carbon monoxide. The values of the activation energies for the loss of oxalic acid and carbon monoxide are: isothermally, 109 and 162 kJ mol −1 ; and by the rising temperature method, 114 and 186 kJ mol −1 . The result also indicate that the loss of oxalic acid from the salt follows an Avrami—Erofeev type expression and the loss of carbon monoxide follows a contracting-sphere model.

The thermal decomposition of oxalates. Part 19. The thermal decomposition of barium oxalate hemihydrates

Abstract The thermal decomposition of barium oxalate hemihydrate is described and the scheme for its decomposition given as Ba·C2O4·0.5 H2O → endothermic 0.5BaC2O4+H2O (weight loss = 3.84%) the barium oxalate then decomposes BaC2O4 → endothermic BaCO3+CO (weight loss =11.5%) there is also a phase change γBaCO3 → exothermic βBaCO3 and for each reaction the associated activation energy is given.