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A novel chemical passivation route is established to obtain microcrystalline solid solutions of binary oxide system Mn1−x Ni x O (0·01

Thermal analysis (TG, DTG, DTA) of a number of basic magnesium carbonate samples, prepared by precipitation using different magnesium salts (magnesium nitrate, sulphate, chloride, and acetate) and precipitating agents (viz. sodium carbonate and bicarbonate and potassium carbonate and bicarbonate) at different concentrations of magnesium salt (0.005–2.0 M), temperatures (0–100°C) and pH9-11 using different modes of mixing in the precipitation and also by ageing the precipitate for different periods (0.5–96 h) has been carried out in the temperature range 30–600°C. The thermal decomposition and surface area of the resulting MgO are found to be strongly influenced by the preparation conditions of basic magnesium carbonate.

A sequence of phenol-formaldehyde and m-cresol-formaldehyde orthonovolac resins were synthesized by varying the mole ratios of phenol or substituted phenol to formaldehyde. The resins were characterized by their thermal properties such as softening temperatures and degradation profile. The non-isothermal procedures of Coats-Redfern and Horowitz-Metzger were applied to their respective differential thermogravimetric plots to ascertain the thermal degradation kinetics of these resins in air. The thermal stability and activation energies (E) of m-cresol-formaldehyde resins in the terminal degradation stage were correlated with those of the phenol-formaldehyde resins. The effect of aromatic ring substitution on the thermal stability is also discussed.

Ultrafine (≍0.4 μm) strontium titanate powder was synthesized using strontium nitrate and potassium titanyl oxalate as precursors. An aqueous (0.1 M) potassium titanyl oxalate solution was added dropwise to a (0.1 M) strontium nitrate solution with continuous stirring at room temperature to precipitate strontium titanyl oxalate (STO). The precipitate, after careful washing with distilled water several times, was air-dried and calcined at 550 °C/6 h to obtain homogeneous, spherical, stoichiometric powder of SrTiO3 ≍0.4 μm in size. The calcined powder was characterized using different techniques such as XRD, DTA/TG/DTG, SEM, and IR.

Thermal decomposition of magnesium hydroxide, prepared by its precipitation from a magnesium salt solution with ammonium hydroxide using different salts and different conditions (concentration of Mg salt, mode of mixing of the Mg salt and ammonium hydroxide solution, pH and temperature of precipitation, and the ageing period of the precipitate) has been investigated by TG, DTG and DTA techniques in the temperature range 30–600°C. The thermal analysis showed that the preparation conditions of magnesium hydroxide have a strong influence on its thermal decomposition to active magnesium oxide. An exothermic DTA peak was observed in the decomposition for only a few of the magnesium hydroxide samples.

VPI-5 and AlPO 4 -8 are crystalline aluminophosphate molecular sieves. An examination of the reported details on the synthesis of these materials revealed several common features suggesting the possibility of transforming the former to the latter by simple thermal treatment: this is confirmed by the thermogravimetric studies reported in the present work.

Thermal decomposition of basic magnesium carbonate impregnated with alkali metal (Li, Na, K, Rb and Cs) carbonate, in the preparation of alkali metal-doped MgO catalysts, has been investigated by TG, DTG and DTA techniques in the temperature range 30–1200°C. The exothermic DTA peak observed for the basic magnesium carbonate around 490 °C is found to be absent from the samples containing alkali metal carbonates, except for the sample with Na/Mg = 0.02. The solid products (i.e. alkali metal-doped MgO) of decomposition at different temperatures have been characterized for its alkali metal content, crystalline phases, surface area and surface basicity. The thermal decomposition of basic magnesium carbonate and properties of solid products of the decomposition are found to be strongly influenced by the addition of alkali metal carbonate to the magnesium carbonate, depending on the type of alkali metal and its concentration. The addition of alkali metal carbonate has resulted in a large decrease in the surface area, but an increase in the density of surface basic sites, of MgO obtained in the decomposition.

A novel method of preparation, involving careful formation of a stoichiometric solid solution of stabilized Mn1-x Mg x O system for eight different concentrations ofx (0.001 ⩽x ⩽ 0.15) is described. A variety of physicochemical techniques such as X-ray diffraction, DTA-TGA, reflectance spectra, magnetic susceptibility and XPS data are used to determine structure-property correlations in the solid solutions, which are (i) X-ray diffraction studies reveal the linear decrease of cubic lattice parameter with increasing x, (ii) DTA-TG-DTG studies which confirm the formation of solid solution and the stability of these solid solutions in air which increases from 515 to 565 K withx, (iii) the diffused reflectance spectra shows nearly perfect octahedral symmetry around Mn2+ ions, (iv) magnetic susceptibility data indicates the usual dilution effects of diamagnetic ions in antiferromagnetic host lattice, (v) XPS studies reveal the presence of mixed phase of Mn2O3-MgO on the surface which protects the bulk MnO from its further oxidation to higher oxides of manganese. This shows the important role of Mg2+ in the chemical passivation of manganous oxide.

Thermal (DTA/DTG/TG) studies have been carried out in order to understand the ferritization reaction leading to the formation of hexagonal strontium ferrite. Two different routes, namely, (a) the conventional ceramic method (solid state reaction) and (b) the chemical coprecipitation method, have been used to prepare the starting materials. Simultaneous DTA/DTG/TG plots clearly exhibit the onset of the exothermic ferritization reaction at T ⋍ 730°C, with an activation energy of 43.872 kcal mol −1 for the precursors derived from the coprecipitation route. On the other hand, the temperature required for the reaction with the ceramic route precursors was greater than 900°C without any accompanying energy change.

Iron citrate decomposes to give α-Fe2O3 as an end product at 460°C via a four-step process. Barium citrate has been found to decompose to a stable barium carbonate at 412°C. It is, however, observed that a mixture of iron and barium citrates decomposes to BaO and either γ-Fe2O3 or Fe3O4 or a mixture of these two oxides. Thus, the mixture does not decompose to give α-Fe2O3 and BaCO3 as obtained in the individual decomposition of iron citrate and barium citrate, respectively. The iron and barium oxides obtained as a result of decomposition of the mixture then chemically combine to form barium ferrite at 600°C.

The thermal decomposition of barium citrate occurs in three stages. During the first stage anhydrous salt is formed while the second stage results in intermediates, possibly aconitic acid and modified itaconic acid moieties formed by dehydration and decarboxylation, and barium carbonate. In the third stage complete decomposition to barium carbonate takes place.

The influence of atmosphere (inert or oxidizing) and addition of diethyl phthalate as plasticizer on the thermal degradation of ethyl cellulose has been investigated by thermogravimetric, differential thermogravimetric and differential thermal analysis techniques. In the present of an inert atmosphere, the decomposition of ethyl cellulose and plasticized ethyl cellulose occurs in one and two endothermic steps, respectively. In the presence of air, the decomposition of ethyl cellulose with or without plasticization is a very complex process occurring in a number of exothermic stages. In the thermal decomposition, the plasticized ethyl cellulose yields more carbonaceous residue.

The thermal degradation of poly(2,6-dimethyl-1,4-phenylene oxide) modified with isocyanate has been studied by thermal analysis in air at a heating rate of 5°C/min. Thermogravimetry (TG) and differential thermal analysis (DTA) data indicate that all the isocyanate modified polymers decompose in two steps. The activation energy of decomposition of these modified polymers has also been determined from TG.

Thermal decomposition behaviour of the citrates of zinc, bismuth and calcium has been investigated individually and as binary mixtures (1:1) consisting of zinc citrate as the essential component. Zinc citrate is found to decompose to zinc oxide at 400 ° C, bismuth citrate decomposes to α-Bi 2 O 3 at 360 ° C and calcium citrate decomposes to calcium oxide at 1150°C. The barium and calcium oxides which are normally formed at a higher temperature during the individual decomposition of the citrates are obtained at lower temperatures, i.e. 1140 and 800 °C, respectively, on decomposition of their mixtures with zinc citrate. Bismuth citrate alone is found to decompose to α-Bi 2 O 3 whereas its mixture with zinc citrate decomposes to the β-phase of bismuth oxide.