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Abstract  

Thermal decomposition of natural siderite and goethite has been studied using Mössbauer spectroscopy and X-ray diffraction. Hematite and magnetite were the principal compounds formed during high temperature treatment of siderite. Natural goethite transformed to hematite at high temperatures. The crystal structures, stoichiometry and the nuclear magnetic properties of Fe-oxides formed are discussed.

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Abstract  

Enthalpies of solution of various terfenadine samples in methanol and in ethanol were measured. Samples were prepared by crystallization in different solvents. The calorimetric results give important information on crystal structure of the terfenadine forms and on the solute/solvent interactions of this compound with the solvents.

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Abstract  

Up to 26 trace elements were determined in 9 different samples of plagioclase, orthopyroxene, clinopyroxene and magnetite and the host pyroclastic matrix material using instrumental neutron activation analysis. Mineral to whole-rock partition coefficients were reported and interrelationships between chemical composition and crystal structure of the minerals were discussed, especially in the case of REE in plagioclase.

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Abstract  

The high-resolution transmission electron microscopy HRTEM study of the atomic scale mechanism of crystal structure organization within the amorphous polymeric structure of the model multicomponent glass TiO2–MgO–Al2O3–SiO2– in the glass transformation temperature range has been undertaken. In the glass transition (T g) temperature range, glass transforms from the solid of rigid amorphous structure into viscoelastic state of weakened chemical bonds. This is an example of nuclei formation and crystal growth in the polymeric amorphous structure of low atomic scale homogeneity due to middle range ordering. It has been demonstrated that in this case crystal structure formation proceeds by successive displacement and local ordering of atoms in the amorphous structure, like disorder-order transformation in crystalline solid bodies. As the consequence in the crystallization by parent structure reorganization mechanism, traditional model of glass crystallization as well as kinetic models of reactions in solid bodies according Avrami or others, are worthy to be revised.

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Abstract  

The 5-nitro-2-anthranilates of lanthanum(III), samarium(III), terbium(III), erbium(III) and lutetium(III) were obtained as hydrates having 2.5 mol of water molecules per 1 mol of compound. The compounds are isostructural. The processes of dehydration and rehydration were investigated. The first step of dehydration does not cause the change of crystal structure. The entire dehydration gives anhydrous compounds with different structure than the structure of hydrates. However, the dehydration of La, Sm, Tb and Er is reversible - the rehydration process gives the complexes having the same crystal structure as the initial compounds. Only the anhydrous lutetium complex under the influence of moisture does not give the starting compound.

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Synthesis of special pigments

A study by means of TA methods

Journal of Thermal Analysis and Calorimetry
Authors: Z. Šolc and M. Trojan

Abstract  

Several TA methods (including dynamic TA, Q-TA, emanation and special conductometric TA) were used in investigations of condensed phosphate synthesis, and in the evaluation and control of the reactivity of the raw materials, when high-temperature stable pigments are developed. Conductometric TA occupies a special position because of its high sensitivity to most changes in crystal structure at the beginning of reactions.

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Abstract  

The thermal stability of push-pull 5-substituted-4-oxothiazolidines was studied by DSC, IC and X-ray diffraction techniques. It was shown that the compounds are stable in the temperature range from room temperature to melting point. The melting is combined with breaking crystal structure and forming glass material as a new phase that forms crystals by cooling it very slowly. The rate constant, activation energy as well as activation parameters of process were determined.

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Abstract  

Potassium tantalate was formed to pyrochlore structures on the tantalum substrate by hydrothermal or electrochemical method. In synthesizing process of potassium tantalate, a crystal structure of the substrate surface seemed to be an important factor. Potassium tantalate was synthesized with a simple equipment only, low temperature of 323 K or over, low concentration of 2–4 mol per liter potassium hydroxide aqueous solution and short time.

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Abstract  

Embedding of barium titanate into porous oxide matrices via sol–gel synthesis and introduction in structured slurry based on fumed oxides has been carried out. Prepared compositions have been studied using XRD, DTA-TG, FTIR, TEM, and adsorption of nitrogen. It has been established that simultaneous formation both barium titanate crystal structure and porous structure of matrices occurs. Crystallites of barium titanate, which arise in pores, possess lesser size in comparison with that for bulk BaTiO3.

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Abstract  

The phase transition and the crystal structures of CuITe were investigated by differential thermal analysis and X-ray powder diffraction measurements in the temperature range between 300 and 683 K. The new phase transition in CuITe was observed at 592 K. The enthalpy of transition is ΔH=0.125 kJ mol-1. The new phase above 592 K belongs to tetragonal system with the space group I41 /amd.

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