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.
Authors:J. Canotilho, F. Costa, A. Sousa, J. Redinha, and M. Leitão
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.
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.
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 (Tg)
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.
Authors:M. Sikorska-Iwan, Renata Mrozek, A. Ostasz, and Z. Rzączyńska
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.
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.
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.
Authors:M. Arai, T. Sakuma, T. Atake, and H. Kawaji
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.
The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order py≪bipy<phen ligands. The significantly higher thermal stability of the complexes with bipyridine and phenanthroline is caused by the presence of dimeric structural units in the crystal structure and intermolecular interactions of the cyanate and heterocyclic ligands.
Authors:C. Beauger, P. Grosseau, B. Guilhot, D. Huguenin, and P. Iacconi
The dependence of the firing conditions on the crystal structure formation of ZnGa2 O4 has been investigated. The effects of temperature and atmosphere were examined and gave evidence of the instability of the
zinc gallate under a reducing atmosphere at temperatures above 600C. A new preparation route has allowed to synthesize ZnGa2 O4 at low-temperature, right from 300C, avoiding the decomposition of the matrix during the annealing.