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Abstract  

A lunar olivin monocrystal (Mg, Fe)2SiO4 of about 0.011 mg was analyzed by neutron activation analysis (NAA) and by X-ray crystal structure research (XRCSR). Both methods demonstrated the presence of small concentrations of Sc, Cr, Mn, and Co, the quantitative results for these elements are in the range of about 102 to 103 ppm. Mg was analysed only by XRCSR. Good agreement between both methods was found for the concentrations of Fe and Na, the Fe excess by NAA can be explained with included impurities.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Ganzerli-Valentini, S. Meloni, V. Caramella-Crespi, and P. Borroni

Abstract  

The adsorption of about 50 ions on molybdenum dibromide, (Mo6Br8)Br4·2H2O, in nitric acid was investigated. The preparation of the adsorber and its characterization is presented and discussed. Adsorption mechanism studies were carried out for some noble metals and chromium. Sorption cannot be ascribed to ion exchange mechanism but to formation of insoluble species, and to settlement of few ions into surface sorption sites or into a limited number of cavities in the cluster crystal structure of the adsorber.

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Abstract  

The complexes of yttrium(III) and lanthanides(III) with 1,2,4,5-benzenetetracarboxylic acid were prepared as crystalline solids of the general formula Ln4(C10H2O8)3⋅14H2O. They are insoluble in water. On heating in air or inert gas atmosphere all compounds lose water molecules; next anhydrous compounds decompose to oxides. The yttrium complex and heavy lanthanide (from Ho to Lu) ones crystallize in monoclinic crystal system. The dehydration does not change the crystal structure of the compounds.

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Abstract  

Lead(II) 2,2'-bipyridine hexachloroplumba tetetrahydrate was synthesized and investigated by DTA, TG and DTG. IR spectroscopy and other methods enabled the identification of some of the decomposition products. Comparative studies on the corresponding chlorides: [Pb(bipy)]Cl2 and [Pb(bipy)3]Cl2, which can be considered as precursors of the hexachloroplumbate, were also undertaken. X-ray measurements enabled the tentative determination of the crystal structure of [Pb(bipy)]Cl2. Hexachloroplumbate decomposes with the liberation of chlorine, water and organic ligands, and the process is accompanied by the simultaneous transition of Pb(IV)→Pb(II). Chlorides release only ligands upon heating. Residues comprised always PbCl2.

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Abstract  

Topochemistry of the initial stages of evaporation and dissolution of monoclinic single crystals of paracetamol and phenacetin was studied. Thermal treatment of these crystals showed that the morphology of etch pits depicts the symmetry of etched planes. The shapes of pits formed during chemical etching of the cleavage plane of a paracetamol crystal by different etchants were not similar to each other. The chemical etching of the cleavage plane of a phenacetin crystal resulted in the formation of pits stretched along the same direction, independently of the chosen solvent. An interpretation of this result is suggested, based on the analysis of the anisotropy of the crystal structure and presence of steric hindrance.

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Abstract  

The calorimetric (DSC) and derivative thermogravimetric (DTG) measurements for crystalline mono- and hemiphosphates of cytidine and deoxycytidine have been performed. The results for four examined salts confirm the influence of presence (or absence) of 2'OH group in ribose ring on stability (or lability) of the crystal structure of examined salts.

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Phase diagrams of perhydrotriphenylene and aromatic compounds

I. Trans stylbene and 4H-cyclopenta[2,1-b∶3,4-b′] dithiophene

Journal of Thermal Analysis and Calorimetry
Authors: G. Di Silvestro, Cui Ming Yuan, A. Terragni, Elisabetta Brenna, and Manuela Gilberti

Perhydrotriphenylene (PHTP) forms channel-like adducts with molecules of different size and molecular weight. In the crystal structure of the adduct the included long sequences of molecules are separated from each other by the channel walls. The optical properties of the included molecules differ from those of the bulk molecules. The phase diagram of mixtures of PHTP and trans stylbene and 4H-cyclopenta [2,1-b∶3,4-b′] dithiophene (CPDT) were determined by DSC experiments. Ideality in the liquid phase was observed only in the PHTP/CPDT system.

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Abstract  

Neutron diffraction measurements have been performed on powder VSe at 294 K. The diffuse scattering theory including correlation effects among thermal displacements of atoms is applied to background function in the Rietveld analysis. The oscillatory scheme of the diffuse scattering intensity from hexagonal VSe is explained by the correlation effects among far-neighboring Se–Se atoms. The values of the correlation effects depend on the inter-atomic distance and not on the crystal structure. The relation between correlation effects and force constants is discussed.

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Abstract  

A scientometric analysis of the publications and of the information flow on all phosphides shows that: the bulk of the publications on semiconducting phosphides relates to gallium phosphide. For non-semiconducting phosphides, most of the articles are connected with phosphides of transition metals. The bulk of the studies feature crystal structure, phase equilibria, diagrams of state and electrophysical and magnetic properties. Most of the articles on phosphides are published in English (53,4%) and in Russian (24.4%). There is a tendency for research to be carried out by groups of researchers of two, three, four or more persons. The present sceintometric analysis helps establish the trend of investigations on phosphides.

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Abstract  

The complex phase transitions involving dielectricity and magnetism on distorted triangular lattice antiferromagnets, "KNiCl3-family" crystals, which have the crystal structures derived from the prototype CsNiCl3, were studied through the heat capacity measurements. These crystals are classified into characteristic three groups from the viewpoint of magnetic and structural properties clarified so far. The results of the dielectric constant measurement as a function of temperature are also presented in detail. The present calorimetric study reveaed that the structural successive phase transitions rather than the magnetic transitions in these crystals are recognized more distinctly as the presence of specific heat anomalies at the respective phase transition points.

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