Four definite compounds exist in the Sm2O3Ga2O3 binary phase diagram, namely: Sm3GaO6, Sm4Ga2O9, SmGaO3, and Sm3Ga5O12. The compound is orthorhombic (space group Pnna - Z.4) with the cell parameters: a = 11.400Å, b = 5.515Å, c = 9.07Å and belongs to the oxysel family. Sm3GaO6 and SmGaO3 melt incongruently at 1715 and 1565°C; Sm4Ga2O9 and Sm3Ga5O12 have a congruent melting point at 1710 and 1655°C. With regard to the Gd2O3Ga2O3 system three definite compounds have been identified: Gd3GaO6, Gd4Ga2O9, and Gd3Ga5O12. Only the garnet melts congruently at 1740°C with the following composition: Gd3.12Ga4.88O12. Gd3GaO6, and Gd4Ga2O9 melt incongruently at 1760 and 1700°C. GdGaO3 is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram. 相似文献
The Tl2S-Sb2S3-Bi2S3 quasi-ternary system (system A) was studied using DTA, X- ray powder diffraction, microstructure examination, and microhardness measurements. TlSbS2-Tl4Bi2S5(TlBiS2, Bi2S3), Sb2S3-TlBiS2, Tl3SbS3-TlBiS2(Bi2S3), and [TlSb0.5Bi0.5S2]-Tl2S isopleths; isothermal sections at 500 K; and liquidus surface projection of system A were constructed. Characteristic features of the title system are extensive fields of solid solutions extended along the
TlSbS2-TlBiS2 quasi-binary section and a continuous solubility belt 1–2 mol % wide extended along the Sb2S3-Bi2S3 binary subsystem. Primary separation fields of phases and the types and coordinates of invariant and monovariant equilibria
in system A were determined. 相似文献
The crystal structures of two polyamides, poly(glycyl-β-alanyl-β-alanine) (nylon 2/3/3) and poly(methylene malonamide) (nylon 1,3), have been investigated by x-ray diffraction and electron microscopy. Crystallization of nylon 2/3/3 from a solution in a mixture of water and formic acid yields lamellar single crystals exhibiting a triangular habit. Doughnut-shaped morphologies diffracting as single crystals are obtained in the crystallization of nylon 1,3. A helical structure of the type known as polyglycine II is found for both polyamides. In such a structure, chains are intermolecularly linked by hydrogen bonds giving a hexagonal lattice of a = 4.79 Å. Insufficient data are available to determine precisely the conformation of the chains. We assume a threefold helix having c = 35.2 Å and c = 18.0 Å for nylon 2/3/3 and nylon 1,3 respectively. No sign of the layered structure familiar in polyamides has been detected for these polymers throughout the experiments made in the present study. 相似文献
CpTiCl(3)/Al(2)O(3)-SiO(2)/NaNp (Cp=cyclopentadienyl, Np=naphthenide anion) system was obtained by a reduction of cyclopentadienyl titanium[IV] complexes supported on alumina-silica gels with sodium naphthenide in dinitrogen or argon atmospheres. The yield of the reduction reactions and the yield of dinitrogen fixation by the systems reduced in dinitrogen depend on the kind of phases which are present on alumina-silica gel surfaces according to their composition. On hydrolysis the nitrogen titanium complexes obtained liberated ammonia. The highest yields of these reactions, above 70% calculated as NH(3)/Ti ratio, were obtained for the systems containing in the carriers 10-, 60-wt%, of Al(2)O(3) and SiO(2Deg) of aerosil type. This relatively high activity was achieved with surface titanium complexes obtained by a reaction of CpTiCl(3) with isolated surface hydroxyl groups of neutral properties present on these gels. The EPR method was used to investigate the titanium[III] complexes formed during reduction of the systems. The signals obtained helped in discussion concerning the way in which titanium complexes undergo transformations during the reactions studied. 相似文献
This is the first study of the SnSbBiTe4-2Bi2Te3 join of the SnTe-Bi2Te3-Sb2Te3 quasi-ternary system by the methods of complex physicochemical analysis over a wide range of concentrations. A phase diagram
was constructed for the title quasi-binary join. The system was found to be of the eutectic type; the eutectic coordinates
are 65 mol % Bi2Te3 and 675 K. The starting components were shown to form solid solutions with extents of 20 mol %. Alloys with compositions
lying within the Bi2Te3-based solid solution region were found to be n-type semiconductors. 相似文献
In order to understand more about the instability of sulfur difluoride, we have investigated the chemical interrelations between each of the monomers SF2 and CF3SF and the corresponding dimers F3SSF and CF3SF2SCF3. Thus we have found that SF2 and CF3SF exist in chemical equilibria with their dimers. These equilibria are unusual because they involve two different bonds (SF and SS). The equilibrium constants and dissociatíon enthalpies have been determined by i.r. and mass spectroscopic measurements. The equilibrium between F3SSF and SF2 is disturbed by a decomposition reaction of these compounds yielding SF4 and SSF2. In both systems (1) and (2) the achievement of the equilibrium is comparatively slow at ?30 to 30 °C. The rates for dissociation and decomposition are strongly surface-dependent and the kinetics of the two processes have been studied separately. Under favorable conditions the half-lives at 298 K for the dissociation of F3SSF and CF3SF2SCF3 are found to be ca. 8.h and ca. 2 h, respectively, and for the decomposition of SF2 to SF4 and SSF2 and CF3SF to CF3SF3 and CF3SSCF3 (p?13 mbar) the values are ca. 10 h and 1 year respectively. 相似文献
