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1.
The crystal structure of 2-bromo-4-cyano-4′-N,N-diethylaminoazobenzene has been determined from X-ray diffraction data: C17H17N4Br, mol. wt = 357·1. Triclinic, Pī (No. 2), α = 13·162(5) Å, b = 7·516(3) Å, c = 8·496(4) Å, α = 101·63(4)°, β = 95·79(4)°, γ = 91·49(4)°, V = 818·10 Å3, Z = 2, Dc = 1·45 g cm?3, F(000) = 378, λ(MoKz) = 0·7107 Å, μ(MoKα) = 26·70 cm?1. The structure was solved by direct methods and refined by full-matrix least-squares to R = 0·053 for 2081 independent reflexions. The molecule possesses an essentially planar azobenzene skeleton. The effects of substituents on the geometry of the azo group are discussed. Significant molecular parameters are: NN, 1·264(6) Å; 1BrC, 1·904(5) Å; mean NC, 1·410(7) Å; NNC, 115·7(2)° and 113·0(2)°; NCC (cis relative to NN), 125·4(3)° and 123·1(2)°; CC(Br)C, 123·0(2)°. 相似文献
2.
Dependence of microwave dielectric properties on the crystal structure of (Zn1/3B2/35+)xTi1 − xO2 (B5+ = Nb, Ta) ceramics was investigated as a function of Zn1/3B2/35+O2 (B5+ = Nb, Ta) content (0.4 ≤ x ≤ 0.7). Dielectric constant (K) and the temperature coefficient of resonant frequency (TCF) of sintered specimens were strongly dependent on the structural characteristics of oxygen octahedra in rutile structure. Cation rattling and the distortion of oxygen octahedra were dependent on the bond length ratio of apical (dapical)/equatorial (dequatorial) of oxygen octahedra. The quality factor (Qf) was dependent on the reduction of Ti ion as well as the microstructure of the sintered specimens. 相似文献
3.
Computational difficulties which have been encountered in using the Krishna—Standart method for calculation of interphase mass transfer rates in multicomponent mixtures are discussed. Consideration is given to various alternative methods of performing the matrix calculations involved and to the stability of such methods. On this basis a computer algorithm is developed which is faster and more reliable than that published previously. 相似文献
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5.
Janusz Lewi
ski Iwona Justyniak Janusz Lipkowski Janusz Zachara 《Inorganic chemistry communications》2000,3(12)
The X-ray structure analysis of [Et2In(μ,λ-O2C)–C6H4–2–NH2]n (1) reveals an extended one-dimensional chain comprised of an array of five-coordinate indium centers. The chain unit repeated along two-fold screw axis is defined by the diethylindium moiety chelated asymmetrically by the carboxylate group with one of the two carboxylate oxygens acting as bridge to the next indium center in the chain. The NH2 group does not participate in the coordination of the metal center but is involved in an intermolecular hydrogen bond. 相似文献
6.
Lian-yi Cui Zhen-gang Sun Zhong-min Liu Wan-sheng You Zai-ming Zhu Lei Meng Hui Chen Da-peng Dong 《Inorganic chemistry communications》2006,9(12):1232-1234
A novel tetrahedrally coordinated zinc phosphonate, Zn[O3PCH(NH2)CH3] · 2H2O, has been synthesized using hydrothermal techniques. X-ray diffraction indicates that this material is a two-dimensional layered structure with the organic part of the phosphonate anion being directed into the interlayer region. The zinc atoms are coordinated by three oxygens of three different phosphonate groups, and by the nitrogen of an additional phosphonate unit. 相似文献
7.
WC-40 vol.%Al2O3 composites were prepared by high energy ball milling followed by hot pressing. The tungsten carbide (WC) and commercial alumina (Al2O3) powders composed of amorphous Al2O3, boehmite (AlOOH) and χ-Al2O3 were used as the starting materials. The phase transformation during sintering, the influence of sintering temperature and holding time on the densification, microstructure, Vickers hardness and fracture toughness and the toughening effects of WC-40 vol.%Al2O3 composites were investigated. The results showed that the amorphous Al2O3, AlOOH and χ-Al2O3 were transformed to α-Al2O3 completely during the sintering process. With the increasing sintering temperature and holding time, the relative density increased and both the Vickers hardness and fracture toughness increased initially to the maximum values and then decreased. When the as milled powders were hot pressed at 1540 °C for 90 min, a relative density of 97.98% and a maximum hardness of 18.65 GPa with an excellent fracture toughness of 10.43 MPa m1/2 of WC-40 vol.%Al2O3 composites were obtained. 相似文献
8.
Sr5(PO4)2SiO4:Eu2+ phosphosilicate phosphor was prepared by high temperature solid-state reaction. Effects of strontium sources (strontium oxide, strontium nitrate and strontium carbonate) and of phosphorus sources (diammonium phosphate, strontium monophosphate) on the reactivity of their mixture during heating and on phase composition, morphology and photoluminescence excitation and emission properties of the phosphors were investigated by TG–DTG–DSC, XRD, SEM and photoluminescence spectroscopy. The sequence of the solid-state reactions when using the different starting reagents was discussed based on the TG–DTG–DSC results. It was found that it is hard to prepare pure Sr5(PO4)2SiO4:Eu2+ phosphor with either of strontium sources studied when stoichiometric (NH4)2HPO4 was used as a phosphorus source. Minor Sr2SiO4 impurity phase was present in the phosphors. The content of impurity phase, the morphology and resultant photoluminescence properties of the phosphors were markedly influenced by the strontium source employed. When SrCO3 was used as the strontium source, the phase purity of the phosphor was improved with the addition of excess (NH4)2HPO4. When (NH4)2HPO4with 5% excess or SrHPO4 in stoichiometric ratio was used as the phosphorus source a pure phase phosphor was obtained. In addition, the morphology and photoluminescence of the phosphor were also influenced by phosphorus source. The possible reasons causing different properties of the phosphors prepared using different raw materials were discussed based on reaction schemes. 相似文献
9.
Anna Kubacka Arturo Martínez-Arias Marcos Fernndez-García Mark A. Newton 《Catalysis Today》2009,145(3-4):288
The behavior of 1 wt% Pd-TWCs (three-way catalysts), containing up to 33 wt% Ce0.5Zr0.5O2 is followed under reducing (CO) and oxidizing (NO) cycling conditions. The dynamic behavior of these systems is analyzed using a synchronous, time-resolved energy dispersive X-ray absorption spectroscopy (XAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) set-up with subsecond time resolution. Two main physico-chemical phenomena corresponding to noble metal morphological (size/shape) changes and the redox behavior of the noble metal–promoter interface are shown to control the TWC response to NO/CO cycling conditions. Metal-only aspects strongly influence N–O dissociation and N–N coupling steps while the metal–promoter interface has a global influence on both N2 and CO2 formation via oxygen handling (storage/release) properties. The relative importance of these two phenomena is studied as a function of the Ce0.5Zr0.5O2 promoter content of the catalysts. 相似文献
10.
Jingping Wang Guoqian Zhang Pengtao Ma Jingyang Niu 《Inorganic chemistry communications》2008,11(7):825-828
The first example of disubstituted Lindqvist-type polyoxomolybdate {[V(2,2-bipy)2]2(4,4-bipy)[Te2Mo4O19]} has been synthesized hydrothermally and characterized by elemental analyses, XPS, IR, TG-DTA and X-ray single crystal diffraction. The structural analysis shows that the neutral molecular unit [V(2,2-bipy)2]2[Te2Mo4O19] consists of a novel Lindqvist-type polyanion [Te2Mo4O19]6− supporting two vanadyl moieties [V(2,2-bipy)2]3+, and such neutral molecules are joined together by π − π stacking interactions between the pyridine groups to form a two-dimensional grid-like network with non-coordinating “guest” 4,4-bipys encapsulated. 相似文献