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81.
82.
The ternary phases existing on the quasi binary section CoSi/FeSi and CoSi2/β‐FeSi2 have been investigated by solid state reactions and chemical transport. The solid solution serie CoxFe1‐xSi can be described as a regular solution. The transport behaviour calculated is in good agreement with the experiments. The phases have been characterized by X‐ray powder diffraction, EDX and ICP‐OES. The temperature dependence of the resistivity has been measured from 20 K up to room temperature on single crystals. 相似文献
83.
Rutile Ni
x
Ti1-3x
Sb2x
O2 solid solution nanoparticles were synthesized by a sol-gel route using propylene oxide as a gelation agent. Titanium oxide
nanopowder and 12% TiCl3 solution were used as the source for titanium to investigate the influence of the titanium precursors on the formation of
the target materials. It was found that the nanoparticles prepared using 12% TiCl3 solution showed a much lower phase formation temperature (700°C) as compared to those prepared from TiO2 nanoparticles (1000°C). This lower phase formation temperature allowed a substantial reduction of the aggregation of the
particles during calcination leading to the formation of nearly mono-dispersed nanoparticles of about 20 nm. The results of
this work show that the epoxide assisted sol-gel method is capable to produce titanium-based ternary oxide solid solution
nanoparticles, owing to the formation of a highly homogeneous precursor gel intermediate. 相似文献
84.
The effect of the addition of n-butanol (BuOH) and n-hexanol (HexOH) on the micellization of sodium dodecylsulfate (SDS) has been investigated using fluorescence quenching methods.
The binding constants were calculated using an expression which relates the total concentration of alcohols and the micelle
concentration. The values of K were 4.67 and 17.6 M-1 for BuOH/SDS and HexOH/SDS, similar to values obtained by other methods. The cmc of SDS decreases on addition of alcohols
and goes through a minimum for the BuOH/SDS system. Micellar aggregation numbers (N) were determined from linear plots of Ln (I
0/I) against [Quencher] at low alcohol concentrations. For 15 mM SDS, in the presence of BuOH the N values decrease on addition of alcohol up to 0.2 M. For HexOH, N can be assumed to be constant up to 4.8 mM, after which N decreases. The polarity of the micellar core containing alcohol was evaluated from the I
1/I
3 ratio of monomeric pyrene. The effect of addition of the alcohol causes a decrease in the I
1/I
3, which corresponds to a decrease in the polarity of the pyrene solubilization site.
Received: 28 October 1996 Accepted: 10 January 1997 相似文献
85.
86.
A novel mixed valent tellurium oxide, SrTe3O8, has been synthesized and its crystal structure was determined ab initio from powder X-ray diffraction data. This oxide, which crystallizes in a tetragonal unit-cell, P42/m space group, with very close a and c cell parameters (6.8257(1) and 6.7603(1) Å, respectively), exhibits a very original structure built up of corner-sharing TeO6 (Te6+) octahedra and Te2O8 (Te4+) twin-pyramidal units. The latter ones form [Te3O8]∞ chains running along the [001] and the [110] directions. Besides the four sided tunnels where the Sr2+ cations are located, there are very large four sided tunnels running along the c-axis which are obstructed by the electronic lone pairs of the Te4+ cations. 相似文献
87.
The new platinum-osmium alkyne cluster complex Pt2Os4(CO)8(3-PhC2Ph)3 (
4-PhC2Ph),2, was obtained from the reaction of Pt2Os4(CO)18,1b, with PhC2Ph and was characterized by IR.1H NMR and single-crystal X-ray diffraction analyses. The cluster of compound2 consists of an osmium capped Pt2Os3 square pyramid. It aLso contains three triply bridging and one quadruply bridging diphenylacetylene ligands. Crystal data for2: space group PI,a = 12.530(2) Å,b = 21.565(4) Å,c = 11.284(2) Å, = 100.31(2), = 111.89(1), = 76.78(2),Z = 2, 3879 reflections,R = 0.032. 相似文献
88.
采用动电位扫描法、电化学交流阻抗法和表面分析方法研究了假单胞菌的加入对A3钢在枝孢霉菌溶液中腐蚀行为的影响. 结果表明, 假单胞菌的存在影响了A3钢在枝孢霉菌体系中阳极的反应过程, 假单胞菌与枝孢霉菌混合体系(简称假-枝混合菌体系)中A3钢的自腐蚀电流小于枝孢霉菌单种菌体系, A3钢的腐蚀速率减小;随着浸泡时间的延长, 从第7天开始, A3钢电极在假-枝混合菌体系中的阻抗值较之同样浸泡天数的枝孢霉菌单种菌体系的阻抗值大, 假单胞菌的存在抑制了枝孢霉菌对A3钢的腐蚀. SEM结果表明, A3钢在枝孢霉菌和假-枝混合菌体系中均发生了点蚀,枝孢霉菌单菌体系中A3 钢的点蚀坑大而深, 假-枝混合菌体系中的点蚀坑与枝孢霉菌体系相比小而浅. 相似文献
89.
Brown crystals of [PMePh3]2[TeBr6(SeBr2)2] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å. 相似文献
90.
J. L. Gautier E. Meza E. Silva C. Lamas C. Silva 《Journal of Solid State Electrochemistry》1997,1(2):126-133
The electrochemical insertion of lithium in the spinel-type manganite with the formula ZnNi
y
Mn2–
y
O4 has been studied. The galvanostatic discharge curves show that the best performance is obtained for y = 0.25, where a tetragonal to cubic structural transformation occurs. The thermodynamics and kinetics of the process of insertion
of the lithium into the tetragonal spinel Li
x
ZnNi0.25Mn1.75O4 (x = 0.05–1.3) have been studied. The molar thermodynamic quantities, such as enthalpy, entropy and free energy determined by
EMF-T measurements, varied with the lithium concentration in the oxide structure, and a major variation was observed around
x = 0.8. The chemical diffusion coefficient of lithium in these spinels was also determined. Structural analysis, degree of
oxidation and magnetic susceptibility measurements were carried out for the lithiated oxides in order to obtain the cationic
distribution as a function of x. It has been possible to demonstrate that, upon lithium insertion, Mn4+ ions on B sites are reduced to Mn3+ and then to Mn2+. A cooperative Jahn-Teller effect is present in these spinel manganese-nickel oxides.
Received: 4 February 1997 / Accepted: 11 April 1997 相似文献