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781.
782.
Crystals of the title compounds were obtained by arc-melting cold-pressed pellets of the elemental components, followed by annealing the reaction products in an argon atmosphere slightly below the melting point. The crystal structures of these isotypic, hexagonal carbides (P63/m, Z=2) were determined from single-crystal X-ray data; Gd3Mn2C6: a=815.0(2) pm, c=504.93(9) pm, R=0.012 for 526 structure factors and 18 variable parameters; Tb3Mn2C6: a=810.5(2) pm, c=500.5(2) pm, R=0.025 (225 F′s, 18 variables). The carbon atoms form pairs with C—C bond distances corresponding to double bonds. The three-dimensional, polyanionic managanese carbon network contains relatively large trigonal-bipyramidal voids formed by three lanthanoid and two manganese atoms. The rationalization of chemical bonding on the basis of the 18-electron rule suggests that these voids are filled by nonbonding electrons of the adjacent manganese atoms. 相似文献
783.
H测定过MgSO_4-C_2H_5OH-H_2三元系在25℃、50℃、75℃的液固平衡和部分不饱和溶液汽液平衡的总压和分压。本文补充了30℃、0℃和-5℃时的溶解度数据,得到分层温度和浓度范围,绘出了溶解度图。测定了25℃和30℃饱和溶液的密度,粘度和平衡总压力。根据Jaques“假二元系”理论用Wilson、Uniquac和NRTL活度方程计算了溶 相似文献
784.
The effect of very low concentrations of ethanol, 2-propanol and phenol on the swelling degree of poly(ethylene-co-vinyl alcohol) (EVAL) in water was investigated. The effect of phenol on the swelling degree of EVAL was remarkably large compared to that of ethanol and that of 2-propanol. Theoretical analysis on the basis of Flory-Huggins theory using three binary interaction parameters could appropriately predict the EVAL swelling degree in ethanol/water and 2-propanol/water mixtures. However, the theoretical swelling degree of EVAL in phenol/water mixtures needed a ternary interaction parameter (χT) to match with experimental data points. An optimum value of χT for the water-phenol-EVAL system was found to be −3.3. The relationship between the ternary interaction parameter and the structure of water from observations of the effect of phenol on the EVAL swelling was discussed. Based on the analysis of low-frequency Raman spectroscopy reported by Suzuki et al. [J. Chem. Phys. 107 (1997) 5890], the contribution of χT to the EVAL swelling was attributed to the increase of the entropy in bulk water due to the effect of phenol on the disruption of the tetrahedral hydrogen-bonded networks of water molecules. This, in turn, induced an increase of water absorption in EVAL. 相似文献
785.
786.
In this review, a summary of our published results, completed with new unpublished data are considered together with some
of other authors’ publications, making an attempt to reveal the mechanism of the third element co-deposition in electroless
Ni–P plating and to define its influence on the ternary coatings’ properties. A model explaining the triple role of Cu added
to the solution for electroless (EL) Ni–P plating is described: as a stabilizer [Cu(I)]; as an accelerator; and as a stability-affecting
agent, forming a dispersed solid phase in the solution. The disproportionation reaction of Cu(I) has been taken into account.
A planned experiment was performed using full-effect factorial design with two levels of three process variables, and the
response surfaces were constructed. The interaction between the factors was revealed. The results are in harmony with the
aforementioned model. In low-tin Ni–Sn–P coatings, the alloy components are uniformly distributed both on the surface and
through the thickness. In contrast, high-tin coatings exhibit three-dimensional areas enriched in Sn and impoverished in Ni
and P. As the reason for their formation, the disproportionation reaction of Sn(II) is suggested, supposed to be locally predominant
over the hypophosphite oxidation. EL deposition of pure Sn onto Ni–Sn–P substrates is shown. The inclusion of Cu or Sn in
EL Ni–P increases the thermal stability of amorphous state, ensures the preservation of a paramagnetic behavior and improves
the corrosion resistance.
Dedicated to the 70th birthday of Professor A. Vaskelis. 相似文献
787.
三元配合物停流—动力学分析法测定铝的研究 总被引:8,自引:0,他引:8
利用自动化动力学分析装置研究了铝与3,5-二溴水杨基荧光酮及表面活性剂形成三元配合物的动力学性质,测定了质子、显色剂及表面活性剂的反应级数及反应活化能。提出了一种简便、快速、精密和准确的分析方法,并用于人发中痕量铝的测定。方法灵敏度较高(ε=1.11×10~5L/mol·cm),大多数元素的干扰均可用动力学方法消除,优于其它测定铝的多元配合物体系。 相似文献
788.
PHASE EQUILIBRIUM FOR THE TERNARY SYSTEM VINYL CHLORIDE-CHLORINATED POLYETHYLENE-POLY(VINYL CHLORIDE) 总被引:1,自引:0,他引:1
Swelling capacity of vinyl chloride (VC) in chlorinated polyethylene (CPE) with 25—40 wt% Cl at temperature 30—57℃was studied and their relationships were correlated with Langmuir and Freundlich adsorption equations. A ternary phase diagram for VC-CPE-PVC was also established. In-situ polymerization conditions of CPE-g-VC were proposed and CPE content control was analyzed for the manufacturing process of CPE-g-VC graft product based on results of phase equilibrium study. 相似文献
789.
A. Wurth D. Johrendt A. Mewis C. Huhnt G. Michels M. Roepke W. Schlabitz 《无机化学与普通化学杂志》1997,623(9):1418-1424
About the Effect of Temperature, Pressure, and Substitution on the Crystal Structure of ARh2P2 (A = Ca, Sr, Eu, Ba) Four compounds ARh2P2 (A = Ca, Sr, Eu, Ba) were prepared by heating mixtures of the elements and investigated by means of single crystal X-ray methods. They crystallize in the ThCr2Si2 type structure (I4/mmm; Z = 2) with P? P distances along [001] reaching from 2.26 Å (CaRh2P2) to 3.74 Å (BaRh2P2). With increasing temperature (EuRh2P2) or increasing pressure (SrRh2P2) a first order phase transition occurs with strong changes of the P? P distances. Substitution of the atoms changes the bond lengths of the compounds too. 相似文献
790.
K3BiSe3, Rb3BiSe3, and Cs3BiSe3 – Derivatives of the Th3P4 Structure Type The compounds K3BiSe3, Rb3BiSe3, and Cs3BiSe3 were synthesized by heating mixtures of Bi2O3 and the respective alkalicarbonate in a stream of hydrogen saturated by selenium at 850°C. Thin crystals of the compounds appear red in transmitted light. They crystallize isostructural with Na3AsS3, space group P213, lattice constants a = 9.771(5) Å, a = 10.161(3) Å, and a = 10.587(5) Å for K3BiSe3, Rb3BiSe3, and Cs3BiSe3, respectively. The Na3AsS3 structure type is a derivative of the Th3P4 structure type. 相似文献