J.H. Byun
,
S.-K.Lee and B.S. Kim (Korea Institute of Machinery and Materials
,
P.O. Box 41
,
Changwon
,
Korea Manuscript received 26 August 1996)
金属学报(英文版)
In order to realize the potential of composite materials, it is imperative to develop a manufacturing process, to understand the microstructures, and to assess the structural performance of the composite. The braided-pultrusion process, which combines the pultrusion process with the braiding technology, has been developed by utilizing a novel resin impregnation device. The goal of the development is to achieve both costeffectiveness and performance of the composite. The tubular composites of diameter 5.3 mm have been produced using Kevlar 49 fiber and polyester resin. In order to assess the mechanical performance of the composites, an analytical method for predicting the elastic constants has been developed. The analysis includes the geometric model of a unit cell, coordinate transformation, and averaging of stiffness and compliance constants of the constituent materials. The analytic predictions compared favorably with experimental results.
关键词:
: braided pultrusion
,
null
,
null
柳云骐
,
李望良
,
刘春英
,
崔敏
,
刘晨光
催化学报
采用水热法合成了不同SiO2/Al2O3比的MCM-41介孔分子筛.并分别以HY/MCM-41/γ-Al2O3, HY/γ-Al2O3和γ-Al2O3为载体,用浸渍法制备了Mo-Ni-P催化剂.以萘为模型化合物,考察了硫化态Mo-Ni-P催化剂的加氢活性.结果表明,不同载体负载的催化剂催化活性均随着活性组分负载量的增大而提高,其中掺杂大比表面MCM-41的HY/MCM-41/γ-Al2O3所负载的催化剂催化活性提高幅度最大.由于MCM-41与HY分子筛在酸性和孔结构上存在互补性,因而催化剂对萘加氢存在协同作用.提出了萘加氢的反应机理,认为反应网络包括两个平行路径: 一是萘加氢生成四氢萘后发生异构化或开环反应; 二是萘加氢生成四氢萘后进一步加氢生成十氢萘,继而发生异构化或开环反应.
关键词:
MCM-41分子筛
,
HY分子筛
,
萘
,
加氢
,
反应机理
Chinese Journal of Chemical Physics
The core-level X-ray photoelectron emission spectra of the quasi-one dimensional spin 1/2 antiferromagnetic system Sr14-xCaxCu24O41 (x = 0, 3.5, 6, 7, 8.4) were measured. The main peak of Cu2P(3/2) was about 933.8 eV, and the full width of half maximum height was about 3.3 eV. Simulation of Cu2P(3/2) by XPSPEAK41 shows that the percents of Cu2+ and Cu3+ in Sr14Cu24O41 are 92.13% and 7.87%, no obvious change to Cu2p core-level is observed by the partial substituting Ca for Sr, and the average valence of Cu in this system is estimated to be 2.08. The main peak of O1s is about 531.0 eV, and the weak shoulder toward the low binding energy direction can be considered as the contribution of Ca-O bond. The binding energies of Ca2P(3/2) and Sr3d(5/2) indicate that their valence in this system are both +2, without mixed valence.
关键词:
Sr1-xCaxCu24O41;core-level X-ray photoelectron emission spectra;electronic structure;superconductivity;ladders;system;scattering;crystal;valence;chains
Acta Physica Sinica
Polycrystalline samples of Sr(14)Cu(24)O(41) and Sr(14) (Cu(0.97) M(0.03))(24) O(41) (M = Zn, Ni, Co) were synthesized by standard solid state reaction method. All samples are single phase as identified by X-ray diffraction, no regular shift of lattice parameters a, c is found, but the lattice parameter b increases slightly with doping magnetic ions Ni and Co, and has no change with doping non-magnetic ion Zn, respectively. Selected area electron diffraction experiments show that Zn,Ni and Co ions may substitute for Cu ions in the chain. All the doping compounds are still semiconductors and have a crossover temperature T(p) like the parent phase Sr(14)Cu(24)O(41). The influence of magnetic ion Ni or Co doping on the resistivity is smaller than that of non-magnetic ion Zn doping, while the influence of non-magnetic ion Zn doping on crossover temperature is smaller than that of magnetic ion Ni or Co doping.
关键词:
spin ladder compound;Sr(14)Cu(24)O(41);B-site doping;transport;property;metal-insulator-transition;single-crystals;sr(14-x)a(x)cu(24)o(41);sr14cu24o41;dynamics;charge;la;gap;ca
Solid State Communications
Considering the image potential, we calculate the binding energies of a shallow donor impurity placed on the centre of a quantum box using the variational approach. The results we have obtained show that there is a great difference of the effects of image potential between the cases including impurity ion image potential and including the image potentials of impurity ion and electron simultaneously. The results also show that the image potential is important, especially when the dimensions of quantum box become small.
关键词:
well;gaas-ga1-xalxas;states
武汉理工大学学报-材料科学版(英文版)
A new process to synthesize polycrystalline samples of Sr(14)Cu(14)O(41) was presented. Firstly, dry gel powder of Sr(14)Cu(21)O(41) was synthesized by the citrates sol-gel method, using Sr(NO(3))(2), Cu(NO(3))(2), ethylene glycol and citrate acid as raw materials. Then, polycrystalline samples of Sr(14)Cu(24)O(4)1 were prepared by solid-state reaction. Thermal Gravimetric and Differential Thermal Analysis(TG-DTA) showed that the temperature for solid-state reaction is at 942 degrees C. The samples are,identified to be single phase by X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM). The SEM pictures showed that the first-step particles were at even size of about 100 nm by this technique. The electronic transport measurements showed that the doping compound were semiconductor with a crossover temperature T(rho) in the Arrhenius plot of the resistivity versus temprature.
关键词:
citrates sol-gel;solid-state reaction;Sr(14)Cu(24)O(41);spin ladder;chains
Journal of Physics-Condensed Matter
Structural properties and hole distribution in the spin-ladder compound Sr(14-x)Ca(x)Cu(24)O(41) have been extensively investigated by transmission electron microscopy (TEM). The complex electron diffraction patterns and high-resolution TEM observations reveal a clear incommensurate structural modulation along the c-axis direction attributable to two mismatched sublattices; this modulation strongly depends on hole distribution in the compounds. The fine structures of the O K and Cu L(2,3) ionization edges for the Sr(14-x)Ca(x)Cu(24)O(41) compounds recorded under different conditions indicate that more doped holes reside in the chains than the ladders, and that substituting Ca for Sr atoms results in a charge redistribution between the chains and ladders. Based on the experimental findings, the theoretical results, including the partial density of states and optical conductivity spectra calculated by the density functional theory, are also discussed.
关键词:
ladder compound sr14cu24o41;ray-absorption spectroscopy;electron-energy-loss;spin-ladder;cuo2 chains;superconductivity
Materials Letters
The thermal behavior of (14-x)SrCO3-xCaCO(3)-24CuO system has been investigated using combined differential thermal analysis (DTA) and X-ray diffraction (XRD) measurements to get a better understanding of solid-state chemical changes resulting in the synthesis of spin-ladder compound Sr14-xCaxCu24O41. In the temperature region 900-1000 degreesC, the DTA curves present one and two endothermic peaks for xless than or equal to5.6 and xgreater than or equal to8.4, respectively. XRD measurements demonstrated that for xless than or equal to5.6, the solid-state reaction consists of three stages and leads to the formation of the single-phase Sr14-xCaxCu24O41. It is found that both XRD and DTA methods can be employed independently to determine the composition or temperature region in which the pure phase forms. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
sintering;X-ray techniques;phase diagrams;superconductors;sro-cao-cuo;phase-relationships
