复合基带外层Ni5W再结晶织构演变的研究

采用X射线四环衍射技术和背散射电子衍射技术,对具有多层结构的NiW合金复合基带外层Ni5W(at%)的形变织构和再结晶织构进行了研究。研究发现,梯度分布的形变织构和多层材料之间的扩散是决定复合基带外层Ni5W织构演变的两个主要因素。这为进一步研究金属合金复合材料各层之间的织构形成及其关联性奠定了基础。     

Synthesis,sinterability and ionic conductivity of nanocrystalline Pr-doped La2Mo2O9 fast oxide-ion conductors

A new series of nanocrystalline La_2−xPr_xMo₂O₉ (0.2 ≤ x ≤ 0.8) powders are synthesized through the pyrolysis of polyacrylate salt precursors prepared via in situ polymerization of the metal salts and acrylic acid. The polymeric precursors are characterized by thermogravimetric and differential thermal analysis (TG/DTA) to determine the thermal decomposition and crystallization temperature, which is found to be at 510 °C. X-ray diffraction analysis indicates that the substitution of La by Pr preserves the single-phase La₂Mo₂O₉ structure up to a Pr dopant concentration of x ≤ 0.7. The particle size and the α → β phase transition of the Pr-doped La₂Mo₂O₉ samples are studied by using a transmission electron microscope (TEM) and differential scanning calorimetry (DSC), respectively. The sintering behaviour of the Pr-doped samples are examined via isothermal and non-isothermal experiments. It demonstrates that the synthesized nanocrystalline powders have good sinterabilty and a relatively low sintering temperature of 800 °C for 4 h is sufficient to reach ∼99% of the theoretical density with good microstructures. Furthermore, the oxide-ion conductivity increases with increasing Pr content and the maximum conductivity is attained at x = 0.5 in La_2−xPr_xMo₂O_9.     

Complex Hydrides for Electrochemical Energy Storage

Complex hydrides have energy storage‐related functions such as i) solid‐state hydrogen storage, ii) electrochemical Li storage, and iii) fast Li‐ and Na‐ionic conductions. Here, recent progress on the development of fast Li‐ionic conductors based on the complex hydrides is reported. The validity of using them as electrolytes in all‐solid‐state lithium rechargeable batteries is also examined. Not only coated oxides but also bare sulfides are found to be applicable as positive electrode active materials. Results related to fast Na‐ionic conductivity in the complex hydrides are presented. In the last section, the future prospects for battery assemblies with high‐energy densities, and Mg ion batteries with the liquid and the solid‐state electrolytes are discussed.     

Yield Strengths of Biaxially Textured Metallic Substrates (Ni and its Alloys) Determined Using a Simplified Test Method

A simple testing method is used to compare the yield strengths (YS) of biaxially textured metallic substrates (Ni and its alloys) presently under development for YBa₂Cu₃O_7−x coated conductors. This method is based on a retired ASTM D3379 tensile test standard method that was originally recommended for single filament materials. Several common textured substrates, such as Ni, Ni-3at.%W, and Ni-5at.%W, procured from different manufacturers, were tested using this method, and the data were compared with the values reported in the literature. A new alloy substrate (constantan (Cu55-Ni44-Mn1wt.%)) that is biaxially textured in-house was also tested using this method, and the YS data were compared with those of other substrates. For the substrates used in this study, the data obtained using this method indicated that Ni substrates have YS of ∼52 MPa, Ni-3at.%W substrates have YS of ∼106 MPa, Ni-5at.%W substrates have YS 163 MPa, and Cu55-Ni44-Mn1 wt.% substrates have YS of 74 MPa.     

Performance evaluation of the ITER Toroidal Field Model Coil phase I: Part 2: M&M analysis and interpretation

The ITER Toroidal Field Model Coil (TFMC), a large (2.7 m × 3.8 m × 0.8 m) superconducting (Nb₃Sn) DC coil designed and constructed in collaboration between EU industries and laboratories coordinated by EFDA, has been tested during 2001 in the TOSKA cryogenic facility at Forschungszentrum Karlsruhe, Germany, achieving the nominal 80 kA at 7.8 T peak field and 86 MJ stored energy as a standalone coil (Phase I). The results of the current sharing temperature (T_CS) measurements at I=80, 69 and 57 kA, presented in a companion paper (Part 1), are evaluated here using the M&M code. The critical properties best fitting the experimental voltage-inlet temperature characteristic of the P1.2 pancake are deduced from the TFMC data under the assumption of an ideal collective behaviour of the strands. The TFMC results are compared first with the expected conductor performance, showing that at the maximal current the performance was borderline with what was expected, while at the minimal current tested it was better than expected. Second, they are compared with the performance of the single strand as measured in the lab, showing that, in order to reproduce the TFMC data, one has to invoke that some degradation, larger at higher current, occurred when going from the strand to the cable.     

Photocatalytic oxidation of cyclohexane over TiO2 nanoparticles by molecular oxygen under mild conditions

The structure, physical characteristics and photocatalytic selective oxidation properties of nanometer‐size TiO₂ particles produced by a sol–gel method were studied by X‐ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X‐ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and photocatalytic selective oxidation measurements. Analysis of the XRD results shows that sol–gel‐produced TiO₂ nanoparticles have the anatase structure at annealing temperatures ≤973 K, that the rutile structure begins to emerge at annealing temperatures ≥973 K and the particles have the pure rutile structure at 1023 K. DRS indicates that the obtained TiO₂ nanoparticles exhibit a blue shift with decreasing crystallite size. Analysis of the XPS results shows that the TiO₂ nanoparticles have a lot of oxygen vacancies. The EPR spectrum of TiO₂ at 77 K is composed of a strong isotropic EPR Surface‐Ti³⁺ signal(I) at g = 1.926 and a weak broad Bulk‐Ti³⁺ signal (II) at g = 1.987. Quantitative EPR indicates that both signals show a size and temperature dependence. Photocatalytic oxidation of cyclohexane into cyclohexanol with high selectivity and activity has been obtained by activation of molecular oxygen over sol–gel‐produced TiO₂ nanoparticles under mild conditions in dry solvent, which reveals that the quantum size effect and surface state effect of nanoparticles are key points for governing the selective photocatalytic reaction. The photocatalytic oxidation mechanism under dry solvent is different from that in aqueous solutions. Copyright © 2003 Society of Chemical Industry     

塑力缆瓦形线芯结构和压辊设计数学模型

系统研究了塑力缆瓦形线芯的结构设计 ,给出使用数学 MATHCAD2 0 0 1软件建立瓦形线芯结构和压辊设计的数学模型 ,并结合示例进行规范化设计。经实践证明该方法简便快捷 ,具有一定使用价值     

Comparison of Electronic Transport Measurements on Organic Molecules

We compile, compare, and discuss experimental results on low‐bias, room‐temperature currents through organic molecules obtained in different electrode–molecule–electrode test‐beds. Currents are normalized to single‐molecule values for comparison and are quoted at 0.2 and 0.5 V junction bias. Emphasis is on currents through saturated alkane chains where many comparable measurements have been reported, but comparison to conjugated molecules is also made. We discuss factors that affect the magnitude of the measured current, such as tunneling attenuation factor, molecular energy gap and conformation, molecule/electrode contacts, and electrode material.     

Hall conductivity of a moving magnetic-field-induced spin-density wave

The influence of the motion of a magnetic-field-induced spin-density-wave (FISDW) on the quantum Hall effect in a quasi-one-dimensional conductor is studied theoretically. In the ideal case, when the pinning and the damping of the FISDW can be neglected, it is found that the counterflow of the FISDW precisely cancels the quantum Hall current, so that the resultant Hall conductivity is zero. In real systems, the Hall conductivity should vanish at the high frequencies where the dynamics of the FISDW is dominated by inertia, and the pinning and the damping can be neglected.This work was partially supported by the NSF Grant No. DMR 89-06958.