The Specific Heat and the Fermi Surface Anisotropy in Sr2RuO4

The influence of the Fermi surface anisotropy on the specific heat jump is studied for the p-wave superconductor with a gap function d = z^(k _x ± ik _y ) in connection with Sr₂RuO₄. It is shown that the normalized specific heat jump, C/T _c , is reduced from its universal value, 1.43, in accordance with experimental findings. We show that this behavior fits well into our present understanding of the quasiparticle spectrum and the impurity effects.     

Uphill permeation model of gold(III) and its separation from base metals using thiourea derivatives as ionophores across a liquid membrane

This work deals with carrier-facilitated membrane transport of Au(III) from chloride media across a polymer-immobilised liquid membrane (PILM) using as organic reagents N-(thiocarbamoyl)benzamide derivatives and N-benzoylthiourea derivatives, denoted as 2a–c and 3a–f, respectively. Both the composition of the organic membrane solvent and the type of carrier have a marked effect on gold permeation. Recovery and permeability of gold using 2a–c and 3a–f across a PILM proceed in the following order: 3e≈3d≈3c?3f>3b≈3a≈2a≈2b≈2c. In view of the performance of these carriers, 3c was selected as a metal receptor for detailed studies of Au(III) in permeation. A model is presented for the permeation of Au(III) (61 μM) in 0.5 M Cl⁻ at pH 2.5 using 3c as a membrane carrier. The mathematical equations describing the rate of permeation are derived to correlate the membrane permeability coefficient with diffusional and equilibrium parameters. The mass transfer coefficient was calculated from the described model as 1.1×10⁻⁵ m s⁻¹, and the thickness of the aqueous boundary was later calculated to be 65 μm. Several polymeric supports were tested for impregnation of the organic extractant, and Durapore (Millipore) afforded the maximum flux for Au(III), yielding a value of 1.1×10⁻¹⁴ mol m⁻² s. The relationship between flux and support characteristics is derived and a mathematical equation is presented. Of the several diluents used, cumene had the most satisfactory performance in terms of PILM stability and metal transport. Of the different reagents used, 0.5 M sodium thiocyanate in 0.5 M NaCl at pH 2.5 served most efficiently as the stripping agent. More than 80% of the Au(III) could be readily separated using 3c in the presence of various metals such as Cu(II), Fe(III) and Zn(II).     

The influence of hydrogen bonding on mechanical anisotropy in oriented nylon-12

The anisotropy of dynamic tensile modulus in uniaxially and uniplanar-axially oriented nylon-12 sheets has been measured over the temperature range encompassing the α′-relaxation process. The influence of hydrogen bonding on the mechanical behaviour has been demonstrated by comparing these anisotropy measurements for specimens which have been subjected to different thermal treatments.     

Study of indentation size effect and microhardness of SrLaAlO<Subscript>4</Subscript> and SrLaGaO<Subscript>4</Subscript> single crystals

The load dependence of the Vickers microhardness of SrLaAlO₄ and SrLaGaO₄ single crystals, using a PMT-3 hardness tester, has been investigated and analysed from the standpoint of various theoretical models. On the (100) and (001) planes of these crystals, reverse indentation size effect was observed. Analysis of the experimental data revealed: (1) the indentation size effect is best described by Meyer's law and the proportional specimen resistance model of Li and Bradt, (2) indentation-induced cracking model for reverse indentation size effect and Meyer's law cannot be used to determine the hardness of the crystals, (3) as shown by the negative values of the load-dependent quantities in Hays-Kendall's approach and Li-Bradt model, the origin of indentation size effect is associated with the processes of relaxation of indentation stresses, and (4) the load-dependent and load-independent quantities of different models are interrelated and are intimately connected with the orientation and chemical composition of the crystals. It was also found that the plots of the ratio of indentation load to indentation diagonal against indentation diagonal for a sample exhibit two different slopes with a transition in the slopes occurring at an indentation diagonal, whose value depends on the indenter orientation, indented plane and chemical composition of the crystals. The physical significance of the appearance of these transitions and the nature of load-independent indentation microhardness are discussed. Electronic Publication     

Anisotropic Thermal Properties of Solid Polymers

This paper discusses the thermal conduction anisotropy in polymers by reviewing currently available theories and experimental methods for studying oriented polymers. The anisotropic thermal conductivity and diffusivity of oriented polymers originate from the difference between the thermal energy transport mechanisms parallel and perpendicular to their molecules. Recent progress in the development of experimental techniques for studying the thermal conduction anisotropy of polymer films with thicknesses near 1 m is discussed in connection with modern microelectronics applications. The data obtained from these techniques are expected to serve for developing sophisticated thermal conduction theories that account for the polymer anisotropy and for performing precise thermal design of organic electronic devices that incorporate highly oriented polymer structures.     

Mean Square End-to-End Distance of a Semiflexible Polymer on the Bethe Lattice

A combinatorial method to calculate the mean square end-to-end distance R ² of a polymer on a Bethe lattice is used. The case of an anisotropic lattice and semiflexible polymers is considered. The distance on the Cayley tree is defined by embedding the tree on an N-dimensional Euclidean space considering that every bend of the polymer defines a direction orthogonal to all the previous ones. The semiflexible polymer is effectively equivalent to a flexible one if one considers an effective (noninteger) coordination number. Although an analytical calculation is performed, a closed expression for R ² is possible only for the isotropic case. Numerical results are shown for the anisotropic case. Plots of R ² against N for different values of the anisotropy parameter y are shown. The power dependence for N does not depend on the anisotropy as expected, but the linear coefficient increases on increasing the anisotropy. The anisotropy tends to stretch the polymer.     

VA-TFT用负介电各向异性液晶材料研究进展

综述了VA-TFT(垂直取向薄膜晶体管驱动)用负介电各向异性液晶的结构及性质.重点介绍了近年来开发出的一些具有大的介电各向异性、低黏度、高清亮点的新型液晶,如侧向氟取代萘环、茚环类,轴向氟代环己烷类,含多氟取代类液晶等.     

Hydrogen permeability of multiphase V-Ti-Ni metallic membranes

Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven to be successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and hydrogen permeability. Electrochemical hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady-state hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 °C.     

Cleavage Stress Required to Produce Fracture Path Deflection in Cold-Drawn Prestressing Steel Wires

Cold-drawn prestressing steel wires exhibit strength anisotropy in the form of fracture path deflection towards a direction approaching the wire axis, or cold drawing line, as a consequence of the pearlitic microstructure orientation induced by the manufacturing procedure. Such a crack path deflection is initiated at certain nuclei (fracture origins) at which axial cracking appears in the cold drawing direction (or wire axis) in the form of micro-cleavage units that produce in the load-displacement curve a macroscopic phenomenon of pop-in. This paper shows that such fracture initiators appear at a certain distance from the fatigue pre-crack tip at which a local maximum of the cleavage stress is located.     

Influence of sub-micrometer notches on the fracture of single crystal silicon thin films

The influence of notches on the fracture of single crystal silicon thin films was investigated. The tests were conducted on notched and smooth tensile specimens micromachined on a silicon wafer. The specimen geometry was 100 μm long, 50 μm wide and 5 μm thick. For the notched specimen, a V‐shaped sub‐micrometer notch was introduced on one edge of it by using a focused ion beam (FIB) process. The notch lengths ranged from 0.07 to 1.3 μm. Four types of specimens with different surfaces and tensile orientations were tested. The smooth specimens showed scattered fracture strengths and ‘collapsed’ fractures. For the restrictive‐shaped notches, the critical length was 0.5 μm. The short‐notched (<0.5 μm) specimens also showed ‘collapsed’ fractures, and the stress concentrations on notch tips decreased their fracture strengths. For the long‐notched (>0.5 μm) specimens, the notch was equivalent to a crack in the Griffith model and the crack mainly propagated on {111} cleaved planes.