Preparation of a pinhole-free Pd–Ag membrane on a porous metal support for pure hydrogen separation

A pinhole-free palladium membrane with a thickness of 3 μm has been prepared on the surface of a porous sintered stainless steel tube coated with a thin silver layer as a diffusion barrier. Filling of aluminum hydroxide gel in the surface pores of the tube is effective in preventing defect formation during electroless plating of the palladium layer, while the volume of the hydroxide beneath the membrane decreases greatly upon thermal treatment up to 500 °C. The hydrogen flux at 400–500 °C is reasonably proportional to the pressure difference between the two sides of the membrane. Addition of a 2 μm Pd_0.8Ag_0.2 alloy layer on the membrane by electroplating does not greatly decrease the hydrogen permeability.     

Dynamical models for fragment formation

The various dynamical models for fragment formation in nuclear collisions are discussed in order to bring out their relative advantages and shortcomings. After discussing the general requirements for dynamical models that aim to describe fragment formation, we consider the various mean-field models that incorporate fluctuations and then turn to models based on molecular dynamics.     

Phase transition and superconductivity of (Ba,Sr,La)2YCu3Oz (z>6.9)

A series of (Ba,Sr,La)₂YCu₃O_z (z>6.9) samples is studied to elucidate the relationship between structure, cation composition and oxygen content. The concentration of La plays an important role in the orthorhombic to tetragonal phase transition. The tetragonal structure is stabilized by increasing oxygen content and decreasing average ionic radius of cations on the Ba site. The phase transition is explained in terms of the random distribution of CuO₅ pyramids in the BaO–CuO_x slab. Superconductivity does not depend significantly on the phase transition.     

First-principles study on field evaporation of surface atoms from W(0 1 1) and Mo(0 1 1) surfaces

The simulations of field-evaporation processes for surface atoms on W(0 1 1) and Mo(0 1 1) surfaces are implemented using first-principles calculations based on the real-space finite-difference method. The threshold values of the external electric field for evaporation of the surface atoms, which are ∼6 V/Å for tungsten and ∼5 V/Å for molybdenum, are in agreement with the experimental results. While the threshold value of the electric field and the local-field enhancement around the evaporating atoms agree with those expected from the conclusion of the previous study using structureless jellium, the induced charge around the surface atom has a significant difference from that obtained by the jellium model.     

Determination of silicon in high-silicon electrical steel by ICP-AES with on-line sample electrolytic dissolution.

A flow-injection procedure combining electrolytic sample decomposition and inductively coupled plasma atomic emission spectrometry (ICP-AES) is proposed in order to rapidly determine the content of silicon in high-silicon electrical steel. This system is characterized by sample decomposition through electrolysis directly coupled to ICP-AES. A steel sample is dissolved by electrolysis using a 6 mol L(-1) HCl solution as an electrolyte with a flow rate of 5 mL min(-1); the electrolyte containing a dissolved sample is subsequently introduced into ICP-AES via a nebulizer. The effects of the electrolysis current and the temperature on the decomposition of the sample were studied. Samples were electrolyzed under the condition of a 1.5 A constant current, at room temperature (25 degrees C) to avoid the hydrolysis of silicon to precipitate. Comparing the analytical results of steel samples obtained by this analytical system with those obtained by the gravimetric method, determined values agreed well quantitatively. The RSD of silicon at approximately 3% was 0.3% (n = 6).