Spontaneous alloying in binary metal microclusters - A molecular dynamics study -

Microcanonical molecular dynamics study of the spontaneous alloying(SA), which is a manifestation of fast atomic diffusion in a nano-sized metal cluster, is done in terms of a simple two dimensional binary Morse model. Important features observed by Yasuda and Mori are well reproduced in our simulation. The temperature dependence and size dependence of the SA phenomena are extensively explored by examining long time dynamics. The dominant role of negative heat of solution in completing the SA is also discussed. We point out that a presence of melting surface induces the diffusion of core atoms even if they are solid-like. In other words, the {\it surface melting} at substantially low temperature plays a key role in attaining the SA.Comment: 15 pages, 12 fgures, Submitted to Phys.Rev.

In situ imaging of microstructure formation in electronic interconnections

The development of microstructure during melting, reactive wetting and solidification of solder pastes on Cu-plated printed circuit boards has been studied by synchrotron radiography. Using Sn-3.0Ag-0.5Cu/Cu and Sn-0.7Cu/Cu as examples, we show that the interfacial Cu6Sn5 layer is present within 0.05 s of wetting, and explore the kinetics of flux void formation at the interface between the liquid and the Cu6Sn5 layer. Quantification of the nucleation locations and anisotropic growth kinetics of primary Cu6Sn5 crystals reveals a competition between the nucleation of Cu6Sn5 in the liquid versus growth of Cu6Sn5 from the existing Cu6Sn5 layer. Direct imaging confirms that the β-Sn nucleates at/near the Cu6Sn5 layer in Sn-3.0Ag-0.5Cu/Cu joints

Electrodynamic trapping of spinless neutral atoms with an atom chip

Three dimensional electrodynamic trapping of neutral atoms has been demonstrated. By applying time-varying inhomogeneous electric fields with micron-sized electrodes, nearly $10^2$ strontium atoms in the $^1S_0$ state have been trapped with a lifetime of 80 ms. In order to design the electrodes, we numerically analyzed the electric field and simulated atomic trajectories in the trap, which showed reasonable agreement with the experiment.Comment: 4pages, 4figures, to appear in Phys. Rev. Let

Nonpolar resistance switching of metal/binary-transition-metal oxides/metal sandwiches: homogeneous/inhomogeneous transition of current distribution

Exotic features of a metal/oxide/metal (MOM) sandwich, which will be the basis for a drastically innovative nonvolatile memory device, is brought to light from a physical point of view. Here the insulator is one of the ubiquitous and classic binary-transition-metal oxides (TMO), such as Fe2O3, NiO, and CoO. The sandwich exhibits a resistance that reversibly switches between two states: one is a highly resistive off-state and the other is a conductive on-state. Several distinct features were universally observed in these binary TMO sandwiches: namely, nonpolar switching, non-volatile threshold switching, and current--voltage duality. From the systematic sample-size dependence of the resistance in on- and off-states, we conclude that the resistance switching is due to the homogeneous/inhomogeneous transition of the current distribution at the interface.Comment: 7 pages, 5 figures, REVTeX4, submitted to Phys. Rev. B (Feb. 23, 2007). If you can't download a PDF file of this manscript, an alternative one can be found on the author's website: http://staff.aist.go.jp/i.inoue

Preparation And Characterization Of Composite Hollow Fiber Reverse Osmosis Membranes By Plasma Polymerization. 2. Reproducibility Of The Plasma Polymerization Process And Durability Of The Resulting Coated Membrane

The reproducibility of the plasma polymerization process was examined in a semicontinuous coating of hollow fibers, 6 fibers in lengths of approximately 12-15 m, by evaluating the performance of reverse osmosis membranes. The uniformity of the coating along the length of hollow fibers, as well as the reproducibility of the process, was found to be satisfactory when electrodes were conditioned in the actual conditions of plasma polymerization to be employed and plasma polymerization conditions were carefully controlled. The durability of the coated hollow fibers was then investigated in the following test media: hot water, low pH, high pH, and 0.1% NaOCl solutions. A threshold value of glow discharge parameter W/FM was found to be crucial In the performance of the reverse osmosis membrane and durability of the coated hollow fibers. Plasma polymerized composite membranes showed remarkable durability. © 1984, American Chemical Society. All rights reserved

Evaluation Of Plasma Polymers Of Silanes As Adhesion Promoters For Organic Paint

Plasma-polymerized coatings were prepared in a bell-jar-type reactor equipped with a magnetron system behind parallel aluminum electrodes using an a.c. source of frequency 10 kHz. Tetramethoxysilane, dimethyldimethoxysilane and hexamethyldisilane were used as monomers. Alkyd paint was coated on titanium plates onto which plasma polymer films had been deposited, to investigate the characteristics of the plasma-deposited films as adhesion promoters. The relationship between the adhesion strength for the paint and the conditions for the plasma polymerization was studied. The properties of the plasma polymers are dependent on the conditions of plasma polymerization manifested by two domains, namely the energy-deficient and the monomer-deficient regions. In the energy-deficient region, the differences due to the monomer structure can be clearly observed; however, in this region the adhesion of the plasma polymer film to the substrate metal is poor, and the plasma polymer does not serve as a good primer for the paint. In the monomer-deficient region (for this study a power input per unit mass of starting material of W/FM ≥ 1.7 x 109 J kg-1) improved adhesion of the paint is obtained; however, in this region the difference due to the monomer structure is found to be minimal. © 1984

PLASMA POLYMERIZATION INVESTIGATED BY THE SUBSTRATE TEMPERATURE DEPENDENCE.

In the reported experiments, plasma polymerization of tetrafluoroethylene (TFE), perfluoro-2-butyl-tetrahydrofuran (PFBTHF), ethylene, and styrene were investigated in various combinations of monomer flow rates and discharge wattages for the substrate temperature range of minus 50 to 80 degree C. The polymer deposition rates can be generally expressed by k//o equals Ae** minus **b**t, where k//o is the specific deposition rate given by k//o equals (deposition rate)/(mass flow rate of monomer), A is the preexponential factor representing the extrapolated value of k//o at zero absolute temperature, and b is the temperature-dependence coefficient. It was found that the value of b is not dependent on the condensability of monomer but depends largely on the group of monomer; that is, perfluorocarbons versus hydrocarbons. The values of A are dependent on domains of plasma polymerization. The kinetic equation is discussed in view of the bicyclic rapid step-growth polymerization mechanisms

Electrical Properties Of Plasma-polymerized Thin Organic Films

The electrical properties of plasma-polymerized films are summarized and compared to those of conventional polymers. Particular attention is devoted to the dielectric relaxation, dielectric breakdown, electric conductivity and photoconductivity, and their control via control of the plasma parameters. © 1983 Plenum Publishing Corporation

Adhesion Of Glow Discharge Polymers To Metals And Polymers

Adhesion of glow discharge polymers to metals and polymers in an adhesive joint was measured by lap‐shear test and immersion in hot water of 70°C for an extended time. A glow discharge polymer was deposited onto polymers [polyethylene and poly(tetrafluoroethylene)] and metals (aluminum and stainless steel) prior to when the polymer and metal were joined. It is found that the lap‐shear strength is enhanced by coating the surfaces of these substrates with plasma film produced from methane, ethylene, and acetylene, and that deterioration of the adhesive bonding part, when immersed in hot water of 70°C, is strongly dependent on the gas used as well as operational conditions where a polymer film is formed. The adhesion of a polymer produced from methane on the polymer and metal is strong enough to apply for durable, adhesive joints. Copyright © 1981 John Wiley & Sons, Inc