Ken Suzuki

Bio: Ken Suzuki is an academic researcher from Tohoku University. The author has contributed to research in topics: Grain boundary & Thin film. The author has an hindex of 15, co-authored 172 publications receiving 789 citations.

The Effect of Chemical Composition and Heat Treatment Conditions on Stacking Fault Energy for Fe-Cr-Ni Austenitic Stainless Steel

Abstract: In order to establish more reliable formulae for calculating stacking fault energies (SFE) from the chemical compositions of austenitic stainless steels, SFE values were measured for 54 laboratory-melted heats and 2 commercial heats The results were checked against those of a first-principle, atomistic calculation approach More than ~20,000 data points for the width and angle of the Burgers vectors were determined from dark-field images of isolated extended dislocations in 56 heats of austenitic stainless steel using weak electron beams with g-3g diffraction conditions Based on these numerous observations and on fundamental thermodynamic analyses, it is concluded that the SFE values for austenitic stainless steels are changed not only by chemical composition but also by heat treatment In this paper, new formulae for calculating SFE values from the chemical compositions in three different heat treatment conditions have been proposed for austenitic stainless steels within given limited chemical composition ranges In these formulae, the SFE values are calculated from the nickel, chromium, molybdenum, silicon, manganese, nitrogen, and carbon contents for the each heat treatment condition The three heat treatment conditions studied were water cooling after solution heat treating (SHTWC), furnace cooling after solution heat treating, and aging after SHTWC

Early stage SCC initiation analysis of fcc Fe―Cr―Ni ternary alloy at 288 °C: A quantum chemical molecular dynamics approach

Abstract: The initiation of stress corrosion cracking in fcc Fe–Cr–Ni ternary alloys was studied by means of quantum chemical molecular dynamics at 288 °C. This study showed that the iron and chromium atoms segregate faster than nickel atoms at the surfaces. The atomic model showed that nickel enrichment occurred at the inner oxide layer. The binding energy helps reduce the mobility of the nickel atoms. The surface morphology showed that Fe, Cr, and O accumulate on the very top surface while Fe, Cr, Ni, and O bonding takes place beneath this revealing the formation of an outer and inner oxide film. The diffusion of oxygen and hydrogen into the surface increases when it is under strain. The deeply diffused hydrogen becomes negatively charged by taking electron from metal atoms. Consequently, the process weakens the metallic bonds following with the result that oxygen can diffuse easily into the surface. It seems that hydrogen effectively functions as an oxygen carrier. This kind of reaction process can take place in the molecular domain of a crack tip and thus play a vital role in initiating the SCC process.

Molecular dynamics simulation of enhanced oxygen ion diffusion in strained yttria-stabilized zirconia

Abstract: The application of strain to yttria-stabilized zirconia (YSZ), which can be realized by sandwiching a thin YSZ film epitaxially between layers of a material with larger lattice constants, is proposed as a means to enhance oxygen ion mobility. The possible mechanism of such an enhancement was investigated by molecular dynamics using a CeO2–YSZ superlattice. The calculated diffusion coefficient of oxygen ions in the superlattice is some 1.7 times higher than in YSZ alone due to a decreased activation barrier from the strain of the YSZ structure.

Quantum chemical molecular dynamics study of stress corrosion cracking behavior for fcc Fe and Fe–Cr surfaces

Abstract: Quantum chemical molecular dynamics simulation was applied to study the oxidation of bare Fe (1 1 1) and Fe–Cr (1 1 1) surfaces with strain in high temperature water. Simulation results implied the surface morphologies differ from Fe to Fe–Cr because of strong bond between oxygen and chromium atoms. Oxygen atoms were trapped around chromium atoms at Fe–Cr surface, whereas oxygen penetrated into the lattice of Fe bare surface. As a result, the oxygen diffusivity into the Fe–Cr crystal surface reduced. It indicated that the preferential oxidation of chromium would take place on Fe–Cr clean surface at the beginning of the oxidation process. Diffusion of hydrogen and oxygen significantly increased when strain applied to the defective surface. Hydrogen atoms being in the lattice of metal possessed the highly negative charge which indicated the surface oxidized by this negative charge H. Negative charged oxygen atoms make bond with the metallic atom which breakage ultimate metal–metal bond. These bond breakages indicated the formation of oxide layer on the surface and play a key role in subsequent localized corrosion nucleation like stress corrosion cracking.

Synthesis of CoMoO4@RGO nanocomposites as high-performance supercapacitor electrodes

Abstract: Pure CoMoO4 nanoplate arrays grew on nickel foam by one-step hydrothermal process, while flower-like nanoflake CoMoO4@RGO nanocomposites grew on nickel foam. Flower-like nanoflake CoMoO4@RGO nanocomposites electrode exhibited higher capacitance than pure CoMoO4 nanoplate arrays electrode. Maximum specific capacitance of 856.2 F g−1 was obtained at current density of 1 A g−1 for CoMoO4@RGO nanocomposites electrode. In addition, after 2000 cycles of continuous galvanostatic charge–discharge cycles, only 5.5% degradation of specific capacitance was found for CoMoO4@RGO nanocomposites. CoMoO4@RGO nanocomposites exhibited lower electrochemical resistance than pure-CoMoO4. This was because that the former had larger specific surface area and average pore diameter than the latter. The flower-like nanoflake CoMoO4 facilitated electrolyte movement during charge or discharge process and provided more active sites for the electrochemical reactions. In addition, the synergetic effect between RGO and CoMoO4 also improved the supercapacitor performance.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

A review of conduction phenomena in Li-ion batteries

Abstract: Conduction has been one of the main barriers to further improvements in Li-ion batteries and is expected to remain so for the foreseeable future. In an effort to gain a better understanding of the conduction phenomena in Li-ion batteries and enable breakthrough technologies, a comprehensive survey of conduction phenomena in all components of a Li-ion cell incorporating theoretical, experimental, and simulation studies, is presented here. Included are a survey of the fundamentals of electrical and ionic conduction theories; a survey of the critical results, issues and challenges with respect to ionic and electronic conduction in the cathode, anode and electrolyte; a review of the relationship between electrical and ionic conduction for three cathode materials: LiCoO2, LiMn2O4, LiFePO4; a discussion of phase change in graphitic anodes and how it relates to diffusivity and conductivity; and the key conduction issues with organic liquid, solid-state and ionic liquid electrolytes. © 2010 Published by Elsevier B.V.

Electronic Transport In Mesoscopic Systems

Abstract: Thank you very much for reading electronic transport in mesoscopic systems. Maybe you have knowledge that, people have look numerous times for their favorite readings like this electronic transport in mesoscopic systems, but end up in harmful downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they juggled with some harmful bugs inside their computer. electronic transport in mesoscopic systems is available in our book collection an online access to it is set as public so you can get it instantly. Our book servers spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Merely said, the electronic transport in mesoscopic systems is universally compatible with any devices to read.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

Abstract: A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling effect is considered to be the principal mechanism of the sensor under small strains.