DENG Yongrui University of Science and Technology Beijing
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Beijing
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ChinaG.S.Ansell Colorado School of Mines
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Golden
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CO 80401
,
USA) Associate professor
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Department of Materials Science and Engineering
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University of Science and Technology Beijing
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Beijing 100083
,
China.
金属学报(英文版)
The growth of thermoelastic martensite in a Cu-29% Zn-3% Al alloy has been investigated experimentally and theoretically.Metallographie observations showed that the growth oc- cured thermoelastically,i.e.reversibly,in the radial direction as well as in the thickening di- rection.This is not consistent with the theories of Conhen and some others.A model has been suggested to explain the thermoelasticity of the growth.The basic idea is:the elastic strain distribution is highly heterogeneous and the growth is controlled by the local elastic strain en- ergy at the growth frontier area.The calculated results from the model based on Eshelby's theory are consistent with the observations.
关键词:
thermoelasticity
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null
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null
Communications in Theoretical Physics
The resonant tunneling of a particle coupled with a set of local bosons can be mapped onto the single-site model in an appropriate time scale. In this paper we investigate the process of the particle through a barrier associated with the dissipative source. The frequency and temperature-dependent tunneling probability has been evaluated explicitly in the spirit of independent boson assumption by using golden rule for transition rate. The character of sideband structure is revealed and the tunneling current with dissipation is also given.
关键词:
Corrosion Science
A golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO4 and sulfuric acid. The corrosion resistance of the coatings was evaluated by electrochemical methods, potentiodynamic polarization experiments and electrochemical impedance spectrum. The experimental results indicated that the corrosion resistance for the conversion coated 304SS in 3.5% NaCl solution increased markedly. The corrosion potential of the treated steel increased to a more noble level, the pitting corrosion potential increased also, the passive potential range was enlarged markedly and the passive current density decreased about one order compared to that of the untreated steel. The cathodic and anodic reaction were both inhibited to some extent. The chemical state of the elements in the coatings was investigated by XPS. The cerium element was in the form of tetravalent state. And AES depth profile analysis suggested that the thickness of the conversion coatings was less than 66 nm. The mechanisms of coatings formation and corrosion resistance are discussed. (C) 2003 Elsevier Ltd. All rights reserved.
关键词:
304 stainless steel;conversion coatings;XPS;Electrochemistry;cerium;x-ray photoelectron;stainless-steels;surface modification;passive;film;al-alloys;behavior;spectroscopy;protection
Thin Solid Films
Laser chemical vapour deposition (LCVD) of TiN and TiC films has been achieved by scanning linear deposition in a dynamic atmosphere on AISI 52100 bearing steel using TiCl4, NH3, C2H4 and H-2 as reactant gases induced by CO2 laser. It has been found in our experiment that hydrogen played an important role in the LCVD TIN process. LCVD TiN film is golden in colour, single phase, stoichiometric in composition and homogeneously distributed. Preferential orientation of LCVD TIN film is correlated with deposition pressure. The microstructure of LCVD TiN film comprises about 2 mu m equiaxial particles, each particle consisting of about 15 nm nanocrystalline grains. The average Knoop microhardness of LCVD TiN films is HK 1400 and the highest is HK 1602.3. The wear resistance of LCVD TIN film is four times that of the substrate. LCVD TiC film, with no preferential orientation, comprises homogeneous stoichiometric single-phase equiaxial particles.
关键词:
chemical vapor deposition;growth mechanism;titanium carbide;titanium;nitride
Corrosion
New golden. yellow-colored cerium chemical conversion coatings on aluminum alloy 2024-T3 (AA2024-T3 [UN A92024]) surface at room temperature were obtained by immersing the alloy into a cerium solution containing zinc chloride (ZnCl2) and hydrogen peroxide (H2O2). Electrochemical methods and immersion tests were used to study the dynamics of the coatings formation and their corrosion resistance in 3.5% sodium chloride (NaCl) solution. The morphologies of the coatings were recorded by scanning electronic microscopy (SEM). Energy-dispersive x-ray (EDX) analysis and x-ray photoelectron spectroscopy (XPS) were used to analyze the chemical composition and the oxidation state of the elements in the coatings. Polarization experiments and immersion tests in 3.5% NaCl solution showed that the sensitivity to pitting corrosion for the conversion-coated AA2024-T3 was greatly lower than that of the untreated specimens, and the corrosion resistance improved markedly. SEM photographs showed that the coatings consisted of a lot of spherical particles. EDX and XPS experimental results showed that the coatings were made up of oxygen, cerium, and aluminum, and the spherical particles contained higher contents of cerium and oxygen than the other sites. Cerium was mainly in the form of Ce4+. The mechanisms of conversion coatings formation and improvement on corrosion resistance also are discussed.
关键词:
aluminum;cerium;conversion coating;corrosion resistance;electrochemistry;scanning electronic microscopy;x-ray photoelectron;spectrum;x-ray-absorption;al-alloys;edge spectroscopy;pitting corrosion;protection;inhibition;surface;xps
WANG Hui-tao
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WANG Hua
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ZHANG Zhu-ming
钢铁研究学报(英文版)
Low temperature exhaust gases carrying large amount of waste heat are released by steel-making process and many other industries, Organic Rankine Cycles (ORCs) are proven to be the most promising technology to recover the low-temperature waste heat, thereby to get more financial benefits for these industries. The exergy analysis of ORC units driven by low-temperature exhaust gas waste heat and charged with dry and isentropic fluid was performed, and an intuitive approach with simple impressions was developed to calculate the performances of the ORC unit. Parameter optimization was conducted with turbine inlet temperature simplified as the variable and exergy efficiency or power output as the objective function by means of Penalty Function and Golden Section Searching algorithm based on the formulation of the optimization problem. The power generated by the optimized ORC unit can be nearly as twice as that generated by a non-optimized ORC unit. In addition, cycle parametric analysis was performed to examine the effects of thermodynamic parameters on the cycle performances such as thermal efficiency and exergy efficiency. It is proven that performance of ORC unit is mainly affected by the thermodynamic property of working fluid, the waste heat temperature, the pinch point temperature of the evaporator, the specific heat capacity of the heat carrier and the turbine inlet temperature under a given environment temperature.
关键词:
waste heat recovery
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organic Rankine cycle
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optimization
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working fluid
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exergy
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pinch point
Philosophical Magazine
We report conjectures on the three-dimensional (3D) Ising model of simple orthorhombic lattices, together with details of calculations for a putative exact solution. Two conjectures, an additional rotation in the fourth curled-up dimension and weight factors on the eigenvectors, are proposed to serve as a boundary condition to deal with the topologic problem of the 3D Ising model. The partition function of the 3D simple orthorhombic Ising model is evaluated by spinor analysis, employing these conjectures. Based on the validity of the conjectures, the critical temperature of the simple orthorhombic Ising lattices could be determined by the relation of KK* = KK ' + KK '' + K ' K '' or sinh 2K - sinh 2(K ' + K '' + (K ' K ''/K)) = 1. For a simple cubic Ising lattice, the critical point is putatively determined to locate exactly at the golden ratio x(c) = e(-2kc) = ((root 5 - 1)/2), as derived from K* = 3K or sinh 2K = sinh 6K = 1. If the conjectures would be true, the specific heat of the simple orthorhombic Ising system would show a logarithmic singularity at the critical point of the phase transition. The spontaneous magnetization of the simple orthorhombic Ising ferromagnet is derived explicitly by the perturbation procedure, following the conjectures. The spin correlation functions are discussed on the terms of the Pfaffians, by defining the effective skew-symmetric matrix A(eff). The true range k(x) of the correlation and the susceptibility of the simple orthorhombic Ising system are determined by procedures similar to those used for the two-dimensional Ising system. The putative critical exponents derived explicitly for the simple orthorhombic Ising lattices are alpha = 0, beta = 3/8, gamma = 5/4, delta = 13/3, eta = 1/8 and nu = 2/3, showing the universality behaviour and satisfying the scaling laws. The cooperative phenomena near the critical point are studied and the results based on the conjectures are compared with those of approximation methods and experimental findings. The putative solutions have been judged by several criteria. The deviations of the approximation results and the experimental data from the solutions are interpreted. Based on the solution, it is found that the 3D-to-2D crossover phenomenon differs with the 2D-to-1D crossover phenomenon and there is a gradual crossover of the exponents from the 3D to the 2D values. Special attention is also paid to the extra energy caused by the introduction of the fourth curled-up dimension and the states at/near infinite temperature revealed by the weight factors of the eigenvectors. The physics beyond the conjectures and the existence of the extra dimension are discussed. The present work is not only significant for statistical and condensed matter physics, but also fill the gap between the quantum field theory, cosmology theory, high-energy particle physics, graph theory and computer science.
关键词:
monte-carlo renormalization;critical-point scattering;order-disorder;problems;low-temperature series;super-exchange antiferromagnet;dynamic critical phenomena;quantum phase-transitions;centered-cubic;lattices;feynman-graph expansion;excluded-volume problem
