王慧吕国志张有宏
腐蚀科学与防护技术
用一个简单的元胞自动机从介观的角度对腐蚀环境中金属表面蚀坑的生长演化过程进行研究.假定腐蚀体系为扩散过程控制的金属腐蚀体系，引入溶液浓度、溶解概率和钝化概率，对腐蚀过程中质量转移、金属溶解和钝化过程进行分析；用模拟过程中的溶解掉的元胞数目表征溶解电流，用二维元胞自动机网格中纵向上溶解掉的元胞数目来表征蚀坑深度，研究了在不同的溶液浓度、溶解及钝化概率下溶解电流随时间的变化规律，其结果表明为服从时间的幂函数关系；并得到了蚀坑深度随时间的变化曲线.
关键词:
腐蚀
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diffusion
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cellular automaton
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simulations
Aiying WANG
,
Kwangryeol Lee
,
Chao SUN
,
Lishi WEN
,
null
,
null
,
null
,
null
材料科学技术（英）
During the growth of the hot filament chemical vapor deposition (HFCVD) diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on the gas physical parameters, including the temperature, velocity and volume density of gas. It was found that, even in the case of optimized deposition parameters, the space distributions of gas parameters were heterogeneous due primarily to the thermal blockage come from the hot filaments and cryogenic pump effect arisen from the cold reactor wall. The distribution of volume density agreed well with the thermal round-flow phenomenon, one of the key obstacles to obtaining high growth rate in HFCVD process. In virtue of isothermal boundary with high temperature or adiabatic boundary condition of reactor wall, however, the thermal round-flow was profoundly reduced and as a consequence, the uniformity of gas physical parameters was considerably improved, as identified by the experimental films growth.
关键词:
Gas physical parameters
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physical
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parameters
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simulations
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di
Physics Letters A
The injected and the displaced fluid are respectively considered as Newtonian and non-Newtonian fluids. Owing to the introduction of the deviation parameter of deviating Newtonian fluid of the displaced fluid, a new flow rate equation of two-phase immiscible displacements is obtained. Viscous fingering (VF) is investigated by means of the successive over-relaxation technique. The sweep efficiency of the displacing fluid decreases along with the increase of the deviation parameter. The computer simulations show a definite crossover from initial diffusion-limited-aggregation-like (DLA-like) fractal growth to compact growth. Between the site number invaded by the displacing fluid and the deviation parameter, a nontrivial scaling relation is exhibited. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
关键词:
simulations
