气体压力对藕状多孔银气孔形貌的影响

发布时间：2018-03-19 19:46

  本文选题：藕状多孔银　切入点：扩散速率　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：金属-气体共晶定向凝固法(常称为"Gasar"工艺)可以很容易地实现对藕状多孔结构的气孔率、气孔尺寸及气孔排列方向的控制而被认为是制备藕状多孔结构的革命性工艺。藕状多孔金属的气孔沿凝固方向定向规则排列于金属基体中,这种气孔结构使藕状多孔金属表现出比传统多孔金属特殊的力学、热学和物理性能。特殊的气孔结构和性能优势预示着藕状多孔金属潜在的广阔应用前景。本论文利用Gasar模铸装置在氢气/氧气和氩气混合气氛以及纯氧气氛下分别制备了多孔银试样。研究了气体压力对多孔银试样气孔结构的影响规律。研究表明,在氢气和氩气的混合气氛下,随着氢气分压的升高,气孔率逐渐降低。多孔银的气孔率受氧气和氩气分压的影响较为显著。当氩气分压一定时,随着氧气分压的升高,气孔率先增加后减少；当氧气分压一定时,随着氩气分压的升高,气孔率减少；当使用纯氧气时,随着氧气压力的升高,气孔率增加。气压对气孔大小的影响也比较显著。对于在纯氧气氛下制备的藕状多孔银试样,平均气孔直径随氧气压力的升高而降低。根据热传导平衡方程计算了金属Ag基体的凝固速率v0,并和金属Cu, Mg基体的凝固v0速率相比较,从而得出：银的凝固速率是铜凝固速率的10倍,是镁凝固速率的30倍。根据扩散的热力学分析以及金属固-液界面前沿气体溶质浓度的分布推导了气体扩散速率：通过对Gasar凝固过程中金属基体的凝固速率和金属固-液界面前沿气体扩散速率的分析,得出了藕状多孔结构的形成条件：当金属基体的凝固速率v0≥气体扩散速率v时,即可形成藕状的多孔结构。
[Abstract]:The metal-gas eutectic directional solidification process (often referred to as "Gasar" process) can easily achieve the porosity of lotus root porous structure. The control of pore size and pore arrangement direction is considered to be a revolutionary process for preparing lotus root porous structure. The pores of lotus root porous metal are arranged regularly in the metal matrix along the directional direction of solidification. This kind of pore structure makes the lotus root porous metal show special mechanics than the traditional porous metal. Thermal and physical properties. Special pore structure and performance advantages indicate the potential wide application prospects of lotus root porous metals. In this paper, Gasar mold casting device is used in hydrogen / oxygen and argon mixed atmosphere as well as pure oxygen atmosphere. The effect of gas pressure on the pore structure of porous silver sample was studied. In the mixed atmosphere of hydrogen and argon, the porosity decreases with the increase of partial pressure of hydrogen, and the porosity of porous silver is affected by the partial pressure of oxygen and argon. When the partial pressure of argon is fixed, the porosity decreases with the increase of partial pressure of oxygen. The porosity decreases with the increase of argon partial pressure, and with the increase of oxygen pressure, when pure oxygen is used, with the increase of oxygen pressure, the porosity increases first and then decreases; when oxygen pressure is fixed, the porosity decreases with the increase of argon partial pressure. The effect of air pressure on pore size is also significant. For the lotus root shaped porous silver sample prepared in pure oxygen atmosphere, The average pore diameter decreases with the increase of oxygen pressure. The solidification rate v0 of Ag matrix is calculated according to the heat conduction equilibrium equation, and compared with that of Cu and mg matrix. It is concluded that the solidification rate of silver is 10 times that of copper. According to the thermodynamic analysis of diffusion and the distribution of gas solute concentration at the front of the metal solid liquid interface, the gas diffusion rate was deduced by the solidification rate of metal matrix and gold during the solidification of Gasar. It belongs to the analysis of the gas diffusion rate at the front of the solid-liquid interface. The formation conditions of lotus root porous structure are obtained: when the solidification rate v0 鈮，

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