本文選題：藕狀多孔銀　切入點(diǎn)：擴(kuò)散速率　出處：《昆明理工大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：金屬-氣體共晶定向凝固法(常稱(chēng)為"Gasar"工藝)可以很容易地實(shí)現(xiàn)對(duì)藕狀多孔結(jié)構(gòu)的氣孔率、氣孔尺寸及氣孔排列方向的控制而被認(rèn)為是制備藕狀多孔結(jié)構(gòu)的革命性工藝。藕狀多孔金屬的氣孔沿凝固方向定向規(guī)則排列于金屬基體中,這種氣孔結(jié)構(gòu)使藕狀多孔金屬表現(xiàn)出比傳統(tǒng)多孔金屬特殊的力學(xué)、熱學(xué)和物理性能。特殊的氣孔結(jié)構(gòu)和性能優(yōu)勢(shì)預(yù)示著藕狀多孔金屬潛在的廣闊應(yīng)用前景。本論文利用Gasar模鑄裝置在氫氣/氧氣和氬氣混合氣氛以及純氧氣氛下分別制備了多孔銀試樣。研究了氣體壓力對(duì)多孔銀試樣氣孔結(jié)構(gòu)的影響規(guī)律。研究表明,在氫氣和氬氣的混合氣氛下,隨著氫氣分壓的升高,氣孔率逐漸降低。多孔銀的氣孔率受氧氣和氬氣分壓的影響較為顯著。當(dāng)氬氣分壓一定時(shí),隨著氧氣分壓的升高,氣孔率先增加后減少；當(dāng)氧氣分壓一定時(shí),隨著氬氣分壓的升高,氣孔率減少；當(dāng)使用純氧氣時(shí),隨著氧氣壓力的升高,氣孔率增加。氣壓對(duì)氣孔大小的影響也比較顯著。對(duì)于在純氧氣氛下制備的藕狀多孔銀試樣,平均氣孔直徑隨氧氣壓力的升高而降低。根據(jù)熱傳導(dǎo)平衡方程計(jì)算了金屬Ag基體的凝固速率v0,并和金屬Cu, Mg基體的凝固v0速率相比較,從而得出：銀的凝固速率是銅凝固速率的10倍,是鎂凝固速率的30倍。根據(jù)擴(kuò)散的熱力學(xué)分析以及金屬固-液界面前沿氣體溶質(zhì)濃度的分布推導(dǎo)了氣體擴(kuò)散速率：通過(guò)對(duì)Gasar凝固過(guò)程中金屬基體的凝固速率和金屬固-液界面前沿氣體擴(kuò)散速率的分析,得出了藕狀多孔結(jié)構(gòu)的形成條件：當(dāng)金屬基體的凝固速率v0≥氣體擴(kuò)散速率v時(shí),即可形成藕狀的多孔結(jié)構(gòu)。
[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，

本文編號(hào)：1635733