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Wetting of alumina and spinel single crystals by molten aluminum.

机译：熔融铝润湿氧化铝和尖晶石单晶。

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摘要

The wetting of sapphire (alpha-Al2O3) and spinel (MgAl2O4) single crystals by molten aluminum was investigated by the sessile drop technique from 1073K to 1473K. The measurements of the contact angle, the surface tension and the work of adhesion were performed by the optimization of the description of experimental aluminum sessile droplets using the Laplace Equation of Capillarity and an objective function. Different factors affecting the aluminum wetting of these single crystals that were studied include: (i) the roughness of the ceramic surface, (ii) the exposure time, (iii) the temperature, (iv) the crystal structure and (v) the inert/reactive character of the interface.; The results of the contact angles indicated that the inert alpha-Al 2O3 (0001)/Al couple increases the contact angles towards wetting with increasing time and temperature. The contact angles are significantly reduced towards non-wetting by increasing the roughness of the alpha-Al 2O3 (0001) substrate. The reactive MgAl2O 4 (111)/Al couple increases the contact angles towards wetting with time, temperature and the roughness of the MgAl2O4 (111) substrate. Relative to the roughness effect the inert sapphire and reactive spinel exhibit opposite trends.; Aluminum wetting of sapphire single crystal indicates that (101¯0) and (112¯0) planes are wetted more by molten aluminum than the (0001) plane. This is because of the structure of the interface. The planes (101¯0) and (112¯0) are oxygen terminated structures, while the (0001) plane is an aluminum terminated structure.; The effect of the crystal structure of MgAl2O4 illustrates that the (100) plane is more wetted than the (111) plane. This is because of the proximity of the Mg2+ ions to the surface and their ability to react with molten aluminum.; The sapphire (0001) and spinel (111) planes show similar wetting characteristics because they have similar O2- ion structural arrangements. This is especially true at lower temperatures, T 1273K. Above 1273K a structural transformation of the alpha-Al2O3 (0001) plane occurs. It creates a lack of O2- ions in the (0001) plane at high temperatures.; Further analysis of the surface tensions validates the results found in the contact angles. It was observed that any change in the contact angle is reflected into the surface tension. This is because there is a droplet curvature change with the different experimental conditions used in this study. The surface tension factor, S, and the roughness factor, R, are helpful to understand the wetting trends of these systems through the surface roughness. Results of the surface tensions and the contact angles suggest new criteria for engineering aspects of reducing or increasing wetting at elevated temperatures through surface roughness modifications.
机译：用固溶滴技术研究了熔融铝对蓝宝石（α-Al2O3）和尖晶石（MgAl2O4）单晶的润湿作用。接触角，表面张力和附着力的测量是通过使用毛细管作用的拉普拉斯方程和目标函数对实验性铝基无固定液滴的描述进行优化来进行的。已研究影响这些单晶铝润湿的不同因素包括：（i）陶瓷表面的粗糙度，（ii）暴露时间，（iii）温度，（iv）晶体结构和（v）惰性/接口的响应字符。接触角的结果表明，惰性α-Al2O3（0001）/ Al偶合随着时间和温度的增加而增加了向润湿的接触角。通过增加alpha-Al 2O3（0001）基板的粗糙度，可以显着减小接触角，使其朝着非润湿的方向发展。反应性的MgAl2O4（111）/ Al对会随着时间，温度和MgAl2O4（111）基材的粗糙度而增加朝向润湿的接触角。相对于粗糙度效应，惰性蓝宝石和反应性尖晶石呈现相反的趋势。蓝宝石单晶的铝润湿表明（101’0）和（112’0）平面比（0001）平面更易被熔融铝润湿。这是由于接口的结构。平面（101’0和（112’0）是氧封端的结构，而（0001）面是铝封端的结构。 MgAl2O4晶体结构的影响表明（100）平面比（111）平面更湿润。这是因为Mg2 +离子靠近表面以及它们与熔融铝反应的能力。蓝宝石（0001）和尖晶石（111）平面显示出相似的润湿特性，因为它们具有相似的O2-离子结构排列。在较低的温度（T <1273K）下尤其如此。在1273K以上，发生α-Al2O3（0001）平面的结构转换。在高温下，它会在（0001）平面上造成O2-离子的缺乏。表面张力的进一步分析验证了在接触角中发现的结果。观察到接触角的任何变化都反映在表面张力中。这是因为在此研究中使用的不同实验条件下，液滴曲率会发生变化。表面张力因子S和粗糙度因子R有助于通过表面粗糙度了解这些系统的润湿趋势。表面张力和接触角的结果为工程方面通过改变表面粗糙度降低或增加润湿性提出了新的标准。

著录项

  • 作者

    Aguilar-Santillan, Joaquin.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Engineering Metallurgy.; Engineering Mining.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 211 p.
  • 总页数 211
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;矿业工程;
  • 关键词

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