The contact angle between liquid iron and a single-crystal magnesium oxide substrate at 1873 K
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Communications The Contact Angle between Liquid Iron and a Single-Crystal Magnesium Oxide Substrate at 1873 K HIROYUKI SHIBATA, XIAOFANG JIANG, MARTIN VALDEZ, and ALAN W. CRAMB The visible contact angle between liquid iron and various ceramic substrates has been the focus of numerous studies over the last 50 years.[1–13] Recent work has indicated that issues such as metal purity, gas-phase oxygen content, surface roughness, and substrate purity must all be controlled in order to accurately determine a visible contact angle.[9–13] In this study, in order to clarify the effect of the oxygen on the interfacial phenomena between magnesium oxide and pure iron, the visible contact angle between liquid iron and a magnesium oxide substrate was measured by the sessile drop technique[1–13] as a function of oxygen partial pressure at 1873 K. The sessile drop technique has been previously described and the details of the experimental apparatus used in this study have been reported.[11,12] Ultra-high-purity argon gas and CO/CO2 gas mixtures were used to control the oxygen partial pressure of the chamber gas. Argon was purified by flowing argon over heated copper ribbon, magnesium tips, and titanium sponge to obtain a very low oxygen partial pressure less than 1016 atm in the reaction tube before entry into the sessile droplet chamber. An oxygen sensor was used to measure the oxygen partial pressure in the exhaust argon gas from the reaction tube. The CO/CO2 was mixed to obtain oxygen partial pressures in the range from 5.2 1014 to 1.0 109 atm. To eliminate issues of magnesium oxide substrate purity, single-crystal magnesium oxide substrate materials were purchased from Alfa Aesar. The surface of the magnesium oxide substrate is the (100) plane, and the surface roughness, Ra, of the single crystal was measured as 0.02 m. The iron samples were also purchased from Alfa Aesar and were of the following chemistry: 99.9985 pct Fe, which included measurable impurity contents of Cu 1 ppm, Mg 2 ppm, and Ti 2 ppm. The weight of the sample was always set to 2.5 g to minimize the effect of line energy on the contact angle, because the purpose of this study is to determine the effect of the partial pressure of the oxygen on the contact angle. Throughout these experiments, the variation of the visible contact angle between liquid iron and a magnesium oxide substrate was observed under different oxygen partial pressures. For oxygen partial pressures from 109 to 1014,
HIROYUKI SHIBATA, Associate Professor, is with Tohoku University, Sendai, Japan. XIAOFANG JIANG, Researcher, is with Bao Steel Technical Center, Dept. of Materials Science and Engineering, Bao Steel, Shanghai, China. MARTIN VALDEZ, Graduate Student, and ALAN W. CRAMB, Posco Professor, are with the Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213. Contact e-mail: [email protected] Manuscript submitted July 24, 2003. METALLURGICAL AND MATERIALS TRANSACTIONS B
atm, a CO/CO2 gas mixture was used. Und
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