Corrosion of Silicon Nitride Ceramics in Aqueous Hydrogen Chloride Solutions |
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| Authors: | TSUGIO SATO YASUKI TOKUNAGA TADASHI ENDO MASAHIKO SHIMADA KATSUTOSHI KOMEYA MICHIYASU KOMATSU TSUNEJI KAMEDA |
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| Affiliation: | Department of Applied Chemistry, Faculty of Engineering, Tohoku University, Sendai 980, Japan;New Material Engineering Laboratory, Toshiba Corporation, Yokohama 235, Japan |
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| Abstract: | The leaching behavior of pressureless sintered and hotpressed Si3N4 containing Y2O3, Al2O3, and AlN and hot isostatically pressed Si3N4 without additives was studied in 0.1 M to 10 M HCl aqueous solutions at 50° to 100°C. Y and Al ions contained in the grain-boundary phase dissolved in HCl solutions, but dissolution of the Si ion from the matrix was negligible. The dissolution of Y and Al ions in HCl solutions was adequately described by a surface-chemical-reaction-controlled, shrinking-core model in <1 M HCl solutions and by a diffusion-controlled, shrinking-core model in >5 M HCl solutions. The rates of dissolution of both Y and Al ions decreased as the degree of crystallinity of the grain-boundary phase increased. The fracture strength of the corroded samples linearly decreased with increasing degree of dissolution of soluble Y and Al ions. |
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