Electrochemical Chromium(III) Oxide Coatings on Non-oxide Ceramic Substrates |
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Authors: | Rachman Chaim Sylvie Almaleh-Rockman Leah Gal-Or Harro Bestgen |
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Affiliation: | Department of Materials Engineering, Technion—Israel Institute of Technology, Haifa, 32000, Israel;Hoechst AG, Keramik Forschung, Frankfurt 80, Germany |
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Abstract: | SiC and TiB2 were electrochemically coated with Cr2O3 from a 0.1 M aqueous solution of chromium nitrate hydrate with ethanol additives. On both substrate materials poly-crystalline Cr2O3 was formed at current densities from 5 to 50 mA/cm2 and deposition durations of 5 to 30 min. The coating weight increased with current density and with deposition time. The as-deposited coatings contained microcracks due to drying shrinkage. Microstructural observations indicate that sintering of the Cr2O3 coatings on TiB2 at 1100°C for 1 n in a reducing atmosphere in a closed graphite crucible causes the densification of the coating via a liquid phase, which forms by oxidation of TiB2. Under similar conditions, the Cr2O3 coatings on SiC may be sintered via an evaporation–condensation mechanism. |
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