氧化鋯含量對矽酸鋁-氧化鋯-碳化複合材料的高溫氧化行為的影響

Abstract

本研究是以熱壓法製成矽酸鋁-氧化鋯-碳化矽顆粒的複合材料，將之暴露 在1000和1200℃的空氣中進行1-500小時的氧化實驗。實驗的主要目的是 要探討陶瓷基地的組成對氧化行為的影響。Mullite/ZrO2/SiCp 複合材料 的氧化程度隨著氧化鋯體積百分比的增加而增加，且存在一氧化鋯臨界體 積百分比。對1000和1200℃的氧化而言，氧化鋯的臨界體積百分比分別 為60 vol% 和20~30 vol% 附近。在複合材料中，當氧化鋯體積百分比超 過臨界值時，則氧化的速率會迅速增加，反之若低於臨界體積百分比，氧 化的程度並不明顯，此現象可用Percolation theory和Effective media theory解釋之。X-射線繞射結果並顯示在1000℃氧化已有微量的 cristobalite 產生，而 1200℃ 氧化產物除了有cristobalite外，並有 氧化產物和基地反應之zircon及coriderite相的生成，這些相的生成與氧 化鋯的含量有關，氧化鋯的含量愈高則愈容易形成。 Mullite/ZrO2/SiC particulate composites with various ZrO2 content were fabricated by hot-pressing, and then exposed in air at 1000 and 1200℃respectively, with holding times from 1 to 500 hr. The effects of the zirconia content on the oxidation behavior were thoroughly elucidated.The results indicate that there exist a critical volume fraction of zirconia content either at 1000 or 1200℃. As the volume fraction of zirconia is beyond the critical value, the oxidation rate dramatically increases. The change in oxidation rate due to the variation of volume fraction of zirconia can be explained by Percolation theory and Effective media theory. XRD results also indicate that cristobalite was formed afteroxidizing at 1000℃, while cristobalite, zircon, and cordierite were formed after exposing at 1200℃. The tendency of these products also increased with increasing zirconia.