ABSTRACT

The ZrB₂–SiC–LaB₆ composite prepared by spark plasma sintering with B₄C and C as additives was isothermally exposed in air at 1500°C for 24 h and the evolved oxide scale examined by scanning and transmission electron microscopy. It was found that a glassy borosilicate (BSG) layer with a thin film of La₂Si₂O₇ had formed on the outermost surface of oxide scale, contributing to protection against oxidation. The detailed investigation of the cross-section of the oxide scale has revealed the formation of a layered microstructure formed by growth involving partial crystallisation of BSG forming ZrSiO₄ along with re-precipitation of La₂Si₂O₇ and ZrO₂ after prior dissolution of La₂O₃ and ZrO₂ in the glassy matrix.

摘要

ZrB ₂ -SiC-LaB ₆复合材料通过放电等离子烧结制备的 B ₄ C 和 C 作为添加剂在 1500°C 的空气中等温暴露 24 小时，并通过扫描和透射电子显微镜检查演化出的氧化皮。发现在氧化皮的最外表面上形成了具有La ₂ Si ₂ O ₇薄膜的玻璃状硼硅酸盐(BSG)层，有助于防止氧化。对氧化皮横截面的详细研究表明，层状微结构的形成是由 BSG 的部分结晶形成 ZrSiO ₄以及 La ₂ Si 的再沉淀所形成的。La ₂ O ₃和ZrO ₂在玻璃状基质中预先溶解之后的₂ O ₇和ZrO ₂。