Effect of Y2O3 addition on alumina-hex boron nitride composites
Effect of Y2O3 addition on alumina-hex boron nitride composites
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DOI：
10.1016/0955-2219(95)00056-z
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发表时间：
1995
影响因子：
5.7
通讯作者：
A. Abreal;D. Goeuriot;F. Thévenot;M. Lagacé;B. Gueroult;M. Rigaud
中科院分区：
文献类型：
--
作者：
A. Abreal;D. Goeuriot;F. Thévenot;M. Lagacé;B. Gueroult;M. Rigaud
热压是唯一能使氧化铝-六方氮化硼复合材料致密化的方法。它必须在1750 °C - 40 MPa下在氮气下施加，但对于氧化铝含量低于70体积%的复合材料，它不会将孔隙率降低到低于8%，并且由于氮化硼片晶垂直于压制轴的取向而导致各向异性复合材料。此外，复合材料在连续铸钢过程中的行为主要是由于孔隙率和各向异性造成的。为了提高其抗氧氧化性和抗钢水腐蚀性，并改变其微观结构的效果，已经使用了一些氧化钇添加剂。氧化钇，通过帮助氧化铝烧结，增加复合材料的致密化，从而提高其机械强度，并通过增加晶粒的凝聚力，它允许我们改变热压程序，以获得更各向同性的复合材料。此外，通过与氧化铝反应，它形成钇石榴石（YAG），钇石榴石（YAG）在与由氮化硼氧化形成的氧化硼反应之后，通过在表面形成保护性液相来保护复合材料免受氧化。然而，该液相被钢水侵蚀，因此不能提高耐腐蚀性，但是可以通过添加氧化钕来阻止这种腐蚀。
Hot-pressing is the only process to densify alumina-hexagonal boron nitride composites. It must be applied at 1750 °C — 40 M Pa, under nitrogen, but it does not reduce the porosity lower than 8% for composites with alumina contents lower than 70 vol%, and leads to anisotropic composites due to the orientation of the boron nitride platelets perpendicular to the pressing axis. Furthermore, the composites' behaviour during their use in the continuous steel casting is mainly due to the porosity and anisotropy. To increase their resistance to oxidation by oxygen and corrosion by molten steel, and to change the effect of their microstructure, some yttrium oxide additions have been used. Yttrium oxide, by helping the alumina sintering, increases the composite's densification and so its mechanical strength, and by increasing the grains cohesion, it allows us to change the hot-pressing programme to obtain a more isotropic composite. Also, by reaction with alumina, it forms yttrogarnet (YAG) which protects the composite from oxidation by forming a protective liquid phase at the surface, following the reaction with boron oxide formed by the boron nitride oxidation. However, this liquid phase is eroded by the molten steel and so, cannot increase the corrosion resistance, but it is possible to stop this corrosion by an addition of neodymium oxide.