稀土元素对氧化铝性能影响的研究进展

Research Progress in the Influence of Rare Earth Elements on Properties of Alumina

在氧化铝中添加稀土元素可提高其热稳定性,还可以改善氧化铝陶瓷在高温下的显微结构和力学性能。在讨论氧化铝载体的制备方法、氢氧化铝与氧化铝及不同氧化铝晶相之间的转化关系、活性氧化铝发生相变的热力学和动力学条件的基础上,指出活性氧化铝发生相变的过程就是O2-和Al3+在空间通过扩散进行重新排列的过程,也是一个形核和晶核长大的过程。为了提高活性氧化铝的热稳定性,一般要加入稀土元素化合物等结构稳定助剂。稀土元素稳定活性氧化铝结构的机理有LnAlO3与Al2O3结构相似稳定模型、稀土氧化物覆盖机理、分散相机理及接触点机理等。稀土元素稳定氧化铝的能力与其离子半径的大小顺序基本一致,即La3+>Ce3+>Pr3+>Nd3+>Sm3+>Er3+>Y3+。稀土元素与碱土金属元素复合后,具有协同效应。稀土元素还可以提高氧化铝陶瓷的密度并改善其力学性能。

Adding rare earth elements to alumina can improve the thermal stability of alumina and improve the microstructure and mechanical properties of alumina ceramics at high temperature.By discussing the preparation methods of alumina carrier,the conversion relations between aluminum hydroxide and alumina and different crystalline phases of alumina,and the thermodynamic and kinetic conditions for the phase change of activated alumina,this paper points out that the phase change of activated alumina is the rearrangement of O2-and Al3+ in space by diffusion,and also the nucleation and growth of crystal nucleus.In order to improve the thermal stability of activated alumina,rare earth element compounds and other structural stabilizers are generally added.The mechanisms of rare earth elements stabilizing the activated alumina structure include the structural similarity stability model of LnAlO3 and Al2O3,the covering mechanism of rare earth oxides,the dispersed phase mechanism and the contact point mechanism.The ability of rare earth elements to stabilize alumina is basically in the same order as the size of ionic radius,i.e.,La3+> Ce3+>Pr3+> Nd3+> Sm3+> Er3+> Y3+.Rare earth elements and alkaline earth metal elements have synergistic effect after combination.Rare earth elements can also increase the density of alumina ceramics and improve their mechanical properties.