ON THE EQUILIBRIUM THICKNESS OF INTERGRANULAR GLASS PHASES IN CERAMIC MATERIALS
ON THE EQUILIBRIUM THICKNESS OF INTERGRANULAR GLASS PHASES IN CERAMIC MATERIALS
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DOI：
10.1111/j.1151-2916.1987.tb04846.x
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发表时间：
1987-01-01
影响因子：
3.9
通讯作者：
CLARKE, DR
中科院分区：
文献类型：
--
作者：
CLARKE, DR
研究了多晶陶瓷的晶间薄膜能否达到平衡厚度的基本问题。提出了两种连续介质方法，一种基于界面能，另一种基于法向边界的力平衡。这表明晶间膜将存在一个稳定的厚度，厚度约为1 nm。平衡厚度的起源是两个相互竞争的相互作用的结果，一个是边界两侧的晶粒之间的范德华-非人相互作用，作用于薄膜变薄，另一个是由于晶间液体的结构而产生的排斥项，反对这种相互作用。由于这两种相互作用的范围都很短（<10 nm），因此平衡厚度自然为1 nm左右，这与在广泛的陶瓷中实验观察到的值相称。文中指出了两个重要的进一步后果。首先是薄的晶间液相能够承受正常的应力。二是相邻晶粒的介电常数对晶间相的厚度起着重要的决定作用。由此得出的结论与观察结果一致，即多相陶瓷的晶间相的厚度在不同相的边界处比在相似相之间的边界处不同。
The fundamental question as to whether thin intergranular films can adopt an equilibrium thickness in polycrystalline ceramics is addressed. Two continuum approaches are presented, one based on interfacial energies and the other on the force balance normal to the boundary. These indicate that there will exist a stable thickness for the intergranular film and that it will be of the order of 1 nm. The origin of an equilibrium thickness is shown to be the result of two competing interactions, an attractive van der Waals‐disperson interaction between the grains on either side of the boundary acting to thin the film and a repulsive term, due to the structure of the intergranular liquid, opposing this attraction. As both of these interactions are of short range (<10 nm), it is a natural consequence that the equilibrium thickness is of the order of 1 nm, a value commensurate with that observed experimentally in a wide range of ceramics. Two further consequences of importance arc indicated. The first is that thin intergranular liquid phases can support a normal stress. The second is that the dielectric constants of the adjacent grains play an important role in determining the thicknesses of the intergranular phase. This leads to the conclusion, consistent with observations, that the thickness of the intergranular phase in polyphase ceramics is expected to be different at boundaries between dissimilar phases than that between like phases.