The influence of the nucleation surface on the growth of CVD α-Al2O3 and κ-Al2O3
1995; Elsevier BV; Volume: 76-77; Linguagem: Inglês
10.1016/0257-8972(95)02584-7
ISSN1879-3347
Autores Tópico(s)Advanced ceramic materials synthesis
ResumoIn this work, in order to increase the understanding of the nucleation and growth of CVD alumina, three different types of specimen have been investigated by cross-section TEM. The alumina layers were deposited onto Ti(C,N) (i) with and (ii) without an intermediate α-bonding layer, and (iii) onto an intermediate Ti2O3 layer. It was found that pure κ-Al2O3 was obtained on the Ti(C,N) layer, while pure α-Al2O3 was obtained on the α-bonding and Ti2O3 layers. As the process parameters of the alumina deposition were the same in all cases, this demonstrates that the resulting alumina polymorph is governed by its nucleation on the intermediate layers. Pores could frequently be observed at the Ti(C,N)-Ti2O3 layer interfaces, while no pores could be detected at the Ti2O3-α-Al2O3, Ti(C,N)-α-Al2O3 or α-bonding-α-Al2O3 interfaces. No orientation relationships between the grains in the α- bonding and the α-Al2O3 layer could be found, while epitaxial growths of κ-Al2O3 on Ti(C,N) and α-Al2O3 on Ti2O3 were frequently observed and are described as: Download : Download high-res image (12KB)Download : Download full-size image Both orientation relationships describe close-packed planes growing on close-packed planes, with close-packed directions being parallel.
Referência(s)