Characterization and Processing of CVD Powders for Fabrication of Composite and Compound Ceramics

Two-component oxide powders were prepared in the systems Al2O3-ZrO2. Al2O3-TiO2. and Al2O3-SiO2 by a CVD (chemical vapor deposition) technique using a combustion flame for the purpose of fabricating respective composite or compound ceramics. The CVD powders were spherical and ultrafine (av. 30–70 nm) with log-normal size distribution, and exhibited either very homogeneous or nanoheterogeneous structure and crystallographic metastability in phases and solid solutions. By starting from these CVD powders, not only uniform and excellent microstructure was achieved in the sintered products, but also better sinterability and novel microstructure became possible owing to the metastability which reflected the formation mechanism of two-component powders at high temperatures. CVD powders, which were previously considered difficult to sinter, proved to be excellent starting materials for fabrication of composite and compound ceramics when improved processing techniques were applied.