PREPARATION OF SUPER PLASTICITY TITANIA BY CHEMICAL VAPOR DEPOSITION

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It has been shown theoretically and experimentally that ceramic consisted of nanometer size grains (so-called nano-ceramic materials) overcame the characteristics of brittle which is the main drawback of the normal ceramics materials, and had high toughness. There has been a high expectation of its application for superior heat resistance and corrosion resistance, however, ceramic materials have not been put into practical materials because of the lower reliability as brittleness. We have been trying to do fundamental studies to create a novel mass-productive technology to make such nano-ceramic materials.The film growth of titania (TiO_2) series nano-ceramic material was tried by chemical vapor deposition (CVD) method in this research. Titanium tetra iso-propoxide (TTIP) is used in the conventional TiO_2-CVD process, however we found that replacement of TTIP with bis(dipivaloylmetanoto) diisopropoxide titanium (Ti(DPM)_2(O-iPr)_2) compound increases stability of reaction and controlla … More bility.In the second year, the new component materials such as Sr and Pb was added and its effect was examined. Our experimental results revealed that the added Pb compound reduced the secondary nucleation process. The recent greatest important issue is to control the grain size of the deposited film, it's also the aim of this research. It's said generally that the grain size of the deposited film was dominated the competition of the secondary nucleation rate and the film growth rate. However, these two rates were changed easily by various experimental conditions, so the control of the grain size has very difficulty. In the film forming process without secondary nucleation, it's known that the initial nucleation density as well as film thickness can dominate the grain size of the film. It's also shown that the fixed experimental condition which gives the most suitable initial nucleation density, and freely selectable deposition time provide us the controllability of the grain size. In conclusion, we have elucidated the novel way to control the grain size of the deposited films in CVD ceramics process. Less