PREPARATION OF SUPER PLASTICITY TITANIA BY CHEMICAL VAPOR DEPOSITION

理论和实验表明，由纳米颗粒组成的陶瓷(即所谓的纳米陶瓷材料)克服了普通陶瓷材料的主要缺点--脆性，具有较高的韧性。陶瓷材料因其优异的耐热性和耐腐蚀性而被寄予厚望，但由于其脆性可靠性较低，还没有投入到实际材料中去。我们一直在进行基础性研究，以创造一种新的规模化生产技术来制备这种纳米陶瓷材料。本研究尝试用化学气相沉积(CVD)的方法来制备二氧化钛(TiO2)系纳米陶瓷材料的薄膜。在传统的二氧化钛化学气相沉积工艺中，我们使用的是四异丙氧基钛(TTIP)，但我们发现用双(二异丙酮基)二异丙氧基钛(Ti(…)_2(O-IPR)_2)化合物取代TTIP，提高了反应的稳定性和控制性第二年，添加了锶、铅等新组份材料，并对其效果进行了检验。我们的实验结果表明，添加铅化合物减少了二次形核过程。目前最重要的问题是控制沉积薄膜的颗粒尺寸，这也是本研究的目的。一般认为，沉积薄膜的晶粒度主要受二次形核速率和薄膜生长速率的竞争。然而，这两种速率很容易被各种实验条件改变，因此对晶粒度的控制非常困难。在无二次成核的成膜过程中，初始成核密度和薄膜厚度可以控制薄膜的晶粒度。实验结果还表明，给出最合适的初始成核密度的固定实验条件和可自由选择的沉积时间提供了晶粒度的可控性。综上所述，我们阐明了在CVD陶瓷工艺中控制沉积薄膜晶粒度的新方法。较少

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