摘要
通过热力学分析研究了超硬无机材料，如ＳｉＣ、Ｓｉ３Ｎ４、ＴｉＣ、ＴｉＮ等纳米粉末的化学气相沉积（ＣＶＤ）合成反应过程和核化过程的有关热力学规律。结果表明：合成物以共价键和以金属键为主的合成反应和化学反应过程对温度、压力均比较敏感，热力学驱动力随温度变化增加比较明显，对外压的敏感表现为增大压力对合成反应不利。合成物以离子键为主时，反应的热力学驱动力随温度变化不明显，外压的影响也不显著。对于核化过程，合成物以金属键和离子键为主的体系，核化所需临界过饱和度较低，ｌｇ（ｐ／ｐ０）在１～１０之间，而对合成物以共价键为主的体系，核化所需过饱和度较高，ｌｇ（ｐ／ｐ０）约在１５～２０之间，因实验过程很难达到这样高的过饱和度，因此合成粉体常以非晶态形式存在。
Thermodynamic analyses for the superhard inorganic material, such as SiC, Si 3N 4,TiC,TiN and so on, nanosized powder CVD synthesis processes were made systematically. For the metallic and the covalent bonding compounds, the synthesis reaction thermodynamic driving forces increased with the synthesis temperature considerably, compared with the ionic bonding compound synthesis reaction. The system pressure increase was of noticeable negative influence on the metallic and covalent bonding compound synthesis, but for the ionic compounds, its effect could be neglected. During the nucleation processes, the critical supersaturation for the metallic and the ionic bonding compound synthesis reaction was about 1～10, much lower than that for the covalent bonding compound synthesis, which was in the range of 15～20. In practice, it was impossible for the covalent bonding compound synthesis reaction to meet the above requirement. Therefore, in most cases the as synthesized powder exists in amorphous state to reduce the nucleation activation energy.
出处
《中国有色金属学报》
EI
CAS
CSCD
1996年第3期71-75,共5页
The Chinese Journal of Nonferrous Metals
关键词
超硬无机材料
纳米粉末
化学气相沉积
热力学
inorganic compounds nanosized powder CVD synthesis thermodynamic analyses
