丙烯化学气相沉积热解碳的原位动力学
详细信息In-situ kinetics on chemical vapor deposition of pyrocarbon from propylene
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摘要: 以丙烯为气源，在800℃～1200℃进行化学气相沉积热解碳。研究了温度、压力和滞留时间对沉积速率和气相产物的影响。采用磁悬浮天平原位实时称量反应过程中的固相产物进行动力学研究；采用气相色谱和质谱联用半定量分析了反应过程中的气体产物。动力学研究结果表明， 800℃～1000℃内活化能为137 kJ/mol±25 kJ/mol，沉积过程为化学动力学控制；高于1000℃时，沉积行为由气相分子的传质和气相成核控制。压力和滞留时间对沉积速率的影响说明，热解碳是经过一系列气相反应和固体表面反应后获得。气相产物分析说明，不同控制机制时形成热解碳的主要物质不同。在此基础上提出了丙烯分解形成热解碳的机制。Abstract: The CVD kinetics of pyrocarbon was investigated via the in-situ magnetic suspending balance，and the gaseous products were analyzed via the out-line gas chromatography coupled with the mass spectrometry (GC/MS) during the pyrolysis of a propylene/argon mixture in the range of 800～1200℃. The kinetic results indicate that pyrocarbon is formed with an apparent activation energy of 137 kJ/mol±25 kJ/mol controlled by chemical kinetic reaction from 800℃ to 1000℃，Whereas，above 1000℃，the deposition behavior is representative of the mass transformation and gas phased nucleation. The dependences of pressure and residence time on deposition rate show that pyrocarbon is obtained after a series of gas phase reactions and solid surface reactions. The key carbon-formed species controled by each mechanism of the deposition process are different. A simplified reaction model describing the kinetic deposition process of pyrocarbon CVD is derived on the basis of the above considerations.
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Keywords:
- in-situ kinetics /
- propylene /
- pyrocarbon /
- chemical vapor deposition
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