以丙烯和氩气为气源,在800～1200℃,1～15 kPa和25～500 sccm条件下进行化学气相沉积热解碳,采用磁悬浮天平实时称量热解碳的生成量进行动力学研究.结果表明,1000℃以下,化学反应控制沉积过程,乙炔的生成为限速步骤;当温度高于1000℃时,转变为气相传质控制,温度是影响沉积机理最重要的热力学参数.压力和滞留时间对沉积速率的影响说明热解碳是通过一系列气相连续反应后形成的.采用实验测得的活化能137士25 kJ/mol和丙烯分压一级反应级数,确定了总的动力学方程式,并用实验结果验证了其有效性.
Detailed kinetics were investigated via in-situ magnetic suspending balance on CVD of PyC from propylene/argon mixture at specific range of temperature(800-1200℃), total flow rate (25-500 sccm) and total pressure(1-15 kPa). Results showed chemical kinetic mechanism controlled the PyC deposition below 1 000℃, and acetylene-forming reaction was the deposition rate-limiting step. Mass transfer was the controlling mechanism over 1000 ℃. Transition(about 1000 ℃) from chemical kinetic control to gas-phase mass transfer control was found to be induced mainly by the increasing of temperature. Results on the influence of residence time and initial partial pressure on PyC deposition suggest that PyC was obtained after a series of consecutive reactions in gas phase. A overall power law expression has been developed from the apparent activation energy of 137±25 kJ/mol and the first-order with C3H6 initial partial pressure, and its validity was test by experimental data.
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