J Mater Sci Technol ›› 2007, Vol. 23 ›› Issue (04): 535-540.

• Research Articles • Previous Articles     Next Articles

Kinetic study of SiO2/S coating deposition by APCVD

Jianxin ZHOU, Hong XU, Li ZHANG, Jinglei LIU, Xuegui QI, Bo PENG   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2006-11-15 Revised:2007-04-30 Online:2007-07-28 Published:2009-10-10
  • Contact: Hong XU

Abstract: To alleviate catalytic coking on the inner surface of radiant tube for ethylene production in petrochemical plants, SiO2/S coatings were deposited on HP40 alloy specimens using dimethyldisulfide (DMDS) and tetraethoxysilane (TEOS) by atmospheric pressure chemical vapor deposition (APCVD). A two-dimension mathematical model was made to predict the growth rate of SiO2/S coating and to study the effects of deposition parameters on the deposition rate. The results show that the predicted deposition rate is in good agreement with the experimental one. The deposition rate mainly depends on the concentrations of precursors in the total gas flow, concentrations of intermediates on the deposition surface, total gas flow rate and deposition temperature. The weight of SiO2/S coating linearly increases with the deposition time. When the gas flow rate is below 0.3 m/s, the rate-limiting step of SiO2/S coating deposition is the diffusions of intermediates. However, the surface reactions of intermediates will be the rate-limiting step after the gas flow rate is above 0.3 m/s. When the deposition temperature is below 780℃, the rate-limiting step of SiO2/S coating deposition mainly depends on the surface reactions of intermediates. When the deposition temperature is above 780℃, the rate-limiting step depends on the diffusions of intermediates. The deposition rate increases with increasing the concentrations of the intermediates. However, when the partial pressures of the intermediates reach 8 Pa, the deposition rate keeps constant.

Key words: APCVD, SiO2/S coating, mathematical model, HP40 steel