Jy. Ofori et Sv. Sotirchos, INVESTIGATION OF THE POTENTIAL OF FORCED-FLOW CHEMICAL-VAPOR INFILTRATION, Journal of the Electrochemical Society, 144(1), 1997, pp. 274-289
A comprehensive study of the forced-flow chemical vapor infiltration p
rocess is presented. A rigorous mathematical model accounting for mass
transport (by bulk and Knudsen diffusion and viscous flow), chemical
reaction, and structure evolution is formulated for the process. We al
so develop a simplified model for the case in which transport is contr
olled by viscous flow and use it to derive analytical results of the p
arametric sensitivity of the process. The effects of pressure, structu
re, flow rate, thermal gradient, reaction reversibility, and periodic
flow reversal on the performance of forced-flow chemical vapor infiltr
ation are examined using both the rigorous and the simplified model. T
he results show that for a given set of operating conditions, there is
an optimal flow rate that produces the best deposition uniformity in
the preform. However, even for operation with the optimal flow rate, f
orced-flow chemical vapor infiltration can outperform the isobaric pro
cess only for large enough values of pressure and pore size. Another i
nteresting result is that periodic flow reversal can lead to a dramati
c improvement of the deposition uniformity, even in the absence of a t
hermal gradient.