Jy. Ofori et Sv. Sotirchos, DYNAMIC CONVECTION-DRIVEN THERMAL-GRADIENT CHEMICAL-VAPOR INFILTRATION, Journal of materials research, 11(10), 1996, pp. 2541-2555
The operation of the process of chemical vapor infiltration using a co
mbination of pressure pulsing and thermal gradients is theoretically i
nvestigated in this study. Past studies had shown that pulsing of the
pressure in the gas phase can lead to a dramatic reduction of the dens
ity gradients in the densifying structure, in comparison to those seen
in isobaric diffusion-driven Pinfiltration, with significant gradient
s present only in the vicinity of the external surface of the preforms
. Using a detailed model for chemical vapor infiltration under unstead
y nonisothermal conditions, we show that temperature gradients, create
d in our study through microwave heating, can, in conjunction with pre
ssure pulsing, eliminate the density gradients in the final product. M
oreover, appropriate tuning of the operational parameters can lead to
a situation where densification proceeds from the interior of the pref
orm toward the external surface.