Densification of porous articles by plasma enhanced chemical vapor infiltration

摘要

A porous article is densified by creating a plasma adjacent to the surface of the article and introducing a source of a densifying species into the plasma. The article is electrically biased with respect to the plasma to a polarization opposite in sign to the energized densifying species and to a first voltage sufficient to deposit the densifying species to the first depth below the surface of the article. The species is deposited for a time sufficient to densify the article at the first depth. If the article has porosity over a range of depths, as is often the case, the voltage is first set to densify the article at the greatest depth, and thereafter the voltage is gradually decreased to reduce the depth of densification until the article is densified over the entire range.