Chemical Vapor Infiltration Rates of ZrO2into MoSi2Porous Bodies and Comparison with Model Calculation

Abstract

Zirconia (ZrO 2 ) was chemical vapor infiltrated (CVI) into a partially sintered MoSi 2 body (preform) by using zirconium n-propoxide (Zr(OC 3 H 7 ) 4 ) as a gas precursor. Infiltration distances at different conditions were compared with the calculated results. Chemical vapor deposition (CVD) film growth rates of ZrO 2 were measured, and the data were incorporated into the model calculations. Two models were used to analyze the observed infiltration distances. Initially a conventional model assuming a pore with constant radius (SP model) was used. With this model, it was possible to predict the approximate infiltration distance. However, the model cannot predict pore closure and the infiltration distances for a variety of CVI conditions. Secondly, a newly proposed model (PC model) from a previous paper was applied to calculate the infiltration distance. Using this model, it was possible to predict the occurrence of pore closure or the formation of the deposition layer on the preform surface.