VAPOR PHASE CHEMICAL INFILTRATION PROCESS OF A MATERIAL INTOA POROUS SUBSTRATE AT CONTROLLED SURFACE TEMPERATURE

摘要

The substrate (10) is placed in an enclosure (12) and is heated so as to establish therein a temperature gradient such that the substrate has a higher temperature in portions that are remote from its exposed surfaces than at its exposed surfaces. A reaction gas constituting a precursor for the material to be infiltrated is admitted into the enclosure, with formation of the material being enhanced in those portions of the substrate that are at higher temperature. At the beginning of the infiltration process, and at least during the major portion thereof, substrate heating is controlled in such a manner as to maintain the temperature of its exposed surfaces at a value that is no greater than the minimum temperature for the reaction gas to deposit the material that is to be infiltrated, while portions of the substrate that are remote from its exposed surfaces are at a temperature that is greater than the minimum temperature for deposition.