Pulsed chemical vapour infiltration of TiN into a fine silica capillary sealed at one end

Optimal pressures and temperatures for isobaric, isothermal chemical vapor infiltration

“…Several approaches have been taken to increase the Correspondence concerning this article should be addressed to S. V. Sotirchos. rate of transport of gaseous reactants and products in the pore space, and, in this way, enable the CVI process to operate at conditions yielding higher reaction rates and, hence, lower processing times, such as high temperatures. Methods investigated along this vein include CVI under conditions of forced flow through the preform without or with a temperature gradient imposed against the pressure gradient (Stinton et al, 19861, CVI under pressure pulsing conditions (Sugiyama and Yamamoto, 1989;Sugiyama and Kurisu, 1992;Sotirchos, 1991, 19931, and CVI in performs heated through volume heating methods such as radio frequency (RF) and microwave heating (Gupta and Evans, 1993;Devlin et al, 1993;Spotz et al, 1993), in which case the temperature tends to increase away from the external surface of the heated object toward the interior.…”

Modelling of the CVI Processes

“…This helps to maintain its surface temperature at a constant, well-known value, and ensure a very strong thermal gradient [23]. Also, pressure pulsing has been investigated [24], where the alternating pressurizations and depressurizations help to remove the reaction by-products and force the reactants to flow inside the pore space. All these CVI modifications have the advantage of allowing to work with higher pressures, higher temperatures, and consequently higher rates and lower processing times.…”