Modelling of SiC-Matrix Composite Formation by Thermal Gradient Chemical Vapour Infiltration

Mechanical properties of ceramics can be dramatically improved by embedding a reinforcement phase (particles, whiskers, or fibres), i.e. producing a Ceramic-Matrix Composite (CMC). An advanced technique for manufacturing the CMC is Chemical Vapour Infiltration (CVI). In this paper, we developed a 1D model describing the Thermal Gradient Chemical Vapour Infiltration (TG CVI) for a formation of a composite with the silicon carbide (SiC) matrix from methyltrichlorsilane (MTS). Within the model, the fibrous substrate (preform) is considered as a complex porous medium with two systems of parallel non-uniformly scaled pores oriented along the preform thickness. Longitudinal convection in the process is governed by the phase transitions due to the matrix material deposition. To allow for the mass exchange between the pore systems, transverse diffusion and convection are accounted for in the model. We analysed the influence of the TG CVI operating conditions, namely the precursor (MTS) concentration in the ambient gas, the pressure in the reactor, the susceptor temperature, and the temperature gradient in the preform on the quality of the composite and the process duration.