MODELING OF GAS-PHASE COMPRESSION OF CARBON COMPOSITES IN THERMOGRADIENT CONDITIONS.

Properties of carbon-based composites depend on the structure of material, which is characterized by the arrangement of reinforcement filaments, their volume and porosity of material. Reduction of composites porosity is achieved by filling their porous structure with carbon using a method for the isothermal compression (thermal-gradient method). Isothermal methods are usually applied for compressing thin-walled articles in flow reactors under two-sided admission of reagent gas. The thermal-gradient method is preferable for thick-walled articles, it is characterized by the alternating temperature field over the composite thickness, conditional changing of thermal conductivity coefficients of the porous composite and pyrolytic carbon. The model of plate-shaped carbon composite has been considered, it has cylindrical pores, which are perpendicular to its surface. The pores surface is smooth and energetically homogeneous. When using the thermal-gradient method the outer side of composite is heated up to the temperature exceeding the temperature of reagent gas, passing over its inner side. The reagent gas temperature in reactor is significantly lower the threshold value, typical for initial phase of homogeneous processes, and the volume of t natural gas, diffusing into the composite porous structure, has quite a low value. The system of equations has been proposed, describing the processes of temperature distribution on the thickened carbon composite taking into account the reagent gas diffusion into the porous structure of material, and deposition of pyrolytic carbon over the pore walls, which causes porosity reduction and thickness increase of this material. [ABSTRACT FROM AUTHOR]