Fabrication and characterization of GCF/PyC composites by TG-CVI densified porous glassy carbon preform

Carbon foams with adjustable three-dimensional architecture are obtained by template method. This paper describes the effects of template content impact on the porous framework, microstructure and mechanical properties of glassy carbon foams. Then a serious of glassy carbon foam/pyrocarbon (GCF/PyC) composites were fabricated by thermal gradient chemical vapor deposition (TG-CVI) using glassy carbon foam with different porosity as preform. After densification, bulk density of glassy carbon foam was increased and defects in carbon foam framework were repaired, which contributes to mechanical properties and ensures higher thermal conductivity. As the porosity increases, compressive strength of carbon foam gradually decreases from 83.03 MPa to 24.52 MPa. The compressive and flexural strengths of obtained GCF/PyC composites first increased and reached the peak values, then decreased. The maximum compressive and flexural strengths of GCF_1/1-C are measured to be 120.5 MPa and 92.21 MPa, which are 135 % and 267 % higher than that of carbon foam GCF_1/1. The thermal conductivity of carbon foam decreases from 1.22 W/m·K to 0.75 W/m·K with the porosity increase. For GCF/PyC composites, thermal conductivity first increases to 4.41 W/m·K then decrease, and GCF_2/1-C has lowest thermal conductivity of 3.26 W/m·K among all GCF/PyC samples, which is 160 % higher than that of GCF_2/1 before densification.