Fabrication of SiCf-CNTs/SiC composites with high thermal conductivity by vacuum filtration combined with CVI

SiCf-CNTs/SiC composites with about 25-30 vol% carbon nanotubes were successfully prepared by vacuum filtration combined with chemical vapor infiltration method. Through this method, the problems of agglomeration and limited amount of introduced CNTs in SiC/SiC composites were solved. The microstructure, thermal conductivity, bending strength and fracture toughness of SiCf-CNTs/SiC were observed. Results showed that the composites were composited by 7 layers of SiCf/SiC and 6 layers of CNTs/SiC, each layer was bonded to another by CVI SiC quite well, which presented the morphology of laminated structure. SiCf-CNTs/SiC had outstanding thermal conductivity as 23.9 W/(m K) at room temperature which was 2.9 times higher than traditional SiC/SiC composites due to the extremely high thermal conductivity and large amount of CNTs. The bending strength and fracture toughness of SiCf-CNTs/SiC composites were 240±7 MPa and 14.1±0.5 MPa m1/2, respectively. The bending strength-displacement curve of SiCf-CNTs/SiC presented zigzag and multi-step-like drop of the strength after reaching the maximum value. The fracture morphologies showed that, cracks defected in the interface of SiCf/SiC matrix, inner SiCf/SiC layer/CNTs/SiC layer and there were pull out of both CNTs and SiC fibers in SiCf-CNTs/SiC composites.