Fabrication and optimization of 3D-Cf/HfC-SiC-based composites via sol-gel processing and reactive melt infiltration

In this work, 3D-C-f/HfC-SiC-based composites were fabricated and optimized via reactive melt infiltration (RMI) of Si into porous C-f/HfC-C preforms prepared by a sol-gel processing. The physical and chemical processes involved during the fabrication were identified and analyzed in details. It is revealed that fibers and interphase of the composites can be eroded during carbothermal reduction process, which can be further aggravated during RMI, with the formation of Hf-containing substance on the fibers surface. The fibers and interphase degradation is mainly induced by the reactions between HfO2 and C/SiC interphase layers at elevated temperatures. Accordingly, a two-step carbothermal reduction treatment was proposed for the optimization of the fabrication procedure. As a result, less fiber/interphase erosion and improved mechanical properties are achieved in the composites, with the bending strength increased by similar to 49 % (from 214.1 +/- 15.7 MPa to 319.0 +/- 26.0 MPa).

Automated summary

During the fabrication process of 3D-C-f/HfC-SiC composites, erosion of fibers and interphase is a major issue due to reactions between HfO2 and C/SiC interphase layers at high temperatures. By implementing a two-step carbothermal reduction treatment, the erosion of fibers/interphase can be reduced and mechanical properties of the composites can be improved.