Papers by Author: Hai Jun Zhou

Abstract: C_f/SiC composites were fabricated through in situ growth of carbon nanotubes (CNTs) on three-dimensional needle-punched carbon fabric via chemical vapor deposition and polymer impregnation and pyrolysis process. The mechanical and thermal properties of the composites were investigated. The flexural strength and fracture toughness were decreased due to the fiber volume fraction loss and much shorter pull-out length of fibers which was caused by the higher interfacial bonding strength between fiber and matrix after the growth of CNTs. Brittle fracture character of CNTs was observed due to the strong interfacial bonding strength between CNTs and matrix. The parallel thermal conductivity and perpendicular thermal conductivity were improved to 14.5% and 8.0% respectively.

Abstract: ZrC-SiC powders were fabricated by means of liquid precursor conversion method, using Zr containing polymer precursor and polycarbosilane. The effects of staring reagents and the pyrolysis temperature on the fabrication of ZrC-SiC powders were studied. Results show that ZrC-SiC powders with different ZrC/SiC ratio could be formed when the staring reagents were different. Pyrolysis temperature affects the pyrolysed product. When temperature was lower, less amount of ZrC was formed in the powder. The size of crystallite and morphology of the synthesized powders were characterized by transmission electron microscopy and scanning electron microscopy.

Abstract: C/SiC composites were prepared by liquid silicon infiltration process, and their microstructure, mechanical and tribological properties were studied in this paper. The results showed that the composites demonstrated non-catastrophic fracture behavior with long fibers pulled out and about 115 MPa flexural strength. The stability of coefficient of friction (COF) was improved and wear rate demonstrated a linear variation with the increasing of rotation speeds. However, wear rate exhibited a higher value (~3.6 μg/m) under a higher load (~150 N), even though the COF curves for C/SiC composites showed no significant changes.