Microstructure and mechanical properties of SiC/SiC joints reinforced by in-situ growth SiC nanowires

A novel two-step joining technology (pyrolysis and C-Si reaction bonding) was used to prepare the SiC/SiC joints with SiC nanowire reinforcements. The microstructure and phase composition of joining layers and joints were characterized, and the effects of pyrolysis temperature, SiC particle size, polycarbosilane content and filler ratio (C/SiC) were investigated. The results indicated that when the temperature was lower than melting point of catalyst, the formation mechanism of SiC nanowires was vapor-solid growth (VS); conversely, the formation mechanism was vapor-liquid-solid growth (VLS). With the increase of SiC particle size, the quantity and diameter of SiC nanowires increased and the thickness of interlayer was slightly smaller. The higher the polycarbosilane content, the thinner the as-prepared interlayer would be. The phases of joints consisted of 6H-SiC and the mixture of 3C-SiC and free Si. The highest flexural strength of joined samples can reach 289 ± 60 MPa and 368 ± 44 MPa at room temperature and 1200 °C, respectively.