In situ synthesis of SiOC ceramic nanorod-modified carbon/carbon composites with sol-gel impregnation and CVI

SiOC ceramic nanorod-modified C/C composites were successfully synthesized by a three-step technique, involving sol-gel impregnation, isothermal chemical vapor immersion and thermal gradient chemical vapor immersion. The morphology, phase composition, microstructure, element qualitative and quantification of the obtained specimens were investigated by SEM, XRD, TEM and XPS, respectively. The results showed that the tapered SiOC ceramic nanorods were coated by pyrolytic carbon, which have a diameter of hundreds of nanometers and a length of several microns. The interlaminar shear strength test showed that the modified composite possessed excellent mechanical properties. Compared with the unmodified ones, the interlaminar shear strength of SiOC ceramic nanorod-modified C/C composites was enhanced by 45.09 %, which can be ascribed to the change of matrix structure and the improvement in fiber/matrix interface. The low-resolution TEM micrograph shows the general morphology of the SiOC nanorod (a) and SiOC (b) powder dispersed on a holey copper grid. The corresponding high-resolution TEM images (HRTEM) and selected area electron diffraction (SAED) patterns were also exhibited in the insets, respectively. From (a), the nanorod with a length about 10 mu m and a tapered shape diameter ranging from 50 to 600 nm was like a single crystalline which may be attributed to the unique formation of the nanorod. Moreover, the nanorods crystal lattice fringe spacing was measured to be 0.25 nm. Moreover, the diffraction rings and the irregular HRTEM image are an inherent characteristic of amorphous SiOC ceramic, as shown in (b). [GRAPHICS] .