Facile synthesis of SiOx spheres or dumbbell-shaped β-SiC whiskers on expanded graphite by silicon vapor deposition

A facile method was developed to synthesize SiO, spheres or dumbbell-shaped beta-SiC whiskers on expanded graphite (SiOx/EG or beta-SiC/EG) by silicon vapor deposition without catalyst. With the carbon black atmosphere, the above hybrids were synthesized above 1100 degrees C in a graphite crucible where silicon powder was placed under the expanded graphite (EG). The growth of SiOx spheres is controlled by vapor-solid mechanism at 1100 degrees C and 1200 degrees C. Namely, the active carbon atoms absorbed SiO (g) and Si (g) to form SiC nuclei. Then, the SiO2, residual SiO (g) and Si (g) deposited on SiC nuclei to form SiO, spheres. At 1300 degrees C and 1400 degrees C, the same SiO, spheres formed on EG as well as many dumbbell-shaped beta-SiC whiskers. The growth of dumbbell-shaped beta-SiC whiskers is controlled by vapor-vapor and vapor-solid mechanism successively. In a word, firstly, the beta-SiC whiskers with defects formed via the reaction between Si (g) and CO (g). After that, the SiO2, residual SiO (g) and residual Si (g) preferentially deposited on defects, then deposited on other parts of beta-SiC whiskers to form dumbbell-shaped SiC whiskers.