Nitridation of Silicon Powders Catalyzed by Cobalt Nanoparticles

The effect of Co nanoparticles ( NP s) on the nitridation of silicon ( Si ) was studied. Co NP s were deposited homogeneously on the surfaces of Si powders using an in situ reduction method using NaBH 4 as a reducing reagent. Si powders impregnated with 0.5–2.0 wt% Co NP s were nitrided in 1200°C–1400°C for 2 h. The resultant silicon nitride powders were characterized by XRD , FE ‐ SEM , TEM , and EDS . The results showed that: (1) Co NP s significantly decreased the Si nitridation temperature, and the nitridation could be completed at 1300°C upon using 2 wt% Co NP s as catalysts. For comparison, the Si conversion could not be completed even at a temperature as high as 1400°C in the case without using a catalyst; (2) many Si 3 N 4 whiskers with 80–320 nm in diameter and tens micrometers in length were generated and uniformly distributed in the final products. They were single‐crystalline α‐Si 3 N 4 grown along the [101] direction. The enhanced nitridation in the case of using Co NP s as a catalyst was attributed two following factors, the increased bond length and weakened bond strength in N 2 caused by the electron donation from the Co atoms to the N atoms.