Large-scale synthesis of α-Si₃N₄ nanofibers and nanobelts from mesoporous silica-carbon nanocomposites

This work presents a low-cost and large-scale synthesis technique for silicon nitride nanofibers and nanobelts based on the use of mesoporous silica-carbon nanocomposites as precursors via a carbothermal reduction and nitridation reaction. The growth mechanisms have been investigated by carrying out heat-treatment of precursors with different C/SiO2 ratios in a flowing nitrogen gas with different flow rates. Highly crystalline silicon nitride nanofibers and nanobelts were obtained after easy separation from the unreacted powder underneath. A higher C/SiO2 ratio gives a better yield of nitride products. The thickness of the ribbons can be maintained as constant while the width of the ribbons can be controlled by tailoring the flow rate of nitrogen gas. The growth direction of Si₃N₄ nanobelts is parallel to the [100] crystallographic orientation of a-Si₃N₄.