Morphology control of single-crystalline Si3N4 nanomaterials

Three kinds of single-crystalline Si3N4 nanomaterials, Si3N4 nanowires, nanobelts and nanosheets, were synthesized by the heat treatment of Si powder in N2 gas. The Si3N4 nanowires and nanobelts are produced when the synthesis temperature and flow rate of N2 gas are lower than 1300 °C and 0.5 l/min, respectively. The number ratio of Si3N4 nanowires to Si3N4 nanobelts decreases with increase in the synthesis temperature and flow rate of N2 gas. When synthesis temperature and flow rate of N2 gas are higher than 1400 °C and 0.75 l/min, respectively, a lot of Si3N4 nanosheets of at least 2 μm in width and ranging from 1.5 to 4 nm in thickness are produced. The width of Si3N4 nanomaterials increased with increase in the flow rate of N2 gas. Thus the morphology of Si3N4 nanomaterials can be controlled by changing not only synthesis temperature but also flow rate of N2 gas.