LDH催化制备单晶α-Si_3N_4纳米线研究

Catalytic preparation of α-silicon nitride single-crystalline nanowires by layered double hydroxides

提出了一种以LDH(水滑石类化合物)为催化剂,纳米硅粉为原料,在N_2-H_2混合气氛下制备单晶α-Si_3N_4纳米线的CVD(化学气相沉积)方法。研究结果表明:当H_2含量小于0.5%时,所制备的Fe/Mg/Al LDH催化剂具有优良的高温热稳定性,在1250℃下煅烧与还原后仍可保持自身结构完整与催化活性。通过降低还原温度与LDH中Fe含量、在LDH中引入Mo元素等手段,有效地降低金属Fe纳米晶粒直径、增大成核密度,所制备单晶α-Si_3N_4纳米线面密度可达5×10^(14)~9×10^(14) m^(-2),直径为30~50 nm,长度达20~80μm(长径比>1000)。进一步研究表明本实验中纳米线为VLS(气液固)生长机制。

α-Silicon nitride single-crystalline nanowires were prepared by direct nitridation of nano-Si powders in N2-H2 mixture gas under the catalysis of layered double hydroxide(LDH)flakes.The results show that when the H2 content is less than 0.5%,the as-prepared Fe/Mg/Al LDH catalyst has excellent high temperature thermal stability,and can maintain its structural integrity and catalytic activity after calcination and reduction at 1250℃.Through decreasing the size and increasing the density of nano Fe particles on LDHs,via reducing the temperature,Fe content in LDHs and adding Mo element into LDHs,the diameter of as preparedα-Si3N4 nanowires can be decreased to 30-50 nm,with the aspect ratio higher than 1000.Further study shows that the growth of nanowires was controlled by the vapor-liquid-solid(VLS)mechanism.