以NaN3作添加剂制取Si3N4晶须

FABRICATION OF Si 3N 4 WHISKER WITH NaN 3 AS ADDITIVE

用ＮａＮ３作添加剂，在０．５—１ＭＰａ的较低氮气压力下，以燃烧合成工艺，制取了柱状及针状氮化硅晶须．ＮａＮ３的分解不仅能够降低燃烧温度和氮气压力，提高氮化率及α－Ｓｉ３Ｎ４的含量，还能作为氮化硅晶须生长的催化剂．作为固态氮化剂加入的ＮａＮ３过多则易形成Ｎａ的硅酸盐，使产物纯度降低；而加入量不足，则不能实现完全氮化．推测燃烧合成的氮化硅晶须是通过气相沉积（ＶＣ）机制生长的．

Cylindrical and acerose Si 3N 4 whiskers were fabricated through combustion of Si with NaN 3 as additive as well as Si 3N 4 as diluent under 0.5—1 MPa of low nitrogen pressure. Decomposition of NaN 3 not only lowers the combustion temperature and nitrogen pressure required, but also increases the mass fraction of α -Si 3N 4. NaN 3 can also act as catalyst for the growth of Si 3N 4 whisker. Though the quantity of NaN 3 added must be sufficient to ensure the complete nitridation of Si under low nitrogen pressure, superabundant NaN 3 would result in the presence of Na 2Si 2O 5.It is inferred that the growth of as_synthesized Si 3N 4 whisker is controlled mainly by VC mechanism.