Preparation of Fiberlike Silicon Nitride from Diatomaceous Earth

Fiberlike Si 3 N 4 was prepared by the carbothermal reduction of diatomaceous earth in a flow of nitrogen and ammonia. Diatomaceous earth, which is an inexpensive raw material, is composed of 82.5 wt% SiO 2 , 5.69 wt% Al 2 O 3 , and a very small amount of metal oxides (K 2 O, CaO, and Fe 2 O 3 ). Two types of fiberlike Si 3 N 4 were obtained, short needlelike fiber and woollike fiber with Fe droplets at 1350°C.