초록 ▼

A process for the preparation of silicon nitride powders, which are suitable for the manufacture of high quality structural ceramics is described. The synthesis process is based on the reduction of silicon dioxide by carbon in a nitrogen stream at elevated temperatures to form alpha silicon nitride.

A process for the preparation of silicon nitride powders, which are suitable for the manufacture of high quality structural ceramics is described. The synthesis process is based on the reduction of silicon dioxide by carbon in a nitrogen stream at elevated temperatures to form alpha silicon nitride. Silicon nitride powders of various morphologies are obtained by this technique by varying either the type of reactants used or the process conditions. Structural ceramics with densities exceeding 99% of theoretical and having satisfactory mechanical strength and oxidation resistance were sintered from powders synthesized by the method of this invention.

대표청구항 ▼

A method for making silicon nitride powder comprising the steps: Step 1 mixing carbon and silicon dioxide having a weight ratio from about 1 to about 4 to form a homogeneous powder mixture; Step 2 heating the powder mixture from step 1 from about 1400°C. to about 1550°C. in a nitrogen stream for a

A method for making silicon nitride powder comprising the steps: Step 1 mixing carbon and silicon dioxide having a weight ratio from about 1 to about 4 to form a homogeneous powder mixture; Step 2 heating the powder mixture from step 1 from about 1400°C. to about 1550°C. in a nitrogen stream for a time sufficient to form silicon nitride, the nitrogen stream having a velocity from about one to about 3 cm/sec, said carbon having an oil absorption value less than 100 ml/100 g; and Step 3 heat treating the product from step 2 in air at about 600°C. to about 700°C. for a time sufficient to completely oxidize residual carbon. A method for making silicon nitride powder in accordance with claim 1 wherein said velocity of said nitrogen stream of step 2 being sufficient to form a silicon nitride powder morphology characterized by the morphology depicted in FIGS. 1 and 2.