Process for preparing a densified beta-phase silicon nitride material having at least one densification aid, and the material resulting therefrom

Reference Number: N 04-12

Inventors: Edler, James P.; Lisowsky, Bohdan

Owner: NISTAC

USPTO Link: 5213729

Invention Summary

A process for preparing an alpha-phase silicon nitride material and thereafter sintering to a densified beta-phase silicon nitride material is disclosed which includes comminuting a slurry including a mixture of silicon powder, water, and at least one densification aid to aid in later densifying of the silicon nitride material, the comminuting being performed to form fresh, non-oxidized surfaces on the silicon powder and to allow substantial chemical reaction between the silicon and the water, reducing the water content of the reacted slurry to a degree sufficient to form a resultant dry mass, nitriding the dry mass by exposure to a sufficient amount of a nitriding gas including at least nitrogen at a sufficient temperature for a sufficient length of time to form a mass of substantially alpha-phase silicon nitride, and sintering the resultant silicon nitride mass at a sintering temperature of from about 1450.degree. C. to about 2100.degree. C. for a sufficient length of time to convert the silicon nitride from a predominantly alpha-phase material to a predominantly densified beta phase silicon nitride material exhibiting a decrease in bulk volume of the silicon nitride due to the densification.