Ford Motor Company Limited

Robert M Williams

Elaine C Beckwith

Harshad Pande

Ultrapure silicon nitride precursor is made by: (a) continuously reacting liquid silicon halide (SiCl.sub.4) with an excess of liquid ammonia (NH.sub.3) (i) in the effective absence of contaminants, (ii) at a reaction situs in an inert atmosphere to form the silicon nitride precursor as a precipitate, and (iii) with a ratio of liquid ammonia to silicon halide (equal to or greater than 21 molar) effective to solubilize any gas reaction products; (b) providing a pressure differential to simultaneously and continuously withdraw a filtered portion of the excess liquid ammonia to leave the silicon nitride precursor precipitate in the reaction situs; and (c) adding ammonia to the excess of ammonia in said reaction situs to replace the withdrawn filtered portion of the liquid ammonia. The reaction is carried out with vigorous stirring of the liquid mixture and the atmosphere over the entire mixture is regulated to contain only ammonia vapor and nitrogen. The temperature of the liquid mixture is maintained between -33.degree. C. to -69.degree. C. by employing a cooling jacket containing dry ice, a slush of dry ice and acetone, isopropanol or cellosolve, and by recycling the withdrawn liquid ammonia and re-adding it to the reaction situs either as a cooling liquid or as a heating gas.

Method of making ultrapure silicon nitride precursor

A method is disclosed of making yttrium silicon oxy compounds, comprising: (a) mixing powdered hydrated metal nitrate with silica in molar equivalent amounts to yield upon heating a desired duo metal oxy compound; (b) agitatingly heating said mixture to melt and decomposition temperatures for the nitrate (e.g., 340.degree.-370.degree. C.), the melt encapsulating the silica particles; and (c) heating the sludge to a temperature (1300.degree.-1550.degree. C.) for a period of time (2-5 hours) effective to stimulate chemical reaction between the decomposed nitrate and silica to form yttrium silicon oxide.

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Livonia, MI, United States of America

Robert M Williams