HIGH DENSITY SILICON NITRIDE CERAMIC MATERIALS

SILICON NITRIDE POWDER HAS SUBSTANTIAL ADVANTAGES OVER OTHER CERAMIC POWDER FOR APPLICATIONS SUCH AS CUTTING TOOL INSERTS, ROTARY SHAFTS FOR TURBINES, AND ENGINE VALVES. CONSEQUENTLY, THE MARKET DEMAND IS EXPECTED TO INCREASE FROM 250,000 LBS TO 2.5 MILLION LBS ANNUALLY BY 1995, PROVIDED AN ECONOMIC PRODUCTION PROCESS IS DEVELOPED. THUS, SUCCESSFUL RESULTS ON THE PRESENT PROJECT COULD RESULT IN SUBSTANTIAL ENERGY SAVINGS IN THE FUTURE. A NOVEL, SUPERSONIC, TWO-STAGE PLASMA REACTOR IS PLANNED FOR EFFICIENTLY PRODUCING HIGH DENSITY SILICON NITRIDE POWDER FROM SILANE AND AMMONIA. AMMONIA IS DISSOCIATED IN THE FIRST NOVEL REACTOR BY A HIGH CURRENT, LOW PRESSURE PLASMA, AND DISSOCIATED FRAGMENTS ARE INJECTED INTO THE SECOND STAGE THROUGH THE NOZZLE AT NEAR MARCH 1 VELOCITIES TO CONVERT THERMAL ENERGY OF THE FRAGMENTS INTO DIRECTED KINETIC ENERGY. A SECOND PLASMA REGION ACTIVATES THE REACTION BETWEEN THE ACTIVATED AMMONIA FRAGMENTS AND THE SILANE. THE LONG REACTION ZONE WILL FAVOR HOMOGENEOUS REACTIONS IN THE GAS PHASE AND NUCLEATION FAVORING THE FORMATION OF PARTICLES. IN THE EVENT TECHNICAL AND ECONOMIC FEASIBILITY IS ESTABLISHED, THE USE OF SILICON NITRIDE WILL ENABLE HIGHER THERMODYNAMIC EFFICIENCIES AND SUBSTANTIAL ENERGY SAVINGS.