PRODUCTION OF COATED BORON POWDERS BY CHEMICAL VAPOR DEPOSITION

BORON POWDER IS DESIRED FOR USE IN PROPELLANT AND EXPLOSIVE APPLICATIONS BECAUSE OF ITS HIGH ENERGY DENSITY, BUT COMMERCIALLY AVAILABLE BORON HAS SEVERE DRAWBACKS. WE PROPOSE TO DEVELOP A PROCESS TO MANUFACTURE HIGH PURITY, OXYGEN-FREE BORON POWDER WITH PARTICLE SIZES IN THE RANGE 1-5 UM. IN PHASE I, WE WILL DEMONSTRATE THE FEASIBILITY OF PRODUCING BORON POWDER BY A TWO-STEP PROCESS. IN THE FIRST STEP, SMALL SEED PARTICLES ARE FORMED BY DECOMPOSITION OF BCL(3) WITH A CO(2) LASER. IN THE SECOND STEP, SEED PARTICLES ENTER A FURNACE WHERE THERMAL PYROLYSIS OF B(2)H(6) PROVIDES A SOURCE OF CONDENSABLE VAPOR. SEED PARTICLES GROWN BY CONDENSATION, WHILE HOMOGENEOUS NUCLEATION IS SUPPRESSED BY THE PRESENCE OF SEED PARTICLES. WE WILL WORK IN PARTNERSHIP WITH CVD, INC., A COMPANY WITH EXPERIENCE IN THE APPLICATION OF COATINGS BY CHEMICAL VAPOR DEPOSITION AND IN SCALING UP CVD PROCESSES, TO IDENTIFY A COATING MATERIAL AND A PROCESS FOR COATING BORON POWDER WITH A THIN, PROTECTIVE LAYER TO INHIBIT SURFACE OXIDE FORMATION. IN PHASE II, WE PLAN TO INCREASE THE SCALE OF THE PROCESS TO GROW PARTICLES IN THE RANGE OF 1-5 UM ON A CONTINUOUS BASIS AND TO INTEGRATE THE COATING STEP INTO THE OVERALL PROCESS.