THE PREPARATION OF HIGH TEMPERATURE INTERMETALLIC COMPOUNDS AT LOW TEMPERATURES

INTERMETALLIC COMPOUNDS, IN PARTICULAR ALUMINIDES, SILICIDES, AND BERYLIDES, ARE KNOWN FOR THEIR HIGH MELTING POINTS AND CORROSION AND OXIDATION RESISTANCE. MANY OF THESE COMPOUNDS HAVE LOW DENSITIES AND VERY HIGH STRENGTHS AND, THEREFORE, ARE OF INTEREST FOR HIGH TEMPERATURE APPLICATIONS. HOWEVER, CONVENTIONAL PROCESSING OF INTERMETALLIC COMPOUNDS SUFFERS SEVERE LIMITATIONS, NAMELY REACTIONS WITH CONTAINERS, POROSITY, CONTAMINATION OF POWDER SURFACES, AND COMPOSITIONAL INHOMOGENEITIES. RECENT WORK ON LOW TEMPERATURE CHEMICAL VAPOR DEPOSITION (CVD) OF METALS FROM ORGANOMETALLIC COMPOUNDS FOR ELECTRONICS APPLICATIONS SUGGESTS THE POSSIBILITY OF FABRICATING CERTAIN INTERMETALLIC COMPOUNDS BY CVD. BECAUSEORGANOMETALLIC CVD OPERATES AT LOW TEMPERATURE, EMPLOYS HIGHLY PURE STARTING MATERIALS, DEPOSITS MATERIAL UNIFORMLY,AND REQUIRES COMPARATIVELY LITTLE MATERIALS HANDLING, IT HASTHE POTENTIAL TO SOLVE THE PROBLEMS DESCRIBED ABOVE. IN THE PHASE I STUDY, A LOW TEMPERATURE CVD TECHNIQUE WILL BE USED TO APPLY COATINGS AND TO INFILTRATE A FIBER PREFORM WITH NIAL. THE TECHNOLOGY DEVELOPED FOR THIS SYSTEM WILL SERVE AS AN EXAMPLE FOR SEVERAL OTHER INTERMETALLIC COMPOUNDS OF INTEREST TO THE DOE DURING PHASE II. MATERIALSMADE BY THESE TECHNIQUES HAVE POTENTIAL USES AS STRUCTURAL ALLOYS IN FUSION ENERGY SYSTEMS, EROSION RESISTANT ALLOYS FOR FOSSIL ENERGY SYSTEMS, AND INTERMETALLIC COATINGS FOR A VARIETY OF HIGH TEMPERATURE HEAT ENGINE MATERIALS.