THE DEVELOPMENT OF NBN-COATED GRAPHITE SUPERCONDUCTING MATERIALS

NIOBIUM NITRIDE (NBN) MATERIALS ARE ATTRACTIVE CANDIDATES FOR VERY HIGH FIELD MAGNETS. NBN MATERIALS HAVE HIGH CRITICAL CURRENT DENSITIES, LOW SENSITIVITIES TO STRAIN DEGRADATION EFFECTS, AND GOOD RADIATION RESISTANCE. MULTIFILAMENT GRAPHITE FIBER IS AN IDEAL SUBSTRATE ON WHICH TO DEPOSIT NBN BECAUSE OF ITS HIGH STRENGTH, FINE FIBRIL DIAMETERS, AND LOW COEFFICIENT OF THERMAL EXPANSION. INVESTIGATORS HAVE DEPOSITED NBN ON MULTIFILAMENT GRAPHITE BY MAGNETRON SPUTTERING AND CHEMICAL VAPOR DEPOSITION METHODS; HOWEVER, DEPOSITION OF ALUMINUM OR COPPER STABILIZER TO LEVELS OF ABOUT 50 VOL % REQUIRED FOR REALISTIC MAGNET APPLICATIONS HAS NOT BEEN ACHIEVED. IN THIS PROJECT IT IS PLANNED TO USE A UNIQUE TITANIUM/BORON CHEMICAL VAPOR DEPOSITION/LIQUID METAL INFILTRATION PROCESS TO ACTIVATE THE NBN COATED GRAPHITE SURFACE AND TO INFILTRATE WITH SUITABLE METAL TO MAKE NBN-COATED GRAPHITE SUPERCONDUCTING MATERIAL WITH ALUMINUM OR COPPER STABILIZER.