Phase characterization and thermal conductivity of carbon alloys obtained by interface reaction between C/C composites and pressed molybdenum silicide

The C/C composites made by laying up the sheets of carbon fibers using a pitch matrix were used as starting materials. After cutting the composites in the parallel (PA) and the perpendicular (PE) directions to the sheets of carbon fibers, the surface of PA and PE substrates obtained were reacted with MoSi2 at 1450degC in argon gas. From XRD (X-ray diffractometer) measurements, the four phases of graphite, MoSi2, MoO3 and α-SiC were observed at the surface of the substrates treating for 3 and 6 h, irrespective of the direction to carbon fiber sheets. A concentration gradient of SiC in the as-prepared substrates was observed in both directions parallel and perpendicular; the concentration of SiC decreases along the depth from the surface of substrates. In the results of line analysis by EDX (Energy Dispersive X-ray) measurements, it was found that the reaction between C/C substrates and MoSi2 occurred in the portion of matrix in the substrates. The thermal conductivity of PA substrates decreased with the increase of the treating time and was lower than that of PA substrates treating below 3 h and without treatment. (author)