Mullite molybdenum composites

The possibility of fabricating continuous mullite/Mo FGMs with density clos ed to theoretical, by pressure slip casting of proof ethyl alcohol based sl urries has been shown. Dense (> 98 th%) homogeneous mullite/Mo (32 vol%) co mposites with two Mo average grain sizes (1.5 and 3 mu m) have been obtaine d at 1650 degrees C in vacuum and under reducing conditions. Depending on t he Mo grain size and processing atmosphere, the K-IC ranged from 4 to 7 MPa m(1/2) and sigma(f) from 370 to 530 MPa. The MoO2-2SiO(2) . 3Al(2)O(3)-Mo were found to be compatible in solid state and a solid solution of approxim ate to 4 wt% of MoO2 in mullite at 1650 degrees C was detected. A solid sta te dewetting of MoO2 from the surface of the Mo particle takes place during sintering. It was found that the absence of MoO2 in the mullite/Mo composi tes by processing in reducing conditions increases the plasticity of the me tal particles strengthening the material by a crack bridging mechanism. Due to this fact, the KIC and the sigma(f) values of the metal/ceramic composi te were found to be approximate to 4 times and approximate to 2 rimes highe r than the ones corresponding to the matrix.