Martin Friess

The morphology of silicon carbide in C/C-SiC composites

Abstract In the present investigations C/C–SiC has been studied by means of SEM, X-ray diffraction (XRD) and TEM to reveal the morphology of the silicon carbide areas. It was found that there exist two different areas of SiC, a fine grained β-SiC layer with a high amount of stacking faults at the C–SiC interface, and a zone of coarser β-SiC at the SiC–Si interface. From these observations, reaction mechanisms governing the siliconization of porous C/C preforms are proposed. After an initial reaction of carbon with silicon vapour, liquid silicon has to diffuse through the already formed SiC. A violent reaction far away from equilibrium conditions and a high number of nucleation sites leads to the observed formation of a fine grained SiC with a high density of stacking faults. Thermodynamically this is an instable configuration so that the coarser grained zone emerges by solution and precipitation.

Manufacturing and Properties of CMCs Containing Ti Filler with Improved Intra-Matrix Bond

Ceramic matrix composites (CMCs) were manufactured via polymer infiltration and pyrolysis) PIP process. In order to improve the performance of CMCs as well as to accelerate the manufacturing process, micro-sized powders of Ti are employed as active fillers. To further increase mechanical properties of the CMC, a novel approach is made to strengthen intra-matrix bond by treating the CMC with titanium(IV)-diisopropylate after first PIP processing prior to each PIP cycle.