| This paper was firstly on the basis of titanium carbide, adding MoSi2, using creep deformation of MoSi2 at high temperature to prepare MoSi2-TiC ceramic matrix composites with a lower thermal expansion coefficient;By adding a small amount of aluminium powder, the mechanics performance of Al-MoSi2-TiC ceramic matrix composites were markedly improved;On this basis, NH4HCO3 was added to prepare a porous Al-MoSi2-TiC ceramic matrix composites;The relationship of composition, function and structure was discussed, and the effect of carbon fibre (asphalt-based and polyacrylamide nitrides-based) to composites was also studied;Volume density, hole percentage, crystal phase, thermal expansion coefficient, mechanics performance, and microstructures were tested by analytical scales, DTA, thermal expansion device (TED), pressure machine, scanning electricity mirror(SEM), X—ray diffraction (XRD) instruments.Survey results show that:MoSi2 markedly lower the sintering temperature of TiC ceramic matrix composite, and the relative density, fractural strength and compressive strength was respectively 76-84.7%, 10~55MPa, 20~52MPa;When TiC have added to 65wt%, the maximum was respectively 84.7%, 55MPa and 52MPa;Thermal expansion coefficient was 4.64~5.81×10-6K-1, when TiC was 60wt%, a minimum of thermal expansion coefficient was 4.64×10-6K-1.XRD diffraction analysis showed that chemical reaction of TiC, MoSi2 and C powder occured in sintering process, new series of Mo2C, Ti0.98Mo0.02C, Ti3SiC2 and Mo5Si3 were produced.The relative density, fractural strength and compressive strength of Al-MoSi2-TiC ceramic matrix composites was respectively 86-92.7%, 50~90MPa, 50~180MPa.When Al was added to 3.5wt%, the maximum was respectively 92.7%, 90MPa and 180MPa;Thermal expansion coefficient between the 6.3~7.8×10-6K-1.Adding carbon fibre(asphalt-based and polyacrylamide nitrides-based) in Al-MoSi2-TiC composites, the mechanics performance of composites markedly lower;The main cause of lower performance was no wetting and no chemical bond between carbon fibre and composites.Hole percentage 34~70vol% of porous materials increased with NH4HCO3 and a linear relationship was got. The relative density, fractural strength and compressive strength of porous Al-MoSi2-TiC ceramic matrix composites was linear reduced with NH4HCO3;The porous C fiber-MoSi2-TiC ceramic matrix composites was 33%~69%;Fractural strength and compressive strength was at the lower rate;Increasing shaped pressure of semifinishedmaterials can improve mechanics performance of ceramic matrix composites, but porous composites was reduced.MTAN30 porous ceramic matrix composites had apparent catalyzation to dry ethanol and wood tar gas of dry basswood;Dry ethanol can be turned into ethylene, and 25.16wt% wood tar gas into organic gases, gas conversion rate was increased by 1.21 times. |
