Research On The Preparation Of Alumina Fibers Composite Foam Ceramics

As an important functional porous ceramics, Al2O3 foam ceramics has perfect properties of good hardness, high temperature resistance, wearing resistance, oxidation resistance and corrosion resistance, etc., which was used in metallurgy, chemical industry and the key parts of aerospace engineering in some susceptible to high temperature gas flow erosion.Al2O3 foam ceramics were successfully prepared by organic monomer gel-foaming and inorganic adhesive (aluminum dihydrogen phosphate) gel-foaming methods respectively. The main research contents and conclusions of the thesis were as follows.Preparation of alumina fibers composite foam ceramics by organic monomer gel-foaming agent(1) The gel-casting process was determined by the viscosity of slurry. It decreased when the adding dispersant was lower than 0.4 wt%, with pH at 9. Instead, it increased when the amount of dispersant was over 0.4 wt%. It rose slowly when the solid content lower than 68 wt%, and the slurry present good flowability. Oppositely, it increased sharply and the flowability weakened slowly when the solid content over 68 wt%. Thence, it came to that, the flowability of slurry can meet the demand of get-casting process with the amount of dispersant at 0.4 wt% and the solid content at 68 wt%.(2) The compressione strength of green body increases with the increase of monomer/crosslinking ratio. The compressione strength and bulk density of the sintered Al2O3 foam ceramics firstly increased and then decreased, the porosity decreased firstly and then increased. The surface of fiber got rough with the lifting of sintering temperature and prolonging of soaking time. (3) The porosity of Al2O3 foam ceramics decreased with the increase of the solid content, on the contrary, the bulk density and compressione increased in the condition. Preparation of Al2O3 foam ceramics by inorganic adhesive (aluminum dihydrogen phosphate) agent(1) The component of sintered Al2O3 foam ceramics by inorganic adhesive agent was detected by XRD method as α-Al2O3、C-AlPO4 and T-AlPO4.(2) The porosity increased by lifting the amount of fiber, and the viscosity of slurry decrease which resulted in the decrease of bulk density and compressione strength, while that increased and the porosity started to decrease when the fiber value was above 20 wt%.(3) By increasing the amount of Al(OH)3, the strength of green body got improved, the thermal conductivity increased, and the porosity decreased with the bulk density and compressione strength rose until the adding amount of Al(OH)3 exceeded 15 wt%.(4) The porosity decrased and compressione strength improved with the rose of sintering temperature.(5) Ceramics soaked for 4 h when sintering showed the highest compressione strength and lowest porosity, which showed the opposite regular when soaked for more than 4 h.