The Preparation Study Of The Alumina-mullite Ceramic Foam

Ceramic foam with high porosity (70%-90%)and a structure of open cells in a three-dimensional network is a new type porous ceramics material made by special technique. It has many good performances such as good chemical stability, high intensity, high temperature resistance, good thermal shock resistance, large specific surface area, and so on. Because of the low cost and high efficacy, alumina-mullite ceramic foams has been widely concerned in the industry.According to those disadvantages of ordinary clayey foam ceramics, such as low strength, low thermal shock resistance, and narrow scope of application, and the high production temperature and high cost of ceramic foams which have single component such as SiC, AlN and ZrO₂, We carried on the study on the preparation of alumina-mullite ceramic foams with polymer-sponge method, gave a systematic research on the effect of different factors on the performance of material. The research results are as follow:(1) Pre-treatment of polymer foam increased the grouting-absorption capacity of polymeric sponge. Choose the polymeric sponge as the precursor of ceramic foams. Through alkali treatment, the film of polymeric sponge between stalks was destroyed, and the roughness of the polymeric sponge surface roughness can be increased. And then with CMC modification added, the wetting ability and grouting-absorption capacity of polymeric sponge were increased.(2) Through adding appropriate dispersant, we can obtain the slurry with high solid content, good equality and stabilization, and excellent rheology. It was found that the best aqueous slurry can be obtained by adding 0.4% quality content PMAA-NH₄. And the slurry was most suitable for the impregnation when solid content was between 68.4%-69.4%. The gap of two-parallel rolls has a closed relationship with the grouting-absorption capacity of precursor. The best d/h(d- the distance of the gap of two-parallel rolls, h-height of polymeric sponge) was 9.45%-10.35%.(3) The compressive strength and yield of complex ceramic foams was increased by microwave drying method. By microwave drying method, elliptical deformation was reduced effectively and the limit of grouting-absorption capacity was enlarged. So the compressive strength and yield of ceramic foams was increased. Moreover it increased the drying efficiency, and saved the energy.(4) According to the research on the sintering temperature of ceramic with different recipe, the evolution of ceramic phase was studied. Through observing the effect of sintering temperature on ceramic performance, the best recipe B was finally confirmed. By studying on different sinter-holding time with recipe B, the influence of holding time on ceramic foam performance was obtained. The optimum sintering temperature of alumina-mullite ceramic foam was determined as 1500℃, and the optimum holding time was 90min. Under this condition, the porosity of alumina-mullite ceramic foam product was increase to 81.2%, the compressive strength was 1.21Mpa, and the thermal shock resistance (D_st) was 0.52.(5) It was found that additives Y₂O₃ and CaO had a promoting effect on the sintering and density improving of alumina-mullite ceramic foams. Moreover, they could improve the compressive strength and thermal shock resistance greatly.Prepare composite ceramic foam with above method can not only solve the problem of low strength and thermal shock resistance, but also reduce the cost and be environmental. It has good prospect for industrial application.