Preparation Of Porous Alumina Ceramics Thermal Insulation Materials By Foaming And Gel-castine Method

The lightweight alumina-based porous thermal insulation material is a promising furnace insulation materials. Widely used in furnace insulation, ceramic fiber has shortcomings of low compressive strength, poor thermal shock stability.It often chalks and cracks in the process of using. Therefore, the research and prepare of a more high-performance porous insulating ceramic material has a significant meaning.In this paper, a new method was explored to prepare porous alumina ceramics by the combination of foaming process and in-situ solidification process. Porous alumina insulating ceramic materials with small pore size, even distribution, high thermal shock stability were successfully prepared by using this new method. Detailed studies of alumina slurry system and surfactant foam system were being made in this paper. The solidificatin process dependence of the microstructure of the porous ceramic and sintering temperature dependence of the properties of porous ceramics were explored.Finally. The toughening mechanism of porous alumina ceramics was studied by adding a certain amount of ZrO2powder in the alumina slurry in order to enhance the thermal stability in high temperature. The microstructure and high temperature stability of porous alumina ceramics were analyzed by means of XRD, SEM and thermal shock cycle experiments.Experiment shows that the best stable slurry can be obtained by adding1.6%quality content of NH4H2PO4and adjusting pH of9. In order to obtain a well forming quality, the solid content of the slurry needs to be80%.In the form system, the combination of3wt%SDS and2wt%rosin soap at the mass ratio of1:2and0.25wt%CMC which was used as foam stabilizing agent can obtain the best foam system which has a high foam height and stability. Microwave solidification process is better than common drying process. When the mass ratio of the foam and slurry was1:10, the sintering temperature was1500℃and the addition of ZrO2was3wt%,alumina porous ceramics with even pore distribution and high thermal shock resistance can be prepared. The property results show that the samples had even pore distribution and the pore size is between50μm and100μm, their average density were0.57g/cm3, the porostity were74.7%, the compressive strength were2.5MPa, the number of cycles of thermal shock were20times and the average thermal conductivity was0.047W/(m·K). The material prepared in this paper can meet the property standards of furnace insulation materials.