Study On Preparation And Properties Of Flaky Inter-locked Porous Alumina Ceramic

Porous ceramics have been used in thermal insulation materials,filter materials,biomaterials,spaceflight permeable materials,catalyst carriers and sound absorbing materials because of their high porosity,high temperature resistance and high stability.The stability of?-Al₂O₃ crystal which is composed of numerous aluminum oxide eight sides by combining together to form macromolecules is high.AlF₃ is a mineralizer,and a large number of literatures have reported that fluorine is beneficial to the formation of flaky alumina.So in this paper,AlF₃ is used as the main raw material to adjust the structure of flaky alumina by adding aluminum hydroxide and silica.By studying the effect of the introduction form of silicon dioxide,the open and sealed calcinations of powder,the ratio of Al/Si and F/Si on the formation of flaky alumina,the best formula to form the flaky alumina is?Al/Si=3:1,F/Si=9/2?.Finally,the inter-locked porous alumina structure ceramics were prepared by pressing the best formula.Considering the influence of the fluorine atmosphere,we adopt two ways of open and sealed sintering,and analyze the structure and micromorphology of the different positions.It is found that the sealed sintering is more favorable for the formation of the inter-locked structure.Secondly,two kinds of silicon sources,amorphous SiO₂ and silica sol?30wt%?,are introduced in the experiment.It is found that the samples with silica sol have better inter-locked structure and the mechanical properties are improved.In order to further improve the mechanical properties of the materials and to improve the granulation problem during the pressing process,and to optimize the structure of the material,mullite fiber was introduced to study its structure and properties after high temperature sintering.It was found that the density of sample pressed by AlF₃-Al?OH?₃-Si-sol with fiber formula increased to0.920g/cm³ after sintered at 1100^oC/2h+1400^oC/2h,and the compressive strength reached 7.11MPa,and porosity is 76.34%,and rebound rate is 50%.