The Preparation And Properties Of Ceramic With Inter-locked Alumina Structure By Gel-casting

High-temperature structural materials were extensively concerned in the hightemperature application field.This kind of materials always had lightweight porous structure,good high temperature properties and proper mechanical performances.Alumina was always used as high temperature structural material.In this work,corundum plates' inter-locked structural material was prepared by gel-casting method with changed raw material proportion based on the AlF3-SiO2 system gas phase reaction.By researching the wafer nucleation-Growth-lifting-Interlock-grew dynamic components of alumina and structural changes of the evolution process,we analyzed the bound form and formation mechanism of the wafer interlocked interface.It will be a new technical approach for the high-temperature heat sealing material designing.By contrast experiments,the applicable formulation formula to the gelcasting system were determined.That is a solids content of 50%.A dispersant is added in an amount of 0.5%,and the initiator addition is 0.7%.The amount of catalyst is 0.4% and the monomer concentration is 20%.The grain boundary between the hexagon plates acted as the jointing points of the structure.In the structure formation process,topaz rods' inter-locked structure first formed in the sample,and then it transformed into hexagonally spherical corundum grains' packed structure.The hexagonally spherical corundum grains transformed into hexagon corundum plates under the catalysis of the fluorine-rich gas.The corundum sheets intersected or jointed with each other to form the inter-locked structure.The volume density,apparent porosity and compression strength of the samples that were prepared at 1100-1500°C were tested to be 0.51~0.51g/cm3,83.2%~75.8%,and 0.21~0.56 MPa,respectively.In this article,a “two-step” method was used to improve the performance of alumina material.After grinding the samples obtained by the first step with heat treatment in various temperature,the powder would be mixed and the go for secondary forming and heat treatment.Two-step process overcomes the defects of the “one-step” method.The strength of the obtained sample reaches 4.81 MPa.The material obtained a volume density of 1.20g/cm3,porosity of 25%,and the thermal conductivity is 0.23W/m·k.Such properties is more suitable to meet the needs of industry.