Preparation Of Alumina And Zirconium Oxide Foam Ceramics By Foaming Method

Because of its special pore structure and excellent high temperature resistance,foam ceramic materials are widely used in many fields such as building insulation,artillery thermal protection structure,metal filtration,sound absorption and sound insulation,high temperature insulation and so on.In view of the application of high temperature insulation,two kinds of foam ceramics,Al₂O₃ and Zr O₂,were designed and experimentally prepared by mechanical stirring foaming,supplemented by ionic surfactant foaming,fiber toughening,and gelcasting by adding molding agents.The raw materials needed to prepare foam ceramic products were determined,including zirconium sol and zirconia fibers for preparing zirconia foam ceramics.The process parameters and microstructure of each process were tested and studied.The research results include the following three parts:Firstly,two kinds of foam ceramics were prepared by foaming gel casting process.The influence of the composition of foaming system and the amount of foaming system on foaming effect were studied.The foaming volume of foaming was tested.The experimental results showed that:sodium rosinate and AES were combined with 1:1 as foaming agent to determine the foam stabilizer of 0.65wt%added to CMC and the ceramic foam.The best foaming effect was obtained.After that,the effects of other components and the amount of other components on the performance of the two kinds of foam ceramics were studied.Porosity,density,compressive strength and thermal conductivity of Al₂O₃ and Zr O₂ foam ceramics were tested respectively.The results showed that the two materials had higher porosity and better thermal insulation performance.The results show that the porosity of alumina ceramics is 73.3～90.2%,the compressive strength is 4.87～6.51MPa,and the minimum thermal conductivity is 0.209W/（m·K）;the porosity of Zr O₂ Ceramics is 74.8～88.4%,the compressive strength is3.46～4.78MPa,and the minimum thermal conductivity is 0.139 W/（m·K）.The thermal conductivity increases with the decrease of porosity of the foam ceramics,and the density decreases with the increase of porosity.It is not difficult to find that the compressive strength of Al₂O₃ foam ceramics is slightly larger than that of Zr O₂ foam ceramics,and its thermal conductivity is slightly higher than that of Zr O₂ foam ceramics.Compared with similar products in the market,both of them guarantee excellent pore heat insulation performance,and the compressive strength can be increased by 25%at most.Finally,the effects of other external parameters of foaming gel process on the properties of ceramic were studied,including stirring rate and time,and sintering temperature.The number and distribution uniformity of bubbles,pore size distribution morphology,and density,porosity and compressive strength of the ceramic materials at different sintering temperatures were measured.The results show that:the faster the stirring rate and the shorter the time,such as stirring at 1500 r/min for 15 min,the better the performance of ceramic pore structure;with the increase of sintering temperature,the porosity decreases,the compressive strength increases,the sintering linear shrinkage increases,and the shrinkage of reheating line decreases.