Studies Of Preparation And Properties For Aluminum Titanate Ceramics

Due to low thermal expansion coefficient and high temperature resistance,aluminum titanate (Al2TiO5, AT) has attracted vast attention. But aluminum titanatehas serious disadvantages, such as poor thermal stability and low mechanical strength,so its application was restricted. In this dissertation, aluminum titanate wassynthesized with alumina and titania. AT ceramic was prepared by two differentmolding methods: gel-casting and dry pressing. This paper is focus on discussing theeffect of the gel-casting condition and sintering temperature on the properties of ATceramic.In this paper, using alumina and titanium dioxide as raw materials, sintering at1350℃,1400℃,1450℃and heat preservation time for4h to synthesize AT powders.It is concluded that the best sintering temperature of synthesizing AT powder is1450℃. After prolong heat preservation time to6h, there is small amount of oxide inthe phase, it is indicated that prolonging heat preservation time has no effect on thereaction. Using MgO (5%) as additive, sintering temperature is1450℃, heatpreservation time is4h. X-ray diffraction (XRD) and scanning electron microscopy(SEM) analyze indicate that magnesia has promoted the synthesis of AT andrestrained the decomposition of AT.Screen out the best conditions of synthesize AT slurry by orthogonal experiment.The experimental results show that the influence of three factors: the monomer andcross-linker concentration> dispersants addition> pH value. And the best conditionof synthesize AT slurry is: the monomer and cross-linker concentration of20wt%,dispersants addition of0.1wt%(vs. powder), pH value of9.On the basis of the orthogonal experiment, this paper carefully studies the effect ofdispersant addition and solid volume on viscosity of slurry, the effect of initiator and catalyst addition on curing time. It is concluded that, with dispersant content(0.1wt%-0.8%, vs. powder) increasing, viscosity of slurry increases first and thendecreases, which reaches a minimum value at0.2wt%. With solid volume increasing,viscosity of slurry increases. Viscosity of slurry increases sharply when the solidvolume exceeds up to50%. When solid volume up to52%, viscosity of slurry is up to800mPa·s, the viscosity is nearing the limit of viscosity of gel-casting. When theinitiator addition is0.02ml/20ml slurry and catalyst addition is0.01ml/20ml slurry,curing time for61min, leave enough time for other step, and finally good AT greenbody is obtained.The paper analyzes the effect of sintering temperature on the bulk density, bendingstrength, microstructure, and thermal expansion coefficient of ceramics. With thesintering temperature increasing, the bulk density, bending strength, thermalexpansion coefficient of ceramics decrease. Ceramic prepared by gel-casting with50%solid volume slurry, sintering at1500℃～1550℃and2h heat preservation time,has excellent properties: bending strength>38.5MPa, thermal expansion coefficient<1.6×10-6/℃. The highest bending strength is50MPa, and the lowest thermalexpansion coefficient is0.7×10-6/℃. AT ceramic prepared under these conditionsshould be able to fulfill the requirements of spray nozzle used in amorphous alloyproduction.