Study On Gelcasting Technique Of Aluminium Titanate And Its Properties

Owing to characteristics of low thermal expansion coefficient, high melting pointand excellent thermal shock resistance, aluminium titanate （Al₂TiO₅） has greatapplication potential in many fields. However, due to the limitation of the formingtechnology, it is difficult to prepare such components with complex shape and precisesize. In addition, its low intensity and liability to decomposition within a certaintemperature range restrict its extensive application. Therefore, the purpose of this articleis to research the gel-casting technology to mold aliminium titanate by low toxicitysystem, also this thesis is to discuss how to improve the strength and thermal stability ofthis ceramic materials.In this paper, α-Al₂O₃, TiO₂（rutile） and additives were formed by gel-casting inwhich the MAM were used as monomer. Besides, factors that influence the moldingwere studied. So by studying the rheological behavior of the Al₂O₃-TiO₂slurries thathave high solid loading and low viscosity, the process parameters of slurry-making suchas content of dispersant, PH, ball mill system had been determined. The process offorming, binders’ burning out and sintering had been optimized by measuring thevolume density, bending strength of the green body and sintered body, as well as theSEM analyses of the fracture surface. The effect of additives on mechanical propertiesand thermal stability of the aluminium titanate had been studied via measuring thebending strength of sintered body along with the XRD analyses, then the activemechanism of additives were analyzed.The following conclusions had been obtained by this research:（1） The factors such as: content of dispersant, PH, solid loading and ball millsystem have great effects on the rheological behavior, while the influence of the contentof organic monomer was very small. With the content of dispersant increased, the slurryviscosity decreased firstly and then increased, when the content arrived at1.4wt%theslurry viscosity was minimum. The slurry had a largest viscosity when the PH value was7and minimum when the PH value was13. With the solid loading increasing, the slurryviscosity had been increased, and the bigger the solid loading, the larger the increaserate of viscosity. The viscosity arrived at the minimum when the ball mill system was165r/min,2.5h. As the content of organic monomer increased from2.4wt%to3.4wt%, the value of the slurry viscosity increased25mPa·s only. The Orthogonal experimentalresults showed that the order of these factors on rheological behavior was as PH> solidloading> content of dispersant> milling time> content of organic monomer.（2） The bending strength and volume density could be affected by the content oforganic monomer or pump-down time. When the content of organic monomer was2.6wt%, the bending strength of the green body and sintered body were20.81MPa,28.86MPa respectively. The volume density of the sample increased with thepump-down time increased, and an appropriate pump-down time was about15minutes.（3） The gelation time could be significantly affected by adding initiator andcatalyzer. When the addition of the initiator and catalyzer were2.5vol%,0.8vol%respectively, the gelation time ranged5to10minutes. And furthermore, the reasonableheating curve of binders’ burning out had been established by differential thermalanalysis.（4） The volume density and bending strength of aluminium titanate could beaffected by sintering temperature and solid loading. The volume density and bendingstrength arrived at the maximum when the sintering temperature was1560℃. With thesolid loading increasing, the bending strength of the green body and sintered bodyfirstly increased in different degrees, and then fell slightly.（5） The bending strength and thermal stability of the aluminium titanate could beimproved by adding additives, such as MgO or SiO₂or complex additives of MgO andrich-Yttrium rare earth. The thermal decomposition of the aluminium titanate have beenrestrained by adding MgO, the effect of which was superior to adding SiO₂or complexadditives of MgO and rich-Yttrium rare earth. On the other hand, SiO₂or complexadditives could improve the bending strength of the aluminium titanate more effectivelythan MgO. On the basis of comprehensive analysis, it was believed that the aluminiumtitanate ceramic could have an excellent comprehensive property when the content ofMgO was X=0.15, so that the bending strength and thermal decomposition were27.99MPa and3.13%respectively.