Study On The Preparation Of Aluminum Titanate Powder At Low Temperature By Using Metal Aluminum As Alumin Source

Aluminum titanate (AT) is an important ceramic material with lowexpansion coefficient. Due to its properties, such as high temperatureresistance, high wear resistance and strong anti-erosion, it becomes an urgentdemand for modern industry as a new type of high temperature ceramicmaterial. Recently, several methods have been reported for its synthesis,including solid-phase method, sol-gel method and vapor-phase method, etc.However, they have many disadvantages, such as relative high synthesistemperature, serious powder agglomeration and expensive equipments, whichlimit its further application. In this paper, aluminum and titaniumtetrachloride were employed as raw materials to prepare aluminum titanatepowder at low temperature via Nonhydrolytic sol-gel method (NHSG)combining reflow and autoclave technology in the gelation process. Theeffects of the phase transition of AT xerogel powder during the heattreatment， mixing orders of raw materials, the sort and amount of oxygendonor, the kinds of solvent and catalyst, the gelation process on synthesis ofAT powders have been investigated by DTA-TG, XRD, TEM and FT-IRanalysis. The relationships of dispersant PEG1000synthesis and dispersionof AT have been studied. The sintering properties of AT powders prepared byreflow and solvent-thermal process have been contrasted. The experimentalresults indicated that:Aluminum titanate powders were prepared by using Al powder and TiCl4as precursor, anhydrous ethanol as oxygen donor, AlCl3as catalyst. Afterrefluxing at80°C for24h and calcining at750°C, pure AT powders wereachieved. Compared with isopropanol and butyl alcohol, anhydrous ethanol isa more suitable candidate as oxygen donor due to its high activity and shortalkyl chain. AlCl3is the best catalyst compared with MgCl2and FeCl3owningto the weak covalent of MgCl2, impurity introduction and powder aggregationof FeCl3. The mixing order is adding TiCl4before AlCl3into aluminumalcohol mixture. TiCl4could active aluminum powder to form chlorinetitanium alkoxide TiCl2(OEt)2·EtOH, which is favorable to heterogeneouspolymerization of aluminum and titanium alkoxide. In this process, theaddition of PEG1000reduces the powder aggregation. However, excessivedispersant would block nonhydrolytic sol-gel reaction.Auxiliary pressure field was formed by the solvent-thermal method in the gelation process. After calcinations at750°C, the small AT powders withaverage particle size of20-30nm and homogeneous distribution was obtainedunder the conditions of2.5mol/L of the precursor concentration,110°C ofthe solvent-thermal temperature and30%of the filling ratio. With thesolvent-thermal temperature increasing, the degree of AT crystallization isincreased, but the higher temperature would cause powder aggregation. Thetoo large filling ratio disturbed the formation of Al-O-Ti heterogeneous bond.Moreover, the AT powders obtained by reflux process and solvent-thermaltreatment were sintered at1450°C for2h under air atmosphere. Due to thegood dispersion and high surface energy, the sintering properties of ATpowder obtained via solvent-thermal treatment were superior to that of refluxprocess. Its flexural strength is14.3MPa. The water absorption and apparentporosity are1.9%and6.3%, respectively. It is expected to become aneffective means to further promote the application of ultrafine aluminumtitanate powders via nonhydrolytic sol-gel method combining solvothermaltreatment.