Preparation Of Stabilized Zirconia/Mullite Composite Ceramics Using Zircon/Alumina By Reaction Sintered Process

As composite Ceramic material, stabilized zirconia/mullite composite ceramics wasmore and more favored by researchers of materials due to its good thermal stability, lowthermal expansion and so on. In this paper, by passing the high purity ZrO₂purificationprocess from zirconium-containing mineral, zirconia/mullite composite ceramics werefabricated using zircon and Alumina as raw materials and appropriate ZrO₂stabilizers asadditive by reaction sintered, its phase, microstructure, mechanical properties andthermal shock performance were characterized and analysed, and specific contents are asfollows:Zirconium Silicate ceramics were prepared with adding different amounts ofY₂O₃/CeO₂into zircon powder by pressureless sintered at1475-1600℃, Archimedesmethod, XRD, SEM and EPMA techniques were used to characterize the bulk density,phase changes,microstructures and elementary composition of samples respectively, theoccurrence of the sintered reaction conditions was researched by thermodynamiccalculations. The results showed that the bulk density of samples increased with theincreasing of both the amounts of additives and sintered temperature between1475℃-1600℃, Higher sintered temperature can promoted the decomposition of ZrSiO₄,and with the increase of the amount of Y₂O₃the extent of decomposition increased, theaddition of CeO₂inhibited the decomposition, both the two additives could increase thestability of ZrO₂crystal from the decomposition reaction.Then the thermodynamicanalysis of the reaction that between ZrSiO₄and Al2O₃generated ZrO₂and mulliteshowed that the reaction could carry on when the temperature was above1094℃.Based on the above results, zirconia/mullite composite ceramics was prepared withZrSiO₄and Al2O₃as raw materials, Y₂O₃as additive, and the structure, phase, andperformance of composite ceramics were studied. The results showed that grains ofsamples with4.34wt.%Y₂O₃at1575℃had consistent size and closely arranged, the bulk density had max value,3.58g/cm3. And the amount of tetragonal phase of samplesat1575℃gradually increased with Y₂O₃augmentation, all ZrO₂of samples was stablephase when Y₂O₃content was higher4.34wt.%. As the sintered temperature increased,flexural strength of samples increased; within a certain range flexural strength of samplealso increased as the content of Y₂O₃increased, samples with4.34wt.%Y₂O₃at1575℃had max bending strength,232MPa. With thermal shock, phase transition of stable ZrO₂from stable phase to monoclinic phase, bending strength of samples reduced with timesof thermal shock increased, but partially stabilized ZrO₂has better thermal shockresistance compared with fully stabilized ZrO₂.