Study On Preparation Technology And Application Of Mullite-Zirconia Composite Ceramics

The research is to solve the problem about the low service life of the blast furnacetuyere, the mullite-zironia composite ceramics were chosen as the the main raw material.The mullite has high refractoriness, good thermal shock resistance, chemical resistance,creep resistance, high refractoriness under load, good volume stability and other properties.Using the zirconia transformation toughening effect and good thermal barrier effect toincrease the strength of ceramics and to get better heat insulation property, to reduce theheat loss and the coke ratio. It has important significance to improve the service life ofblast furnace tuyere, to improve blast furnace productivity and to optimize each economytechnology index.The experimental component is comprised mullite powder as matrix powder andadded a small amount of alumina and silica micro powder. Adding5Y-ZrO₂（the content ofY₂O₃is5mol%） for strengthening phases to improve heat insulation property in ceramicmaterials. And the proper amount of MgO and TiO₂are added to improve the ceramicdensity, to promote sintering, and to increase the strength of the material. The experimentprocess includes the following steps. The first step is to made up PVB binder solution. Allkinds of the powders are weighted according to the ratio and then the nano powders aredispersed. At the same time mixing powder is done. After mixing, the vacuum drying boxis used to dry the powders, The dried powders are homogenized in a ball mill for15minutes. The final step is made the powders pass the sieve of80mesh. In order to getbetter molding effect, the dry pressing is first used, and then cold isostatic pressing is used.The experimental row of plastic range is from room temperature to1050℃.The sinteringrange is1490¹640℃. At last, the samples need to do thermal shock experiment, scanningelectron microscopy （SEM） and energy diffraction spectrum analysis （EDS）.The experiment results show that the samples are porcelain and not cracking at1580℃to1640℃sintering. Moreover, each component samples have larger shrinkage. So the temperature range is more suitable as sintering temperature. The ellipsoidal or sphericalZrO₂particles are mainly distributed in the matrix to toughened ceramics. With of thecontent of ZrO₂increasing, ZrO₂based solid solution is increasing and toughening effect isaccordingly increasing. But the addition must be strictly controlled. When sinteringtemperature is higher, the ZrO₂grain is grown and leads to appear grains transgranularcracking phenomenon. The temperature and composition have important influence on theformation of stomata. The samples of containing20%and30%ZrO₂are not cracking afterheat shock tests, so they have good thermal shock resistance. Comprehensive consideration,the optimum sintering temperature is from1610℃to1640℃and30%ZrO₂content of thesample is the optimum formulation.