Research On Structure And Properties Of ZrO₂ Composite Ceramic Materials

In this paper, the ZrO₂ powder possesses an average size of 300nm.ZrO₂ceramics composite powders were prepared by direct physical mix and were formedwith dry press, then at optimum heat treatment system as 400℃,800℃for 30minrespectively, solstice 1300℃for 2h, the ZrO₂ ceramic were sintered at a normalpressure. By some mechanical methods such as compression strength,SENB andsome testing methods such as XRD,SEM,TG-DTA were studied. The relationshipamong the friction properties,the mechanical properties and the microstructure wasalso analyzed. Meanwhile; the effect of molding press and different additives on themechanical properties of ZrO₂ ceramic were investigated. The high-Performancezirconia based composite ceramic were prepared by study scientifically.At first, The powders were formed with dry Press at the pressure of 200MPa,250MPa, 300MPa, 350MPa, 400MPa, respectively, and then were made into ZrO₂ceramic sintering at a normal pressure and a temperature of 1300℃. By mechanicalmethods such as SENB and testing methods such as XRD,SEM and TG-DTA. Theresults indicate ZrO₂ ceramic can get favorable friction properties,mechanicalproperties when the forming pressure is 350MPa. The compression strength and thefracture toughness are 67.65 MPa and 1.498 MPa·m^1/2.Respectively, the relative density decreases with the increase of molding press400MPa. The lower relative density leads to the growth of porosity, and then resultsin the decrease of effective loading area,the compression strength and the fracturetoughness.The analyses show that fine powders can improve the density of ceramics. Thegrain size is less than the critical size of phase transformation and hence can keep thepartly stabilized tetragonal ZrO₂ phase, which is favorable to the mechanicalproperties by stress inducing phase transformation. And the mixed of ZrO₂ powdersand other powders can confine each other during sinter to avoid the powder growingabnormally which make the grain boundary expansion and more energy is needed when the fracture route is meandering, result in high fracture toughness.Owing to zirconia at about 1150℃occurs tetragonal (T) to monocline (M),accompanied 5% volume expansion. It shows abnormal high fracture toughness,brings transformation toughening and obtains high tenacity, high-wearing featureowing to substantive fracture energy forth taken by bulk effect of phasetransformation, when zirconia T→M transformation temperature settle down to roomtemperature and make T→M phase transformation induced by stress. So zirconiawere mixed with some high modulus of elasticity compound, in order to reserve partof t-ZrO₂ in room temperature. The high-Performance zirconia matrix compositeswere prepared by this way.Therefore, different additives (Al₂O₃,SiC,SiO₂,CaO and TiO₂, etc.) effects onceramic composite material, which is base on zirconia and alumina are investigatedin the paper. From the summary of fundamental phenomena and law. It shows that:Effects of different additives Al₂O₃,SiC,SiO₂,CaO,TiO₂ in ZrO₂ ceramics onstructure and properties of ZrO₂ ceramics materials have been investigated, and itsmechanism is analyzed. With all additives adding, the extent of material'sdensification increase, but SiC and SiO₂ have little effect on densification, while TiO₂has the most effect on material's densification. Al₂O₃,SiC,CaO and TiO₂ increase thecompression strength and fracture toughness property of ZrO₂ based ceramicmaterials, and TiO₂ has obvious function especially. When CaO add to the ceramicmaterials, the ceramic's mechanical properties get worse, the compression strengthand fracture toughness property decrease.