| Zirconia ceramics have high mechanical properties and low thermal conductivity,and titanium dioxide has excellent photocatalytic properties,therefore,these two kinds of ceramics have been widely used in mining,aerospace,environmental pollution and so on.However,the sintering temperature of zirconia ceramics is higher.Therefore,a kind of sintering assistant is needed to reduce the sintering temperature.On the other hand,the properties of zirconia and titanium dioxide single-phase ceramics are relatively low,so it is necessary to improve their properties by adding materials.On the one hand,TiO2 can solute in ZrO2,which affects the structure and properties of ZrO2,on the other hand,TiO2 can also be used as sintering assistant to reduce the sintering temperature of ZrO2 ceramics.Therefore,the study of ZrO2-TiO2 multiphase ceramics has a certain significance.In this study,ZrO2-TiO2 multiphase ceramics were prepared by pressureless sintering with industrial zirconia powder as raw material,Y2O3 as stabilizer and MnO2-TiO2(mass ratio 1:1)as sintering additive.The basic test,mechanical properties,thermal conductivity and high temperature conductivity properties of the prepared multiphase ceramics were carried out to characterize the properties of the ceramics,and the phase and cross section microstructure of the ceramics were tested and analyzed.The effect of sintering process and the amount of TiO2 on the properties of multiphase ceramics and the mechanism of sintering additives in liquid phase sintering at low temperature were discussed.By studying the preparation and properties of ZrO2-TiO2 multiphase ceramics,the following conclusions are obtained:1)MnO2-TiO2(mass ratio 1:1)can reduce the sintering temperature of Y-TZP ceramics.The matrix can be densified when the sintering aid is 0.5wt%and sintering temperature is 1350?.Under this condition,the relative density of ceramic matrix is 97.16%,the microhardness is 2080HV,the flexural strength of 300.74MPa,fracture toughness is 8.35MPa.m1/2.The mechanism of liquid-phase sintering is as follows:On the one hand,changing the mass transfer mode of the matrix;on the other,MnO2 can promote the nucleation of grain;on the other hand,the crystal lattice distortion and defects caused by the solid solution of MnO2,TiO2 in ZrO2 will promote the completion of sintering.2)The relative density of multiphase ceramics varies with the amount of TiO2.The optimum sintering temperature of 1%,3%,5%,7%,10%is 1350?,1400?,1400?,1500?,1450?.The relative density of 10%TiO2 was the highest when sintered at 1450?,and the relative density was 97.9%under this condition.3)The sintered ceramics have various phases,contains the monoclinic,tetragonal,cubic and TiZrO4 phases.Some diffraction peaks of zirconia deviate to a certain extent,which is caused by the lattice distortion of TiO2 solid solution in ZrO2.The multipeak phenomenon occurred and the diffraction intensity decreased with the increase of TiO2 content in crystal surface(200),(220),(311).The sintered multiphase ceramics had very small grains and nanocrystalline.The fracture modes of ceramics are transgranular fracture and intergranular fracture.4)The prepared multiphase ceramics have better mechanical properties,and the mechanical properties vary with the amount of TiO2.The microhardness of 0%is the highest at 1350?,and the highest is HV2032.8.When TiO2 adding 5%and sintering 1400?,the maximum flexural strength and fracture toughness are obtained.Under this condition,the flexural strength and fracture toughness are 527.01MPa and 19.47 MPa.m1/2,respectively.The wear resistance of the matrix is consistent with the density of the matrix,and the friction coefficient of the matrix decreases first and then increases with the increase of TiO2 content.Its wear mechanism has adhesive wear,abrasive wear.5)The multiphase ceramics have lower thermal conductivity,and 10%have the lowest thermal conductivity when sintered at 1450?,and the thermal conductivity under this condition is 1.2050W/mk.Both the additive and the microstructure have an effect on the thermal conductivity of the multiphase ceramics.At high temperature,the electronic conductance of the matrix with the addition of TiO2 is one order of magnitude smaller than that of the matrix without the addition of TiO2.That is,the addition of TiO2 can reduce the conductivity of zirconia ceramics at high temperature.The high temperature electronic conductance of the prepared ceramics is between the insulator and the semiconductor... |
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