| Ceramic materials are widely used in aerospace,medical,electronic,mechanical and other fields owing to their excellent characteristics,such as high chemical stability,high wear resistance,high hardness and high bending strength.However,due to the fatal weakness of high brittleness,ceramic materials have poor impact resistance and low toughness,which greatly limits the application of ceramic materials in a wide range of fields,so it should be toughened and modified.In this paper,different sizes of Al2O3 and ZrO2 powders were used as raw materials to toughen and modify the light-cured alumina-based ceramics in order to improve the comprehensive properties.In this paper,the UV-curing kinetics of Al2O3/ZrO2 composite ceramics were studied by Differential Scanning Calorimetry（DSC）,and ceramics apparent activation energy and reaction order were characterized.Ceramic green parts were prepared by Digital Light Processing（DLP）molding technology,and the green bodies were degreased and sintered to prepare ceramic materials.The crystal phase transformation and fracture microstructure of ceramic materials during sintering were characterized by XRD and SEM.At the same time,the physical and mechanical properties such as shrinkage,density,hardness,bending strength and fracture toughness of ceramic materials with different powder content were studied in detail.The results show that the UV-curing process of Al2O3/ZrO2 composite ceramics is very sensitive to UV energy and powder type.With the increase of UV energy,the maximum reaction rate of curing reaction increases,the time to reach the maximum reaction rate decreases,and the conversion rate of liquid slurry to solid ceramics increases obviously.When the content of ZrO2 in Al2O3/ZrO2 composite ceramic slurry is 25wt%,50wt%and 75wt%,the apparent activation energy of UV-curing reaction is 407.1kJ/mol,530.1kJ/mol and 622.9 kJ/mol,respectively.And the reaction order is 0.99 constantly,indicating that the curing reaction of light-cured ceramics is close to the first-order reaction.The shrinkage and density of nanocomposite alumina ceramics with nm-Al2O3 powder increase with the rise of nm-Al2O3 powder content,and the bending strength increases with the rise of nm-Al2O3 powder content and slurry solid content.Compared with micron pure alumina ceramics,the solid content of the slurry is 44vol%,the ceramics bending strength with the addition of 75wt%nm-Al2O3 powder reach the maximum value of 107.58 MPa,and the fracture toughness is 4.32 MPa·m1/2.Under the condition of the same solid content of the slurry,the bending strength of the Al2O3/ZrO2 composite ceramics composite ceramics is 123.13 MPa,and the fracture toughness is 8.97 MPa·m1/2.Compared with the 75wt%nm-Al2O3 alumina ceramics with the same solid content,the bending strength of ceramics with 20wt%nm-ZrO2 powder increased by 14.45%and the fracture toughness increased by 92.82%.The fracture and surface of Al2O3/ZrO2 composite ceramics with 20wt%and 10wt%nm-ZrO2 powder were characterized by XRD.The results show that part of zirconia has phase transformation during the fracture process,which plays a role in toughening.The fracture surfaces of the ceramic materials sintered at four different temperatures were characterized by SEM when the solid content of the powder was 44vol%and the addition amount of Al2O3/ZrO2 ZrO2 powder was 20wt%.The results showed that the Al2O3/ZrO2 composite ceramics were the densest and the mechanical properties were the best when the sintering temperature was 1600℃. |
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