Preparation And Mechanical Properties Of Al₂O₃ceramics Based On SLS/Sol Infiltration Process

Alumina ceramic has a broad application prospect in the preparation of catalyst carrier,filter,mechanical parts,electronic components and other fields because of its excellent performance of high temperature resistance,high hardness and oxidation resistance.However,the traditional preparation process is difficult to prepare complex three-dimensional structure ceramic parts,which seriously limits the application and development of alumina ceramics.As one of the advanced molding technologies,selective laser sintering（SLS）has the advantages of various materials,no mould and high precision,and can be used to prepare complex structures.But 3D printing ceramic materials based on SLS still have some problems,such as low density and poor mechanical properties.Improving the density and mechanical properties of 3D printing ceramic materials has become a research hotspot in the field of 3D printing ceramic materials.Therefore,this paper studied the process of SLS combined with sol infiltration to prepare 3D printing alumina ceramics,and analyzed the influence of sintering temperature,sol infiltration method,sol solid content,infiltration period and other factors on the microstructure and mechanical properties of 3D printing alumina ceramics prepared by SLS combined with sol infiltration.（1）The effects of sintering temperature,infiltration parameters and sol-solid content on the microstructure and mechanical properties of 3D printing alumina preforms were studied.When the sintering temperature rising from 1450℃to1600℃,the density of 3D printing alumina preforms increases continuously.However,when the sintering temperature reaches 1600℃,the grain growth phenomenon appears,and the mechanical properties of 3D printing alumina preforms decrease.With the increase of vacuum degree and pressure during infiltration,the volume density and mechanical properties of 3D printing alumina preforms increase first and then decrease.When the vacuum degree and pressure are too high,there are different degree of layered and longitudinal connectivity porosity defects in the specimen,which leads to the increase of porosity,the decrease of volume density and the decrease of mechanical properties.With the increase of sol-solid content of alumina,the volume density and mechanical properties of 3D printing alumina preforms are improved first and then decreased.When the sol-solid content of alumina is 15wt%,the pore filling inside the billet is good,and the forming precision is also good,and the volume density and mechanical properties reach the maximum.（2）The effects of infiltration period,solid content of alumina sol and zirconia content in the sol on the microstructure and mechanical properties of 3D printing alumina ceramics were studied.The results show that with the increase of infiltration period,the volume density and mechanical properties of 3D printing alumina ceramics increase rapidly at first,then the growth rate gradually slows down,and the porosity gradually decreases and tends to be stable.After 7 cycles of infiltration sintering,the weight gain of 3D printing alumina ceramic material is less than 1%,and its mechanical properties are basically stable.The porosity,volume density,bending strength,compressive strength and fracture toughness are 22.06%,2.93 g/cm³,132.99 MPa,219.71 MPa and 2.08 MPa·m^1/2,respectively.With the increase of the solid content of alumina sol,the volume density of 3D printing alumina ceramics increases,the porosity decreases,and the mechanical properties also improve.When the solid content of alumina sol is25wt.%,the porosity,volume density,bending strength,compressive strength and fracture toughness of 3D printing alumina ceramics are 14.79%,3.14 g/cm³,165.31 MPa,450.18 MPa and 2.35 MPa·m^1/2,respectively.When the solid content of the composite sol is 25wt.%,with the increasing of zirconia content in the composite sol,the porosity of 3D printing alumina ceramic material first decreases and then increases,the volume density,bending strength and compressive strength first increases and then decreases,and the fracture toughness increases.