Study Of Transparent Alumina Ceramic Shaped By Stereolithography Method

Transparent alumina,as a kind of classical ceramics material,has been widely applied in in electronic chemical and military filed for its advantages of high hardness,good chemical stability,wear resistance and so on.In addition,due to its good biocompatibility and excellent optical properties,transparent alumina is also commonly used as raw materials for biomedical and implant components?especially in the field of dentistry?.However,at present,the production of key components of transparent alumina is limited by the forming process,and there are such problems as excessive dependence on the mold,difficult preparation of complex shapes and structures,high post-processing cost,long production cycle,etc.,which is restricting the promotion and application of transparent alumina ceramics.To introduce additive manufacturing technology into the forming process of ceramic parts,problems above colud be effectively solved,and the rapid preparation of transparent alumina ceramic parts with complex shapes and structures could be realized.The process of alumina ceramic forming is realized via stereolithography technology.By contrasting the SL and DP-CIP alumina pressureless sintering behavior,found that compared with DP-CIP sample,the sintering curve both of density and grain size of SL sample are obvious hysteresis,and the interval of temperature is about 250?³00?.The causes of this phenomenon is the obvious difference of green body existing between SL and DP-CIP,that almost 7 vol%difference of the initial blank density and the uniformity of the body.Namely that the SL sample is in a state of general sparse and uneven,which mean it need more absording energy in its early sintering period to achieve colser rearragement of particles.And in the middle and last period,some sintered defects would be more likely to occur,such as over-growing,non-uniform of grain size and residual porosity.Through the analysis of the aperture nanoscale and sub-micron,the homogeneous difference of alumina between different processing,that stereolithography?SL?,dry processing?DP?and dry-cold isolated processing?DP-CIP?has been studied,which caused the sintering behavior difference of SL and DP-CIP.The further reason could be traced into forming principle and processing,including low solid content,disadvantage of non-obvious pressure and weak inter-layer,a long processing period and low reliability.Aiming at the problems of slow sintering rate and many residual pores existing in stereolithography alumina,the uniform introduction of the second phase(Mg²⁺,Y³⁺,La³⁺,Al³⁺)was achieved by using the liquid phase precursor leaching-in-situ precipitation process,so as to promote the growth of alumina grains and eliminate some pores.On this basis,by introducing H₂ atmosphere sintering process,the preparation of seearlithography transparent alumina ceramics was realized,and the transparent alumina supporting bracket for orthodontics was printed.The prepared transparent alumina sample had a VHS hardness of 15.1±0.9 GPa,a fracture toughness of 3.4±0.6 MPa·m^1/2,a three-point bending strength of 195.3±18.5 MPa,and a linear light transmittance of 1.85%at 800nm.