Study On The Additive Manufacturing Of Al₂O₃-based Ceramics With Enhanced Strength,Fracture Toughness And Thermal Conductivity

With the rapid development of electronic information technology,the requirements for heat sinks are getting higher and higher,not only need to have high thermal conductivity,but also need to take into account good mechanical properties.Alumina?Al₂O₃?ceramics have the advantages of excellent insulation,good chemical stability,rich resource reserves and low operating costs,and have been widely used in heat sinks.However,the relatively low thermal conductivity and bending strength limit the further development of Al₂O₃heat sinks.In order to improve the thermal and mechanical properties of Al₂O₃ceramics,this paper uses layered composite ceramic design and prestressing strengthening,superimposing Al N phase with high thermal conductivity and low thermal expansion coefficient on the surface of alumina to achieve the simultaneous improvement of Al₂O₃ceramics thermal and mechanical properties.First,dry press molding is used to optimize the basic formula of the inner core layer Al₂O₃ceramics.On this basis,the effect of the powder process on the performance of the inner core layer Al₂O₃ceramics is studied through sterolithography technology;Then,by dry press molding,the Al N content and sintering temperature of the surface Al N-Al₂O₃composite ceramics were studied,and the effects of the coating process and the ball milling process on the properties of 10wt%Al N-Al₂O₃composite ceramics were compared;Finally,the preparation of layered composite ceramics by dry press molding was used to verify the feasibility of prestressing strengthening,and the properties of layered composite ceramics were studied by sterolithography technology.Through the above research,the following main research results are obtained:In the dry press molding study,when the Mg O content is 0?0.4wt%,the thermal conductivity of the prepared Al₂O₃ceramics is similar,and the density is?99.5%;The flexural strength of Al₂O₃ceramics increases first and then decreases with the increase of Mg O content.When the Mg O content is 0.2wt%,the flexural strength is 421.93±6.76MPa.Y₂O₃as a sintering aid,the thermal conductivity of Al₂O₃decreases with the increase of the amount of Y₂O₃,and the flexural strength decreases first and then increases and then decreases with the increase of the amount of Y₂O₃.When the amount of Y₂O₃is 5wt%,the flexural strength is 466.87±24.89MPa.The effect of Y₂O₃?5wt%?blended by ball milling and coating process on the properties of Al₂O₃ceramics was compared using sterolithography technology.It is found that the coating process is beneficial to the dispersion of Y₂O₃and improves the flexural strength of Al₂O₃.Compared with the ball milled sample,the strength of the coated sample is increased by 36.78%;Then through powder modification,the effect of 1wt%oleic acid?OA?on the rheological properties,curing characteristics,mechanical properties,thermal conductivity and microstructure of Al₂O₃was studied.It was found that the surface modification of Al₂O₃powder using 1wt%OA,reduce the viscosity,curing width and curing depth of Al₂O₃ceramic slurry,improve the bending strength and thermal conductivity of Al₂O₃ceramics.The properties of Al N-Al₂O₃composite ceramics were studied and optimized by dry pressing.The research showed that the density of Al₂O₃-Al N composite ceramics decreased with the increase of Al N content;The density of 10wt%Al N-Al₂O₃multiphase ceramic increases with temperature and then decreases,and the thermal conductivity decreases with the increase of sintering temperature;Compared with the ball milling process,the coating process is beneficial to improve the mechanical and thermal properties of 10wt%Al N-Al₂O₃composite ceramics.The thermal conductivity,flexural strength,Vickers hardness and fracture toughness of the coated samples are 34.10W·m^-1·K^-1,477.53±34.11MPa,16.90±0.22GPa and 5.74±0.52MPa·m^1/2.Its thermal conductivity,flexural strength and fracture toughness increased by 9.6%,21.68%and 20.84%,respectively.The feasibility of prestressed reinforcement was verified by ball milling process and dry press forming,and the layered composite ceramics were prepared by sterolithography technology.The results show that the layered structure design is beneficial to improve the flexural strength and thermal conductivity of Al₂O₃.When the sintering temperature is1650?,the bending strength,fracture work and thermal conductivity of the sample?0.2+2.6+0.2#?are 528.336±47.06MPa,2304.41J/m²and 30.31W·m^-1·K^-1,compared with the monolithic Al₂O₃ceramic,its flexural strength and breaking work increased by 11.87%and 50.83%,respectively.The surface ceramic and the inner core ceramic are strongly interface bonded,and there are no problems such as crack defects.Based on the above experimental results,0.2+2.6+0.2#layered samples were prepared by digital light processing?DLP?3D printing,and its flexural strength was 447.45±33.52MPa,which was 9.8%higher than that of the monolithic Al₂O₃ceramic.