Effect Of Adding SiO₂ With Different Particle Sizes On 3D Direct Writing Printing Of Al₂O₃ Ceramics

3D Direct Ink Writing technology can realize fine-grained,high-resolution active control of the physical properties of the molding process.Direct Ink Writing equipment can realize fine-grained,high-resolution active control of the physical properties of the molding process.The output 3D solid parts not only carry high-density physical property information,but also can add high-resolution material function information,so that the final product's molding and qualitative realization can be completed simultaneously.The structural design and performance of advanced ceramics in different application scenarios have made this technology more and more important in the field of ceramic molding.This paper draws on the nacre structure of natural mollusks and uses direct writing printing technology as a starting point to prepare a series of ceramic slurries with excellent molding properties.It has better solved the problems of direct-write printing nozzle clogging and poor mechanical properties of molded samples.In this paper,alumina powder with a particle size of 4?m and silica powder with a particle size of 80 nm,500 nm,and 2?m are used as raw materials.The main organic additives are sodium alginate,polyvinylpyrrolidone K30,and polyethylene glycol 6000.The alumina-silica ceramic composite ceramic slurry was prepared by the mechanical stirring method at a speed of 600-1000 r/min for 2 to 3 h for Direct Ink Writing technology.The main research contents of this paper are as follows:(1)The effect of the addition of SiO₂ with different particle sizes on the rheological properties of Al₂O₃ ceramic slurry was studied.The preparation method of 3D printing bionic structure high-strength and high-toughness alumina composite ceramics was studied.The ceramics were formed by bottom-up and free extrusion molding to imitate the strengthening and toughening behavior of the shellfish middle-layer stacking structure.The effects of silica with different particle sizes on the rheological and mechanical properties of doped alumina ceramics were studied.Three different sizes of(80 nm?500 nm?2?m)silica are mixed into the ceramic slurry as additives.Studies have shown that after the slurry is uniformly mixed,the addition of silica particles effectively reduces the rheological properties of the alumina composite ceramic slurry.Among the three particle sizes,500 nm has the most significant effect,and the addition amount is 3 wt.%of the total slurry,the solid content at this time accounts for about 69wt.%of the slurry.The decrease in rheological properties provides the possibility to further increase the solid content of the alumina main material.While keeping the silica content unchanged,the maximum solid content of alumina-silica was increased to 75wt.%of the composite ceramic slurry.After high temperature heat treatment at 1600?for 2 hours,SiO₂ reacts with Al₂O₃,and SiO₂ promotes the formation of sintering necks between Al₂O₃,thereby changing the properties of the sintered body.The results show that with the increase of solid content,the volume shrinkage rate decreases,while the compressive strength increases.The maximum compressive strength is about 53.59MPa.(2)The printable concentration of alumina-silica(500 nm)ceramic slurry was studied.The highest printable concentration of pure alumina slurry was 68 wt.%,and the highest printable concentration of alumina-silica(500 nm)was 75 wt.%.It is stated that for 3D Direct Ink Writing,the preparation of a slurry that can be smoothly extruded first needs to have shear thinning characteristics,and that good shear thinning characteristics can ensure that the slurry is smoothly extruded from the nozzle;and further pointed out After the printing slurry is extruded,the viscoelastic reversal behavior of the elastic modulus G"and the viscous modulus G'will occur.Research shows that:in the rheological performance test,when the solid content of the alumina-silica ceramic slurry is increased to 75 wt.%,the molding effect is the best at this time,and the elastic modulus reaches about 7.5×10⁵ Pa.At the same time,Direct Ink Writing alumina ceramics were sintered at different temperatures to observe the microstructure.The sintering performance at 1600?is better,the sintering is dense,and the microstructure pores under the electron microscope are the smallest.