Research On Manufacturing Al₂O₃ Ceramics With High-precision By Stereolithography

The multiple scattering of ceramic powder for UV light,the single polymerizable functional group of photosensitive resin,and the poor compatibility between powder and resin in stereolithography can affect significantly the curing properties of slurry and limit the application of stereolithography in priting of dark powder and fabrication of gradient structure materials.In this paper,we chose the Al₂O₃ceramics as prototype to explore the effect of surface modifier,photosensitive resin ratio on the rheological properties of ceramic slurry and its curing properties,aiming to obtain the resin formula suitable for Al₂O₃ceramics high-precision stereolithography.We investigated systemically the effects of UV wavelength,powder particle size and printing process parameters on the slurry curing accuracy of the as-printed green body as well.The main conclusions are as follows:（1）When the ratio of resin with high curing accuracy and curing performances is m（2-Ethylhexyl acrylate）:m（1,6-Hexanediol diacrylare）:m（Trimethylolpropane triacrylate）:m（oligomer bisphenol A expoxy acrylate）=（1.4:3.5:2.1）:3 and and the photoinitiator 4265 accounts for 0.5wt%of the resin,refractive index of mixed resin is 1.4857.Meanwhile,we successfully obtained black green body.（2）Methacrylic acid（MAA）,Oleic acid（OA）,γ-aminopropyl trimethoxysilane（KH550）,γ-glycidyl ether oxypropyl trimethoxysilane（KH560）andγ-（methylacryloxy）propyl trimethoxysilane（KH570）can reduce powder aggregation,decrease viscosity of slurry by changing the resin network,improve the scattering length of UV light,and number of free radical.All can benefit to the improvement of the curing accuracy of slurry.The viscosity of 0.5 wt%MAA modified 50 wt%slurry is 3.27Pa·s at the shear rate of 30 S^-1.MAA could participate in the photocuring reaction to improve the curing efficiency and the density of the body.The critical exposure energy of 0.5 wt%KH560 modified 45 wt%slurry is 2.6×10^-6mJ/cm².The penetration depth of 1.0 wt%OA modified 45 wt%slurry is 0.0337 cm.The relative error of 0.5 wt%KH560 modified 45wt%slurry monolayer is 3.1×10^-5.（3）The gravity and exposure energy attenuation in slurry during printing cause low particle accumulation density at the interlayer and the appearance of pores,which leads to the anisotropy of shrinkage and difference in sintering behavior in the X-Z-axis direction（printing direction）and X-Y-axis direction.However,with the increase of sintering temperature and holding time,the anisotropy of the body can be decreased.The activation energy of interlamellar and non-interlamellar grains is 379.97 KJ/mol and 334.13 KJ/mol.Their grain growth constant is 1.93 and 1.78,respectively.When the solid content of slurry is 50 wt%,slice thickness and exposure time are 20μm and 5 S,respectively.The relative error of body size（10 mm×3 mm×30 mm）using the resin above can be below 1%.When the sintering temperature is 1600℃and the holding time is 10 h,the density and Vickers hardness of the samples are 94%and 1456.9 Hv0.3,respectively.The average maximum difference between X-Y plane and X-Z plane is 0.671μm and 0.351μm,respectively.This thesis consists of 59 figures,7 tables,and 106 references.