| SLA-3D printing technology can produce high-precision ceramic parts with complex structure,and the properties of printing materials,SLA-3D printing forming process and debinding sintering process will affect the precision and properties of ceramic parts.3D printing materials are divided into slurry and paste,the slurry fluidity is good,but there are some problems such as low solid content and large shrinkage of formed parts.The paste can greatly increase the solid phase content,which is conducive to improving the shrinkage deformation and sintering cracking in the process of SLA-3D printing.Paste ceramic material can also play a certain role in supporting parts,but it has the problem of high viscosity.With the increase of solid phase content,the influence of viscosity is more obvious.Therefore,in this study,Al2O3 and AlN were selected as components to prepare a kind of high solid/low viscosity ceramic paste suitable for SLA-3D printing,which can reduce the shrinkage deformation in the forming process of parts,improve the dimensional accuracy of the formed parts,solve the problems of high solid phase ceramic paste viscosity and forming difficulties.Furthermore,the influence of printing and sintering process parameters on the forming and performance of ceramic parts was further studied,and a set of SLA-3D printing process for the preparation of high-performance ceramic parts was formed.The specific research work of this paper is as follows:The preparation and properties of high solid/low viscosity ceramic paste system were studied.①The rheological properties of A12O3 and AlN ceramic pastes with different solid phase contents were studied,and the viscosity changes at different shear rates were analyzed.The effects of solid content changes on paste viscosity were compared.The results showed that the rheological properties of ceramic pastes decreased with the increase of solid phase content,and the two kinds of ceramic pastes showed similar rules.The viscosity curve decreases sharply at first,and then tends to be gentle at a certain node.②The effect of four rheological additives on the viscosity of high solid phase ceramic paste was studied,and the viscosity of high solid phase ceramic paste was reduced by changing the ratio and content of rheological additives.The results showed that the viscosity of ceramic paste with composite dispersant was the lowest,and the viscosity of 85wt%Al2O3 ceramic paste was 51733mPa·s at the shear rate of 30s-1.③By studying the rheological mechanism of ceramic paste system and establishing the viscosity prediction model,the viscosity characteristics of ceramic paste containing rheological additives can be predicted.The effect of SLA-3D printing technology on the forming accuracy and surface quality of ceramic parts was studied.①The influence of laser power on the curing performance of ceramic was studied.By measuring the size of single layer wafer and single curing line formed under different laser power,the influence of laser power on the vertical and horizontal direction of curing was analyzed.The results showed that the curing depth of A12O3 ceramic paste could guarantee the bonding strength between layers when the laser power was 20-50mW.AlN ceramic paste requires laser power greater than 1 50mW to meet the strength of the interlayer connection.②The influence of forming Angle and scanning distance on the surface roughness of the parts was studied.The surface roughness of the parts was measured by laser microscope,and the influence of different forming Angle and scanning distance on the forming quality of the sample was analyzed.The results show that the surface roughness increases first and then decreases when the forming Angle increases from 0 to 90°.The surface roughness value reaches the maximum when the forming Angle reaches 60°,Ra=10.909.The scanning distance increases from 0.05mm to 0.12mm,the surface roughness increases gradually,and the forming quality deteriorates.③The effects of different printing processes on the dimensional accuracy of parts were studied,and the hole structure sizes were measured and analyzed under different laser power and scanning spacing.The results show that the dimensional accuracy decreases with the increase of scanning spacing and laser power.When the scanning spacing is 0.05mm and the laser power is 65mW,the printing error is the smallest and the precision is the highest.④The influence of three different laser scanning spacing on the warpage of parts was studied,and the optimal process of reducing the warpage of parts was analyzed.The results showed that the larger the scanning spacing,the less the warpage deformation of parts.The effects of debinding and sintering on the size and mechanical properties of ceramic parts were studied.①Study the size changes of ceramic parts at different stages in the direction of length,width and height,measure the shrinkage rate of parts at each stage,analyze the stages and reasons for the biggest changes in the size of parts.For Al2O3 ceramics,the size change after sintering is the largest.Due to the shrinkage and densification of pores at high temperature,the size of parts is reduced by 15.2%,17.4%and 1 7.7%,respectively,compared with that after laser curing.②The composition changes of ceramic parts at different stages were studied,and the crystal shape changes of Al2O3 ceramic parts at different temperatures were analyzed.The XRD analysis of the sintered final parts showed that the sample was completely transformed from θ-Al2O3 to α-Al2O3 after sintering at 1600℃,which has higher mechanical properties.③The influence of different sintering parameters on the bending strength was studied.By comparing the bending strength of Al2O3 ceramic parts sintered under different sintering temperature,holding time and heating/cooling rate,the optimal sintering temperature curve was analyzed and summarized.The results show that high performance A12O3 ceramics with bending strength up to 642MPa can be obtained by sintering at 1600℃,holding for 4h and heating and cooling at 1℃/min.Through the preparation of paste system of high solid/low viscosity ceramic,printing forming process,debinding and sintering process,the forming of SLA-3D printing ceramic parts with low deformation,high precision,high surface quality and high strength was realized in this paper. |
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