Materila Preparation And Process Study Of Stereolithographically Printed Zirconia Ceramics

Stereolithography（SLA）for the preparation of zirconia（ZrO₂）ceramics has attracted widespread attention for its advantages such as high molding accuracy and freedom,and no need for molds,but there are still some shortcomings in the previous related studies.Firstly,the composition and correlation of organic components in ZrO₂ ceramic slurries can directly affect the printability of the slurry as well as the generation of heat treatment defects,while previous studies have been conducted on its single component,limiting the application and development of ZrO₂ slurries.Secondly,the choice of layering thickness is not only related to the speed and accuracy of the part,but also has a significant impact on the mechanical properties of the part,which has not been systematically studied.In addition,the design of a reasonable heat treatment process and guiding the design of the part according to the dimensional changes of the part during the heat treatment process is a guarantee of high mechanical properties and high precision parts,which need to be investigated in more depth.Therefore,this paper addresses these issues in a systematic way.Firstly,this paper establishes the principles and methods of slurry design based on the principal approach of SLA printing of ZrO₂ ceramics,and investigates the influence of the composition of its organic components and their correlation on SLA printability.Specific conclusions were obtained as follows:（1）Single functional group,long-chain stearic acid（SA）can improve the powder dispersibility of ZrO₂ more effectively than Silane coupling agent KH560（KH560）,which has multiple functional groups and short chains after hydrolysis,and is more suitable as a surface modifier for ZrO₂.（2）Although dispersant Disperbyk-111（BYK111）competes with surface modifier SA for adsorption and the former is more effective in reducing the viscosity of the slurry,a small amount（1 wt.%）of SA can improve the area of action of BYK111 by increasing the dispersibility of the particles and thus enhance its effect on viscosity reduction.（3）The mass ratio of diluent 1,6-hexanediol diacrylate（HDDA）and acryloyl morpholine（ACMO）to crosslinker trimethylolpropane triacrylate（TMPTA）is 35:35:30,which not only allows the slurry to have a low viscosity but also ensures a high strength of the blank（38±6 MPa）.The effect of the printing process parameters on the forming effect and the strength of the blanks was then investigated.The results show that the layered thickness directly affects the strength of the blanks:when the curing depth is less than twice the layered thickness,the resin cures incompletely,resulting in blanks that are not strong enough and prone to interlayer cracking,which is not conducive to the cleaning of blanks and the printing of large-sized parts.Finally,the effect of the heat treatment process on the parts was investigated.The results show that（1）HDDA and ACMO compounding can broaden the temperature range for the decomposition and discharge of organic matter in the sample parts,which can effectively inhibit the formation of defects caused by the rapid decomposition and removal of resin during the heat treatment process.（2）When the curing depth is four times the thickness of the layered part,not only does the printed blank have a high density and good interlayer bonding,but the interlayer bonding of the degreased and sintered part is also better,with the density of the sintered part reaching 99.2%and the three-point bending strength reaching 845±124 MPa.（3）Dimensional shrinkage of the part occurs during both degreasing and sintering,but mainly during the sintering process The shrinkage rate in the three directions of the part is not uniform,and the shrinkage rate of the part in the Z-axis direction is greater（19%）.This study not only provides new insights into the preparation of ZrO₂slurries,but also optimizes the production process for SLA printing of ZrO₂.In addition,this paper is able to provide guidance for the preparation of the remaining ceramic parts by SLA.