Investigating And Manipulating Macro-microscale Defects In Zirconia Ceramics Fabricated By Stereolithographic Additive Manufacturing

Stereolithographic additive manufacturing technology possesses great application prospects in the field of personalized dental restoration field,due to its ability to prepare high-performance zirconia ceramic parts with fine and complex structure.However,the poor dispersion of slurry and inhomogeneous local sintering in the current process of stereolithographic additive manufacturing leading to poor structural integrity and easy cracking of the product,which has become a bottleneck problem restricting its practical application.Therefore,it is urgent to develop homogeneous zirconia ceramic slurry suitable for the manufacturing of stereolithography and corresponding thermal treatment process.In this thesis,the work starts from two aspects of curing and crosslinking behavior of photo-cured zirconia ceramic slurry and subsequent thermal treatment process were explored.Firstly,the defects during the entire process for fabricating zirconia ceramic based on stereolithography technique were characterized and the mechanism of the defects was revealed,which provided a theoretical foundation for the subsequent process.Secondly,the influence of curing crosslinking,rheological behavior of slurry and thermal decomposition behavior on the macro properties of products was analyzed,and the zirconia slurry and heat treatment process suitable for the manufacture of light curing material were optimized.Thirdly,the asynchronous sintering of ceramic body during sintering process was studied,and the relationship between heat treatment process and zirconia ceramic structure was discussed.Finally,based on the above experimental results,a high-performance zirconia ceramic restoration was successfully fabricated by optimizing the slurry and heat treatment process.The main innovative results were listed as follows.Different functional photosensitive resins and prepolymers were selected to adjust the curing cross-linking reaction of photo curable slurry.The relationship between light-curing characteristics of the slurry and the green body formability was established,and the relationship between the organic composition of the slurry and the structural integrity of zirconia ceramic products was explored.A crack-free zirconia ceramic with 99.4%relative density was successfully fabricated by adjusting the decomposition of the organic matter in green body through thermal treatment process.Meanwhile,the cycle of thermal treatment process was shortened from 120.5 h to 35 h.The microstructure evolution of prepared parts during sintering process was systematically studied.The "asynchronous sintering" phenomenon between the surface and interior of the body was revealed at a lower temperature.The simultaneous sintering of outer surface and interior has been realized by optimizing the sintering process.Through the above-mentioned experimental results and the optimization of the supports,zirconia single crown restoration with good dimensional accuracy and mechanical properties meeting the demands of dental clinical restoration standards was successfully achieved.After sintering at 1600?,the three-point bending strength,hardness,and fracture toughness of the samples are 1057 MPa,12.6 GPa,6.06 MPa·m1/2,respectively.And,the dimensional accuracy reached 50 ?m.This research shows that ceramic additive manufacturing based on stereolithography has great potentials in fabricating zirconia ceramic parts with customized design.The structural defects can be controlled and manipulated by adjusting cross-linking behavior and optimizing thermal treatment process.These works provide a theoretical basis and data support for the practical application for preparing high-performance zirconia ceramics by stereolithography.