Research On Preparation Technology And Performance Of Colored Zirconia Ceramics Based On SLA-3D Printing

Because zirconia ceramics need high sintering temperature,common colorants can not maintain good coloring performance and stability at high temperature,and will affect the compactness of zirconia ceramics.Traditional coloring process is also difficult to achieve uniform internal coloring and complex processing.This paper mainly studies the preparation of uniform colored zirconia ceramics by SLA-3D printing technology.The overall research idea is as follows:Firstly,component formulation design of zirconia-colorant-photosensitive resin for SLA-3D printing was studied,and paste system of colored zirconia photosensitive ceramics with rheological and photosensitive properties was prepared.Secondly,the optimization process of SLA-3D printing,degreasing and sintering of colored zirconia ceramics was carried out to improve the mechanical properties and formability of the materials.Finally,the color mechanism of zirconia ceramics was analyzed deeply,and the influence of colorant on the color and mechanical properties of zirconia ceramics was explored.This research has wide application prospect and important theoretical and practical significance.The specific research work of this paper is as follows:According to the serviceability requirement of photosensitive ceramic paste system,the composition and dosage of liquid phase,solid phase and additive components were analyzed.The effect of dispersant dosage on the performance of the paste system of colored zirconia ceramics was studied.When the dispersant content was 1 wt.%,the viscosity of the paste system was reduced from 38104 MPa-s to 20284 MPa·s at the shear rate of 30 s-1,and the paste system of blue and green was evenly spread on the printing platform.It is conducive to defect control during printing.Irgacure 651 and Irgacure 369 were selected to be mixed as photoinitiators for dark zirconia photosensitive ceramics paste system.The optimal total amount of photoinitiators was 4 wt.%,and the ratio of Irgacure 651 to Irgacure 369 was 9:1,at this time,the color zirconia ceramic paste system has good photosensitive properties and rheological properties,curing quickly,viscosity around 20000 MPa·s.The method of powder modification was determined and its effect on the rheological properties of ceramic paste system was studied.The silane coupling agent KH560 was selected as the surface modifier for 60 min.The viscosity of the paste system was reduced from above 50000 MPa-s before modification to below 20000 MPa·s at the shear rate of 30 s-1.The SLA-3D printing process of colored zirconia ceramics was optimized.Firstly,the influence of laser power on the formability of zirconia in different color systems was studied,and the laser power based on different colorant types and dosages was optimized.Secondly,the effect of laser scanning speed on the formability of zirconia in different color systems is studied.When the scanning speed is lower than 4000 mm/s,the color zirconia has good formability.Finally,the forming ability of the optimized printing process is evaluated.The minimum diameter of circular hole of blue series zirconia ceramics and green series zirconia ceramics can be formed is Φ0.6 mm andΦ0.4 mm respectively,and the minimum side length of square hole is 0.6 mm and 0.4 mm respectively.The post-processing technology of degreasing sintering of colored zirconia ceramics was optimized by SLA-3D printing.Comparing the degreasing condition of colored zirconia in air and argon,argon atmosphere was used to protect the degreasing sintering process.According to the thermogravimetric curve of zirconia ceramic body,three main weight loss temperature regions were determined,and then the heating and insulation mechanism in the degreasing process was optimized.The effect of sintering temperature on mechanical properties of colored zirconia ceramics was studied.The results show that the bending strength and hardness increase first and then decrease slightly with the increase of sintering temperature.When the sintering temperature is 1450℃,the obtained colored zirconia ceramic parts have relatively excellent properties,and the bending strength is greater than 550 MPa.The Vickers hardness is greater than 10 GPa.The holding time of sintering process was optimized.For SLA3D printing color zirconia ceramic materials,the optimal holding time was 120 min.The chromic mechanism of colored zirconia ceramics was studied.For the zirconia ceramics with Cr2O3 as colorant,the solid solution with(Al1-XCrX)2O3 structure is formed after adding alumina coloring agent.The green ceramic billet appears pink purple after sintering,while the ceramics without alumina are still green after sintering.For blue zirconia ceramics with Co3O4 as colorant,Co3O4 and Al2O3 form spinel structure CoAl2O4 after sintering at high temperature,making the parts show cobalt blue.Then,the influence of colorant on the color performance of colored zirconia ceramics was studied,and the change of chroma value of colored zirconia ceramics was tested when the colorant dosage changed.The optimal range of colorant addition for green zirconia ceramics is 1～5 wt.%.The optimal addition range of colorant for pink purple zirconia ceramics is 1～5 wt.%.The optimal colorant addition range of blue zirconia ceramics is 1～4 wt.%.