Microstructure and surface roughness are two critical factors governing the transparency of transparent ceramics.The manufacturing mechanism of additive manufacturing(AM)layer by layer is destined that the layer thick...Microstructure and surface roughness are two critical factors governing the transparency of transparent ceramics.The manufacturing mechanism of additive manufacturing(AM)layer by layer is destined that the layer thickness has an important influence on the microstructure and surface quality of the printed workpiece.Simultaneously,the occurrence of the stair-stepping phenomenon unavoidably results in a significant surface roughness.Therefore,in this study,yttria(Y_(2)O_(3))transparent ceramics with different printing layer thicknesses were fabricated by AM to investigate the effect of layer thickness on its optical and mechanical properties.The findings indicate that an increase in the layer thickness correlates with a heightened density in the printed green bodies,subsequently leading to enhanced transmittance in the final sintered body.When the layer thickness approximates or falls below the size of large particle agglomerations found in ceramic powders,numerous pores,and voids emerge within the green bodies.Significantly,at a layer thickness of 45µm,the in-line transmittance of Y_(2)O_(3)can reach up to 97.73%of the theoretical limit.In addition,the surface roughness of the Y_(2)O_(3)ceramics decreased as the layer thickness increased.To facilitate the further transition from translucent to transparent 3D Y_(2)O_(3)structures,a vibration-assisted chemical-mechanical polishing technique was developed by replacing water with a colloidal SiO_(2) suspension.This technique resulted in a significant reduction in the surface roughness of the Y_(2)O_(3)ceramics by 95.42%and eliminated the stair-stepping phenomenon caused by AM,thus increasing 66.12%of the in-line transmittance.These enhancements expand their potential applications in laser amplification,optical communications,and other areas requiring high-transparency materials.The method developed in this study can be used for the AM-based fabrication of transparent 3D polycrystalline ceramics.展开更多
In this work,we present a digital light processing(DLP)-flashing-based functionally graded additive manufacturing(FGAM)process for fabricating highly aesthetic zirconia(ZrO_(2))dental crowns with simultaneous color an...In this work,we present a digital light processing(DLP)-flashing-based functionally graded additive manufacturing(FGAM)process for fabricating highly aesthetic zirconia(ZrO_(2))dental crowns with simultaneous color and translucency gradation.Color gradation was achieved by controlled iron oxide(Fe2O3)doping(ranged from 0.0 to 0.10 wt%)in zirconia powders,whereas translucency gradation was simultaneously attained by controlling the isotropic cubic phase(c-ZrO_(2))in the sintered crowns using three different grades of yttria-stabilized ZrO_(2)(3,4,and 5 mol%yttria-stabilized ZrO_(2)powders,i.e.,3YSZ,4YSZ,and 5YSZ,respectively).The crowns were printed through flashing illumination:0.2 s flash time and 1 s off-time between consecutive ultraviolet(UV)flashes to overcome the scattering-induced overcuring associated to continuous printing that degraded the structural accuracy of the design and posed post-processing challenges and property deterioration.International Commision on Illumination’s Lab(CIELAB)color assessments indicated successful coloring indices(L^(*),a^(*),and b^(*)values)matching the graded appearance of natural teeth.Mechanical properties and sintering shrinkage were slightly affected by the Fe_(2)O_(3)and yttria contents of the various compositions.The highest translucency parameter(above 20)was possible with an undoped 5YSZ composition at the top part(incisor)of the crown.The processing challenges during FGAM of ceramic materials were successfully overcome through a flashing mechanism,and the color and translucency gradation of the ZrO_(2)dental crown was simultaneously maintained with enhanced printing precision,which is a potential breakthrough advancement in esthetic dentistry.展开更多
基金financially supported by the Fundamental Research Program of Korea Institute of Materials Science(No.PNK9590).
文摘Microstructure and surface roughness are two critical factors governing the transparency of transparent ceramics.The manufacturing mechanism of additive manufacturing(AM)layer by layer is destined that the layer thickness has an important influence on the microstructure and surface quality of the printed workpiece.Simultaneously,the occurrence of the stair-stepping phenomenon unavoidably results in a significant surface roughness.Therefore,in this study,yttria(Y_(2)O_(3))transparent ceramics with different printing layer thicknesses were fabricated by AM to investigate the effect of layer thickness on its optical and mechanical properties.The findings indicate that an increase in the layer thickness correlates with a heightened density in the printed green bodies,subsequently leading to enhanced transmittance in the final sintered body.When the layer thickness approximates or falls below the size of large particle agglomerations found in ceramic powders,numerous pores,and voids emerge within the green bodies.Significantly,at a layer thickness of 45µm,the in-line transmittance of Y_(2)O_(3)can reach up to 97.73%of the theoretical limit.In addition,the surface roughness of the Y_(2)O_(3)ceramics decreased as the layer thickness increased.To facilitate the further transition from translucent to transparent 3D Y_(2)O_(3)structures,a vibration-assisted chemical-mechanical polishing technique was developed by replacing water with a colloidal SiO_(2) suspension.This technique resulted in a significant reduction in the surface roughness of the Y_(2)O_(3)ceramics by 95.42%and eliminated the stair-stepping phenomenon caused by AM,thus increasing 66.12%of the in-line transmittance.These enhancements expand their potential applications in laser amplification,optical communications,and other areas requiring high-transparency materials.The method developed in this study can be used for the AM-based fabrication of transparent 3D polycrystalline ceramics.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS2024-00407234).
文摘In this work,we present a digital light processing(DLP)-flashing-based functionally graded additive manufacturing(FGAM)process for fabricating highly aesthetic zirconia(ZrO_(2))dental crowns with simultaneous color and translucency gradation.Color gradation was achieved by controlled iron oxide(Fe2O3)doping(ranged from 0.0 to 0.10 wt%)in zirconia powders,whereas translucency gradation was simultaneously attained by controlling the isotropic cubic phase(c-ZrO_(2))in the sintered crowns using three different grades of yttria-stabilized ZrO_(2)(3,4,and 5 mol%yttria-stabilized ZrO_(2)powders,i.e.,3YSZ,4YSZ,and 5YSZ,respectively).The crowns were printed through flashing illumination:0.2 s flash time and 1 s off-time between consecutive ultraviolet(UV)flashes to overcome the scattering-induced overcuring associated to continuous printing that degraded the structural accuracy of the design and posed post-processing challenges and property deterioration.International Commision on Illumination’s Lab(CIELAB)color assessments indicated successful coloring indices(L^(*),a^(*),and b^(*)values)matching the graded appearance of natural teeth.Mechanical properties and sintering shrinkage were slightly affected by the Fe_(2)O_(3)and yttria contents of the various compositions.The highest translucency parameter(above 20)was possible with an undoped 5YSZ composition at the top part(incisor)of the crown.The processing challenges during FGAM of ceramic materials were successfully overcome through a flashing mechanism,and the color and translucency gradation of the ZrO_(2)dental crown was simultaneously maintained with enhanced printing precision,which is a potential breakthrough advancement in esthetic dentistry.
