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Background: Zirconia is a widely used material in the dental industry due to its excellent mechanical and aesthetic properties. Recently, a new 3D printing process called suspension-enclosing projection stereolithography (SEPS) was introduced to fabricate zirconia dental restorations. However, the effect of the sintering time and temperature on the properties of zirconia produced via SEPS has not been fully investigated. Methods: Zirconia slurries were prepared with varying percentages of zirconia powders and 3D printing resins, and 5Y-TZP (5 mol% yttria-stabilized zirconia) (n = 40) and 3Y-TZP (3 mol% yttria-stabilized zirconia) (n = 40) bar specimens were fabricated via SEPS manufacturing. The specimens were sintered at different temperatures and dwell times, and their flexural strength, density, and phase composition were measured. The viscosity of the slurries was also measured. Statistical analysis was performed using Welch's ANOVA and Kruskal–Wallis tests to evaluate the impact of the sintering conditions. Results: Significant differences in flexural strength (p < 0.01) were observed between the 5Y-TZP samples, with those sintered at 1530 °C for 120 min showing an average strength of 268.34 ± 44.66 MPa, compared to 174.16 ± 42.29 MPa for those sintered at 1450 °C for 120 min. In terms of density, significant differences (p < 0.01) were noted for the 3Y-TZP specimens, with an average density of 6.66 ± 0.49 g/cm3 for samples sintered at 1530 °C for 120 min, versus 5.75 ± 0.55 g/cm3 for those sintered at 1530 °C for 10 min. X-ray diffraction confirmed the presence of a predominantly tetragonal phase in both materials. Conclusions: Zirconia printed via SEPS manufacturing can be sintered at a higher temperature with shorter dwell times, thereby producing high density samples. Different sintering conditions can be used to fully sinter 3D-printed zirconia for potential dental applications. [ABSTRACT FROM AUTHOR]

In recent years, ceramic fabrication using stereolithography (SLA) has gained in popularity because of its high accuracy and density that can be achieved in the final part of production. One of the key challenges in ceramic SLA is that support structures are required for building overhanging features, whereas removing these support structures without damaging the components is difficult. In this research, a suspension-enclosing projection-stereolithography process is developed to overcome this challenge. This process uses a high-yield-stress ceramic slurry as the feedstock material and exploits the elastic force of the material to support overhanging features without the need for building additional support structures. Ceramic slurries with different solid loadings are studied to identify the rheological properties most suitable for supporting overhanging features. An analytical model of a double doctor-blade module is established to obtain uniform and thin recoating layers from a high-yield-stress slurry. Several test cases highlight the feasibility of using a high-yield-stress slurry to support overhanging features in SLA. [ABSTRACT FROM AUTHOR]

We report a novel approach to fabricate dense zirconia-toughened alumina (ZTA) ceramics with excellent properties via an additive manufacturing process based on stereolithography. The XRD patterns show the ZTA sample consists of α-Al 2 O 3 and t-ZrO 2 with the dominance of α-Al 2 O 3 . The zirconia grain with the average size of 0.35 µm is small enough to trigger the toughening behavior of zirconia in the ZTA. The prepared ceramics showed a density, Vickers hardness, bending strength, and fracture toughness of 4.26 g/cm 3 , 17.76 GPa, 530.25 MPa, and 5.72 MPa m 1/2 , respectively. These properties are comparable to those for ceramics obtained through conventional ceramic processing. [ABSTRACT FROM AUTHOR]

In this study, Al 2 O 3 ceramics were printed by stereolithography from particles with different particle size distributions, which are the micro-sized Al 2 O 3 , nano-sized Al 2 O 3 , and a mixture of both. The influence of the particle size and the debinding method on the density and morphology of the sintered bodies were investigated. The density of the samples containing both micro-sized and nano-sized alumina particles is highest among the three samples. Furthermore, the samples subjected to the vacuum debinding showed a higher density compared with the samples subjected to the traditional thermal debinding. The results suggest that the combination of a powder with a bimodal particle size distribution and the vacuum debinding process offers an effective way to print 3D ceramics with a good performance through stereolithography. [ABSTRACT FROM AUTHOR]

In this study, we report a novel approach, integrating stereolithography and liquid precursor infiltration techniques, to fabricate fine-grained alumina ceramics. The XRD patterns of the sample immersed with Zr 4+ or Zr 4+ (Y 3+ ) show that the sintered body contains Al 2 O 3 and t-ZrO 2 as the major phase and minor phase, respectively. Moreover, the t-ZrO 2 phase in the sample immersed with Zr 4+ (Y 3+ ) shows intense peaks compared to the composite immersed with Zr 4+ . On the other hand, the sample immersed with Mg 2+ contained Al 2 O 3 and MgAl 2 O 4 as the major phase and minor phase, respectively. The microstructure of the sample immersed with Zr 4+ shows that ZrO 2 particles are homogeneously distributed in the Al 2 O 3 matrix, thus inhibiting the grain growth of alumina particles. Moreover, the sample immersed with Mg 2+ shows a more dense and fine-grained structure. Compared to the non-infiltrated sample, the average grain size of the alumina sample immersed with Zr 4+ or Mg 2+ decreased. The sample infiltrated with Zr 4+ (Y 3+ ) had the smallest alumina average grain size of 1.14 µm. The ceramics prepared by infiltration showed a higher hardness (19.54 GPa), but a slightly lower fracture toughness (4.02 MPa m 1/2 ) compared to the samples (17.2 GPa, 4.13 MPa m 1/2 ) without infiltration. [ABSTRACT FROM AUTHOR]

A dense defect-free alumina cutting tool was fabricated via stereolithography process. Different drying processes and debinding profiles were then tested and compared to find the optimal way for the preparation of the sintered body. The experimental results showed that using PEG400 as a liquid desiccant results in a lower deformation of the body compared to the natural drying process. Compared with vacuum debinding or air debinding, a two-step debinding process, which consisted of both a vacuum pyrolysis step and the following air debinding, is allowed to control the pyrolysis rate while suppressing the formation of defects in the alumina body. After optimization of the postprocessing, the relative density of the sample as high as 99.3%, and the Vickers hardness ∼17.5 GPa. These properties are similar to the properties of alumina bodies prepared via the conventional shaping method. [ABSTRACT FROM AUTHOR]