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Due to high light absorption and high refractive index of silicon nitride (Si3N4) ceramic, it is difficult to prepare Si3N4 slurry with favorable curing ability, high solid loading and low viscosity at the same time, and thus the high-quality Si3N4 parts are hard to fabricate via Digital Light Processing (DLP). In this paper, the oxidation process was used to enhance the curing behavior of Si3N4 slurry, and then silane coupling agent (KH560) was used to improve the rheological properties of the oxidized Si3N4 slurry. The effect of Si3N4 slurry with oxidation and modification on its rheological behavior, light absorption, curing ability and stability have been systematically investigated. A Si3N4 slurry with abundant photocuring ability, high solid loading, low viscosity and reliable stability was fabricated by the oxidized (1 h) and KH560 (1 wt.%) modified Si3N4 powders, and the dense Si3N4 ceramic parts were produced by this slurry via DLP 3D printing. Subsequently, the influence of oxidation and modification on microstructure, mechanical properties and thermal conductivity have been investigated. Finally, the microstructure and performances of Si3N4 ceramic were compared between different forming processes (including: DLP and cool isostatic pressing). [ABSTRACT FROM AUTHOR]

In this work, we report a novel approach to fabricate titanium carbide (TiC) ceramics toughened by Y2O3introduced via chemical precipitation method. TiC ceramics with and without Y2O3addition were consolidated by SPS, and the densification, microstructure and fracture toughness were investigated. Compared to the additive-free counterpart, improved density and finer grain microstructure were found for TiC ceramics with Y2O3sintered at 1600 °C, indicating that Y2O3additive homogeneously scattered in TiC matrix could not only improve the density but also inhibit grain growth. In addition, the grain boundary was strengthened due to Y2O3pinning in grain boundary, leading to a fracture behaviour transformation from intergranular type to the mixed mode of intergranular and transgranular fracture. Because of the improved density and strengthened grain boundary, the fracture toughness increased from 4.3 to 5.3 MPa·m1/2, which is improved by ~23% compared with that of additive-free TiC sample. [ABSTRACT FROM PUBLISHER]