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Incorporation of additives into silicon carbide (SiC) ceramics in low temperature, atmospheric pressure sintering is challenging because uniform mixing of additives and raw SiC powders is quite difficult. Herein, an impregnation coating process in which a precise amount of Al 2 O 3 is introduced to raw SiC granules on the nanoscale is described and high-performance SiC ceramics can be processed by atmospheric pressure sintering. The uniform coating promotes densification of SiC via enhanced liquid mass transfer and inhibits grain growth and recombination during sintering. The effects of the doping content on the ceramic structure and mechanical properties are studied. Coating a single layer of Al 2 O 3 nano-particles on SiC particles yield the best interfacial activity, sintering density, and mechanical properties. The SiC sample with 7.5 wt% Al 2 O 3 possesses the best properties such as a relative density of 97.98%, flexural strength of 434.40 MPa, fracture toughness of 5.23 MPa·m1/2, and Vickers hardness of 28.21 GPa. The sintering kinetics analyzed by the isothermal sintering method fits the Singh model with an apparent activation energy of 574.64 kJ/mol. The sintering rate is governed by both the interface reaction and diffusion and the model and experimental results provide insights with respect to materials design and commercial batch production. Unlabelled Image • A facile Al 2 O 3 coating technique for SiC powders is described. • Raw SiC granules are evenly coated with a precise amount of Al 2 O 3 on the nanoscale. • High-quality SiC ceramic samples are prepared by atmospheric pressure sintering. • The sintering kinetics is analyzed by the isothermal method. • The sintering rate is determined by the interface reaction and diffusion. [ABSTRACT FROM AUTHOR]

Quartz and clay are substituted gradually by fly ash using a triaxial ceramic formulation under simulated industrial conditions and the effects of fly ash substitution on the macroscopic properties and microstructures of the sintered ceramics are evaluated systematically. With the substitution of 35 wt% (1250 °C), the ceramic sample exhibited optimal properties, including linear shrinkage of 15.61%, bulk density of 2.39 g cm-3, water absorption of 0.62% and flexural strength of 41.70 MPa, due to the accelerated densification and fly ash-spurred needle-shaped mullite. The microstructure analysis shows that the sintered matrix consists of three types of particles, quartz-, clay- and feldspar-like particles showing sintering behavior with respect to filling the glassy matrix with preserved morphology, precipitating mullite crystals, and fusing with the surrounding glassy matrix, respectively. The strength of the fly ash - containing ceramics is analyzed by the dispersion-strengthening mechanism and porosity and the results indicate that the fly ash particles affect the mechanical strength due to Griffith flaws when the total porosity is less than 25% and pores at higher total porosity. This study provides a viable strategy to recycle industrial fly ash in the production of architectural ceramics. [Display omitted] • Quartz and clay are substituted by fly ash in a triaxial ceramic formulation. • The ceramic preparation is under simulated industrial conditions. • The substitution effects on macro-properties and microstructures are evaluated. • Three types of particles exist acting as quartz, clay, and feldspar, respectively. • The strength is analyzed by the dispersion strengthening mechanism and porosity. [ABSTRACT FROM AUTHOR]