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Green bodies of porous silicon nitride ceramics were shaped by the extrusion technique using starch simultaneously as binder during extrusion and as pore-maker during subsequent thermal debinding. The different porosities, microstructures, and mechanical properties after the extrusion, drying, debinding, and sintering stages were investigated. The results showed that the porosity, density, microstructure, and flexural strength of samples varied greatly through the whole process stages. The resultant samples had a 160 MPa flexural strength at a porosity of 43% and a uniform fibrous interlocking microstructure consisting of well-developed rod-like β-Si3N4 grains. In addition, porosity, microstructure, and strength can be further tailored by sintering conditions such as the sintering nitrogen pressure. Extrusion using cheap starch as binder and pore-maker is a promising preparation route for manufacturing cost-effective porous silicon nitride ceramics. [ABSTRACT FROM AUTHOR]

Abstract: The effect of bentonite addition on extrusion behavior, open porosity, microstructure, and mechanical properties was investigated. The results showed that paste with an appropriate amount of bentonite had a good extrusion behavior. The resultant microstructures consisted of rod-like silicon nitride grains and some intergranular amorphous phase. Furthermore, superior mechanical properties were obtained. Using cheap but effective bentonite as inorganic binder as well as sintering aid is a promising eco-friendly preparation route for cost-effective porous silicon nitride ceramics. [Copyright &y& Elsevier]

Abstract: Self-reinforced silicon nitride ceramics were synthesized by introducing 5 wt% previously prepared β-Si3N4 seeds into a mixture of α-Si3N4 and 8 wt.% of sintering additive. The microscopic evidence indicates that β-Si3N4 seeds play an important role in microstructural development and mechanical properties for silicon nitride ceramics. The growth of β-Si3N4 grains is initiated from the seeds, resulting in a core/shell microstructure observed in the abnormal grain growth. The internal dislocation, π-boundary, and Moire fringes are present in Si3N4 grains, which were formed to compensate the mismatch and compositional differences between the two grains. Coalescence can occur at the final stage of sintering. [Copyright &y& Elsevier]

Abstract: Silicon carbide (SiC) ceramics were fabricated by plasma-activated sintering. The sintering was accomplished at relatively low temperatures within a short time. The grain growth of the SiC ceramics was considerably inhibited, and finally SiC ceramics with a higher bending strength (853.7MPa) and fracture toughness (8.34MPam1/2) could be fabricated. [Copyright &y& Elsevier]