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Si3N4/TiN ceramic composites have been prepared by hot pressing in a nitrogen atmosphere using fine Si3N4 and Ti powders and CaO–Al2O3 sintering aids and investigated. The results demonstrate that hot pressing was accompanied by titanium nitridation, yielding titanium nitride with the composition TiN0.9. Reaction between silicon nitride and the sintering aid led to the formation of a Ca-α-SiAlON with the composition Ca0.67(Si10Al2)(N15.3O0.7). In addition to the major phases, calcium aluminosilicate with the composition Ca3Al2Si3O12 was identified. Increasing the percentage of titanium nitride in the composites prepared at a temperature of 1650°C led to an increase in their density and Vickers microhardness: from 3.18 ± 0.03 to 4.33 ± 0.03 g/cm3 and from 17 ± 1.1 to 29.4 ± 0.9 GPa, respectively. [ABSTRACT FROM AUTHOR]

Si3N4-based ceramics have been produced by hot pressing in the temperature range 1550–1650°C using α-Si3N4 starting powder and CaO–Al2O3 (48 : 52 wt %) sintering aids. The powders and the ceramics have been characterized by dilatometry, scanning electron microscopy, and X-ray diffraction, and we have measured the microhardness and density of the ceramic samples. The results demonstrate that the sintering aid reacted with Si3N4 to form Ca-α-SiAlON. At 40 wt % sintering aids, all of the silicon nitride was converted into Ca-α-SiAlON. We have clarified general trends in the effect of the amount of sintering aids on the properties of the ceramic samples. [ABSTRACT FROM AUTHOR]