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To the first time, thermal conductivities of spark plasma sintered β-sialons (Si3Al3O3N5) procured from combustion synthesis (CS) with no sintering additive were measured by the laser flash method at room temperature. A full densification occurred when these materials were sintered at 1600 °C with a simultaneous pressure of 50 MPa. XRD analyses indicated that single phase β-sialons were formed after SPS though the combustion synthesized β-sialon powders had considerable amounts of silicon impurities. Thermal conductivity values increased with sintering temperature and attained a maximum of 5.49 W m−1 K−1 for fully densified β-sialons sintered at 1700 °C for 10 min.

Fully dense multiwall carbon nanotubes (MWCNT)/SiO2 nanocomposites with MWCNTs contents of 5 and 10 vol% have been processed by spark plasma sintering, and the electrical conductivities of the nanocomposites were evaluated at temperatures ranging from 5 to 300 K. It has been found that the incorporation of MWCNTs converted an insulating silica nanoceramic into metallically conductive composites. The room-temperature conductivities of the nanocomposites, with over 14 orders of magnitude compared with pure silica, are in the range of 8 and 65 S/m. Also, it was interestingly found that the conductivity increased linearly with temperature from 5 to 300 K.

The mechanical response of four different types of hot pressed yttrium stabilized α/β composite SiAlON ceramics was investigated by scratch testing in order to interpret their severe wear behavior. A progressive loading scratch tester with both rough and smooth spherical diamond styluses was used to analyze the variation in mechanical response with roughness of stylus. The extent of subsurface damage produced by the different styluses on a 50% β-content composite was also investigated using a visualization technique with plasma etching, which has been previously developed by one of the authors. When scratched by the rough stylus, quasi-plastic deformation recognized in the form of grain release after plasma etching was present predominantly in the surface, and the use of this stylus was regarded to be more appropriate for comparing the results of scratch tests with those of severe wear due to similarity of crack formation between grain dislodgement in severe wear and subsurface damage in the scratch tests. The work required to produce damage and groove formation ( W dg ) when scratched by the rough stylus was evaluated for all test materials and it was found that the worn volume under severe wear follows the reverse order of W dg .

The influence of diluent addition on purities of β-Si5AlON7 powders synthesized by mechanically activated combustion synthesis (MA-CS) under a very low nitrogen atmosphere of 1 MPa was investigated. The purity of β-Si5AlON7 powders increased with diluent concentrations in raw materials and had a maximum value of 91% when 40 mass% of diluents were added, a 25% more pure when compared to powders procured without diluents. In contrast, when diluents were included 50% or more, the combustion synthesis (CS) reaction did not occur due to reduced exothermic heat. The results also showed that the particle sizes of β-Si5AlON7 powders synthesized with 40 mass% of diluents were only one-tenth when compared to powders synthesized without diluents.

Fine β-sialon (Si6−zAlzOzN8−z, 1