The effects of beta-seeds on the electrical and mechanical properties of Si3N4-TiN composites
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Si3N4-TiN composites, with varying TiN content from 0-50 wt% and beta-Si3N4 seeds up to 5 wt%, were examined in respect of their electrical resistivity and fracture toughness. The composites are produced by liquid phase sintering using 3%Al2O3+7%Y2O3 as additive. beta-seed particles with different particle shape and aspect ratio were used in this investigation. The electrical conductivity of composites exhibits a percolative behaviour, which is characterised by an abrupt decrease in resistivity in composites with 36 wt%TiN. In composites with beta-Si3N4, for the same percolation concentration of TiN, the electrical resistivity is higher than in composites without seed particles. The fracture toughness shows a considerable improvement in Si3N4-36%TiN with 3 and 5 wt% seeds. High fracture toughness of 6.10 MPa m(1/2) could be achieved due to the controlled bimodal microstructure consisting of elongated beta-Si3N4 incorporated into a composite matrix.
Keywords:Si3N4-TiN composites / beta-seeds / sintering / fracture toughness / electrical resistivity
Source:Silicates Industriels, 2004, 69, 7-8, 299-304
- 4th International Symposium on Nitrides, Nov 17-19, 2003, Mons, Belgium