Si3N4–TiN Nanocomposite by Nitration of TiSi2 and Consolidation by Hot Pressing and Spark Plasma Sintering

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Abstract:

Homogeneous nanostructured Si3N4–TiN composite powder was obtained by nitration of a TiSi2 powder precursor in a nitrogen flow. Mechanoactivation of titanium disilicide increases the nitration rate and reduces the temperature of formation of the Si3N4 and TiN. The properties of hot pressing (HP) and spark plasma sintering (SPS) of the nanostructured Si3N4–TiN composite with Y2O3 and Al2O3 additives have been studied. In the case of the HP-prepared composite the processing conditions are sufficient to form a stable, equilibrated grain boundary framework. The SPS consolidation is extremely rapid, low-temperature process and the sintering temperature was 300–400 °C lower than that of the hot pressing temperature. As a result the grain boundary framework was underdeveloped. Post-sintering anneal of the SPS-prepared samples caused significant improvement of their mechanical properties. The SPS and HP-derived Si3N4–40 mass% TiN–6 mass% Y2O3–2 mass% Al2O3 nano-composite of 98.4% and 98.9% of relative density demonstrate the Vickers hardness values of 13.2 and 13.7 GPa, respectively. The grains of Si3N4 and TiN were much finer in the case of the SPS-derived ceramic composite. However, the better development of the grain boundary framework in the case of the higher temperature HP treatment in comparison to the SPS significantly reduced the advantage of nanocrystallinity. In both cases the fracture toughness was comparable even after the improvement of grain boundary framework during the SPS consolidation. The K1c, of 7.83 MPa·m1/2 of the sample prepared according to the best SPS regime is also comparable to K1c of 8.30 MPa · m1/2 of much coarser hot pressed ceramic with very similar relative density.

Keywords: NANO-COMPOSITE; NANOPOWDER; NANOSTRUCTURED NITRIDE CERAMIC; SI3N4-TIN; SPS; SYNTHESIS

Document Type: Research Article

DOI: http://dx.doi.org/10.1166/jnn.2009.1344

Publication date: November 1, 2009

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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