TEM analysis on TaSi2-containing ultra-high temperature ceramics (Comunicazione a convegno)

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Label
  • TEM analysis on TaSi2-containing ultra-high temperature ceramics (Comunicazione a convegno) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Alternative label
  • Silvestroni L.; Sciti D.; Bellosi A.; Kleebe H. (2010)
    TEM analysis on TaSi2-containing ultra-high temperature ceramics
    in 34th International Conference and Exposition on Advanced Ceramics and Composites, Daytona Beach- Florida
    (literal)
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  • Silvestroni L.; Sciti D.; Bellosi A.; Kleebe H. (literal)
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  • In: ICACC - 34th International Conference and Exposition on Advanced Ceramics and Composites (Daytona Beach- Florida, 24-29 gennaio 2010). (literal)
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  • Ultra-high temperature ceramics are suitable structural ceramics for applications under high heat fluxes at temperature that can exceed 1600°C. Future hypersonic vehicles have a potential use temperature above 2000°C and require oxidation resistant materials. The ceramics object of this study, namely ZrB2, HfB2, HfC and TaC, possess a unique combination of properties including high melting point temperature (ZrB2: 3245°C, HfB2: 3250°C, HfC: 3890°C, TaC:3985°C), high hardness and strength, good oxidation resistance and high thermal conductivity. Ceramics based on borides and carbides of Zr, Hf and Ta were hot pressed at 1750°C-1900°C to full density thanks to the addition of 15 vol% of TaSi2. TaSi2 was selected to promote the densification, due to its high melting point (2200°C), its ductility at the sintering temperature and its capability to provide increased oxidation resistance. The microstructure of the composites was analyzed by X-ray diffraction, scanning and transmission electron microscopy in order to investigate the densification mechanisms occurring during sintering. In the boride-based composites the formation of (Ta,Me)B2 solid solution growing epitaxially on the matrix with low-angle grain boundary was observed. The chemistry of the triple points suggest that cation transfer is an active process and the passage through a liquid phase is also strongly hypothesized. The secondary phases identified were SiC, Ta5Si3 and Ta-oxides. Concerning the carbide-based materials, a higher solubility between Ta and Hf was observed both in the carbide grains and in the silicide. Also in these systems, Ta-rich solid solutions were observed surrounding the matrix. The microstructure evolution is discussed with respect to the chemistry of the elements involved, the phase diagrams and the thermodynamics (literal)
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  • CNR-ISTEC, Faenza, IAG-TUD, Institute of Applied Geoscience-Technical University of Darmstadt (literal)
Titolo
  • TEM analysis on TaSi2-containing ultra-high temperature ceramics (literal)
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