Factors inducing degradation of properties after long-term oxidation of Si3N4-MoSi2 electroconductive composites (Articolo in rivista)

Type
Label
  • Factors inducing degradation of properties after long-term oxidation of Si3N4-MoSi2 electroconductive composites (Articolo in rivista) (literal)
Anno
  • 2004-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1557/JMR.2004.0210 (literal)
Alternative label
  • Valentina Medri; Alida Bellosi (2004)
    Factors inducing degradation of properties after long-term oxidation of Si3N4-MoSi2 electroconductive composites
    in Journal of materials research
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Valentina Medri; Alida Bellosi (literal)
Pagina inizio
  • 1567 (literal)
Pagina fine
  • 1574 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 19 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroFascicolo
  • 5 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • CNR-ISTEC, Institute of Science and Technology for Ceramics, 48018 Faenza, Italy (literal)
Titolo
  • Factors inducing degradation of properties after long-term oxidation of Si3N4-MoSi2 electroconductive composites (literal)
Abstract
  • The effects of heat treatments on strength and electrical conductivity after 100 h in air up to 1500 °C were evaluated on hot-pressed Si3N4-35 vol% MoSi2 composite. The long-term oxidation involves microstructural changes at the material surface and subsurface, such as the formation of oxide scales and of a multilayered microstructure. At T ? 1200 °C, a glassy silicate phase is formed, which embeds cristobalite grains and highly textured Y2Si2O7 crystals. At the same time, MoSi2, assisted by oxygen, reacts with Si3N4 forming Mo5Si3, Si2N2O, and SiO2. The decrease of the room temperature flexural strength reached about 25% in the samples exposed at 1000 °C for 100 h, compared to the as-produced materials. On the contrary, after treatments at higher temperatures, the strength decrease is lower at 1500 °C, the residual strength is 836 ± 62 MPa with a strength decrease of about 8%. The surface oxide scale is an insulator and, consequently, the electrical resistivity of the composite rises from 10-3 to 107-109 ohm cm. (literal)
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