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Anomalous oxidation behaviour of pressureless liquid-phase-sintered SiC

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Title: Anomalous oxidation behaviour of pressureless liquid-phase-sintered SiC
Authors: Rodríguez-Rojas, F.1, Ortiz, A.L.1 alortiz@unex.es, Guiberteau, F.1, Nygren, M.2
Source: Journal of the European Ceramic Society. Nov2011, Vol. 31 Issue 13, p2393-2400. 8p.
Subjects: Silicon carbide, Oxidation, Sintering, Ceramics, Thermogravimetry, X-ray diffractometers, Crystallization, Scanning electron microscopy
Abstract: Abstract: The oxidation behaviour of pressureless liquid-phase-sintered (PLPS) SiC, an important non-oxide engineering ceramic, was investigated, and was found to be universally anomalous. Thermogravimetry oxidation tests performed in oxygen in the temperature range 1000–1225°C on three PLPS SiC ceramics fabricated with different combinations of Al2O3–RE2O3 (RE=Gd, Sc, or Sm) as sintering aids indicated that the oxidation is in all cases passive and protective, but unexpectedly anomalous in the sense that the oxidation resistance does not scale inversely with temperature. In particular, in all cases it was observed that there is less oxidation above 1100°C than below, in clear contradiction to the expectation for a diffusional process. Exhaustive characterization of the oxide scales by scanning electron microscopy, X-ray energy dispersive spectrometry, and X-ray diffractometry, together with detailed modeling of the oxidation curves, showed that the origin of this universal anomalous oxidation behaviour lies in the marked crystallization within the oxide scale of rare-earth silicates that act as effective barriers against the inward diffusion of oxygen thus improving notably the oxidation resistance. A strategy is proposed to provide PLPS SiC, and probably other SiO2-scale-forming ceramics that are sintered using rare-earth oxides, with the superior oxidation resistance at moderate temperatures (i.e., <1100°C) that they do not currently have. [Copyright &y& Elsevier]
Copyright of Journal of the European Ceramic Society is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
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  Data: Abstract: The oxidation behaviour of pressureless liquid-phase-sintered (PLPS) SiC, an important non-oxide engineering ceramic, was investigated, and was found to be universally anomalous. Thermogravimetry oxidation tests performed in oxygen in the temperature range 1000–1225&#176;C on three PLPS SiC ceramics fabricated with different combinations of Al2O3–RE2O3 (RE=Gd, Sc, or Sm) as sintering aids indicated that the oxidation is in all cases passive and protective, but unexpectedly anomalous in the sense that the oxidation resistance does not scale inversely with temperature. In particular, in all cases it was observed that there is less oxidation above 1100&#176;C than below, in clear contradiction to the expectation for a diffusional process. Exhaustive characterization of the oxide scales by scanning electron microscopy, X-ray energy dispersive spectrometry, and X-ray diffractometry, together with detailed modeling of the oxidation curves, showed that the origin of this universal anomalous oxidation behaviour lies in the marked crystallization within the oxide scale of rare-earth silicates that act as effective barriers against the inward diffusion of oxygen thus improving notably the oxidation resistance. A strategy is proposed to provide PLPS SiC, and probably other SiO2-scale-forming ceramics that are sintered using rare-earth oxides, with the superior oxidation resistance at moderate temperatures (i.e., &lt;1100&#176;C) that they do not currently have. [Copyright &amp;y&amp; Elsevier]
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  Data: &lt;i&gt;Copyright of Journal of the European Ceramic Society is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder&#39;s express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.&lt;/i&gt; (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1016/j.jeurceramsoc.2011.05.015
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 8
        StartPage: 2393
    Subjects:
      – SubjectFull: Silicon carbide
        Type: general
      – SubjectFull: Oxidation
        Type: general
      – SubjectFull: Sintering
        Type: general
      – SubjectFull: Ceramics
        Type: general
      – SubjectFull: Thermogravimetry
        Type: general
      – SubjectFull: X-ray diffractometers
        Type: general
      – SubjectFull: Crystallization
        Type: general
      – SubjectFull: Scanning electron microscopy
        Type: general
    Titles:
      – TitleFull: Anomalous oxidation behaviour of pressureless liquid-phase-sintered SiC
        Type: main
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            NameFull: Rodríguez-Rojas, F.
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            NameFull: Ortiz, A.L.
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            NameFull: Guiberteau, F.
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            NameFull: Nygren, M.
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            – D: 01
              M: 11
              Text: Nov2011
              Type: published
              Y: 2011
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              Value: 31
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            – TitleFull: Journal of the European Ceramic Society
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