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Novel class of precursor-derived Zr–La–B–C(O) based ceramics containing nano-crystalline ultra-high temperature phases stable beyond 1600 °C.

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Title: Novel class of precursor-derived Zr–La–B–C(O) based ceramics containing nano-crystalline ultra-high temperature phases stable beyond 1600 °C.
Authors: Nanda, Gokul1 (AUTHOR), Thiyagarajan, Ganesh Babu1,2 (AUTHOR), Kumar, KC Hari2,3 (AUTHOR), Devasia, Renjith1,4 (AUTHOR) d_renjith@vssc.gov.in, Kumar, Ravi1,2 (AUTHOR) nvrk@iitm.ac.in
Source: Ceramics International. Jan2022, Vol. 48 Issue 2, p1981-1989. 9p.
Subjects: Silicon nitride, Heat treatment, Boron, Transmission electron microscopy, Thermodynamic equilibrium, Chemical decomposition, Chemical resistance, Ceramics
Abstract: In this work, a novel ultra-high temperature resistant precursor-derived ceramic containing Zr, La, B, and C was synthesized through precursor modification of phenol formaldehyde resin. The thermal stability and resistance to crystallization of the ceramic at a temperature of 1600 °C was investigated and was found to be profoundly influenced by the boron content in the starting precursors. The ceramics remained amorphous at 1600 °C for 2 h in argon and upon sustained heat-treatment for up to 16 h resulted in nano-crystalline ultra-high temperature phases such as ZrB 2 , ZrC, LaB 6 and La 2 Zr 2 O 7. Thermodynamic equilibrium phase calculations show that even longer durations of heat treatment may be required to achieve thermodynamic equilibrium. High-resolution transmission electron microscopy revealed encapsulation of nanocrystals (<5 nm) in an amorphous matrix surrounded by turbostratic layers of carbon inhibiting its growth. Spectrochemical techniques confirmed the presence of boron substituted carbon in the amorphous matrix of the ceramic. The unique nature of the amorphous matrix lends the ceramic resistance to crystallization and chemical degradation that can surpass the likes of classical silicon-based precursor-derived ceramics. [ABSTRACT FROM AUTHOR]
Copyright of Ceramics International 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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  Data: Novel class of precursor-derived Zr–La–B–C(O) based ceramics containing nano-crystalline ultra-high temperature phases stable beyond 1600&#160;&#176;C.
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  Data: &lt;searchLink fieldCode=&quot;JN&quot; term=&quot;%22Ceramics+International%22&quot;&gt;Ceramics International&lt;/searchLink&gt;. Jan2022, Vol. 48 Issue 2, p1981-1989. 9p.
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  Data: In this work, a novel ultra-high temperature resistant precursor-derived ceramic containing Zr, La, B, and C was synthesized through precursor modification of phenol formaldehyde resin. The thermal stability and resistance to crystallization of the ceramic at a temperature of 1600 &#176;C was investigated and was found to be profoundly influenced by the boron content in the starting precursors. The ceramics remained amorphous at 1600 &#176;C for 2 h in argon and upon sustained heat-treatment for up to 16 h resulted in nano-crystalline ultra-high temperature phases such as ZrB 2 , ZrC, LaB 6 and La 2 Zr 2 O 7. Thermodynamic equilibrium phase calculations show that even longer durations of heat treatment may be required to achieve thermodynamic equilibrium. High-resolution transmission electron microscopy revealed encapsulation of nanocrystals (&lt;5 nm) in an amorphous matrix surrounded by turbostratic layers of carbon inhibiting its growth. Spectrochemical techniques confirmed the presence of boron substituted carbon in the amorphous matrix of the ceramic. The unique nature of the amorphous matrix lends the ceramic resistance to crystallization and chemical degradation that can surpass the likes of classical silicon-based precursor-derived ceramics. [ABSTRACT FROM AUTHOR]
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  Data: &lt;i&gt;Copyright of Ceramics International 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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      – Type: doi
        Value: 10.1016/j.ceramint.2021.09.283
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 9
        StartPage: 1981
    Subjects:
      – SubjectFull: Silicon nitride
        Type: general
      – SubjectFull: Heat treatment
        Type: general
      – SubjectFull: Boron
        Type: general
      – SubjectFull: Transmission electron microscopy
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      – SubjectFull: Thermodynamic equilibrium
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      – SubjectFull: Chemical decomposition
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      – SubjectFull: Chemical resistance
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      – TitleFull: Novel class of precursor-derived Zr–La–B–C(O) based ceramics containing nano-crystalline ultra-high temperature phases stable beyond 1600 °C.
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            NameFull: Nanda, Gokul
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            NameFull: Kumar, KC Hari
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              M: 01
              Text: Jan2022
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              Y: 2022
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