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<p>Vacuum sintering of Cr, Al, graphite, and TiC or Ti powders at 1300°C was used to obtain products of two MAX phases: 312 and 211, the predominant formation of which depends on whether TiC or Ti is taken as the precursor. The 312 MAX phase (Cr<sub>2/3</sub>Ti<sub>1/3</sub>)<sub>3</sub>AlC<sub>2</sub> predominates in the synthesis from Cr:Al:TiC:C, while the 211 MAX phase Cr<sub>1.5</sub>Ti<sub>0.5</sub>AlC is the predominant product in the synthesis from Cr:Al:Ti:C; α-Al<sub>2</sub>O<sub>3</sub>, carbides, and chromium oxides are present in these samples as impurities. A combination of x-ray diffraction and x-ray photoelectron spectroscopy methods revealed significant differences in the chemical and phase composition on the surface and in the bulk of these samples. Aluminum and chromium oxides as well as a carbide (Cr<sub>7</sub>C<sub>3</sub>) are formed on the surface of these MAX phases during the synthesis. Similar behavior is found in the thermal oxidation of Cr<sub>2</sub>AlC with the formation of a protective surface layer of α-Al<sub>2</sub>O<sub>3</sub>/Cr<sub>7</sub>C<sub>3</sub>. Formation of a protective layer is essential for producing Cr–Ti–Al–Cbased materials with high thermochemical stability in aggressive environments.</p>

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Synthesis and Structure of MAX-Phases Cr2/3Ti1/3)3AlC2 and Cr1.5Ti0.5AlC Obtained by High-Temperature Sintering in Vacuum

  • 期刊论文

  • 发表日期：

    2026年1月15日

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  • E. A. Ovodok,
  • M. I. Ivanovskaya,
  • A. E. Seleznev,
  • S. V. Zlotsky,
  • V. V. Uglov,
  • A. A. Vereschaka

摘要

Vacuum sintering of Cr, Al, graphite, and TiC or Ti powders at 1300°C was used to obtain products of two MAX phases: 312 and 211, the predominant formation of which depends on whether TiC or Ti is taken as the precursor. The 312 MAX phase (Cr2/3Ti1/3)3AlC2 predominates in the synthesis from Cr:Al:TiC:C, while the 211 MAX phase Cr1.5Ti0.5AlC is the predominant product in the synthesis from Cr:Al:Ti:C; α-Al2O3, carbides, and chromium oxides are present in these samples as impurities. A combination of x-ray diffraction and x-ray photoelectron spectroscopy methods revealed significant differences in the chemical and phase composition on the surface and in the bulk of these samples. Aluminum and chromium oxides as well as a carbide (Cr7C3) are formed on the surface of these MAX phases during the synthesis. Similar behavior is found in the thermal oxidation of Cr2AlC with the formation of a protective surface layer of α-Al2O3/Cr7C3. Formation of a protective layer is essential for producing Cr–Ti–Al–Cbased materials with high thermochemical stability in aggressive environments.