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Page 8 of 18                        Chong et al. J Mater Inf 2023;3:21  https://dx.doi.org/10.20517/jmi.2023.17

























































                Figure 5. Surface morphologies and distribution of elements from EPMA of the alloy Pt Al  after 100 h oxidation in air at 1,300 °C. (A)
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                Surface morphology; (B1)-(B3) Pt, Al, and O map distribution, respectively; (C) Linear distribution of Pt, Al, and O.
               Figure 5 shows the EPMA elemental maps of Pt Al  oxidized at 1,300 °C for 100 h. Obviously, the light
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               areas are fcc phase (mainly Pt), and the dark areas are Al O  according to the EPMA analysis; see Figure 5A.
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               The Al O  layer is not fully dense. Figure 6 shows the cross-sectional EPMA of Pt Al  after oxidation at
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               1,300 °C for 100 h. The oxide scale on the Pt Al  surface is continuous and intact, which is from 10.1 to
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               13.3 μm in thickness, as shown in Figure 6A. However, the discontinuous Pt-rich layer is also observed
               outside the oxide layer, which is probably due to the deposition of the Pt vapor above 1,000 °C .
                                                                                              [10]
               Pt Al Cr 6
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               Figure 7 shows the XRD patterns of the Pt Al Cr  alloy after oxidation at 1,300 °C for 100 h. It reveals that
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               the α-Al O  is the major phase in the oxide layer with small peaks identified as Pt, indicating that Cr
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               promotes the formation of α-Al O . Different from the case of Pt Al , after oxidation at 1,300 °C for 100 h,
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               the Pt Al Cr  alloy exhibits a smooth and dense surface. No spallation or crack is observed, and the Al O
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