Thermo-Optical Properties of LaMAl11O19 (M = Mg, Mn, Fe) Hexaaluminates for High-Temperature Thermal Protection Applications


  • This work was financially supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 51002038 and 51021002), and the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRET1.2010006).

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LaMAl11O19 (M = Mg, Mn, Fe) ceramics are fabricated by pressureless-sintering method at 1700°C for 10 h in air. The microstructure and thermo-optical properties of LaMAl11O19 ceramics are studied by the X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy measurements. The transition metallic elements such as Mn and Fe at M2+ site can effectively enhance the emissivity of LaMAl11O19 ceramics at short wavelengths. LaFeAl11O19 has the highest emissivity value of more than 0.8 in the wavelength range of 2.5–6 μm at 500°C. However, the measured emissivity of different LaMAl11O19 ceramics shows a similar trend in the wavelength range of 6–14 μm. LaFeAl11O19 is a promising protective coating material for metallic thermal protection system due to its high emissivity of above 0.7 over the whole wavelength range of 2.5–14 μm at temperatures up to 900°C.