Microwave-absorbing functionalization of LaMgAl ₁₁O ₁₉ composite thermal barrier coatings by atmospheric plasma spraying

Thermal protection of the hot-end components of ultra-high-flying vehicles requires the microwave absorption of thermal barrier coating (TBC). In this work, the microwave-absorbing functionalization of LaMgAl₁₁O₁₉ (LMA) TBC was successfully realized by adding FeSiAl (FSA) absorber to the LMA thermal barrier ceramic matrix to adjust electromagnetic parameters. Due to the formation of the layered lamellae structure during atmospheric plasma spraying, the LMA–FSA composite TBCs have better electromagnetic wave (EMW) absorbing property than the feed powders. The EMW absorption of TBCs is mainly controlled by the magnetic loss and the natural resonance is the main mechanism of magnetic loss. The TBCs exhibit a minimum RL value of -13.4 dB and the EAB of RL< -10 dB is up to 3.11 GHz at a simulated thickness of 2 mm. Phase and structure stability of the TBCs and microwave absorption property could be relatively well preserved even after heat-treatments at 600–1000 ℃ for 3–50 h. The thermal conductivity of the LMA–FSA composite TBCs with FSA contents of 30–50 wt.% are about 2.84–3.05 W×m^-1×K^-1 at 800 ℃. The LMA–FSA composite TBCs with heat-resistant, heat-insulation and EMW absorbing properties might find the attractive potential applications in the thermal protection for the light alloys hot-end components in civil and military industry.