Multilayer synergistic design of NbSi₂/Nb₂O₅-SiO₂/MoSi₂ ceramic coating on niobium alloys for multiple thermal protection properties

A novel NbSi₂/Nb₂O₅-SiO₂/MoSi₂ multilayer thermal protection ceramic coating is designed and fabricated via halide-activated pack cementation and liquid-plasma-assisted particle deposition and sintering technology, endowing the coating with multiple high-temperature protective properties. The incorporation of MoSi₂ nanoparticles not only gives superior high-temperature oxidation resistance/hot corrosion resistance of coating by forming a dense SiO₂ barrier layer, but also promotes passive radiative heat dissipation. When NbSi₂/Nb₂O₅-SiO₂/MoSi₂ coating was prolonged exposure to air at 1250 °C for 50 h of oxidation and at 900 °C for 100 h of corrosion, the mass gains are only 0.37 mg/cm² and − 0.52 mg/cm², respectively. The multilayer coating exhibits enhanced emissivity (>0.88) over the thermal infrared range of 3–20 µm, due to the lattice vibrational absorption-matching synergy of Nb₂O₅, SiO₂, and MoSi₂, as well as the mutual doping of SiO₂/Nb₂O₅, mismatch of atoms at the interface, and a high degree of lattice distortion within the coating.