Abstract:Molybdenum disilicide (MoSi₂) sheath and aluminum oxide (Al₂O₃) core blended powders were fabricated by spray drying. A derived coating material was produced for the application as microwave absorbers using the as prepared powders by atmospheric plasma spray (APS) technology. The effects of MoSi₂/Al₂O₃ mass ratio on the dielectric and physical mechanical properties of the composite coatings were investigated. When the MoSi₂ content of the composites increases from 0 to 45%, the flexure strength and fracture toughness improve from 198 to 324 MPa and 3.05 to 4.82 MPa∙m^1/2 then decline to 310 MPa and 4.67 MPa∙m^1/2, respectively. The dielectric loss tangent increases with increasing MoSi₂ content, and the real part of permittivity decreases conversely over the frequency range of 8.2−12.4 GHz. These effects are due to the agglomeration of early molten MoSi₂ particles and the increase of the electrical conductivity with increasing MoSi₂ content.

Key words: MoSi₂/Al₂O₃ composite coating; atmospheric plasma spraying; mechanical properties; dielectric properties