A novel plasma-sprayed Ti₄O₇/carbon nanotubes/Al₂O₃ coating with bifunctional microwave application

High-performance microwave absorption coatings are critically required in the stealth defense system of military platforms. Regrettably, just optimizing the property but neglecting the application feasibility seriously inhibits its practical application in the field of microwave absorption. To face this challenge, the Ti₄O₇/carbon nanotubes (CNTs)/Al₂O₃ coatings were successfully fabricated by a plasma-sprayed method. For the different oxygen vacancy-induced Ti₄O₇ coatings, the enhanced ε' and ε'' values in the frequency of X-band is due to the synergistic manipulation of conductive path, defects and interfacial polarization. The optimal reflection loss of Ti₄O₇/CNTs/Al₂O₃ sample (0 wt% CNTs) is -55.7 dB (8.9 GHz of 2.41 mm), while the electromagnetic interference shielding effectiveness of Ti₄O₇/CNTs/Al₂O₃ sample (5 wt% CNTs) increases to 20.5 dB as the enhanced electrical conductivity. In special, the flexural strength of Ti₄O₇/CNTs/Al₂O₃ coatings first increases from 48.59 MPa (0 wt% CNTs) to 67.13 MPa (2.5 wt% CNTs) and then decreases to 38.31 MPa (5 wt% CNTs), demonstrating that an appropriate amount of CNTs evenly dispersed in the Ti₄O₇/Al₂O₃ ceramic matrix can effectively play the role of CNTs as the strengthening phase of the coatings. This research will provide a strategy by tailoring synergistic effect of dielectric loss and conduction loss for oxygen vacancy-mediated Ti₄O₇ material to broaden the application of absorbing or shielding ceramic coatings.