Ti 3 SiC 2 exhibits considerable potential for high-temperature microwave absorption due to its relatively high melting point and conductivity. In this study, we successfully prepared Ti 3 SiC 2 /Al 2 O 3 -13%TiO 2 heterogeneous coatings through granulation and plasma spraying techniques. This investigation covered composition, microstructure, oxidation resistance, and a focused analysis of the temperature-dependent permittivity of the coatings. The augmentation in Ti 3 SiC 2 content leads to an escalation in the polarized component, consequently elevating susceptibility to dielectric dispersion. With rising temperature, polarization within the coatings gradually establishes, prompting a transition from polarization relaxation loss to conduction loss as the dominant dielectric loss mechanism. At 5 wt% Ti 3 SiC 2 content, the coating achieves an effective bandwidth of 2.2 GHz at 873 K, with a mere 1.4 mm thickness. Moreover, the coating maintains exceptional oxidation resistance below 700 °C. Ti 3 SiC 2 /Al 2 O 3 -13%TiO 2 coatings manifest as strong contenders for high-temperature microwave absorption applications, and plasma spraying emerges as a promising technique for fabricating high-performance microwave absorption coatings.
High entropy alloys (HEAs) show great potential in electromagnetic-wave absorption (EMA), but impedance matching and environmental stability are still difficult problems to solve. Solid-solution strengthening is an effective means to enhance the performances of EMA materials. The multi-element co-penetrated FeCoCrMn HEAs are prepared using urea (CH4N2O) as the multi-element source by a green mechanochemical approach. The phase structure, magnetic properties, corrosion and oxidation resistance, and EMA properties of HEAs are investigated in detail. The results show that the crystal structure of HEAs is significantly altered by multi-element introduction. It is noteworthy that Ms is significantly enhanced on increasing the multi-element co-penetration level. The dielectric loss and magnetic loss of HEAs are significantly enhanced to optimize the impedance matching and attenuation properties, so as to achieve excellent EMA performances. Multi-element co-penetrated FeCoCrMn HEAs achieve a reflection loss (RL) of −59.6 dB at 6.06 GHz while achieving an ultra-wide effective absorption bandwidth (EAB) of 6.86 GHz at 1.32 mm. In addition, HEAs exhibit excellent corrosion resistance, indicating suitability in harsh environments. This study provides a new strategy for the design of highly effective EMA materials.
Ni–Co/ZrO 2 nanocomposite coatings were produced by high-frequency pulse electrodeposition in a modified Watt’s bath containing ZrO 2 particles. The surface morphology, microstructure, and high temperature oxidation resistance of the coatings were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, and isothermal oxidation tests. It was found that the presence of ZrO 2 particles resulted in changes in the morphology and structure of the coatings. The results also confirmed the nanostructure and uniform distribution of ZrO 2 particles of Ni–Co/ZrO 2 nanocomposite coatings. The addition of ZrO 2 did not change the preferred orientation (200), but remarkably affected the relative intensity of planes of Ni–Co alloy. The influence of duty cycle, average current density, and frequency on the amount of incorporated ZrO 2 particles in the Ni–Co/ZrO 2 nanocomposite has been also investigated. The Ni–Co/ZrO 2 nanocomposite coatings with highest ZrO 2 content (11.6 wt%) were prepared under the condition of duty cycle of 40 %, average current density of 5 A dm −2 , and frequency of 100 kHz. Moreover, the embedded ZrO 2 particles significantly improved the high temperature oxidation resistance of Ni–Co alloy coatings. The oxidation rate of Ni–Co/ZrO 2 nanocomposite coatings decreased with increasing the ZrO 2 content of the coatings.
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