Rational Construction of Uniform CoNi-Based Core-Shell Microspheres with Tunable Electromagnetic Wave Absorption...

Area of Science:

• Materials Science
• Nanotechnology
• Electromagnetics

Background:

• Core-shell structures with ferromagnetic cores and dielectric shells are crucial for microwave absorption.
• Cobalt-Nickel (CoNi) microspheres are promising candidates but require optimization for broader frequency absorption.
• Dielectric coatings enhance the electromagnetic wave absorption (EMA) properties of ferromagnetic materials.

Purpose of the Study:

• To synthesize and characterize core-shell CoNi@TiO2 composite particles for microwave absorption.
• To investigate the effect of TiO2 coating on the EMA performance of CoNi microspheres.
• To compare the performance of CoNi@TiO2 with CoNi@SiO2 and bare CoNi microspheres.

Main Methods:

• Synthesis of CoNi microspheres using a liquid-phase reduction method.
• Coating CoNi microspheres with titanium dioxide (TiO2) to form core-shell structures.
• Characterization of particle morphology, structure, and electromagnetic properties.

Main Results:

• CoNi@TiO2 core-shell particles with approximately 40 nm TiO2 shells were successfully synthesized.
• CoNi@TiO2 exhibited a maximum reflection loss of 76.6 dB at 3.3 GHz, significantly outperforming bare CoNi (54.4 dB at 17.8 GHz).
• The TiO2 coating shifted the absorption band from Ku to S band and improved impedance matching through polarization effects.

Conclusions:

• CoNi@TiO2 core-shell microspheres demonstrate excellent microwave absorption capabilities.
• The unique core-shell structure and TiO2 dielectric shell contribute to enhanced EMA performance.
• TiO2 shells provide superior protection against particle agglomeration during annealing compared to SiO2, leading to better absorption.