Wave-absorbing material is a class of materials that can absorb the energy of electromagnetic waves projected onto its surface.In engineering application, the requirements of wave absorption material are very high, in addition to the wave absorption material in a wider frequency band of electromagnetic waves has a high absorption rate, but also requires it to have light quality, temperature resistance, humidity resistance, corrosion resistance and other properties. With the development of modern science and technology, the influence of electromagnetic wave radiation on the environment is increasing.At the airport, due to electromagnetic interference, mobile phones often interfere with the normal operation of various electronic medical instruments.Therefore, it has become a major topic of material science to find a material of electromagnetic pollution that can resist and weaken the electromagnetic wave radiation. Electromagnetic radiation causes direct and indirect damage to the human body through thermal effect, non-thermal effect and cumulative effect.Research have confirmed that ferrite absorption material has excellent performance, which has the characteristics of high absorption frequency band, high absorption rate and thin matching thickness.Using this material in electronic equipment can eliminate electromagnetic interference.According to the law of electromagnetic wave propagation in the medium from low magnetic orientation to high magnetic conductivity direction, the high magnetic conductivity ferrite is used to guide the electromagnetic wave, absorb a large amount of radiation energy of electromagnetic wave through resonance, and then convert the energy of electromagnetic wave into heat energy through coupling.
The loss mechanism of wave-absorbing materials can be roughly divided into the following categories:
1 Resistance loss Such absorption mechanism and the conductivity of the material, that is, the larger the conductivity, the greater the macroscopic current caused by the carrier (including the current caused by the electric field change and the vortex caused by the magnetic field change), which is conducive to the conversion of electromagnetic energy into thermal energy.
2 Dielectric loss It is a kind of dielectric loss absorption mechanism related to the electrode, that is, through the “friction” generated by the electromagnetic energy into thermal energy dissipation.The dielectric polarization process includes: electronic cloud displacement polarization, polar dielectric moment steering polarization, electroferroelectric domain steering polarization and wall displacement.
3 Magnetic loss Such absorption mechanism is a kind of magnetic loss related to the dynamic magnetization process of ferromagnetic media, which can be refined into: hysteresis loss, magnetic vortex current, damping loss and magnetic aftereffect effect. Its main sources are magnetic domain steering, magnetic domain wall displacement and magnetic domain natural resonance similar to the magnetic hysteresis mechanism.In addition, the microwave loss mechanism of nanomaterials is a hot spot in the analysis of wave-absorbing materials today.
