There is a certain wave absorbing material in the shielding box, so it can produce a certain effect. Is the wave absorbing material the same? In fact, absorbing materials can be roughly classified into the following categories according to their loss mechanisms:
First, resistive loss. Its absorption mechanism is related to the conductivity of the material, that is, the greater the conductivity, the greater the macro current (including the electric field caused by the change of the electric field and the eddy current caused by the change of the magnetic field) caused by carriers, and thus is conducive to the conversion of electromagnetic energy into heat energy.
Second, the dielectric loss. It is a kind of electrode-related dielectric loss absorption mechanism, that is, through the "rubbing" effect caused by the repeated polarization of the medium, the electromagnetic energy is converted into heat to dissipate energy. The dielectric polarization processes include: the shift polarization of the electron cloud, the polarization of the electrical polarity of the polar medium, the steering polarization of the electric iron domain, and the wall displacement.
Third, magnetic loss. This type of absorption mechanism is a type of magnetic loss associated with the dynamic magnetization process of ferromagnetic media. Such losses can be categorized into hysteresis loss, vortex eddy current, damping loss, and post-magnetic effects. Its main source is magnetic domain steering, magnetic domain wall displacement, and magnetic domain natural resonance similar to the hysteresis mechanism. In addition, the latest nanomaterials microwave loss mechanism is a hot spot for today's wave absorbing material analysis.
With the development of modern science and technology, the impact of electromagnetic radiation on the environment is increasing. In airports and planes, flights are delayed due to electromagnetic wave interference. In hospitals and mobile phones, they often interfere with the normal work of various electronic diagnostic and therapeutic equipment. Therefore, to control electromagnetic pollution and find a material that can withstand and weaken the radiation of electromagnetic waves, wave-absorbing materials, has become a major issue in materials science.
2018-03-29