Hello everyone, I am the editor. Today, I will introduce the absorbing materials to you. The following content is organized by the editor, and the relevant content is for reference.
There are many absorbing materials nowadays, and there are different types, scopes and effects of use. But when the family owner was choosing, he didn't even understand the basic types of materials and didn't know how to choose. But if you have troubles in this regard, you can look at the following introduction to understand what the absorbing materials are, and then look at what the absorbing materials are, and find products that are more in line with your expectations.
What are the absorbing materials
Wave absorbing materials can be selected from wedge-shaped absorbing materials, single-layer flat-shaped, double-layer or multi-layer flat-shaped, coating-shaped and other materials.
1, the wedge shape
The absorber used in the microwave anechoic chamber is often made into a wedge shape (the shape of a tower of gold), which is mainly composed of polyurethane foam type, non-woven fabric flame-retardant type, and silicate plate metal film assembly type. As the frequency decreases (wavelength increases), the length of the absorber also increases greatly. The ordinary wedge-shaped absorber has an approximate relationship of L/λ≈1, so at 100MHz, the wedge length reaches 3000mm, which is not only difficult to achieve in the process , And the effective available space of the microwave anechoic chamber is also greatly reduced.
2. Single layer flat shape
The first absorber developed abroad is a single-layer flat plate, and the absorber made later is directly attached to the metal shielding layer, which is thin in thickness and light in weight, but has a narrow working frequency range.
3. Double or multilayer flat shape
This kind of absorber can work in a wide operating frequency range and can be made into any shape. For example, NEC Corporation of Japan disperses ferrite and short metal fibers evenly in a suitable organic polymer resin to make composite materials, and the working frequency band can be expanded by 40% to 50%. Its disadvantages are large thickness, complicated process and high cost.
4. Coating shape
Only coating-type absorbing materials can be used on the surface of the aircraft, which broaden the frequency band, and generally use composite coatings. For example, when the thickness of the lithium cadmium ferrite coating is 2.5mm～5mm, it can attenuate 8.5dB in the centimeter band; when the thickness of the spinel ferrite coating is 2.5mm, it can attenuate 24dB at 9GHz; ferrite When the thickness of the neoprene coating on the body is 1.7mm～2.5mm, the attenuation is about 30dB at 5GHz～10GHz.
5. Structural shape
Incorporating absorbing materials into engineering plastics makes them have both absorbing characteristics and load-bearing capacity, which is a direction for the development of absorbing materials.
Nowadays, in order to further improve the performance of absorbent materials, several complex types of absorbent bodies with combinations of shapes have been developed abroad. For example, a microwave anechoic chamber made of this type of absorber in Japan has performances: 136MHz, 25dB; 300MHz, 30dB; 500MHz, 40dB; 1GHz-40GHz, 45dB.
What is the absorbing material
Electromagnetic radiation causes direct and indirect damage to the human body through thermal, non-thermal, and cumulative effects. Studies have confirmed that ferrite absorbing materials have the best performance, which has the characteristics of high absorption frequency band, high absorption rate, and thin matching thickness. Applying this material to electronic equipment can absorb leaked electromagnetic radiation and achieve the purpose of eliminating electromagnetic interference. According to the law of electromagnetic waves propagating in the medium from low magnetic to high magnetic permeability, high magnetic permeability ferrite is used to guide electromagnetic waves, through resonance, a large amount of radiant energy of electromagnetic waves is absorbed, and then the energy of electromagnetic waves is converted into heat energy through coupling.
Two issues should be considered when designing the absorbing material
1) When electromagnetic waves encounter the surface of the absorbing material, pass through the surface as much as possible to reduce reflection;
2) When the electromagnetic wave enters the inside of the absorbing material, the energy of the electromagnetic wave should be lost as much as possible;