Microwave absorbing materials, also known as radar absorbing materials or radar stealth materials, are materials that can absorb microwave and electromagnetic energy while reducing reflection and scattering. The basic principle is to convert microwave energy into other forms of energy through physical actions, and convert it into thermal energy through energy dissipation. The absorption mechanism can be achieved through electrical induction, magnetic induction, electromagnetic induction, and electromagnetic scattering.
According to different applications and working principles, microwave absorbing materials can be classified into coating type, patch type, structural type, interference type, and absorption type.
The coated microwave absorbing material is generally made of polymer solution or lotion as the base material and added with an absorbent. The widely used coatings currently mainly include absorbents such as ferrite, iron and its alloy micro powders. This material is easy to construct and has a low cost. While it is suitable for complex shaped objects, it may affect the aerodynamic characteristics of the equipment.
Surface mount microwave absorbing materials achieve absorption function through surface mount. The materials for surface mount include rubber sheets, ceramic sheets, plastic sheets, etc. Although patch type materials can achieve complex structural designs, they are not very suitable for complex shapes.
Structural microwave absorbing materials are made by using non-metallic composite materials as carriers and adding absorbers. Common matrix materials include epoxy resin and thermoplastic materials, while absorbents include ferrite, graphite, and carbon black. This material not only reduces the scattering of electromagnetic waves, but also has a certain strength and stiffness, and is relatively lightweight.
Interference type microwave absorbing materials mainly rely on the interference of electromagnetic waves to achieve absorption effects, by reversing the phase of the incident electromagnetic wave and the reflected electromagnetic wave (with a phase difference of 180 °), thereby canceling each other out. This material has the characteristic of a narrow frequency range, can be used at high frequencies, and can be manufactured into thinner materials.
Absorption type microwave absorbing materials utilize the dielectric and magnetic losses in objects to convert incident electromagnetic wave energy into thermal energy or other forms of energy. Absorption materials are mainly divided into two categories: electrical loss materials and magnetic loss materials. Among them, electrical loss materials are more suitable for absorbing high frequencies, while magnetic loss materials are more suitable for absorbing low frequencies. By combining these two materials, absorbing materials with a wide frequency range can be manufactured. Electric loss type microwave absorbing materials are usually based on carbon powder or metal particles, and the gradient dielectric properties of absorbing materials are achieved by adjusting the thickness, depth, and filler type. Magnetic loss type microwave absorbing materials achieve their absorption effect by filling them with magnetic materials such as iron.
In summary, microwave absorbing materials have important application value in absorbing microwave and electromagnetic energy. According to different needs and working principles, suitable coating type, patch type, structural type, interference type or absorption type microwave absorbing materials can be selected.
