With the rapid advancement of modern science and technology, the environmental impact of electromagnetic radiation has become increasingly significant. At airports, aircraft takeoffs can be delayed or even prevented due to electromagnetic interference. In hospitals, mobile phones often disrupt the operation of sensitive electronic medical equipment. As a result, controlling electromagnetic pollution has become a critical challenge in materials science, driving the need for materials capable of absorbing and reducing electromagnetic radiation.
Absorbing materials are designed to capture the energy of electromagnetic waves that strike their surface. In practical applications, these materials must not only exhibit high absorption rates across a wide frequency range but also possess desirable properties such as low weight, heat resistance, moisture resistance, and corrosion resistance. These characteristics make them suitable for use in various industries and environments.
The development of electromagnetic wave absorbing materials dates back to World War II, when countries like the United States, Britain, and Germany conducted extensive research for military purposes, including radar detection and counter-reconnaissance. In the 1960s, the U.S. began using such materials in fighter jets like the F-14, F-15, F-18, and the stealth aircraft F-117. Since the 1980s, global efforts have intensified, with many nations investing heavily in research. With the growth of telecommunications, absorbing materials have found new applications in communication systems, environmental protection, and human safety.
Electromagnetic radiation can harm the human body through thermal effects, non-thermal effects, and cumulative exposure. Ferrite-based absorbing materials are known for their superior performance, offering a broad absorption band, high absorption efficiency, and thin matching thickness. When applied to electronic devices, they can effectively absorb leaked electromagnetic radiation, reducing electromagnetic interference. These materials work by guiding electromagnetic waves toward regions of high magnetic permeability, where resonance and coupling convert the wave energy into heat.
In urban areas, tall buildings reflect electromagnetic waves, creating signal dead zones. Applying absorbing materials to building structures can help mitigate this issue. Microwave chambers made from these materials are widely used in radar systems, communications, and aerospace. Additionally, they play a vital role in enhancing the compatibility of airborne radar systems and improving overall system performance.
On radar targets, absorbing materials are used to reduce the effective radar cross-section of weapons, making them harder to detect by enemy radars. This enhances the effectiveness of anti-radar strategies and provides an advantage in combat against infrared-guided missiles and laser weapons. Absorbing materials are also useful for airport navigation equipment, such as landing lights, mast structures, submarine periscopes, and ventilation ducts.
By incorporating absorbing materials into consumer electronics like TVs, stereos, computers, smartphones, and microwave ovens, electromagnetic leakage can be reduced to safe levels (below 10 microwatts per square centimeter), ensuring public health and safety. They are also essential in protecting operators of high-power radar systems, medical devices, and microwave breakers from harmful electromagnetic exposure.
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