With the rapid advancement of modern science and technology, the impact of electromagnetic radiation on the environment has become increasingly significant. In airports, aircraft takeoffs can be disrupted by electromagnetic interference, while in hospitals, mobile phones often interfere with sensitive medical equipment. As a result, controlling electromagnetic pollution and developing materials capable of absorbing and reducing electromagnetic radiation have become key challenges in the field of materials science.
Absorbing materials are designed to capture and dissipate 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 be lightweight, heat-resistant, moisture-proof, and resistant to corrosion. These properties make them highly versatile for various industries.
During World War II, countries like the United States, Britain, and Germany began extensive research into electromagnetic wave-absorbing materials for military purposes, such as radar detection and counter-detection. In the 1960s, the U.S. incorporated these materials into fighter jets like the F-14, F-15, F-18, and the stealth aircraft F-117. Since the 1980s, global efforts to develop advanced absorbing materials have intensified. With the growth of telecommunications, these materials have found 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. Studies have shown that ferrite-based absorbing materials offer the best performance, with features such as a broad absorption band, high absorption efficiency, and a thin matching thickness. When applied to electronic devices, they can effectively absorb leaked electromagnetic radiation, reducing interference and ensuring safer operation.
In urban areas, high-rise buildings reflect electromagnetic waves, creating signal "shadows." Applying absorbing materials to building surfaces can help mitigate this issue. Microwave chambers made from such materials are widely used in radar, communications, and aerospace applications. Additionally, these materials play a crucial role in improving the compatibility of airborne radar systems and enhancing overall system performance.
On the surface of radar targets, absorbing materials are used to reduce the effective radar cross-section of weapons, making it easier for them to bypass enemy radar defenses. This serves as an effective countermeasure against radar reconnaissance and is also useful in defending against infrared-guided missiles and laser weapons. Absorbing materials are also applied to airport navigation equipment, such as landing lights, masts, and submarine periscopes.
By incorporating absorbing materials into consumer electronics like TVs, stereos, computers, and mobile phones, electromagnetic leakage can be reduced to safe levels—below 10 microwatts per square centimeter. This helps protect public health. These materials are also essential in high-power systems like radar, medical microwave devices, and microwave breakers to safeguard operators from harmful radiation exposure.
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