Radar stealth technology mainly refers to the stealth technology of radar working in the range of 3MHz ~ 300GHz, in which the centimeter band (2 ~ 18GHz) is a very important radar detection band, and it is also the research of ultra-wideband radar stealth technology that countries all over the world strive to break through at the present stage. the key of. With the development of radar detection technology and the target shape technology are more and more limited by tactical indicators, the original radar stealth materials have shortcomings such as narrow frequency band, low efficiency and high density. The application range is limited, and it is urgent to develop new suction. Wave materials and corresponding stealth techniques. At present, at home and abroad, while further improving and improving the performance of traditional stealth materials, we are working on a variety of new materials. Carbon nanotube materials, conductive polymer materials, and nanomaterials are gradually applied to radar wave stealth materials to meet the requirements. The new generation of radar stealth materials absorbs strong, frequency bandwidth, light weight and thin thickness.
2. Conductive polymer absorbing materialThe conductive fiber is blended into the conventional powder absorbent, which can greatly improve the absorbing properties of the material. The blending amount of the conductive fibers has an optimum value. Broadband radar absorbing materials can be made by appropriate matching. However, the obtained material has poor absorbing effect in the low frequency band. How to solve the radar absorbing performance of the low frequency band material should be further explored and verified. Due to the low density of the conductive polymer and good medium and low temperature performance, it has been widely studied and applied in recent years. Krishadham et al. studied polyphenylacetylene, polyacetylene and p-phenylene-benzobisthiophene conductive polymer absorbing materials doped with iodine by chemical or ion implantation, and the polymer monolayer was prepared by doping. The wave coating has a reflection attenuation of -15 dB and an absorption bandwidth of up to 3 GHz. The polypyrrole, polyaniline, and poly-3-octylthiophene studied by Oldedo et al. have an absorption rate of 8 dB or more in the 3 cm band. TruongVT et al. studied a absorbing material with a thickness of 2.5 mm and containing 2% polypyrrole, which has a reflectance of less than -10 dB at 12 to 18 GHz. Kong Deming et al. doped polyaniline (PAn) and FeCl3 with hydrochloric acid. The doped H2SO4-PAn was mixed in a certain ratio and tested in the frequency range of 8 to 14 GHz. The average attenuation of the absorbing material in the frequency range of 3.66 GHz was 13.37 dB, and the maximum attenuation was 26.70 dB.
3. Magnetic particle-based absorbing materialsMagnetic particle-based absorbing materials mostly have high magnetic loss tangent angles, mainly relying on polarization attenuation such as hysteresis loss, domain wall resonance and aftereffect loss to absorb electromagnetic waves. Common ferrite, metal micropowder, polycrystalline iron Fiber, etc. Ferrite is the earliest mature absorbing material, mainly nickel-zinc ferrite, manganese-zinc ferrite and lanthanide ferrite. Its absorbing mechanism is the natural resonance of magnetic domains. The ferrite is divided into a spinel type, a garnet type and a magnetoplumbite type. Among them, the hexagonal crystal sheet magnetoplumbite type has the best absorbing property, and the hexagonal crystal sheet magnetite type ferrite is used. It has a high magnetic anisotropy equivalent field, and its natural resonance frequency is high, showing excellent high frequency absorbing properties. The hexagonal crystal ferrite absorbing material prepared by MeshramMR and the like has a maximum absorption of 16.5 dB and a minimum absorption of 8 dB in the frequency range of 8 to 12 GHz. Zhang Yongjing et al. prepared a ferrite absorber with a thickness of 2 mm and an areal density of 5 kg/m2, and the absorption rate in the range of 8 to 18 GHz was greater than 10 dB. In addition, due to the large specific surface area of ​​the nano-ferrite particles, the surface atomic band structure is different from that in the body, and has a high coercive force, which can cause absorbing mechanisms such as hysteresis loss, interfacial polarization and multiple scattering; The size is much smaller than the wavelength of electromagnetic waves, and the transmittance of electromagnetic waves is much higher than that of general absorbing materials. Ruan et al. found that the maximum reflectance of a ferrite sample with a particle size of 5 μm is -17 dB, the bandwidth with a reflectance of less than -10 dB is 3.5 GHz, and the maximum reflectance of a ferrite sample with a particle size of 65 nm is -28.5 dB. The bandwidth with a reflectivity of less than -10 dB is up to 5 GHz. Huang Xixia et al. studied the effect of particle size of Fe3O4 on the electromagnetic wave absorption efficiency in the frequency range of 1 to 1000 MHz. The results show that the smaller the particle size of nano-scale Fe3O4, the higher the absorbing efficiency. Magnetic metal micropowder is a kind of absorbing material with both free electron absorbing and magnetic loss. It mainly contains fine powders such as cobalt, nickel, cobalt-nickel alloy, iron-nickel alloy, aluminum-nickel alloy and various organic modified metals. The famous F/A-18c/D "Hornet" stealth aircraft uses carbonyl iron micro-powder absorbing materials. The magnetic metal micropowder has high magnetic permeability and good temperature stability, but its anti-aging, acid and alkali resistance, and spectral characteristics are poor. Polycrystalline iron fibers have strong eddy current loss, hysteresis loss and dielectric loss. As a good conductor of polycrystalline iron fiber, when there is an external alternating electric field, the free electrons in the fiber oscillate and generate an oscillating current, which converts part of the electromagnetic wave energy into heat energy. The polycrystalline iron fiber absorbing coating developed by 3M Company of the United States can attenuate 30dB in the 5-16 GHz band. The combination of conductive polymer and magnetic particles takes into account the dielectric and magnetic loss absorbing characteristics. Although some progress has been made, there are still some shortcomings. To develop a conductive high polymer/magnetic particle composite absorbing material with light weight, strong absorption, wide frequency, adjustable electromagnetic parameters and good comprehensive performance, further research is needed in the following aspects: 1 combination of macro and micro Discuss the absorbing mechanism of conductive high polymer/magnetic particle composite; 2Select and optimize the size and type of materials; 3Prepare the process and technology of composite absorbing materials.
4. Broadband lightweight conductive polymer absorbing materialAC Contactor switch mainly used for making or breaking circuit at a long distance, suitable for controlling starting\stopping\reversing of AC motor. AC Contactor of korlen conforms to the requirement of IEC60947-4-1& GB14048.4 standards.
Except AC Contactor, there are many different types of low voltage electric appliances, such as Thermal Relay,Manual Motor Startor ,led light, Circuit Breaker, etc.
AC Contactor,Magnetic Contactor,Wafer Style Valve
Wenzhou Korlen Electric Appliances Co., Ltd. , https://www.korlen-electric.com