RFI门禁读卡器铁氧体吸波材料中英对照

铁氧体吸波材料在高频上可以用于RFID读卡器或者门禁读卡器在受到金属干扰情况下的防护与隔离作用，使之提升读写性能完善产品性能
厚度0.1-0.5，导磁率150，供应厂家：深圳市兆荣软磁材料有限公司

铁氧体吸收材料是利用铁氧体磁损耗对电磁波进行吸收的原理制成的材料。比其它介质的吸收材料具有频率高、频带宽、厚度等优点。把铁氧体软磁材料用作吸波材料，常用的有锰锌、镍铜锌、镁铜锌、镍镁锌以及平面型六角晶系的频软磁铁氧体等由它们制成的吸收体，磁导率可在150-280间变化，频率由几MHz直至微波频段(100GHz)，厚度0.1～50mm。常把铁氧体(烧结温度宜采取损耗增大的高温区)粉末与氯丁橡胶、泡沫塑料等混合，制成带状、瓦状、海绵状吸收体，或直接用粉末涂敷。主要用于制作电波暗室吸收壁、微波系统匹配负载.

当电磁波入射到铁氧体吸波材料表面时，由于介质的共振吸收和极化损耗，电磁波被吸收导致其衰减或者消失， 这种将电磁波能量转换为热能或其他能量的材料称为铁氧体吸波材料。铁氧体具介电损耗和磁损耗。铁氧体吸波材料电磁特性的两个基本参数复磁导率 (μ) 和复介电常数 (ε)，其复数形式：ε = ε′ - jε″ μ = μ′ - jμ″实部 ε′代表吸波材料在交变电场作用下发生的极化程度，表征储存电荷或能量的能力；虚部 ε″为材料在交变场下，材料电偶极矩发生重排引起能量损耗的量度；实部 μ′代表吸波材料在外加磁场作用下发生极化或者磁化的程度，虚部 μ″代表材料磁偶矩发生重排引起的损耗量度。因此，磁导率和电导率的虚部μ″和ε″ 共同决定着材料的吸波性能，因此我们期望制备的铁氧体材料具有较大的介电常数和磁导率虚部。通常铁氧体具备较大的 ε″和 μ″值，且价格低廉、吸收频段高、 匹配厚度薄和吸收，因此在微波吸收领域有着广泛的应用。
铁氧体的粒径对其吸波性能有着重要影响。相对于微米级的铁氧体材料，纳米尺寸的铁氧体吸收能力更强，频带更宽。在一定范围内，随粒径的减小，铁氧体材料的吸收能力增强。在传统的铁氧体吸波频带和吸收能力受限的情况下，通过改变铁氧体材料的颗粒尺寸，制备超细铁氧体粉来改变其电磁吸收性能。
铁氧体的形貌一般可分为针状、棒状、片状、 球状等，与制备方法和工艺条件有关。材料的电磁性能很大程度上依赖于自身的微结构。改变铁氧体的制备方法及改进工艺条件等来获取不同形貌的铁氧体材料都是为了获得更好的电磁性能。
针状铁氧体不易成形，易团聚，性能上没有片状、球状的铁氧体优良，相关研究不多。棒状铁氧体，具有一定的各向异性，磁性能比针状铁氧体有 了很大提高，特别是纳米级的棒状铁氧体。片状结构是电磁吸波材料的形状，六方晶系磁铅石型铁氧体是性能的吸波材料，既具有片状结构，又有较高的磁损耗正切角，还具有较高的磁晶各向异性等效场。片状铁氧体材料具有很好的应用前景。铁氧体的饱和磁化强度和磁晶各向异性与其晶体结构有很大关系，晶体结构不同导致畴壁共振和自然共振的效果不同，进而对吸波性能产生很大影响，并且单一结构的铁氧体能力有限。铁氧体材料按其晶体结构划分，大致可以分为立方晶系尖晶石型、石榴石型和六角晶系磁铅石型三个主要系列。它们的晶体结构各不相同，性能差别也较大。它们的静磁性和不同微波频率下的电磁特性各有特点，在吸波领域中的应用范围也各不相同。
纳米化：铁氧体颗粒为纳米尺寸时，会出现小尺寸效应、宏观隧道效应、表面效应和量子尺寸效应， 在一定程度上增加其对电磁波的衰减能力，显著提高铁氧体的微波吸收能力；复合化：将铁氧体磁性材料与其他材料如碳纳米管、石墨烯、导电聚合物、金属粉末复合，使铁氧体复合材料介电电损耗增加，同时兼具磁损耗，可以优势互补，复合材料的吸波性能显著提高；控制形貌：铁氧体形貌对铁氧体性能有着重要的影响。对多孔或者空心铁氧体比较关注，这也是其未来的一个重要研究方向；薄膜化：铁氧体薄膜具有较高的磁晶各向异性及合适的饱和磁化强度，相对于粉体材料，其质轻、厚度薄。Ferrite absorbing material is made of the principle of absorbing electromagnetic wave by ferrite magnetic loss. Compared with other absorbing materials, it has the advantages of high frequency, wide frequency band and thickness. The ferrite soft magnetic material is used as the microwave absorbing material. The commonly used absorbers are manganese zinc, nickel copper zinc, magnesium copper zinc, nickel magnesium zinc, and plane type hexagonal ultra-high frequency soft magnetic ferrite, which are made of them. The permeability can vary between 150-280, the frequency is from several MHz to 100 GHz, and the thickness is 0.1-50 mm. The ferrite (sintered temperature should be used in the high temperature area where the loss is increased) is mixed with neoprene and foam plastics to form banded, tile like, sponge like absorbers, or directly coated with powder. Mainly used for making anechoic chamber absorption wall, microwave system matching load
When the electromagnetic wave is incident on the surface of the ferrite absorbing material, due to the resonance absorption and polarization loss of the medium, the electromagnetic wave is absorbed and causes its attenuation or disappearance. The material that converts the electromagnetic wave energy into heat energy or other energy is called ferrite absorbing material. Ferrite has dielectric loss and magnetic loss. The complex permittivity (ε) and the complex permittivity (ε) are the two basic parameters of the electromagnetic properties of the ferrite absorbing materials. In the complex form, ε = ε '- J ε ″ μ = μ' - J μ ″ the real part ε 'represents the polarization degree of the absorbing materials under the action of the alternating electric field and the ability to store the electric charge or energy; the imaginary part ε "is the measurement of the energy loss caused by the rearrangement of the electric dipole moment of the material in the alternating field; the real part μ 'represents the polarization or magnetization degree of the absorbing material under the action of the external magnetic field, and the virtual part μ" represents the loss measurement caused by the rearrangement of the magnetic couple moment of the material. Therefore, the virtual part μ "and ε" of the permeability and conductivity together determine the microwave absorption performance of the material. Therefore, we expect the ferrite material to have a larger dielectric constant and virtual part of the permeability. Generally, ferrites have large values of ε "and μ", low price, high absorption band, thin matching thickness and high absorption efficiency, so they are widely used in microwave absorption field.
The particle size of ferrite has an important influence on its microwave absorbing performance. Compared with micro ferrite, nano ferrite has stronger absorption capacity and wider frequency band. In a certain range, with the decrease of particle size, the absorption capacity of ferrite material increases. Under the condition that the traditional absorption band and absorption capacity of ferrite are limited, the electromagnetic absorption performance of ferrite material can be changed by changing the particle size and preparing ultrafine ferrite powder.
The morphology of ferrite can be generally divided into needle, rod, flake, ball and so on, which is related to the preparation method and process conditions. The electromagnetic properties of materials depend on their microstructure to a great extent. In order to obtain better electromagnetic properties, we need to change the preparation method of ferrite and improve the process conditions to obtain different ferrite materials.
Acicular ferrite is not easy to form and agglomerate, and its properties are not as good as those of flaky and spherical ferrite. The magnetic properties of rod ferrite are much higher than that of needle ferrite, especially the nanometer rod ferrite. The lamellar structure is the shape of electromagnetic absorbing material. The hexagonal lead ferrite is a kind of absorbing material, which has not only lamellar structure, but also high tangent angle of magnetic loss and high equivalent field of magnetocrystalline anisotropy. The flaky ferrite material has a good application prospect. The saturation magnetization and magnetocrystalline anisotropy of ferrite have a great relationship with its crystal structure. Different crystal structures lead to different effects of domain wall resonance and natural resonance, which have a great influence on the absorption performance, and the ferrite with a single structure has a limited ability. According to its crystal structure, ferrite materials can be roughly divided into three main series: cubic spinel type, garnet type and hexagonal magnetoplumbite type. They have different crystal structures and different properties. Their magnetostatics and electromagnetic properties at different microwave frequencies have their own characteristics, and their application ranges in the field of microwave absorption are also different.
Nano scale: when the ferrite particles are nano scale, there will be small size effect, macro tunnel effect, surface effect and quantum size effect, To a certain extent, it can increase its attenuation ability to electromagnetic wave and significantly improve the microwave absorption ability of ferrite; compounding: compounding ferrite magnetic materials with other materials such as carbon nanotubes, graphene, conductive polymer and metal powder, so as to increase the dielectric loss of ferrite composite materials, at the same time, it has both magnetic loss and complementary advantages. The microwave absorption performance of composite materials is significant Improve; control morphology: ferrite shape has an important influence on the performance of ferrite. More attention is paid to porous or hollow ferrite, which is also an important research direction in the future; Filmization: ferrite film has high magnetocrystalline anisotropy and appropriate saturation magnetization, compared with powder material, its quality is light and thickness is thin.