Microwave Absorption in the GHz Range of Nanostructure Produced by Disproportionation Reaction of Rare Earth-Iron Compound

对于1- 5GHz频率范围，尖晶石型铁氧体和金属磁性材料都可以用作电磁波吸收剂。然而，因为后者材料具有较大的饱和磁化强度值，它们的Snoek极限处于较高的频率，因此它们的相对复磁导率值在该频率范围内保持较高。因此，可以用金属磁性材料制造更薄的吸收体。导电磁性材料的磁化强度，由电磁波感应，由于涡流损耗而降低。出于这个原因，最好是使用较小的颗粒，相比skindepth，当从这样的材料制造电磁波吸收剂。本文研究了利用Sm_2Fe_3化合物的还原反应<17>制备具有精细α-Fe结构的粉末的可能性，以用作GHz频段的电磁波吸收剂。细α-Fe ...更多信息 Sm_2Fe_2化合物在氢气或空气中分解后分别形成亚微米级的α-Fe/ SmH_2或α-Fe / SmO结构<17>。通过这种方法，获得了具有精细α-Fe结构的磁粉。在氢气气氛中焙烧的粉末，在空气中加热氧化Sm的氢化物，得到α-Fe / SmO两相结构，从而提高粉末的电阻率。用该粉末制备了环形环氧树脂复合材料，并测量了这些样品的微波吸收性能。未纯化的样品在该频率范围内未显示出任何电磁波吸收。然而，纯化的样品（在氢气中在873 K下加热1小时，研磨30分钟，并在空气中在473 K下氧化2小时）表现出电磁波吸收（R.L.在频率（f_m）为0.73 ~ 1.30GHz范围内，吸收体厚度（dm）为13.1 ~ 7.9mm时，吸收体的吸收强度分别小于-20dB。在空气中（473 K加热2 h，球磨30 min）处理的样品也表现出良好的电磁波吸收性能（f_m=-1.21 ~2.50GHz，d_m= 8.0 ~ 4.2GHz）。结果表明，无论是在氢气中还是在空气中，均能有效地制备出具有良好α-Fe结构的粉末，这种粉末可用于工作在几GHz范围内的微波吸收剂。少

For the 1-5 GHz frequency range, both Spinel-type ferrites and metallic magnetic materials can be used as electromagnetic wave absorbers. However, because the latter materials have larger values of saturation magnetization, their Snoek's limit are at a higher frequency and so their values of relative complex permeability remain high in this frequency range. Therefore, it is possible to make thinner absorbers from metallic magnetic materials.The magnetization of electrically conductive magnetic materials, induced by electromagnetic waves, decreases due to eddy current losses. For this reason, it is best to use smaller particles, compared to the skindepth, when making electromagnetic wave absorbers from such materials. In this study, the possibility of using the disproportionation reaction of the Sm_2Fe_<17> compound for the production of powders with a fine α-Fe structure was investigated, for use as electromagnetic wave absorbers that can operate in the GHz frequency range. A fine α-Fe … More / SmH_2 or α-Fe / SmO structure with a sub-micrometer size is formed from the Sm_2Fe_<17> compound after disproportionation in hydrogen or air, respectively. In this way, magnetic powders with a fine structure of α-Fe were obtained. The powders disproportionated in hydrogen, were heated in air in order to oxidize the Sm hydride, to give a α-Fe / SmO two-phase microstructure, and thereby increase the resistivity of the powders. Toroidally shaped epoxy-resin composites were made from this powder, and the microwave absorption properties of these samples were measured. An undisproportionated sample did not show any electromagnetic wave absorption in this frequency range. However, the disproportionated samples (heated in hydrogen at 873 K for 1 hour, milled for 30 minutes and oxidized at 473 K for 2 hours in air) exhibited electromagnetic wave absorption (R.L.< -20dB) in the frequency (f_m) range 0.73 to 1.30 GHz, for absorber thicknesses (dm) ranging from 13.1 to 7.9 mm, respectively. The disproportionated samples in air (heated at 473K for 2 hours and milled for 30 minutes) also showed good electromagnetic wave absorption properties (f_m=-1.21 - 2.50 GHz and d_m= 8.0 - 4.2 GHz). It is concluded that the disproportionation reaction, in either hydrogen or in air, is a useful method for the production of powders with a fine α-Fe structure, which can be used for microwave absorbers that operate in the several GHz range. Less