纳米复合材料外文翻译

浙江师范大学生化学院本科毕业设计(论文)外文翻译译文1-Fe-Fe3B-Y2O3纳米复合材料在千兆赫范围内的电磁微波吸收性能刘九荣a、伊藤正博a、Ken-ichi Machidaaa大阪大学尖端科学技术合作研究中心吹田市, 大阪565-0871,日本接到于2003年2月24日，2003年9月8日录用摘要:-Fe-Fe3B-Y2O3 纳米复合材料采用熔体纺技术研发，其电磁微波吸收性能在0.05-20.05 GHz范围内。与-Fe/Y2O3复合物相比，-Fe-Fe3B-Y2O3的共振频率转移到一个较高的频率范围，这归因于四方-Fe3B的大各向异性场HA（0.4 MA/m）。其相对介电常数（）一直在低于0.5-10 GHz的地区，这表明复合粉体具有高电阻率（）。含质量分数80 %，厚度6-3 mm的-Fe-Fe3B-Y2O3粉末的树脂复合材料分别在2.7-6.5 GHz频率范围内获得有效的电磁微波吸收（反射损耗-20 dB）。在吸收体厚度4 mm、4.5 GHz条件下观察到最低反射损耗为-33 dB。关键词：-Fe-Fe3B-Y2O3纳米复合材料； 电磁微波； 吸收性能1. 引言最近，就业通信设备使用的电磁波范围为1-6 GHz，（包括移动电话，智能交通系统，电子收费系统和局域网络系统）已经飞速发展。因此，严重的电磁干扰问题已经恶化。对这些问题的关注，促使研究抗电磁干扰涂层的电磁波吸收材料、自我隐身技术以及运用于民用和军用的微波暗室。材料的复磁导率（）和复介电常数（）决定了反射和衰减电磁波的吸收特性。对磁性电磁波吸收剂来说，吸收厚度（dm）和磁损耗()之间有如下关系：根据方程式（1）： （1） 其中，c表示光速，fm表示相匹配的频率。金属磁性材料有高的饱和磁化率和在高频率处有Snoeks限1-3。因此，在如此高的频率范围，他们的复磁导率仍保持在高位值。所以，有可能从这些材料中制备薄的吸收剂。然而，这些材料磁化的减少是由于涡流损耗引起的电磁波。因为这个原因，最好使用那些绝缘材料孤立的较小微粒。杉本等人已经报道了-Fe/SmO复合物在0.73-1.3 GHz范围内具有良好的电磁微波吸收特性，其来源于通过传统电弧熔炼技术制备的一种稀土金属间化合物Sm2Fe174,5。我们也已经报道了通过熔炼技术制备的-Fe/Y2O3复合物在2.0-3.5 GHz范围内表现出良好的电磁微波吸收特性，这归因于-Fe的细粒度（约20 nm）6。磁性稀土纳米复合材料，比如Fe3B/Nd2Fe14B，已经被当作高性能磁铁，这可能是通过退火非晶熔纺带制造的7,8。纳米复合材料的微观结构强烈依赖于退火温度和时间以及合金成分。本研究的目的是探讨由Fe3B/Nd2Fe14B制备的-Fe-Fe3B-Y2O3纳米复合材料的电磁波吸收特性，并与-Fe/Y2O3作比较。2. 实验步骤2.1 材料准备Y5Fe77.5B17.5的三元合金锭第一次通过在氩气流下感应熔化铱、铁、硼三种金属（纯度大于99.9 %）被制备出来。通过在单辊快淬设备，在轧辊表面以20米/秒的速度，使用早期锭为起始原料制备出1.5毫米宽、约30毫米厚度的非晶态合金带Y5Fe77.5B17.5。球磨之后，粒子尺寸2-4毫米的粉末在氦气流下被加热到953 K，以每分钟40 K的加热速度加热10分钟。在随后的2小时573 K的氧气流中加热，结合成粉末并通过XRD表征。在高分辨率的扫描电子显微镜（HITACHI S-5000）观察到微观结构。2.2 特性通过均匀混合含20 wt%环氧树脂的复合粉末制备环氧树脂复合材料，并把它压成圆柱形压块。这些压块在453 K下加热30分钟被加工处理，然后切成外径7.00毫米和内径3.04毫米的环形试样。通过使用惠普8720B网络矢量分析仪测量环形试样的散射参数（S11，S21）。相对渗透率和电容率值取决于在0.05-20.05 GHz频率范围内测量的散射参量。根据以下方程，在给定频率、吸收厚度的相对渗透率和电容率的条件下计算出反射损耗曲线。 （2） （3）其中，f 表示电磁微波的频率，d 表示吸收剂的厚度，c 表示光速，Z0 表示空气的阻抗，Zin 表示吸收器的输入阻抗。3. 结果与讨论3.1 结构特征 图1表示典型的X射线衍射非晶态Y5Fe77.5B17.5粉末衍射图：（a）直接获得，（b）在氦气流953 K热处理10分钟后，（c）在氧气流573 K不成比例氧化样品（b）2 h后。从图1（a）可以发现，用熔纺技术制备的Y5Fe77.5B17.5合金粉末是非晶态的。图1（b）是经过热处理的，其粉末是由Fe3B和Y2Fe14B两相物质组成的。经不规则氧化后，Y2Fe14B相消失了。图1（b）的X射线衍射图与图1（c）的作比较，我们看到Fe3B的主要峰值强度（2=44.5），这只是-Fe的一个主要峰值（110），其比氧化后的强。这个结果表明-Fe的形成是因为把Y2Fe14B氧化成-Fe，Fe3B和Y2O3纳米粒子。但是从图1（c）中没有观察到Y2O3的峰；其原因可能是Y2O3粒子尺寸太小以至于没有被检测到。通过使用罗谢勒公式，决定从X射线衍射峰的扩大线确定Fe3B和-Fe的晶体尺寸大约30 nm。这个测量结果同高分辨率扫描电子显微镜的一致。频率依赖于树脂复合材料的相对介电常数，包括如图2（a）中含80 %的-Fe/Fe3B/Y2O3粉末。相对介电常数的实部（）和虚部（）在大于0.5-10 GHz范围几乎是常数，因此相对介电常数（）显示几乎是常数（），（）。这个发现暗示是高电阻率的复合材料。-Fe/Fe3B/Y2O3复合物的电阻率值测出来大约100 m，但是Nd2Fe14B化合物的电阻率被报道出来为1.410-6 m9。高电阻率纳米复合材料被认为是Fe3B，-Fe和Y2O3粉末的组分。氧化钇被嵌入Fe3B和-Fe之间，起着绝缘体的作用。3.2 电磁微波 相对磁导率的实部（）和虚部（）在图2（b）绘制出了一个频率的函数。相对磁导率的实部随着频率从1.6下降到0.9。然而，相对磁导率的虚部在大于1-7.1 GHz范围从0.1增加到0.6，然后在较高的频率范围内下降。相对磁导率的虚部在一个宽频率范围（2-9 GHz）呈现一个峰。在图2（b）中，与-Fe/Y2O3 作比较，-Fe/Fe3B/Y2O3复合物的磁导率的实部和虚部呈现一个较低值。这些较低值归因于Fe3B的磁化比-Fe的小。因此，-Fe/Fe3B/Y2O3比a-Fe/Y2O3有一个比较小的相对磁导率，是-Fe与Fe3B相互作用的效果。然而，-Fe/Fe3B/Y2O3磁导率虚部曲线上的极大点转移到较高频率值（7.1 GHz）。因此，纳米复合材料具有显著的特征是电磁微波吸收在更高频率的区域。 3.3 吸收特性 图3（a）是含80 %-Fe/Fe3B/Y2O3粉末的树脂复合材料的反射损耗与频率之间的典型关系。首先，随着厚度的增加，最小反射损耗被发现移向较低的频率区域。其次，分别在2.7-6.5 GHz频率范围，厚度6-3 mm下获得树脂复合材料RL-20 dB。尤其是，与样品相匹配的厚度（dm=4 mm）在4.5 GHz观察到最低RL=-33 dB，最小dm=3 mm在6.5 GHz被观察到（RL=-27 dB）。众所周知，选择合适的电磁波吸收材料的标准之一是其自然共振频率的位置（）。自然共振频率与各向异性场（HA）有关，根据方程： （4）其中，是激发态的核磁比，HA是各向异性场。许多工作者已经报道了应用于电磁波吸收材料的M-型铁氧体的最大HA值导致在自然共振的高频率范围的一个显著变化10-12。因此，可以预期，通过改变材料的自然共振频率可以控制金属磁性微波吸收的频率。图3（b）是含80 %-Fe/Y2O3粉末的树脂复合材料的频率与RL的依赖关系。在2.0-3.5 GHz频率范围内观察到树脂复合材料的RL-20 dB。在优化条件下制备的-Fe/SmO，-Fe/Y2O3，-Fe/Fe3B/Y2O3树脂复合材料的电磁微波吸收特性被概括在表1。样品-Fe/Fe3B/Y2O3与-Fe/Y2O3作比较表明最小反射点已经从2.6 GHz转移到一个更高的频率4.5 GHz。这种转变是因为用立方的-Fe部分替换了四方的Fe3B，这导致自然共振频率的增加（如图2（b）。在-Fe/Fe3B/Y2O3纳米复合物中，-Fe和Fe3B的存在如同磁体一样。与-Fe（1.6 GHz）作比较，Fe3B具有更宽的自然共振频率（14 GHz）正如方程（4）计算的一样，这归因于大的各向异场性场（0.4 MA/m）13。因为他们的相互影响，-Fe/Fe3B/Y2O3的自然共振频率（fr）在-Fe和Fe3B之间。然而，-Fe/Y2O3吸收体在2.7-3.5 GHz范围对应厚度dm比-Fe/Fe3B/Y2O3的薄（如图3），因为在这个频率范围-Fe/Y2O3的比-Fe/Fe3B/Y2O3的大。对于磁电磁波吸收材料，fm，RL-20 dB是由自然共振频率（fr）造成，其与各向异性场（HA）相关。因此，根据方程式（1），磁损耗（）决定了吸收体厚度。起初的结果与方程式（1）一致。此外，与-Fe/Y2O3作比较，-Fe/Fe3B/Y2O3吸收体的电磁波吸收带宽从1.5 GHz扩大到3.8 GHz，在RL99 %）中制备Ba3Co1.8Fe23.6Cr0.6O41。通过在乙烷中将Ba3Co1.8Fe23.6Cr0.6O41（100 m）和-Fe粉末（325网筛目）进行球磨，分别获得含-Fe（38，70，85 vol%）的-Fe/Ba3Co1.8Fe23.6Cr0.6O41纳米复合材料。在氩气流，623 K干燥2 h后，通过X射线衍射对合成粉末进行表征并通过高分辨率的扫描电子显微镜对微观组织进行分析（HR-SEM）。一个振动样品磁力仪记录了磁化滞回曲线。同样地，通过将环氧树脂与33.5 %粉末混合并将其压成圆柱形压块，制备了环氧树脂复合材料。这些压块在453 K下处理30分钟，然后将其切成环形样品（外直径：7.00 mm，内直径：3.04 mm）。在0.05-20.05 GHz，使用网络分析仪测量环形样品相的磁导率（）和介电常数（）（Agilent Technologies E8363A）。根据给定频率、吸收厚度下的相对磁导率和介电常数计算出反射损失曲线（RL），根据以下方程式13： （1） （2）其中f表示电磁波的频率，d是吸收体的厚度，c是光速，Z0 表示空气的阻抗，Zin表示吸收器的输入阻抗。根据方程式（1）和（2），RL=-20 dB相当于99 %的电磁波吸收，因此RL-20 dB）。值在0.1-18 GHz范围随着频率迅速从5.4减少到0.5。此外，值也随着频率从1.5减少到0.3，其0.1-18 GHz内没有呈现铁磁共振峰（图2），虽然，相对介电常数（）在2-18 GHz范围保持几乎不变（=17，=1.5）。但是，-Fe/Ba3Co1.8Fe23.6Cr0.6O41树脂复合材料的一个铁磁共振峰在4-18GHz范围被观察到（图2（c）。早期的结果表明，在Ba3Co1.8Fe23.6Cr0.6O41添加-Fe粉末形成纳米复合材料对减少涡流损耗具有显著影响。总之，通过将-Fe和Ba3Co1.8Fe23.6Cr0.6O41进行球磨，已经分别制备了-Fe/Ba3Co1.8Fe23.6Cr0.6O41（38，70或85 vol%-Fe）纳米复合材料，其中Ba3Co1.8Fe23.6Cr0.6O41具有磁体和绝缘体压制的涡流损耗的双重作用。-Fe/Ba3Co1.8Fe23.6Cr0.6O41纳米复合材料具有比-Fe和Ba3Co1.8Fe23.6Cr0.6O41更高的Hc值。与铁氧体相比，含70或85 vol%-Fe的-Fe/Ba3Co1.8Fe23.6Cr0.6O41纳米复合材料有希望在较低频率范围生产更薄、更轻的电磁波吸收材料。 这项工作得到了日本教育、科学、体育、文化部门和从2003年的新能源和工业技术发展组织的研究奖助金的支持（NEDO）。卡号：15205025原文1Electromagnetic wave absorption properties of a-Fe/Fe3B/Y2O3nanocomposites in gigahertz rangeJiu Rong Liu, Masahiro Itoh, and Ken-ichi Machidaa)a Collaborative Research Center for Advanced Science and Technology Osaka University, 2-1 Yamadaoka,Suita, Osaka 565-0871, Japan(Received 24 February 2003; accepted 8 September 2003)Abstract: Nanocomposites a-Fe/Fe3B/Y2O3 were prepared by a melt-spun technique, and the electromagneticwave absorption properties were measured in the 0.0520.05 GHz range. Compared witha-Fe/Y2O3 composites, the resonance frequency (fr) of a-Fe/Fe3B/Y2O3 shifted to a higher frequency range due to the large anisotropy eld (HA) of tetragonal Fe3B (0.4 MA/m). The relative permittivity () was constantly low over the 0.510 GHz region, which indicates that the composite powders have a high resistivity (). The effective electromagnetic wave absorption (reection loss 99.9 % in purity) by means of induction melting in Ar. Amorphous Y5Fe77.5B17.5 alloy ribbons with 1.5 mm in width and about 30 mm in thickness were prepared by the single-roller melt-spun apparatus at a roll surface velocity of 20 m/s using the earlier ingots as the starting materials. After ball milling, the powders with particle sizes of 2-4 m were heated to 953 K in He with a heating rate of 40 K/min for 10 min. Subsequent heating at 573 K for 2 h in O2 stream gave the resultant powders which were characterized by x-ray diffraction (XRD). The microstructures were observed on a high-resolution scanning electron microscope (HITACHI S-5000).3. Results and discussion3.1. Structure characteristics Epoxy resin composites were prepared by homogeneously mixing the composite powders with 20 wt% epoxy resin and pressing into cylindrical shaped compacts. These compacts were cured by heating at 453 K for 30 min, and then cut into toroidal shaped samples of 7.00 mm outer diameter and 3.04 mm inner diameter. The scattering parameters (S11, S21) of the toroidal shaped sample were measured using a Hewlett-packard 8720B network analyzer. The relative permeability (r) and permittivity (r) values were determined from the scattering parameters as measured in the frequency range of 0.05-20.05 GHz. The reection loss(RL) curves were calculated from the relative permeability and permittivity at given frequency and absorber thickness with the following equations: (2) (3)where f is the frequency of the electromagnetic wave, d is the thickness of an absorber, c is the velocity of light, Z0 is the impedance of air, and Zin is the input impedance of absorber.FIG. 1. The XRD pattern of Y5Fe77.5B17.5 powders:（a）as obtained,（b）after annealing at 953 K for 10 min in He gas, and（c）oxidation-disproportionating the sample（b）in O2 at 573 K for 2 h.Figure 1 shows the typical x-ray diffraction patterns measured on the amorphous Y5Fe77.5B17.5 powder: (a) as obtained,（b）after annealing at 953 K for 10 min in He, and（c）after oxidation-disproportionating sample （b）at 573 K for 2 h in O2 . From Fig. 1（a）, it was found that the Y5Fe77.5B17.5 alloy powders prepared by using the melt-spun technique were amorphous. After annealing as shown in Fig. 1（b）, the powders were composed of both the Fe3B and Y2Fe14B phases. After oxidation-disproportionation, the phase of Y2Fe14B disappeared. Comparing the XRD pattern in Fig.1（b） with that of Fig. 1（c）, we see that the intensity for the main peak of Fe3B（2=44.5）, which is just a main peak of a-Fe（110）, is much stronger after oxidation. This result indicates that a-Fe is formed because of the oxidation of Y2Fe14B into a-Fe, Fe3B and Y2O3 nanoparticles. But no peak of Y2O3 was observed Fig. 1(c); the reason could be that the Y2O3 particle size was too small to be detected. The grain sizes of Fe3B and a-Fe, about 30 nm, were determined from the line broadening of the XRD peaks using the Scherrers formula. This measurement agrees with the observation results by high-resolution scanning electron microscopy.3.2. Microwave propertiesThe frequency dependence on the relative permittivity for resin composites, including 80 wt% a-Fe/Fe3B/Y2O3 powders, is shown in Fig. 2(a). The real part and imaginary part of relative permittivity were almost constant over the 0.510 GHz range, and hence the relative permittivity () showed almost constant (=15，=0.6). This nding indicates high resistivity of the composites. The measured resistivity value was around 100 m for the a-Fe/Fe3B/Y2O3 composites, but the electric resistivity of the Nd2Fe14B compound was reported as 1.410-6 m9.The high resistivity of the nanocomposites is ascribed to the powders constituents: Fe3B, a-Fe, and Y2O3 nanoparticles. Embedded among Fe3B and a-Fe particles,Y2O3 plays a role as the insulator.The real part and imaginary part of relative permeability are plotted as a function of frequency in Fig. 2(b). The real part of relative permeability declined from 1.6 to 0.9 with frequency. However, the imaginary part of relative permeability increased from 0.1 to 0.6 over a range of 1-7.1 GHz, and then decreased in the higher frequency range. The imaginary part of relative permeability exhibited a peak in a broad frequency range(2-9 GHz). Compared with a-Fe/Y2O3 , the a-Fe/Fe3B/Y2O3 composites showed lower values in both the real () and imaginary () parts of permeability as shown in Fig. 2(b). These lower values are due to the smaller magnetization of Fe3B than a-Fe. Therefore, a-Fe/Fe3B/Y2O3 has a smaller relative permeability than a-Fe/Y2O3 because of the cooperative effect of a-Fe and Fe3B. However, the maximum point of curve for the a-Fe/Fe3B/Y2O3 composites shifted to the higher frequency value(7.1 GHz). As a result, the nanocomposite powders possess a remarkable feature for electromagnetic wave absorption in the higher frequency region.FIG. 2. Frequency dependences of relative permittivityr(a)and permeability r (b) for the resin composites with 80 wt % of a-Fe/Y2O3 and a-Fe/Fe3B/Y2O3 powders.3.3. Absorption performanceFigure 3(a) shows a typical relationship between RL and frequency for the resin composites with 80 wt% a-Fe/Fe3B/Y2O3 powders. First, the minimum reection loss was found to move toward the lower frequency region with increasing the thickness. Second, the RL values of resin composites less than -20 dB were obtained in the 2.7-6.5 GHz frequency range, with thickness of 6-3 mm, respectively. In particular, a minimum RL value of -33 dB was observed at 4.5 GHz on a specimen with a matching thickness (dm) of 4 mm, and the minimum dm value of 3 mm was obtained at 6.5 GHz (RL=-27 dB).It is well known that one criterion for selecting a suitable electromagnetic absorption material is the location of its natural resonance frequency (fr). The natural resonance frequency is related to the anisotropic eld (HA) value by the following equation: (4)where is the gyrometric ratio and HA is the anisotropic eld. Many workers have reported that the large HA values of the M-type ferrites used as electromagnetic wave absorption materials result in a remarkable shift to high frequency range in fr1012. Therefore, one can expect that the frequency of microwave absorption for the metallic magnets can be controlled by changing the fr value of materials. Figure 3(b) shows the frequency dependence of RL, for resin composites with 80 wt% a-Fe/Y2O3 powders. The RL value of the resin composites less than -