納米復(fù)合材料外文翻譯--納米復(fù)合材料在千兆赫范圍內(nèi)的電磁微波吸收性能

1、<p>　　中文3050字，2200單詞，11500英文字符</p><p>　　文獻(xiàn)出處：Liu J R, Itoh M, Machida K. Electromagnetic wave absorption properties of α-Fe/Fe 3B/Y2O3 nanocomposites in gigahertz range[J]. Applied Physics Letters, 2003

2、, 83(19):4017-4019.</p><p><b>　　原文1</b></p><p>　　Electromagnetic wave absorption properties of a-Fe/Fe3B/Y2O3nanocomposites in gigahertz range</p><p>　　Jiu Rong Liu, Mas

3、ahiro Itoh, and Ken-ichi Machidaa)</p><p>　　a Collaborative Research Center for Advanced Science and Technology Osaka University, 2-1 Yamadaoka,</p><p>　　Suita, Osaka 565-0871, Japan</p>

4、<p>　　(Received 24 February 2003; accepted 8 September 2003)</p><p>　　Abstract: Nanocomposites a-Fe/Fe3B/Y2O3 were prepared by a melt-spun technique, and the electromagneticwave absorption properties we

5、re measured in the 0.05–20.05 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.

6、4 MA/m). The relative permittivity () was constantly low over the 0.5–10 GHz region, which indicates that the composite powders have a high resistiv</p><p>　　Keywords: Nanocomposites a-Fe/Fe3B/Y2O3; Electrom

7、agnetic; Absorption performance </p><p>　　1. Introduction</p><p>　　Recent employment of communication devices using the electromagnetic wave range of 1–6 GHz, (e.g., mobile telephones, intellig

8、ent transport systems, electronic toll collection systems, and local area network systems)has rapidly expanded. Therefore, serious electromagnetic interference problems have worsened. Concern for these problems has promp

9、ted the study of electromagnetic wave absorbing materials with antielectromagnetic interference coatings, self-concealing technology, and microwave darkro</p><p>　　The complex permeability () and permittivit

10、y() of materials determine the re?ection and attenuation characteristics of the electromagnetic wave absorbers. For magnetic electromagnetic wave absorbers, there is a relationship between absorber thickness (dm) and mag

11、neticloss () according to the Eq. (1):</p><p><b>　　(1)</b></p><p>　　where c is velocity of light and fm the matching frequency.Metallic magnetic materials have a large saturation mag

12、netization and the Snoek’s limit is at the high frequency[1–3]. Consequently, their complex permeability values still remain high in such high frequency range. Therefore, it is possible to make thin absorbers from these

13、materials. However, the magnetization of these materials decreases due to eddy current losses induced by electromagnetic wave. For this reason,it is better to use sma</p><p>　　Sugimoto et al. have reported t

14、he good electromagnetic wave absorption properties of a-Fe/SmO composites in the 0.73-1.3 GHz range derived from a rare earth intermetallic compound Sm2Fe17 prepared by a conventional arc-melting technique[4,5]. We also

15、have reported that a-Fe/Y2O3 composites prepared by melt-spun technique showed good electromagnetic wave absorption properties in the 2.0–3.5 GHz range due to the ?ne particle size of a-Fe (~20 nm)[6].</p><p&g

16、t;　　2. Experimental procedure</p><p>　　2.1. Materials preparation</p><p>　　Rare earth magnets of nanocomposite materials, such as Fe3B/Nd2Fe14B, have been noted as high-performance magnets, whic

17、h could be fabricated by annealing the amorphous melt-spun ribbons7,8. The microstructure of nanocomposites is strongly dependent on the annealing temperature and time as well as the alloy composition. The purpose of thi

18、s study was to investigate the electromagnetic wave absorption properties of a-Fe/Fe3B/Y2O3 nanocomposites, which are prepared from Fe3B/Nd2Fe14B, and compare th</p><p>　　2.2. Characterization</p><

19、;p>　　Ternary alloy ingots of Y5Fe77.5B17.5 were ?rst prepared from Y, Fe, and B metals (>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 3

20、0 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

21、 µm were heated to 953 K in He with a heating rate of 40 K/min for 10 m</p><p>　　3. Results and discussion</p><p>　　3.1. Structure characteristics</p><p>　　Epoxy resin composit

22、es 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 s

23、haped 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 permeabili

24、ty (μr) and permittivity (εr) values wer</p><p><b>　　(2)</b></p><p><b>　　(3)</b></p><p>　　where f is the frequency of the electromagnetic wave, d is the thic

25、kness of an absorber, c is the velocity of light, Z0 is the impedance of air, and Zin is the input impedance of absorber.</p><p>　　FIG. 1. The XRD pattern of Y5Fe77.5B17.5 powders:（a）as obtained,（b）after ann

26、ealing at 953 K for 10 min in He gas, and（c）oxidation-disproportionating the sample（b）in O2 at 573 K for 2 h.</p><p>　　Figure 1 shows the typical x-ray diffraction patterns measured on the amorphous Y5Fe77.5

27、B17.5 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 pr

28、epared 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</p><p>　　3.2.

29、Microwave properties</p><p>　　The 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

30、 relative permittivity were almost constant over the 0.5–10 GHz range, and hence the relative permittivity () showed almost constant (=15，=0.6). This ?nding indicates high resistivity of the composites. The measured resi

31、stivity value was around 100 Ωm for the a-Fe/Fe3B/Y2O3 composites, but the electric resistivity of the </p><p>　　The real part and imaginary part of relative permeability are plotted as a function of frequ

32、ency 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 decr

33、eased 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 compos</p><p>　　FIG. 2. Fre

34、quency dependences of relative permittivityεr(a)and permeability µr (b) for the resin composites with 80 wt % of a-Fe/Y2O3 and a-Fe/Fe3B/Y2O3 powders.</p><p>　　3.3. Absorption performance</p><

35、;p>　　Figure 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 re?ection loss was found to move toward the lower frequency region

36、 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 -3

37、3 dB was observed at 4.5 GHz on a specimen with a matching thickness</p><p>　　It is well known that one criterion for selecting a suitable electromagnetic absorption material is the location of its natural r

38、esonance frequency (fr). The natural resonance frequency is related to the anisotropic ?eld (HA) value by the following equation:</p><p><b>　　(4)</b></p><p>　　where is the gyrometric

39、 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

40、fr[10–12]. 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 resi

41、n composites with 80 wt% a-Fe/Y2O3 po</p><p>　　FIG. 3. Frequency dependences of RL for the resin composites with 80 wt % of（a）a-Fe/Fe3B/Y2O3 and （b）a-Fe/Y2O3 powders.</p><p>　　4. Conclusions<

42、/p><p>　　In conclusion, the nanocomposites a-Fe/Fe3B/Y2O3 powders have been uniformly prepared by a melt-spun technique and the subsequent annealing and oxidation-disproportionation treatments. The excellent el

43、ectromagnetic wave absorption properties are due to the low relative permittivity and high relative permeability value during 2.7-6.5 GHz range. Our study of a-Fe/Fe3B/Y2O3 demonstrates the possible application of three-

44、phase type composites as electromagnetic wave absorbers.</p><p>　　This work was supported by Grant-in-Aid for Scienti?c Research No. 15205025 from the Ministry of Education, Science, Sports, and Culture of J

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