納米復(fù)合材料外文翻譯

1、<p>　　浙江師范大學(xué)生化學(xué)院本科畢業(yè)設(shè)計(論文)外文翻譯</p><p><b>　　原文1</b></p><p>　　Electromagnetic wave absorption properties of a-Fe/Fe3B/Y2O3nanocomposites in gigahertz range</p><p>　　J

2、iu Rong Liu, Masahiro 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, J

3、apan</p><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 absorpti

4、on properties were 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 tetr

5、agonal Fe3B (~0.4 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/Fe3

6、B/Y2O3; Electromagnetic; 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 tele

7、phones, intelligent transport systems, electronic toll collection systems, and local area network systems)has rapidly expanded. Therefore, serious electromagnetic interference problems have worsened. Concern for these pr

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

9、 and permittivity() 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 thickn

10、ess (dm) and magneticloss () 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 larg

11、e saturation magnetization 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 absor

12、bers from these 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.

13、 have reported the 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 techniqu

14、e[4,5]. We also 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].<

15、;/p><p>　　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-performan

16、ce magnets, which 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. Th

17、e purpose of this 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. Characterizatio

18、n</p><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 w

19、idth 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 parti

20、cle sizes of 2-4 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>　　Epox

21、y 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

22、 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 rel

23、ative permeability (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 wav

24、e, 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.</p><p>　　FIG. 1. The XRD pattern of Y5Fe77.5B17.5 powders:（a）as obtai

25、ned,（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.</p><p>　　Figure 1 shows the typical x-ray diffraction patterns measured on the am

26、orphous 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

27、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</p>

28、<p>　　3.2. 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 im

29、aginary part of 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. T

30、he measured resistivity 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 f

31、unction 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 GH

32、z, 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 compos</p><p&

33、gt;　　FIG. 2. Frequency 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 performanc

34、e</p><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

35、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 minimu

36、m RL value of -33 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

37、of its natural resonance 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 i

38、s 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 fre

39、quency range in 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

40、 of RL, for resin 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.

41、 Conclusions</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.

42、The excellent electromagnetic 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 appli

43、cation of three-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,

44、and Culture of Japan.</p><p>　　References</p><p>　　[1] S. Yoshida, J. Magn. Soc. Jpn. 22, 1353（1998）.</p><p>　　[2] S. Yoshida, M. Sato, E. Sugawara, and Y. Shimada, J. Appl. Phys. 8

45、5,4636 ~1999.</p><p>　　[3] J. L. Snoek, Physica ~Amsterdam! 14, 207（1948）.</p><p>　　[4] T. Maeda, S. Sugimoto, T. Kagotani, D. Book, M. Homma, H. Ota, and Y. Houjou, Mater. Trans., JIM 41, 1172（

46、2000）.</p><p>　　[5] S. Sugimoto, T. Maeda, D. Book, T. Kagotani, K. Inomata, M. Homma, H.Ota, Y. Houjou, and R. Sato, J. Alloys Compd. 330, 301（2002）.</p><p>　　[6] J. R. Liu, M. Itoh, and K. Mac

47、hida, Chem. Lett. 32,394（2003）.</p><p>　　[7] Y. Q. Wu, D. H. Ping, B. S. Murty, H. Kanekiyo, S. Hirosawa, and K.Hona, Scr. Mater. 45, 355（2001）.</p><p>　　[8] S. Hirosawa, H. Kanekiyo, Y. Shigemo

48、to, K. Maurakami, T. Miyoshi, and Y. Shioya, J. Magn. Magn. Mater. 239, 424（2002）.</p><p>　　[9] M. Sagawa, S. Fujimura, N. Togawa, H. Yamamoto, and Y. Matuura, J.Appl. Phys. 55, 2083（1984）.</p><p&

49、gt;　　[10] M. Matsumoto and Y. Miyata, J. Appl. Phys. 8, 5486（1996）.</p><p>　　[11] S. Sugimoto, K. Okayama, S. Kondo, H. Ota, M. Kimura, Y. Yoshida, H.Nakamura, D. Book, T. Kagotani, and M. Homma, Mater. Tran

50、s., JIM 10,1080（1998）.</p><p>　　[12] S. B. Cho, D. H. Kang, and J. H. Oh, J. Mater. Sci. 31, 4719（1996）.</p><p>　　[13] W. Coene, F. Hakkens, R. Coehoorn, D. B. de Mooij, C. de Waard, J.Fidler, a

51、nd R. Grossinger, J. Magn. Magn. Mater. 96, 189（1991）.</p><p><b>　　原文2</b></p><p>　　Magnetic and electromagnetic wave absorption properties of -Fe/Z-type Ba-ferrite nanocomposites<

52、;/p><p>　　Jiu Rong Liu, Masahiro Itoh, and Ken-ichi Machidaa</p><p>　　Center for Advanced Science and Innovation, Osaka University, 2-1 Yamadaoka</p><p>　　Suita, Osaka565-0871, Japan&l

53、t;/p><p>　　(Received 16 August 2005; accepted 6 December 2005; published online 7 February 2006)</p><p>　　The saturation magnetization values (Ms) of -Fe / Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites pre

54、pared by mechanically alloying-Fe with Ba3Co1.8Fe23.6Cr0.6O41 powders increased with increasing the concentration of-Fe.-Fe / Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites showed higher coercivity values than а-Fe and Ba3Co1.8F

55、e23.6Cr0.6O41 because of the effects of shape anisotropy and exchange bias. The resin compacts with 33.5 vol% -Fe/Ba3Co1.8Fe23.6Cr0.6O41 (38, 70, 85 vol% а-Fe) powders provided good electro</p><p>　　Ferrites

56、, as conventional electromagnetic (EM) wave absorbing materials, have been widely studied from megahertz to igahertz (GHz) range because of their strong magnetism and high electric resistivity[1–3]. For EM wave applicati

57、ons there is an increasing interest in using ferrite-polymer ?lms rather than bulk ferrites. But, the thickness of ferrite-polymer ?lms has to be thick for ef?cient EM wave absorption, since it is dif?cult to increase th

58、e permeability values in GHz range owing to Snoek’s </p><p>　　Ba3Co1.8Fe23.6Cr0.6O41 was prepared by a conventional solid-state reaction method from the starting materials of BaCO3, Co3O4,Cr2O3, and Fe2O3 po

59、wders (purity 99 %)[12].-Fe/ Ba3Co1.8Fe23.6Cr0.6O41(38, 70, 85 vol%-Fe) nanocomposites were obtained by ball-milling Ba3Co1.8Fe23.6Cr0.6O41 (<100 μm) with -Fe powders (325 mesh) in hexane, respectively. After drying a

60、t 623 K for 2 h in Ar, the resultant powders were characterized by x-ray diffraction (XRD), and the microstructures were analyzed by a hig</p><p><b>　?。?）</b></p><p><b>　?。?）&l

61、t;/b></p><p>　　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 free space, and Zin is the input impedance of ab

62、sorber. The RL value of ?20 dB is comparable to the 99% of EM wave absorption according to Eqs. (1) and (2), and thus “RL<?20 dB” is considered as an adequate EM absorption.</p><p>　　FIG.1. XRD patterns o

63、f（a）-Fe,（b） Ba3Co1.8Fe23.6Cr0.6O41,and（c）,（d）,（e）-Fe/ Ba3Co1.8Fe23.6Cr0.6O41 nanocomposite powders with 38, 70, or 85 vol % -Fe, respectively.</p><p>　　Figure 1 shows the typical XRD patterns measured on the

64、-Fe, Ba3Co1.8Fe23.6Cr0.6O41, and -Fe/Ba3Co1.8Fe23.6Cr0.6O41 powders. From Fig.1(b), it was found that Ba3Co1.8Fe23.6Cr0.6O41 compound was formed by the solid-state reaction. All the peaks could be indexed as the hexagona

65、l lattice of Ba3Co1.8Fe23.6Cr0.6O41 (JCPDS 19-97). After ball milling the mixture of -Fe with Ba3Co1.8Fe23.6Cr0.6O41 powders at 200 r/min for 30 h in hexane and subsequent drying, only the peaks of -Fe were observed. The

66、 peak</p><p>　　FIG. 2. Frequency dependences of relative permittivity εr(a), real part (b), and imaginary part (c) of relative permeability for the resin composites with 33.5 vol% of -Fe, Ba3Co1.8Fe23.6Cr0.

67、6O41, and -Fe/Ba3Co1.8Fe23.6Cr0.6O41(38, 70, or 85 vol% -Fe)nanocomposite powders, respectively.</p><p>　　Figure 2(a) shows that the real part () and the imaginary part () of relative permittivity for the re

68、sin composites with 33.5 vol% -Fe/Ba3Co1.8Fe23.6Cr0.6O41 powders containing 38, 70, or 85 vol% -Fe were almost constant between 2 and 18 GHz, for which the relative permittivity () showed less variation (=10,10,11 and =0

69、.4, 0.4, 0.5, respectively). For the resin composites with 33.5 vol% Ba3Co1.8Fe23.6Cr0.6O41 powders, the and values were low constant and almost independent of frequency in the </p><p>　　FIG. 3. Frequency

70、dependences of RL for the resin composites with 33.5 vol% of(a) Ba3Co1.8Fe23.6Cr0.6O41, and（b）-Fe/Ba3Co1.8Fe23.6Cr0.6O41（70 vol % -Fe）powders</p><p>　　Figure 3(a) shows the typical relationship between RL an

71、d frequency for the resin composites with 33.5 vol% Ba3Co1.8Fe23.6Cr0.6O41 powders. The RL values less than ?20 dB were obtained in the 4.6-12.4 GHz with absorber thickness of 2.8-5.4 mm. For the resin composites with 33

72、.5 vol% -Fe/Ba3Co1.8Fe23.6Cr0.6O41（70 vol% -Fe）powders, the RL values less than ?20 dB were recorded in the 5.4-10.5 GHz with absorber thickness of 1.6-3.0 mm. In particular, a minimum RL of ?51 dB was obtained at 7.0 GH

73、z wi</p><p>　　In conclusion, -Fe/Ba3Co1.8Fe23.6Cr0.6O41(38, 70, or 85 vol%-Fe) nanocomposites have been prepared by ball-milling-Fe with Ba3Co1.8Fe23.6Cr0.6O41 powders, respectively, of which Ba3Co1.8Fe23.6C

74、r0.6O41 plays the double roles as magnet and insulator for suppressing the eddy current loss. -Fe/Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites showed higher Hc values than -Fe and Ba3Co1.8Fe23.6Cr0.6O41. Comparing with ferrites

75、, -Fe / Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites with 70 or 85 vol% -Fe are promising for </p><p>　　This work was supported by Grant-in-Aid for Scienti?c Research No. 15205025 from the Ministry of Education, Sc

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