• Title/Summary/Keyword: magnetic absorption

검색결과 342건 처리시간 0.025초

Preparation and Microwave Absorption Properties of the Fe/TiO2/Al2O3 Composites

  • Li, Yun;Cheng, Haifeng;Wang, Nannan;Zhou, Shen;Xie, Dongjin;Li, Tingting
    • Nano
    • /
    • 제13권11호
    • /
    • pp.1850125.1-1850125.12
    • /
    • 2018
  • To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.

A Study on Multi-Layered EM Wave Absorber Using Natural Lacquer as a Binder

  • Choi, Dong-Han;Kim, Dong-Il;Choi, Chang-Mook;Li, Rui
    • 한국항해항만학회지
    • /
    • 제30권9호
    • /
    • pp.767-772
    • /
    • 2006
  • Generally, a silicone rubber and a chlorinated polyethylene(CPE) have been used as a binder for the development of high-performance composite EM(Electro Magnetic) wave absorbers. In this paper, the EM wave absorption performance of natural lacquer, which is newly proposed as a binder was investigated. The prepared MnZn ferrite EM wave absorbers are mixed with natural lacquer showed excellent EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers which are mixed with the conventional binders. MnZn ferrite EM wave absorbers mixed with natural lacquer were prepared and their absorption ability was also investigated The EM wave absorbers are fabricated in different proportions of MnZn, or NiZn ferrite and natural lacquer, and their reflection coefficients are measured. The permittivity and permeability are calculated by using the measured reflection coefficients. The EM wave absorption abilities are calculated according to different thicknesses of the EM wave absorbers.

A Study on the EM Wave Absorber for Improving Electromagnetic Environment of Wireless LAN at 2.4 GHz

  • Yoo, Gun-Suk;Kim, Dong-Il;Choi, Dong-Soo;Choi, Dong-Han
    • 한국항해항만학회지
    • /
    • 제34권7호
    • /
    • pp.539-542
    • /
    • 2010
  • In this paper, we designed and fabricated the Electro-Magnetic (EM) wave absorber for wireless LAN by using Amorphous and CPE. The material constants and the absorption properties were measured for the samples containing 50 %, 60 %, and 70 % weight fraction of Amorphous. Moreover, the EM wave absorption abilities were simulated for the EM absorbers in different thicknesses by adopting the measured permittivity and permeability, and then the EM wave absorber was fabricated based on the simulated design values. As a result, the EM wave absorber with the composition ratio in Amorphous : CPE = 60 : 40 wt.% with the thickness of 4 mm has the absorption ability more than 35 dB at 2.4 GHz. Thus, it is expected the wireless LAN environment can be improved by using the developed absorber.

A Study on Multi-Layered EM Wave Absorber Using Natural Lacquer as a Binder

  • Choi, Dong-Han;Kim, Dong-Il;Choi, Chang-Mook;Li, Rui
    • 한국항해항만학회:학술대회논문집
    • /
    • 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
    • /
    • pp.157-161
    • /
    • 2006
  • Generally, a silicone rubber and a chlorinated polyethylene(CPE) have been used as a binder for the development of high-performance composite EM(Electro Magnetic) wave absorbers. In this paper, the EM wave absorption performance of natural lacquer, which is newly proposed as a binder was investigated. The prepared MnZn ferrite EM wave absorbers are mixed with natural lacquer showed excellent EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers which are mixed with the conventional binders. MnZn ferrite EM wave absorbers mixed with natural lacquer were prepared and their absorption ability was also investigated. The EM wave absorbers are fabricated in different proportions of MnZn, or NiZn ferrite and natural lacquer, and their reflection coefficients are measured. The permittivity and permeability are calculated by using the measured reflection coefficients. The EM wave absorption abilities are calculated according to different thicknesses of the EM wave absorbers.

  • PDF

연자성 합금 분말의 입자크기에 따른 전자파 흡수 특성 비교 (Study of Electromagnetic Wave Absorption Properties with Particle Size in Soft Magnetic Alloy Powder)

  • 홍순호;손근용;박원욱;남정미;문병기;송용설
    • 한국분말재료학회지
    • /
    • 제14권4호
    • /
    • pp.261-264
    • /
    • 2007
  • The electromagnetic wave (EM) absorption properties of various particle size have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_{7}Nb_{3}Cu_{1}$ alloy powder. With decreasing the average particle size, the complex permeability (${\mu}_{r}$) and permittivity (${\varepsilon}_{r}$) increased and the matching frequency is shifted toward lower frequency. The fabricated EM wave absorbers showed permeability $2{\sim}6$, permittivity $17{\sim}23$ for a $-325{\sim}+400$ mesh sample, and the calculated power absorption was as high as 80% in the frequency range over 2 GHz.

X-Band 영역에서의 세라믹/샌더스트-알루미노실리케이트 복합재의 초고온 전자파 흡수 거동 (Ultra-high Temperature EM Wave Absorption Behavior for Ceramic/Sendust-aluminosilicate Composite in X-band)

  • 최광식;심동영;최원우;신준형;남영우
    • Composites Research
    • /
    • 제35권3호
    • /
    • pp.201-215
    • /
    • 2022
  • 본 연구에서는 초고온 환경에서 내화학성 및 열적 안정성이 우수한 지오폴리머 기반의 알루미노실리케이트 레진과 세라믹 섬유를 활용한, 목표주파수 X-band(8.2 GHz to 12.4 GHz)에서 전자파를 흡수하는 세라믹 복합재(Radar-absorbing ceramic composite, RACC)를 구현하였다. 주 성분이 FeSi인 판형 구조의 샌더스트 자성 입자를 분산시킨 알루미노실리케이트 레진은 목표 주파수 대역에서 자성 및 유전손실 특성을 발휘하였고, 입도와 무게분율별 유전특성을 Cole-Cole Plot으로 표현하였다. 샌더스트가 분산된 알루미노실리케이트 레진의 미세구조, 화학적 성분 및 결정, 자기 및 열적 특성 등을 분석하기 위해 SEM, EDS, VSM 및 TGA를 측정하였다. 샌더스트의 입도 크기 35 ㎛, 무게분율 40 wt.%를 분산시킨 레진의 유전손실 특성을 활용하여, X-band에서 약 1.51 GHz 대역폭에 대해 -10 dB 이하의 반사손실 성능을 발휘하는 단층형(t = 1.585 mm) RACC를 설계 및 제작하였다. 제작된 RACC의 초고온(25℃ to 1,000℃)에서 전자파 흡수 거동을 살피기 위해 개발된 초고온 환경 자유공간측정 장비를 활용하여 X-band 대역에서 그 성능을 검증하였다.

물분해 수소제조를 위한 SI cycle에서의 EMIm[$EtSO_4$]를 이용한 $SO_2/O_2$ 분리공정 ($SO_2/O_2$ Separation Process with EMIm[$EtSO_4$] in SI Cycle for the Hydrogen Production by Water Splitting)

  • 이기용;김홍곤;정광덕;김창수
    • 한국수소및신에너지학회논문집
    • /
    • 제22권1호
    • /
    • pp.13-20
    • /
    • 2011
  • $SO_2$ has been absorbed and separated selectively by an ionic liquid from $SO_2/O_2$ mixture decomposed from sulfuric acid during the thermochemical SI cycle for the water splitting. In order to design and operate high pressure $SO_2/O_2$ separation system, the solubility of $SO_2$ in [EMIm]$EtSO_4$ (1-ethyl-3-methylimidazolium ethylsulfate) has been measured by Magnetic Suspension Balance at high pressure and temperature. Based on the measured solubility, a pressurized separation system was set up and operated. 194 L/h of $SO_2$($SO_2:O_2$=0.65:1) has been separated with 99.85% of $O_2$ at the vent of absorption tower, which is 22.7% of the theoretically ideal capacity of the system. This discrepancy results from the reduced contact between the gaseous $SO_2$ and the ionic liquid. Increased $SO_2$ supply, scale-up of the absorption column, and a faster ionic liquid circulation speed were suggested to improve the separation capacity.

마이크로웨이브-질산용출과자력/수력선별에의한자연금및자철석의선별효과 (The Selection Effect of Native Gold and Magnetite by Microwave-nitric Acid Leaching and Magnetic/hydro Separation)

  • 이종주;박천영
    • 자원환경지질
    • /
    • 제53권2호
    • /
    • pp.183-196
    • /
    • 2020
  • 본 연구는 마이크로웨이브-질산용출과 자력/수력선별을 이용하여 정광으로부터 자연 금을 회수하는 것을 목표로 하였다. 마이크로웨이브-질산용출실험을 통해 용출용액으로부터 불용성-잔류물을 여과하였다. 용출용액을 원자흡수분광기(AAS)로 분석한 결과 Au는 전혀 용출되지 않은 것을 그리고 불용성-잔류물을 후방산란전자영상(BSE)으로 관찰한 결과 자연 금이 단체분리된 것으로 확인되었다. 불용성-잔류물을 자력/수력선별 하여 자성광물과 비-자성광물로 선별하였다. 자성광물에서 자철석이 회수되었고, 비-자성광물을 다시 수력선별한 결과 자연 금이 회수되었다. 자연 금은 X선 회절 분석(XRD)과 BSE 영상에서 확인되었다.

Synthesis of Core@shell Structured CuFeS2@TiO2 Magnetic Nanomaterial and Its Application for Hydrogen Production by Methanol Aqueous Solution Photosplitting

  • Kang, Sora;Kwak, Byeong Sub;Park, Minkyu;Jeong, Kyung Mi;Park, Sun-Min;Kang, Misook
    • Bulletin of the Korean Chemical Society
    • /
    • 제35권9호
    • /
    • pp.2813-2817
    • /
    • 2014
  • A new magnetic semiconductor material was synthesized to enable separation after a liquid-type photocatalysis process. Core@shell-structured $CuFeS_2@TiO_2$ magnetic nanoparticles were prepared by a combination of solvothermal and wet-impregnation methods for photocatalysis applications. The materials obtained were characterized using X-ray diffraction, transmission electron microscopy, ultraviolet-visible, photoluminescence spectroscopy, Brunauer-Emmett-Teller surface area measurements, and cyclic voltammetry. This study confirmed that the light absorption of $CuFeS_2$ was shifted significantly to the visible wavelength compared to pure $TiO_2$. Moreover, the resulting hydrogen production from the photo-splitting methanol/water solution after 10 hours was more than 4 times on the core@shell structured $CuFeS_2@TiO_2$ nanocatalyst than on either pure $TiO_2$ or $CuFeS_2$.

전기폭발법에 의해 제조된 자성 Fe2O3 나노 분말의 자기적 특성연구 (Study of Magnetic Fe2O3 Nano-particles Synthesized by Pulsed Wire Evaporation (PWE) Method)

  • 엄영랑;김흥회;이창규
    • 한국분말재료학회지
    • /
    • 제9권5호
    • /
    • pp.341-345
    • /
    • 2002
  • Nanoparticles of $Fe_2O_3$ with a mean particle size of 4-30 nm have been prepared by a pulsed wire evaporation method, and its structural and magnetic properties were studied by SQUID magnetometer and Mossbauer spectroscopy. From the main peak intensity of XRD and absorption rate of Mossbauer spectrum, the amounts of $\gamma-Fe_2O_3$ and $\alpha-Fe_2O_3$ in as-prepared sample are about 70% and 30%, respectively. The coercivity (53 Oe) and the saturation magnetization (14 emu/g) are about 20% of those of the bulk $\gamma-Fe_2O_3$. The low value of coercivity and saturation magnetization indicate that the $\gamma-Fe_2O_3$ phase nearly shows the spin glass-like behavior. Analysis of the set of Mossbauer spectrum indicates a distribution of magnetic hyperfine fields due to the particle size distribution yielding 20 nm of average particle size. The magnetic hyperfine parameters are consistent with values reported of bulk $\gamma-Fe_2O_3$ and $alpha-Fe_2O_3$. A quadrupole line on the center of spectrum represents of superparamagnetic phase of $\gamma-Fe_2O_3$ with a mean particle size of 7 nm or below.