• 제목/요약/키워드: ${\alpha}-Fe_2O_3$ nanoparticles

검색결과 15건 처리시간 0.031초

NiO의 첨가에 따른 α-Fe2O3 나노입자 센서의 에탄올 가스 검출 특성 향상 (Improved Ethanol Gas Sensing Performance of α-Fe2O3 Nanoparticles by the Addition of NiO Nanoparticles)

  • 박성훈;강우승
    • 한국표면공학회지
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    • 제49권1호
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    • pp.69-74
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    • 2016
  • In order to investigate the effect of NiO on the ethanol gas sensing performance of ${\alpha}-Fe_2O_3$ nanoparticles, NiO and ${\alpha}-Fe_2O_3$ nanoparticles are synthesized by hydrothermal method. The sensor with ${\alpha}-Fe_2O_3$ and NiO nanoparticles mixed at an optimum ratio of 7:3 showed 3.8 times improved sensing performance for 200ppm ethanol gas at $200^{\circ}C$. The enhanced gas sensing performance can be considered to be caused by pn heterojunction at the grain boundaries of ${\alpha}-Fe_2O_3$ and NiO nanopartcles.

Synthesis of $TiO_2$ nantubes coupled with ${\alpha}-Fe_2O_3$ nanoparticles and investigation of their photoelectrochemical activity

  • Mao, Aiming;Park, Jong-Hyeok;Han, Gui-Young
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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    • pp.99-102
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    • 2009
  • $TiO_2$ nanotube arraysdecorated with ${\alpha}-Fe_2O_3$ were prepared by forming a nanotube-like $TiO_2$ film on a Ti sheet using an anodization process, followed by electrochemical deposition treatment to decorate hematite (${\alpha}-Fe_2O_3$) nanoparticles on the $TiO_2$ nanotube arrays. The SEM and XRD results revealed that the ${\alpha}-Fe_2O_3$ nanoparticles were homogeneously embedded on the surface of the $TiO_2$ nanotube arrays. The activity of hydrogen production by photocatalytic water decomposition for the ${\alpha}-Fe_2O_3/TiO_2$ nanotube array composite was examined under visible light irradiation.

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Magnetic Property of α-Fe2O3 Nanoparticles Prepared by Sonochemistry and Take-off Technique

  • Koo, Y.S.;Yun, B.K.;Jung, J.H.
    • Journal of Magnetics
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    • 제15권1호
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    • pp.21-24
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    • 2010
  • A new synthetic method for the formation of uniform $\alpha-Fe_2O_3$ nanoparticles was reported and their magnetic properties were investigated. The sonochemical synthesis and the subsequent take-off technique resulted in spherical shaped $\alpha-Fe_2O_3$ nanoparticles with an average diameter of 60 nm. The temperature- and applied magnetic field-dependent magnetization of the $\alpha-Fe_2O_3$ nanoparticles was explained by the sum of two contributions, i.e., the Morin transition and superparamagnetism, because the critical size for superparamagnetism was within the size variation of the nanoparticles.

복합 전기방사법을 이용한 Fe-doped TiO2/α-Fe2O3 이중구조 나노와이어의 합성 및 자성 특성 (Synthesis of Fe-Doped TiO2/α-Fe2O3 Core-Shell Nanowires Using Co-Electrospinning and Their Magnetic Property)

  • 구본율;안효진
    • 한국재료학회지
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    • 제24권8호
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    • pp.423-428
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    • 2014
  • We synthesized Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell nanowires(NWs) by means of a co-electrospinning method and demonstrated their magnetic properties. To investigate the structural, morphological, chemical, and magnetic properties of the samples, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used, as was a vibrating sample magnetometer. The morphology of the nanostructures obtained after calcination at $500^{\circ}C$ exhibited core/shell NWs consisting of $TiO_2$ in the core region and ${\alpha}-Fe_2O_3$ in the shell region. In addition, the XPS results confirmed the formation of Fe-doped $TiO_2$ by the doping effect of $Fe^{3+}$ ions into the $TiO_2$ lattice, which can affect the ferromagnetic properties in the core region. For comparison, pure ${\alpha}-Fe_2O_3$ NWs were also fabricated using an electrospinning method. With regard to the magnetic properties, the Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell NWs exhibited improved saturation magnetization(Ms) of approximately ~2.96 emu/g, which is approximately 6.1 times larger than that of pure ${\alpha}-Fe_2O_3$ NWs. The performance enhancement can be explained by three main mechanisms: the doping effect of Fe ions into the $TiO_2$ lattice, the size effect of the $Fe_2O3_$ nanoparticles, and the structural effect of the core-shell nanostructures.

화염법으로 제조된 산화철 나노입자의 특성평가 (Characterization of Iron Oxide Nanoparticles Synthesized by Flame Synthesis)

  • 양상선;이고르알트만;피터피키차;최만수
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.1162-1165
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    • 2004
  • Size and crystalline phase changes of $Fe_{2}O_{3}$ nanoparticles formed in a $H_{2}/O_{2}$ flame have been investigated. At flame temperatures below $1350^{\circ}C$, the mean particle size increased monotonously with the distance from the burner edge; but in high-temperature flames above $1650^{\circ}C$, it suddenly decreased from 20 nm to ${\sim}3$ nm with the distance from the burner edge. The results of X-ray diffraction and HRTEM showed that this sudden reduction of the size of nanoparticles was accompanied by a partial phase transformation from ${\gamma}$-$Fe_{2}O_{3}$ into ${\alpha}$-$Fe_{2}O_{3}$. We suggest the structural instability due to ${\gamma}-$ to ${\alpha}-phase$ transformation as a mechanism for a rapid fragmentation of 20 nm particles into 3 nm ones.

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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
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    • 제9권5호
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    • pp.341-345
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    • 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.

부양가스응축법에 의해 제조된 철산화물 나노 분말의 자기적 특성연구 (A Study on Magnetic Iron Oxide Nano Particles Synthesized by the Levitational Gas Condensation (LGC) Method)

  • 엄영랑;김흥회;이창규
    • 한국분말재료학회지
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    • 제11권1호
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    • pp.50-54
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    • 2004
  • Nanoparticles of iron oxides have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters were evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of iron oxide with particle size of 14 to 30 nm in a chamber filled with mixtures of Ar and $O_2$ gases. It was found that the phase transition from both $\gamma$-$Fe_2O_3$ and $\alpha$-Fe to $Fe_3O_4$, which was evaluated from the results of Mossbauer spectra, strongly depended on the $O_2$ flow rate. As a result, $\gamma$-$Fe_2O_3$ was synthesized under the $O_2$ flow rate of 0.1$\leq$$Vo_2$(Vmin)$\leq$0.15, whereas $Fe_3O_4$ was synthesized under the $O_2$, flow rate of 0.15$\leq$$Vo_2$(Vmin)$\leq$0.2.

Flame Synthesis of Silica-Coated Iron Oxide Nanoparticles and Their Characterization

  • Jun, Kimin;Yang, Sangsun;Lee, Jeonghoon;Pikhitsa, Peter V.;Choi, Mansoo
    • 한국입자에어로졸학회지
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    • 제9권4호
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    • pp.209-219
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    • 2013
  • We have used the modified diffusion flame burner to synthesize silica coated iron oxide nanoparticles having enhanced superparamagnetic property. Silica-encapsulated iron oxide particles were directly observed using a high resolution transmission electron microscope. From the energy dispersive X-ray spectroscopy (EDS) and zeta potential measurements, the iron oxide particles were found to be completely covered by a silica coating layer. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that the iron oxide core consists of ${\gamma}-Fe_2O_3$ rather than ${\alpha}-Fe_2O_3$. Our magnetization measurements support this conclusion. Biocompatibility test of the silica-coated iron oxide nanoparticles is also conducted using the protein adsorption onto the coated particle.

Multiferroic Bi2/3La1/3FeO3 나노입자의 Mössbauer 연구 (Mössbauer Studied of Multiferroic Bi2/3La1/3FeO3 Nanoparticles)

  • 이승화
    • 한국자기학회지
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    • 제16권1호
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    • pp.28-33
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    • 2006
  • [ $Bi_{2/3}La_{1/3}FeO_3$ ]분말을 졸-겔법을 이용하여 제조하였다. 결정학적 및 자기적 성질을 열분석장치(TG-DTA), x-선 회절분석기(XRD), 주사전자현미경(SEM) 및 Mossbauer분광기를 이용하여 연구하였다. $Bi_{2/3}La_{1/3}FeO_3$ 단일상은 $600^{\circ}C$에서 3시간 동안 공기 중에서 열처리하여 얻을 수 있었으며, x-선 회절분석 결과 $Bi_{2/3}La_{1/3}FeO_3$ 분말은 rhombohedral 형태로 변형된 단순 perovskite 구조를 가졌으며 이때 격자상수 $=3.985\pm0.0005{\AA},\;\alpha=89.5^{circ}$이었다. Mossbauer스펙트럼 분석결과 $Bi_{2/3}La_{1/3}FeO_3$의 Neel온도는 $680\pm3K$임을 알 수 있었다. $Bi_{2/3}La_{1/3}FeO_3$의 이성질체이동 값은 0.27mm/s 값을 가졌으며, 이는 $Bi_{2/3}La_{1/3}FeO_3$.의 Fe 이온이 가지는 이온가는 $Fe^{3+}$의 high spin상태임을 보여주었다. $Bi_{2/3}La_{1/3}FeO_3$의 결정내의 Debye 온도는 $305\pm5K$ 평균 초미세 자기장 $H_{hf}(T)$$T/T_N<0.7$영역에서 $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.42(T/T_N)^{3/2}-0.13(T/T_N)^{5/2}$로 spin wave가 결정 내에서 잘 여기 됨을 알 수 있었다.

전기선폭발법으로 제조된 철산화물의 뫼스바우어분광연구 (Study of Mössbauer Spectroscopy for Iron Oxides Synthesized by Pulsed Wire Evaporation (PEW))

  • 엄영랑
    • 한국자기학회지
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    • 제24권5호
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    • pp.135-139
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    • 2014
  • 물리적 기상합성법인 전기선폭발법을 이용하여 챔버내 산소분압을 바꾸면서 철산화물을 제조하였다. 제조된 철산화물은 산소 분압에 따라 $Fe_2O_3$$Fe_3O_4$상으로 제조되었다. 산소분압이 30 %인 경우 ${\gamma}-Fe_2O_3$${\alpha}-Fe_2O_3$와 같이 $Fe^{3+}$의 형성이 용이함을 확인 하였다. 산소 분압을 15 %로 줄이면 $Fe_3O_4$가 형성되어 $Fe^{2+}$ 이온을 확인할 수 있었다. 뫼스바우어분광분석을 활용하여 ${\gamma}-Fe_2O_3$$Fe_3O_4$상 분석을 수행하였다. 13 K에서 295 K까지의 뫼스바우어 스펙트럼으로부터 자기정렬구조가 사라진 면적비로부터 약 12 % 정도의 ${\gamma}-Fe_2O_3$상이 초상자성 특성을 보임을 확인하였다.