• 한국자기학회지
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• 제16권2호
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• pp.144-148
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• 2006

초상자성 나노입자의 제작이 가능한 sol-gel법을 이용하여 초상자성 나노입자 $CoGa_{0.1}Fe_{1.9}O_4$를 제조하여 입자의 크기 및 자기적 성질을 x-선 회절법(XRD), 주사전자현미경(SEM) 측정과 $M\ddot{o}ssbauer$ 분광법, 진동시료 자화율 측정기(VSM)를 이용하여 연구하였다. SEM및 x-선 회절실험으로부터 250"C 이상에서 열처리한 입자가 순순한 cubic spinel구조를 가지며, $250^{\circ}C$에서 열처리한 $CoGa_{0.1}Fe_{1.9}O_4$의 평균입자 크기는 10 nm로 나타났으며 균일한 구형상 임을 알 수 있었다. VSM 측정 결과로부터 $250^{\circ}C$에서 열처리한 $CoGa_{0.1}Fe_{1.9}O_4$의 경우 상온에서 초상자성의 특성을 나타냈다. $M\ddot{o}ssbauer$ 분광실험으로 $250^{\circ}C$에서 열처리한 입자가 상온에서 초상자성의 특성을 가지고 있음을 확인할 수 있었으며 초상자성의 특성을 잃어버리는 차단온도 $T_B$는 250 K로 결정하였으며, 또한 자기이방성상수 $K=3.0X10^5\;ergs/cm^3$의 값을 얻었다 $250^{\circ}C$에서 열처리한$CoGa_{0.1}Fe_{1.9}O_4$의 경우 4.2K에서의 초미세 자기장은 $H_{hf}(B)=518,\;H_{hf}(A)=486\;kOe$이며, 이성질체 이동값은 $\delta_B=0.34$, $\delta_A=0.30$ 이 값은 A, B자리 모두 $Fe^{3+}$에 해당된다.

• 대한화학회지
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• 제20권1호
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• pp.35-42
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• 1976

사면체 구조를 갖는 철(III)-옥살산 착화합물 5개와 팔면체 구조를 갖는 착화합물을 3개를 합성한 후 화학분석과 적외선스펙트럼을 이용하여 이들 착이온의 구조에 관하여 연구하였다. 이들중 $[FeC_2O_4Br_2]^-,$ $[FeC_2O_4(NCS)_4]^{3-}$ 및 $[Fe_2(C_2O_4)_3Cl_4]^{4-}$등의 3개의 피리딘염은 아직 보고되지 않은 새로운 착물이며, 특히 이합체로 생각되는 착물 $(PyH)_4[Fe_2(C_2O_4)_3Cl_4]$는 광화학 반응성이 아주 큼을 알 수 있었다. 이들 여러 철(III)-옥살산 착물의 물전기전도도와 자기화율에 관한 측정결과도 함께 보고하였다.

• 한국재료학회지
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• 제11권1호
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• pp.34-38
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• 2001

Fe-28%Al($Fe_3Al$)과 Fe-28%Al-4%Cr($Fe_3Al-4Cr$) 금속간화합물을 대기중 1073, 1273, 1473k의 온도에서 최고 17일까지 장시간 산화시켰다. $Fe_3Al-4Cr$의 산화저항은 근본적으로 $Fe_3Al$과 거의 비슷하거나, 약간 우수하였다. $Fe_3Al$ 위에 형성된 산화물은 거의 순수한 ${\alpha}-AL_2O_3$로만 구성되어 있었으며, $Fe_3Al-4Cr$ 위에 형성된 산화물은 약간의 Fe와 Cr 이온이 고용된 ${\alpha}-AL_2O_3$로 구성되어 있었다. 외부산화막을 형성하기 위해 모재원소의 외부확산에 의해 산화물-모재 계면에는 Kirkendall 기공이 존재하였다. $Fe_3Al(-4Cr)$ 표면에 형성된 산화막은 1273k가지는 비교적 얇고 치밀하였으나, 1473k에서 산화막의 박리와 함께 상대적으로 큰 무게증가가 발생하였다.

• 전기학회논문지
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• 제57권4호
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• pp.625-628
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• 2008

Ba-Zn ferrite powders for electromagnetic insulator were synthesized by self-propagating high-temperature synthesis(SHS) with a reaction of $xBaO_2+(1-x)ZnO+0.5Fe_2O_3+Fe{\rightarrow}Ba_xZn_{1-x}Fe_2O_4$. In this study, phase indentification of SHS products was carried out by using x-ray diffractometry and quasi-nano sized Ba-Zn powders were prepared by a pulverizing process. SHS mechanism was studied by thermodynamical analysis about oxidation reaction among $BaO_2,\;ZnO,\;Fe_2O_3$, and Fe. As oxygen pressure increases from 0.25 MPa to 1.0 MPa, the SHS reactions occur well and make clearly the SHS products. X-ray analysis shows that final SHS products formed with the ratio of $BaO_2/ZnO$ of 0.25, 1.0 and 4.0, are mainly $Ba_xZn_{1-x}Fe_2O_4$. Based on thermodynamical evaluation, the heat of formation increases in the order of $ZnFe_2O_4,\;BaFe_2O_4$, and $Ba_xZn_{1-x}Fe_2O_4$. This supports that $Ba_xZn_{1-x}Fe_2O_4$ phase is predominately formed during SHS reaction. The SHS reactions to form $Ba_xZn_{1-x}Fe_2O_4$ depends on oxygen partial pressure, and the heat of formation during the SHS reaction. The SHS reactions tends to occur well with increasing the oxygen partial pressure and BaO2/ZnO ratio in the reactants This means that the SHS reaction for the formation of Ba-Zn ferrite includes the reduction of BaO2/ZnO and the oxidation of Fe. $Ba_xZn_{1-x}Fe_2O_4$ powders after pulverizing is agglomeratedwith a size of about $50{\mu}m$, in which quasi-nano sized particles with about 300nm are present.

• 자원리싸이클링
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• 제26권4호
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• pp.95-100
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• 2017

본 연구에서는 폐 PCB(printed circuit board) 표면을 긁어내어 회수한 구리분말을 용융하는 과정에서 용융온도 저감과 정제를 위하여 플럭스로 $Fe_2O_3$를 첨가하였으며, $Fe_2O_3$ 첨가량 및 온도에 따른 구리의 회수율과 불순물 농도에 미치는 영향을 조사하였다. 구리 회수율은 반응온도와 $Fe_2O_3$의 첨가비율이 증가할 수 록 증가하였다. 그리고 구리 중 산소, 실리콘, 철의 농도는 $Fe_2O_3$ 첨가량이 증가할수록 감소하였다. $Fe_2O_3$를 첨가하여 반응시킨 후의 슬래그를 XRD로 분석하여 fayalite($2FeO{\cdot}SiO_2$)와 철산화물을 확인하였다. 따라서 fayalite 슬래그의 생성에 의한 슬래그의 융점과 점도 감소가 구리 회수율의 증가에 크게 기여한 것으로 생각된다.

• 한국세라믹학회지
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• 제45권3호
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• pp.179-184
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• 2008

(40-x)BaO${\cdot}xFe_2O_3{\cdot}60P_2O_5$ glasses with $5{\leq}x{\leq}35mol%$ were investigated by ESR spectroscopy. Two resonances observed near g=2.0 and g=4.3. The line at g=4.3 disappeared with the increase of the $Fe_2O_3$ content. The resonance at $g{\approx}2.0$ displayed characteristic signal consisting of superposed extremely broad and narrow components. The broader one indicates the presence of the association of two or more $Fe^{3+}$ ions, antiferromagnetically and the narrow one is related to the microclusters involving iron ions. Temperature dependence of the ESR integrated intensity revealed short-range antiferromagnetic character for $x{\geq}15mol%$.

• Bulletin of the Korean Chemical Society
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• 제18권7호
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• pp.743-749
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• 1997

Local structure refinement of the BaFe1-xSnxO3-y system (x=0.00-0.50) has been carried out with Fe K-edge x-ray absorpion spectroscopic studies. It is found out that the Fe ions are placed in two different symmetric sites such as tetrahedral and octahedral sites in the compounds by comparison with Fe K-edge x-ray absorption near edge structure (XANES) spectrum of the γ-Fe2O3 compound as a reference. Small absorption peaks of dipole-forbiden transitions appear at a pre-edge region of 7111 eV due to the existence of Fe ions in the tetrahedral and octahedral sites. The peak intensity decreases with the substitution amount of Sn ion. Three different absorption peaks of 1s→4p dipole-allowed transition appear on the energy region between 7123 and 7131 eV. The peaks correspond to 1s→4p main transition of Fe ions in tetrahedral and octahedral sites and 1s→4p transition followed by the shakedown process of ligand to metal charge transfer. The bond distances between Fe ions in the tetrahedral site and nearest neighboring oxygen atom (Fe-4O), and those in octahedral site (Fe-6O) are determined with the extended x-ray absorption fine structure (EXAFS) analysis. Two different interatomic distances increase with the substitution amount of Sn ion and also the bond lengths of Fe-4O are shorter than those of Fe-6O in all compounds.

• Applied Microscopy
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• 제45권3호
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• pp.177-182
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• 2015

The boiler tubes of X20CrMoV12.1 used in fossil-fired power plants were obtained and analyzed for the effect of water treatment on the steam corrosion-induced oxide scale in an effort to better understand the oxide formation mechanism, as well as pertinent method of maintenance and lifetime extension. The specimens were analyzed using various microscopy and microanalysis techniques, with focuses on the effect of water treatment on the characters of scale. X-ray diffraction analysis showed that the scales of specimens were composed of hematite ($Fe_2O_3$), magnetite ($Fe_3O_4$), and chromite ($FeCr_2O_4$). Electron backscatter diffraction analysis showed that the oxides were present in the following order on the matrix: outer $Fe_2O_3$, intermediate $Fe_3O_4$, and inner $FeCr_2O_4$. After all volatile treatment or oxygenated treatment, a dense protective $Fe_2O_3$ layer was formed on the $Fe_3O_4$ layer of the specimen, retarding further progression of corrosion.

• 한국자기학회지
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• 제6권4호
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• pp.225-234
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• 1996

자기 기록용 전구체에 적합한 침상형 $\alpha-Fe_{2}O_{3}$ 입자를 수열반응법에 의해 수용액 중에서 비정질 수산화제이철로부터 직접 제조하였다. Ellipsoidal 또는 rectangular 형상의 $\alpha-Fe_{2}O_{3}$ 입자는 염기도 10.75~11.75 범위에서 생성되었다. 구연산 농도가 증가함에 따라 침상 입자의 길이와 침상비는 점차 감소하였으며, 구연산 농도 $1.5{\times}10^{-4}\;mol$ 이상 일때는 침상형 $\alpha-Fe_{2}O_{3}$ 입자로의 결정화가 저해되었다. 수열 반응 온도 $140^{\circ}C$에서 가장 침상성이 우수한 $\alpha-Fe_{2}O_{3}$ 입자가 제조되었으며, $220^{\circ}C$ 이상에서는 침상형 입자의 생성을 기대할 수 없었다.

• 한국세라믹학회지
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• 제53권4호
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• pp.400-405
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• 2016

Ferric oxide (${\alpha}-Fe_2O_3$, hematite) is an n-type semiconductor; due to its narrow band gap ($E_g=2.1eV$), it is a highly attractive and desirable material for use in solar hydrogenation by water oxidation. However, the actual conversion efficiency achieved with $Fe_2O_3$ is considerably lower than the theoretical values because the considerably short diffusion length (2-4 nm) of holes in $Fe_2O_3$ induces excessive charge recombination and low absorption. This is a significant hurdle that must be overcome in order to obtain high solar-to-hydrogen conversion efficiency. In consideration of this, it is thought that elemental doping, which may make it possible to enhance the charge transfer at the interface, will have a marked effect in terms of improving the photoactivities of ${\alpha}-Fe_2O_3$ photoanodes. Herein, we report on the synthesis by pulsed electrodeposition of ${\alpha}-Fe_2O_3$-based anodes; we also report on the resulting photoelectrochemical (PEC) properties. We attempted Ti-doping to enhance the PEC properties of ${\alpha}-Fe_2O_3$ anodes. It is revealed that the photocurrent density of a bare ${\alpha}-Fe_2O_3$ anode can be dramatically changed by controlling the condition of the electrodeposition and the concentration of $TiCl_3$. Under optimum conditions, a modified ${\alpha}-Fe_2O_3$ anode exhibits a maximum photocurrent density of $0.4mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE) under 1.5 G simulated sunlight illumination; this photocurrent density value is about 3 times greater than that of unmodified ${\alpha}-Fe_2O_3$ anodes.