• 한국자기학회지
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• 제8권1호
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• pp.1-5
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• 1998

침상형 Fe-Co 합금입자는 고밀도 기록용 자성분말로 응용이 기대되는 재료이다. Co 조성변화에 따른 자기적 성질 중 특히 최미세자기장에 미치는 효과를 Mossbauer 분광법과 투과 전자현미경 (TEM), 그리고 X-선 회절실험 등을 이용하여 조사하였다. 침상형 FenCo(n=5,4,3,2) 합금입자는 화학적 공침법으로 제조하였고, silica 코팅 후에 수소분위가에서 환원 처리하였다. 결정구조는 모든 조성 영역에 걸쳐 체심입방구조로서 Co 조성값의 증가와 함께 격자상수 값은 감소하였다. Mossbauer 분광 실험을 통하여 Co 조성 증가에 기인된 Co 원자들의 국부적 분포 변화는 초미세 자기장 값의 감소를 초래하였다.

• 전자공학회논문지A
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• 제29A권4호
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• pp.22-27
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• 1992

The cyclic voltammogram characteristics at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics/(($10^{-3}$M KCI + p-Si powders) and /(($10^{-4}$M CsNO$_3$ + n-GaAs powders) suspension interfaces have been studied using the microelectrophoresis and the cyclic voltammetric method. The negatively charged ions are specifically absorbed on the virgin and the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics surfaces. The zeta potentials of the p-Si and n-GaAs colloidal semiconductors are + 41mV and -44.8mV, respectively. The magnetization effects act as potential barriers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The positivelely charged p-Si and the negatively charged n-GaAs colloidal semiconductors act as potential barriers at the virgin SrO${\cdot}6Fe_{2}O_{3}$ interfaces. On the other hand, the charged p-Si and n-GaAs colloidal semiconductors act as potential barrier scavengers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The magnetization effects and the charged colloidal semiconductor effects are irreversible and interdependent.

• Bulletin of the Korean Chemical Society
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• 제12권3호
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• pp.332-334
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• 1991

The reaction and coordination chemistry of chiral ferrocenylaminophosphines such as 2-(diphenylphosphino)-1-(N,N-dimethylaminoethyl) ferrocene (PPFA), and 1',2-bis(diphenylphosphino)-l-(N,N-dimethylaminoe thyl) ferrocene (BPPFA), with various iron carbonyls have been investigated. PPFA reacted with iron carbonyls, Fe$(CO)_5$, $Fe_2(CO)_9$, or $Fe_3(CO)_{12}$ to give an iron complex of the type (${\eta}^1$-PPFA-P)Fe$(CO)_4$ (1) as a single product regardless the choice of the iron carbonyls. The bisphosphine ligand BPPFA afforded two products (${\eta}^1$-BPPFA-P)Fe$(CO)_4$ (2) and (${\mu}$,${\eta}^1$-BPPFA-P,P)$Fe_2(CO)_8$ (3) in which BPPFA acts as a monodentate and a bridging ligand, respectively. In all cases coordination to the -Fe$(CO)_4$ moiety is made through the phosphine rather than the amino group and, in the case of 2, the coordination is made through the phosphine substituted at the $C_5H_4$ ring to reduce the steric congestion.

• 한국세라믹학회지
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• 제34권5호
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• pp.453-460
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• 1997

Sr-ferrite having magnetoplumbite structure is similar to Ba-ferrite in magnetic characteristics, but better magnetic characteristics for using motor application. To improve remanence magnetic flux density(Br) and coercive force(iHc), it is necessary that sintered ferrites must have high density and grain size less than 1 $\mu$m. By varying n values in SrO.nFe2O3 basic composition, calcination temperature, and BaO addition, Sr-ferrite powder and sintered specimen was prepared. The n values, calcination temperature, and BaO addition affected secondary phase formation, particle size, and particle shape. BaO addition enhanced Fe2O3 secondary phase and hexagonal shape particle. Fe2O3 phase reduced sintered density which greatly decreased Br.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1991년도 춘계연구발표회 논문개요집
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• pp.7-8
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• 1991

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 추계연구발표회 논문개요집
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• pp.36-37
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• 1998

• 한국재료학회지
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• 제22권5호
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• pp.253-258
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• 2012

Activated magnetite ($Fe_3O_{4-{\delta}}$) was applied to reducing $CO_2$ gas emissions to avoid greenhouse effects. Wet and dry methods were developed as a $CO_2$ removal process. One of the typical dry methods is $CO_2$ decomposition using activated magnetite ($Fe_3O_{4-{\delta}}$). Generally, $Fe_3O_{4-{\delta}}$ is manufactured by reduction of $Fe_3O_4$ by $H_2$ gas. This process has an explosion risk. Therefore, a non-explosive process to make $Fe_3O_{4-{\delta}}$ was studied using $FeC_2O_4{\cdot}2H_2O$ and $N_2$. $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$ were used as starting materials. So, ${\alpha}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method. During the calcination process, $FeC_2O_4{\cdot}2H_2O$ was decomposed to $Fe_3O_4$, CO, and $CO_2$. The specific surface area of the activated magnetite varied with the calcination temperature from 15.43 $m^2/g$ to 9.32 $m^2/g$. The densities of $FeC_2O_4{\cdot}2H_2O$ and $Fe_3O_4$ were 2.28 g/$cm^3$ and 5.2 g/$cm^3$, respectively. Also, the $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by CO. From the TGA results in air of the specimen that was calcined at $450^{\circ}C$ for three hours in $N_2$ atmosphere, the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was estimated. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was 0.3170 when the sample was heat treated at $400^{\circ}C$ for 3 hours and 0.6583 when the sample was heat treated at $450^{\circ}C$ for 3 hours. $Fe_3O_{4-{\delta}}$ was oxidized to $Fe_3O_4$ when $Fe_3O_{4-{\delta}}$ was reacted with $CO_2$ because $CO_2$ is decomposed to C and $O_2$.

• 한국자기학회지
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• 제5권3호
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• pp.210-215
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• 1995

Glass\Cr/sub 40 .angs. /\[Cr/sub 10 .angs. /\NiFe/sub 50 .angs. /]/sub N/ 다층박막을 층수 N = 1, 2, 3, 4, 5, 6, 10에 따라 dc magnetron sputtering 방법에 의해 제작하였다. 이때 자기 이방성의 형성을 위해 제작 중에 자장을 200 Gauss 가했다. 전류 방향과 외부 자장이 수평, 수직에 따라 자기저항 곡선 MR(xx), MR(xy)를 조사하였다. MR(xx) 곡선의 경우 N = 1, 5, 10 경우 자기저항비가 거의 나타나지 않았으며, 나머지 층수의 경우는 외부 자장에 따라 저항이 증가하는 positive magnetoresistance 현상을 보였다. 또한 곡선의 모양도 H = 0 Oe 근처에서 특이하게 반전되는 자기정항 곡선을 보였다. 이런 현상의 물리적 해석을 NiFe 단층박막의 자기저항 곡선과 비교하여 설명 하였다.

• 한국재료학회지
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• 제8권8호
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• pp.720-725
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• 1998

환원.확산법에 의해 $Sm_{2}Fe_{17}N_{x}$ 계 희토류 영구자석을 제조하기 위한 기초연구로서, 우선 $Sm_{2}Fe_{17}$ 금속간화합물의 제조를 위하여, 금속 Ca에 의한 $Sm_2O_3$의 환원반응과 Fe분말중에 Sm의 확산반응을 검토하였다. 그 결과 전자는 $1000^{\circ}C$이상의 고온의 경우에 매우 빠르게 완료되지만, 후자의 Fe분말의 중심까지 Sm의 확산반응의 완료(완전한 균질화조건)는 $1100^{\circ}C$에서 3h 정도의 R-D 반응이 필요하며, 이 확산반응이 전체반응에 있어서 율속단계임을 알았다. Sm-Fe 계의 금속간화합물들의 성장은$ 1000^{\circ}C$이하에서는 $SmFe_2$, $SmFe_3$,$Sm_{2}Fe_{17}$금속간화합물의 3개의 상이 관찰되었으나, $1100^{\circ}C$에서는 $Sm_{2}Fe_{17}$ 금속간화합물의 상만이 관찰되었다. 본 연구에서 얻어진 최종시료의 산소 및 Ca량은 각각 0.72wt% 및 0.11wt%이었다.

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.