• 한국지구과학회지
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• 제25권1호
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• pp.48-51
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• 2004

The light element candidates such as S, O, Si, and K are discussed for the reasonable compositions in the earth's core since the available data show density difference from pure iron core. These candidates are favored by the some evidences such as depletion in the crust and mantle, and lower eutectic temperature of Fe-FeS melt for sulfur. FeO phase for oxygen, lighter mass than sulfur and solubility in metallic phases for silicon, and partitioning in Fe-FeS melt for potassium. However, other problems such as short experimental data, initial compositions of these elements, and oxidation state during the formation of the earth should be solved simultaneously to confirm these light elements.

• 한국광물학회지
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• 제21권4호
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• pp.415-423
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• 2008

외핵은 대부분 철로 이루어져 있으나 외핵의 밀도를 10% 정도 줄일 수 있는 희석 원소가 존재해야 한다. 외핵에서 존재할 가능성이 있는 가벼운 희석원소가 수소와 산소라는 가정 하에, 고압 하에서 수소의 열역학적 안정성을 적철석($Fe_2O_3$) + 수소($H_2$) $\to$ 괴타이트(FeOOH) + 철(Fe) 반응관계식을 이용하여 계산하였다. 열역학적 해석 결과, 상온 및 상압에서 이러한 화학반응의 깁스자유에너지는 12.62 kJ/mol로 계산되었다. 상온에서 압력이 증가함에 따라 깁스자유에너지 값은 감소하여 0.068 GPa에서 '0 kJ/mol'을 나타내었다. 압력이 증가함에 따라 깁스자유에너지 값은 일정한 비율로 점차적으로 감소하여 200 GPa에서는 -208.26 kJ/mol을 나타내었다. 이러한 열역학적 분석 결과로 볼 때 고압 하에서 수소와 철산화물이 반응하여 철원소와 철 수산화물을 생성하는 환원반응이 선호되며, 수소와 산소가 철수산화물의 형태로 원시지구 핵 내에 존재하게 되었을 가능성을 배제할 수 없다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1167-1168
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• 2006

In this study, the pure iron powder was treated with aqueous phosphoric acid to produce phosphate insulating layer on the surface. After drying the powder, it was compacted in a mold with a diameter of 20mm at 800MPa. The powder compacts were then heat treated at $500^{\circ}C$ for 1 hour. The results showed that insulated iron powder was obtained with uniform phosphate layer by chemical reaction. With increased amount of phosphate layer, the core loss and density of compacts were decreased. It was also found that the addition of ethyl alcohol during insulating reaction resulted in improved core loss value.

• Journal of Magnetics
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• 제22권1호
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• pp.100-103
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• 2017

We studied the microstructure and magnetic properties of Fe nanosized powder synthesized by the pulsed wire evaporation method. The x-ray diffraction spectrum confirmed that this powder had a pure ${\alpha}$-Fe phase. Scanning electron microscope and transmission electron microscope measurements indicated that the prepared powder had uniform spherical shape with core-shell structure. The mean powder size was about 35 nm and the thickness of the surface passivation layer was about 5 nm. Energy dispersive X-ray spectroscopy measurement indicated that the surface passivation layer was iron oxide. Magnetic field dependent magnetization measurement at room temperature showed that the maximum magnetization of the prepared powder was 177.1 emu/g at 1 T.

• 전자공학회논문지A
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• 제28A권9호
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• pp.721-728
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• 1991

In this paper, a magneto-optic modulator has been designed by using single crystal BSO and polycrystal ZnSe as Faraday cells. And practical core-type optical current sensors using pure iron and permalloy have been prepared and experimented. In order to obtain efficient magnetic field detection, LED(NEC OD08358, 0.87 $\mu$m) was used as optical source, PIN-PD(OD-8454)as optical receiver and multi-mode optical fiber (100/140$\mu$m) as transmission line. The characteristics matrix of the optical element was calculated by Stokes parameter, and optic modulation characteristics equations were derived by Muller matrix. Electromagnetic analysis program (FLUX 2D, micro VAX 3600) by finite element method was used to find the magnetic flux density around the core. The measuring error of the output voltage to input current has been masured below 5% in the range of 50A to 1000A. As the temperature was changed from -20$^{\circ}C$ to 60$^{\circ}C$, the maximum measurement error of the optical output has been found to be 0.5% at 60$^{\circ}C$. These experimental results show good temperature and linearity characteristics. The SNR of the overall system was 47dB in case of 600A (250.2 Oe) conductor current and the system has good noise immunity.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.902-907
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• 2023

To understand the eutectic reaction mechanism and the relocation behavior of the core debris is indispensable for the safety assessment of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). This paper addresses reaction products and their distribution of the eutectic melting/solidifying reaction of boron carbide (B₄C) and stainless-steel (SS). The influence of the existence of carbon on the B₄C-SS eutectic reaction was investigated by comparing the iron boride (FeB)-SS reaction by Raman spectroscopy with Multivariate Curve Resolution (MCR) analysis. The scanning electron microscopy with dispersive X-ray spectrometer was also used to investigate the elemental information of the pure metals such as Cr, Ni, and Fe. In the B₄C-SS samples, a new layer was formed between B₄C/SS interface, and the layer was confirmed that the formed layer corresponded to amorphous carbon (graphite) or FeB or Fe₂B. In contrast, a new layer was not clearly formed between FeB and SS interface in the FeB-SS samples. All samples observed the Cr-rich domain and Fe and Ni-rich domain after the reaction. These domains might be formed during the solidifying process.

• Advances in nano research
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• 제4권1호
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• pp.1-14
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• 2016

Superparamagnetic iron oxide nanoparticles (Nps), composed of magnetite, $Fe_3O_4$, or maghemite, ${\gamma}-Fe_2O_3$, core and biocompatible polymer shell, such as dextran or chitozan, have recently found wide applications in magnetic resonance imaging, contrast enhancement and hyperthermia therapy. For different diagnostic and therapeutic applications, current attempt is focusing on the synthesis and biomedical applications of various ferrite Nps, such as $CoFe_2O_4$ and $MnFe_2O_4$, differing from iron oxide Nps in charge, surface chemistry and magnetic properties. This study is focused on the synthesis of manganese ferrite, $MnFe_2O_4$, Nps by most commonly used chemical way pursuing better control of their size, purity and magnetic properties. Co-precipitation syntheses were performed using aqueous alkaline solutions of Mn(II) and Fe(III) salts and NaOH within a wide pH range using various hydrothermal treatment regimes. Different additives, such as citric acid, cysteine, glicine, polyetylene glycol, triethanolamine, chitosan, etc., were tested on purpose to obtain good yield of pure phase and monodispersed Nps with average size of ${\leq}20nm$. Transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), $M\ddot{o}ssbauer$ spectroscopy down to cryogenic temperatures, magnetic measurements and inductively coupled plasma mass spectrometry were employed in this study.

• 한국광물학회지
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• 제5권2호
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• pp.72-78
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• 1992

지구외핵은 순수한 철원소 이외에, 철보다 원자량이 낮은 원소가 상당량 포함되어 있다. 수소도 외핵내에 존재할 가능성이 있는 성분 중의 하나로 인식되고 있다. 따라서, 철수화물에 대한 압력에 따른 수소의 용해도에 대한 연구와 병행하여, 기타 금속수화물에 대한 연구의 확대 또한 중요하다. 수소는 또한 석유의 대체물질로써 그 가능성이 매우 높으며, 금속수화물상태로 수소를 보다 효율적으로 저장할 수 있는 설정구조에 대한 연구 역시 요구된다. 이러한 두가지 이류로, $TiH_2$를 철수화물의 결정구조적 유사물로 선택하여, 고온-고압하에서 특성화 현상을 연구하였다. 결정질 $TiH_2$ 분말시료에 대하여 두가지 다른 온도-압력 조건하에서 고온-고압실험이 시해되었다. 이러한 실험 중 하나는 소형 고온 발생장치가 부착된 피스톤-실린더 다이아몬드 앤질기기를 이용하여 압력은 최고 15 GPa 까지, 온도는 500${\circ}$에 고정시킨 상태에서 처리한 시료를 상온-상압상태로 변환시켜 X-선 회절실험을 하였다. 이러한 실험에서, 11.3 GPa 압력 이상에서 고온-고압처리한 시료로 부터 사방정계 결정구조를 보이는 비가역성의 새로운 광물상을 발견하였는데 이는 Ti수화물이 고압하에서 안정한 결정 격자구조를 보이는 새로운 것이다. 이 상변이에 따른 몰부피의 변화는 약 10%이다.