• 한국진공학회지
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• 제16권1호
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• pp.1-6
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• 2007

우리는 O/Fe(100)의 원자적 구조와 MgO/Fe(100) 표면의 계면의 구조를 LEED I/V curve를 이용하여 분석하였다. 산소를 Fe(100) 표면에 흡착시켰을 때 Fe 표면의 첫 번째 층간 간격은 약 16 % 정도 팽창하는 것을 확인하였다. 1ML MgO를 Fe(100) 표면에 성장하였을 때, MgO의 O가 Fe의 on-top 위치에 자라나는 것을 확인하였고, MgO/Fe 계면의 층간 간격이 확장되는 것을 확인하였다. AIA(average intensity mixing approximation) 계산을 사용하여 단층 MgO 성장한 Fe(100) 계의 계면구조는 MgO/FeO/Fe(100)와 MgO/Fe(100)의 계면구조를 갖는 것을 확인하였다. 이것은 확장된 FeO 층의 존재를 보이고 MgO/FeO/Fe(100)와 MgO/Fe(100) 두가지 계면 구조의 공존을 보인 EELS 실험 결과를 뒷받침 한다.

• 한국세라믹학회지
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• 제32권2호
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• pp.234-238
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• 1995

MgFe2O4 formation, grain growth in Fe2O3, Fe solid-solution limit in MgO for MgO-Fe2O3 mixture were studied by means of investigating the distribution of phases and compositions in reaction area between MgO and Fe2O3. The reaction area at equlibrium was composed with MgO-FexO matrix and MgFe2O4 precipitation, MgFe2O4 was formed by precipitating from MgO-FexO matrix dependent on oxygen partial pressure. Fe contents was exponentially decreased with diffusion distance in MgO single crystal, and thus Fe solid-solution limitation in MgO was about 4mol%. The grain growth rate in Fe2O3 base was increased with Mg contents diffused from MgO single crystal.

• 한국세라믹학회지
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• 제34권7호
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• pp.738-746
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• 1997

MgO clinker and two kinds of dolomite clinkers with different microstructures and CaO contents were used as starting materials, and the effects of Fe2O3 addition on the properties of MgO and dolomite were investigated in the range of 2 to 8 wt% of Fe2O3 content. Secondary phases contributed to densification of MgO-Fe2O3 and dolomite-Fe2O3 were magnesioferrite and dicalciumferrite, respectively. Sinterabilities of MgO-Fe2O3 and dolomite-Fe2O3 were directly proportional to the amount of secondary phases. Also, sinterability of dolomite itself was dependent on the microstructure of starting material including distribution of CaO and MgO as well as the addition amount of Fe2O3. The flexural strength of MgO-Fe2O3 content was almost constant. The hydration resistance of dolomite with large size of MgO and discontinuous distribution of CaO was higher than that of dolomite with small size of MgO and continuous distribution of CaO. Also, the minimum content of Fe2O3 to prevent they hydration of dolomite was about 4wt%. As increasing Fe2O3 content, the penetration resistance of MgO-Fe2O3 was improved by the increment of magnesioferrite. On the other hand, the penetration resistance of dolomite-Fe2O3 was decreased because of the increment of dicalciumferrite having low melting point.

• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.831-840
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• 1997

Core/shell structured composite metal oxides of Fe2O3/MgO were prepared by thermal decomposition of Fe(acac)3 adsorbed on the surface of MgO cores. The morphology of the composites conformed to that of the MgO used as the cores. Broad powder X-ray diffraction peaks shifted toward larger d, large BET surface area (∼350 m2/g), and the size of crystalline domains in nano range (4 nm), all corroborate to the nanocrystallinity of the Fe2O3/MgO composite which was prepared by using nanocrystalline MgO as the core. By use of microcrystalline MgO as the core, microcrystalline Fe2O3/MgO composite was prepared, and it had small BET surface area of less than 35 m2/g. AFM measurements on nanocrystalline Fe2O3/MgO showed a collection of spherical aggregates (∼80 nm dia) with a very rough surface. On the contrary, microcrystalline Fe2O3/MgO was a collection of plate-like flat crystallites with a smooth surface. The nitrogen adsorption-desorption behavior indicated that microcrystalline Fe2O3/MgO was nonporous, whereas nanocrystalline Fe2O3/MgO was mesoporous. Bimodal distribution of the pore size became unimodal as the layer of Fe2O3 was applied to nanocrystalline MgO. The macropores in a wide distribution which the nanocrystalline MgO had were absent in the nanocrystalline Fe2O3/MgO. The decomposition of CCl4 was largily enhanced by the overlayer of Fe2O3 on nanocrystalline MgO making the reaction between nanocrystalline Fe2O3/MgO and CCl4 be nearly stoichiometric. The reaction products were environmentally benign MgCl2 and CO2. Such an enhancement was not attainable with the microcrystalline samples. Even for the nanocrystalline MgO, the enhancement was not attained, if not with the Fe2O3 layer. Without the layer of Fe2O3, it was observed that the nanocrystalline domain of the MgO transformed into microcrystalline one as the decomposition of CCl4 proceeded on its surface. It appeared that the layer of Fe2O3 on the particles of nanocrystalline Fe2O3/MgO blocked the transformation of the nanocrystalline domain into microcrystalline one. Therefore, in order to attain stoichiometric reaction between CCl4 and Fe2O3/MgO core/shell structured composite metal oxide, the morphology of the core MgO has to be nanocrystalline, and also the nanocrystalline domains has to be sustained until the core was exhausted into MgCl2.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.281-284
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• 2005

The Fe/MgO catalysts with different Fe loadings (1, 4, 6, 15 and 30 wt% Fe) were prepared by a wet impregnation with iron nitrate as precursor. All of the catalysts were characterized by BET surface analyzer, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The maximum removal capacity of $H_2S$ was obtained with 15 wt% Fe/MgO catalyst which had the highest BET surface area among the measured catalysts. XRD of Fe/MgO catalysts showed that well dispersed Fe particles could be present on Fe/MgO with Fe loadings below 15 wt%. The crystallites of bulk $\alpha$-$Fe_2O_3$ became evident on 30 wt% Fe/MgO, which were confirmed by XRD. TPR profiles showed that the reducibility of Fe/MgO was strongly related to the loaded amounts of Fe on MgO support. Therefore, the highest removal efficiency of $H_2S$ in wet oxidation could be ascribed to a good dispersion and high reducibility of Fe/MgO catalyst. XPS studies indicated that the $H_2S$ oxidation with Fe/MgO could proceed via the redox mechanism ($Fe^{3+}\;{\leftrightarrow}\;Fe^{2+}$).

• 한국재료학회지
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• 제31권2호
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• pp.61-67
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• 2021

Fabrication of a ferromagnetic composite powder for the magnesium and BaFe12O19 system by mechanical alloying (MA) is investigated at room temperature. Mixtures of Mg and BaFe12O19 powders with a weight ratio of Mg:BaFe12O19 = 4:1, 3:2, 2:3 and 1:4 are used. Optimal MA conditions to obtain a ferromagnetic composite with fine microstructure are investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that Mg-BaFe12O19 composite powders in which BaFe12O19 is dispersed in Mg matrix are successfully produced by MA of BaFe12O19 with Mg for 80 min. for all compositions. Magnetization of Mg-BaFe12O19 composite powders gradually increases with increasing the amounts of BaFe12O19, whereas coercive force of MA powders gradually decreases due to the refinement of BaFe12O19 powders with MA time for all compositions. However, it can be seen that the coercivity of Mg-BaFe12O19 MA composite powders with a weight ratio of Mg:BaFe12O19=4:1 and 3:2 for MA 80 min. are still high, with values of 1260 Oe and 1320 Oe compared to that of Mg:BaFe12O19=1:4. This clearly suggests that the refinement of BaFe12O19 powders during MA process for Mg:BaFe12O19=4:1 and 3:2 tends to be suppressed due to ductile Mg powders.

• Journal of Magnetics
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• 제11권1호
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• pp.25-29
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• 2006

Recent experiments have demonstrated high TMR ratios in MTJs with the MgO barrier [1,2]. The CoFeB/MgO/CoFeB junctions showed better properties than the CoFe/MgO/CoFe junctions because the MgO layer had a good crystalline structure with (001) texture and smooth and sharp interface between CoFeB/MgO [3]. The amorphous CoFeB with 20 at%B starts the crystallization at $340^{\circ}C$ [4] and this crystallization of the CoFeB helps obtaining the high TMR ratio. In this work, the compositional changes in the MgO barrier and at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization were studied in annealed MTJs. XPS depth profiles were utilized. TEM analyses showed that the MgO barrier had (100) texture on CoFeB in the junctions. B in the bottom CoFeB layer diffused into the MgO barrier and B-oxide was formed at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.366-366
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• 2010

Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichorism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spins switch from out-of-plane direction in Fe/NiO/MgO(001) to in-plane direction in Fe/NiO/Ag(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90o-coupling between the in-plane NiO spins and the in-plane Fe spins which causes a switching of the NiO spins during the Fe magnetization reversal.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.304-304
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• 2011

We investigated the effect of different spin direction of anti-ferromagnetic layer on the magnetic properties of ferromagnetic layer in Fe-NiO and Fe-CoO bi-layer systems. For Fe-NiO system, we prepared the clean MgO(001) surface half-covered with 20 nm Ag films as a substrate for magnetic layers. Then we grew NiO wedge layers on the substrate, and added 8 monolayer(ML) Fe layers on the wedge layer. We examined magnetic properties of the bi-layer system using the surface magnetic optical Kerr effect(SMOKE) and X-ray magnetic linear dichroism(XMLD). From SMOKE measurement we observed the coercivity enhancement due to the set-up of anti-ferromagnetic order of NiO films in both of the Fe/NiO/MgO(001) and Fe/NiO/Ag/MgO(001) system. The most remarkable results in our observation is that the coercivity enhancement of Fe/NiO/Ag/MgO(001) is much larger than that of Fe/NiO/MgO(001). XMLD experiments confirmed the out-of-plane spin direction of NiO layers in Fe/NiO/MgO(001) and in-plane spin-direction of NiO layers in Fe/NiO/Ag/MgO(001), and we concluded that the origin of large enhancement of coercivity is due to the strong parallel coupling between Fe layers and NiO layers. We also confirmed that this strong parallel coupling maintained across the thin Ag layer inserted between Fe and NiO layers. For Fe-CoO system, we prepared Fe/CoO/Ag(001) and Fe/CoO/MnO(001) systems and observed much larger coercivity enhancement in Fe/CoO/Ag(001).

• Asian-Australasian Journal of Animal Sciences
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• 제23권8호
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• pp.1043-1048
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• 2010

This study investigated the effects of Fe-soy proteinate (Fe-SP) and magnesium oxide (MgO) dietary supplements on eggshell quality in laying hens. A total of 800 26-wk-old Hy-Line Brown hens were assigned to four dietary treatments: control (C), Fe-SP 100 (100 ppm Fe-soy proteinate), MgO (3 g MgO/kg diet), and Fe-SP 100+MgO. Each treatment had five replicates of 40 hens. The FT-IR (Fourier transform infrared) and XRD (X-ray diffraction) spectra of Fe-soy proteinate were different from those of $FeSO_4$ and soy digest. There were no significant differences among treatments in hen-day egg production, hen-house egg production, broken and soft egg rate, feed intake, or feed conversion. The MgO and Fe-SP 100+MgO treatments showed significantly (p<0.05) higher egg weights than the control group. Eggshell strength and thickness were significantly (p<0.05) higher in the MgO supplemented groups. The lightness and yellowness of the eggshells decreased, and the redness increased significantly in the Fe-SP treated groups. There were no significant differences among treatments in leukocyte level, but hemoglobin (Hb) concentrations were higher with Fe-SP treatments. In conclusion, supplementation with Fe-SP significantly affects eggshell color and hemoglobin concentration, whereas MgO supplementation increases eggshell strength and thickness. Egg weight and egg shell quality can be improved by supplementation of 100 ppm Fe in the form of Fe-SP and 3 g MgO/kg diet.