• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3730-3734
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• 2010

A simple, inexpensive and less time consuming electrochemical methods were carried out to prepare ordered mesoporous cobalt films. Ordered mesoporous cobalt films were successfully synthesized by templated electrodepostion of hexagonal $H_1$-e Co ion. The electrodeposited mesopores films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), low angle X-ray diffraction (XRD) and voltammetric methods. The applicability of thin films as high - performance super capacitors electrode materials is demonstrated electrochemically using cyclic voltammetry (CV) technique.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.112-112
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• 2013

Well-defined surfaces of single-crystalline solid materials are starting points of self-organizationof nanostructures and chemical reactions controlled in nanoscale. Although highly ordered atomicarrangement can be obtained on semiconductor surfaces, they can be maintained only in vacuumand not in air or in aqueous environment. Since single-crystalline metal oxide surfaces arechemically stable and no further oxidation occurs, their atomic structures can be utilized fornanofabrication in liquid processes, nanoelectrochemistry and nanobiotechnology. Sapphire is oneof the most stable metal oxides and its crystalline quality is excellent, as can be applied to electronicdevices that require ultralow defect densities. We recently found that chemical phase separationoccurs on sapphire surfaces by annealing processes and the formed nanodomains exhibit specificproperties in air and in water [1,2]. In our experiments, highly selective and controllable adsorptionof various protein molecules is observed on the phase-separated surfaces though the materials andcrystallographic orientations are identical [3,4]. Planar lipid bilayers supported on thephase-separated sapphire surface also exhibit a specific formation site selectivity [5]. Chemicalnanodomains appear on other metal-oxide surfaces, such as well-ordered titania surfaces. Wedemonstrate that surface chemistry of the nanodomains can be characterized in aqueousenvironment using atomic force microscopy equipped with colloidal tips and then show adsorptionand desorption behaviors of various proteins on the phase-separated surfaces.

• Nanomaterials
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• 제12권20호
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• pp.3704-3718
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• 2022

Among various iron carbide phases, χ-Fe₅C₂, a highly active phase in Fischer-Tropsch synthesis, was directly synthesized using a wet-chemical route, which makes a pre-activation step unnecessary. In addition, χ-Fe₅C₂ nanoparticles were encapsulated with mesoporous silica for protection from deactivation. Further structural analysis showed that the protective silica shell had a partially ordered mesoporous structure with a short range. According to the XRD result, the sintering of χ-Fe₅C₂ crystals did not seem to be significant, which was believed to be the beneficial effect of the protective shell providing restrictive geometrical space for nanoparticles. More interestingly, the protective silica shell was also found to be effective in maintaining the phase of χ-Fe₅C₂ against re-oxidation and transformation to other iron carbide phases. Fischer-Tropsch activity of χ-Fe₅C₂ in this study was comparable to or higher than those from previous reports. In addition, CO₂ selectivity was found to be very low after stabilization.

• 한국자기학회지
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• 제26권1호
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• pp.7-12
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• 2016

전기비저항이 높아 1 MHz 이상 고주파용 코어재료로 적합한 Fe-9%Si-2%Cr 합금분말의 열처리 온도에 따른 투자율 거동과 규칙-비규칙 전이에 대해 연구하였다. 분무과정에서 B2 규칙상의 생성이 억제되지 않았으며, $550^{\circ}C$ 이상에서 열처리 했을 경우 $DO_3$ 상의 회절선을 검출할 수 있었다. 열처리 온도가 증가할수록 격자상수와 보자력은 감소하였으나 $450^{\circ}C$에서 보자력의 갑작스런 큰 증가가 있었다. $150^{\circ}C$의 비교적 낮은 열처리 온도에서 가장 높은 투자율을 나타내었고, 이후 열처리 온도가 증가할수록 투자율은 감소하였다. 이상의 거동은 $DO_3$ 규칙상의 생성과 이에 따른 비저항의 변화로 설명할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.381-382
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• 2012

• 한국전자거래학회:학술대회논문집
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• 한국전자거래학회 2004년도 e-Biz World Conference
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• pp.89-97
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• 2004

1. Introduction; Fundamental Difference between conventional old commerce and e-commerce？ 2. "Quantity changes into Quality"; Phase transition and Critical phenomena Logarithmic Convergence and Emergence of Quality 3. Networked Small World; Indications from Genomics; Power-Law Ordered Plain Structure of Super-Complex System ⇔ The Structure of e-Biz. 4. Uniquitous Crisis to Ubiquitous Critical Points for the Emergence of Qualified Business with e-strucrure

• Journal of Magnetics
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• 제7권1호
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• pp.1-3
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• 2002

Piezomagnetic behaviors have been observed far above the Neel temperature in the perovskite-type layer structure compound $(C_{18}H_{37}NH_3)_2MnCl_4$undergoing structural phase transitions. Our observations were well explained by the magnetic and the structural orders coupled together via a magnetostructural coupling attributable to the Dzyaloshinsky-Moriya interaction.

• 한국세라믹학회지
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• 제40권4호
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• pp.333-339
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• 2003

Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BCN) has a 1:2 ordered hexagonal structure. Q-value of BCN increased with increasing sintering temperature however, it significantly decreased when the sintering temperature exceeded 140$0^{\circ}C$ Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BZN) has the 1:2 ordered hexagonal structure and the degree of the 1 : 2 ordering decreased with the increase of the sintering temperature. The Q value of the BZN increased with increasing the sintering temperature and BZN sintered at 140$0^{\circ}C$ for 6h has a maximum Q-value. For (1-x) Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$-zBa(Zn$_{1}$ 3/Nb$_{2}$ 3/)O$_3$[(1-x)BCN-xBZN] ceramics the 1:2 ordered hexagonal structure was observed in the specimens with x$\leq$0.3 and the BaNb$_{6}$ O$^{16}$ second phase was found in the specimens with x$\geq$0.6. Grain Growth, which is rotated to the BaNb$_{6}$ O$^{16}$ second phase occurred in the specimens with x$\geq$ 0.5. In this work, the excellent microwave dielectric properties of $\tau$r=0.0 ppm/$^{\circ}C$$\varepsilon$r=34.5 and Q,$\times$f=97000GHz sere obtained for the 0.7BCV-0.3BZN ceramics sintered at 1400$0^{\circ}C$ for 20h.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.49-53
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• 1996

Crystal structures of N $a_{x}$W $O_3$(0.5$\leq$x$\leq$1.0) were investigated. Transmission electron microscopy (TEM) studies indicate that there is an ordering of sodium ions when x=0.75. The direction of ordering is [110] and the wavelength of ordering is twice of the interplanar distance of (110) plane. It has been confirmed that a superlattice containing eight N $a_{0.75}$W $O_3$is the unit cell of ordered structure. In this unit cell, Na sites at (100) and ($\frac{1}{2}$$\frac{1}{2}$$\frac{1}{2}$) are vacant. The ordered phase was preserved after the annealing at $600^{\circ}C$ in the air. In reduced N $a_{x}$W $O_3$with x=0.5 and 1.0, extra phases were found to coexist with the partially ordered perovskite phase. After annealing at $600^{\circ}C$, theses phases were transformed into the phases found in calcined specimens.ens.s.

• Journal of Korean Vacuum Science & Technology
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• 제2권2호
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• pp.63-77
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• 1998

The oxidation of NiAl(110) was investigated in the temperature regime between 300K and 1300 K using LEED (low energy electron diffraction), TPD (temperature programmed desorption) and HREELS (high resolution electron energy loss spectroscopy). The adsorption of N2O and O2 up to reconstructions. Stepwise annealing of the oxygen-saturated sample from 600 K to 1300K in UHV (ultra-high vacuum,) results in firstly the onset of randomly oriented then finally fairly well-ordered. 5 ${\AA}$ Al2O3 film with quasi-hexagonal periodicity. Ordered thicker oxide films of 18-30 ${\AA}$ seem to be grown on this interfacial oxide layer by direct oxidation of sample at elevated temperature between 1150 and 1300 K because of the LEED pattern consisting of new broad hexagonal spots and the previous 5 ${\AA}$ spots. Although the periodicity of surface oxygen arrays shows no significant change from an hexagonal close-packing, the O-O distance changes from ∼3.0 ${\AA}$ film to ∼2.9 ${\AA}$ for thicker oxides. with the appearance of Auger parameter, for the 5${\AA}$ film can be described better as an interfacial oxide layer. The observation of three symmetric phonon peaks can be also a supporting evidence for this phase assignment since thicker oxide films on the Same Ni2Al3(110) show somewhat different phonon structure much closer to that of the ${\gamma}$-Al2O3. The adsorption/desorption of methanol further proves the preparation of less-defective and/or oxygen-terminated Al2O3 films showing ordered phase transitions with the change of oxide thickness between 5 ${\AA}$ to 30 ${\AA}$.