• 전기화학회지
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• 제2권1호
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• pp.38-45
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• 1999

Electrochemical lithium intercalation into a PECVD (plasma enhanced chemical vapour deposited) carbon film electrode was investigated in 1 M $LiPF_6-EC$ (ethylene carbonate) and DEC (diethyl carbonate) solution during lithium intercalation and deintercalation, by using cyclic voltammetry supplemented with ac-impedance spectroscopy. The size of the graphitic crystallite in the a- and c-axis directions obtained from the carbon film electrode was much smaller than those of the graphite one, indicating less-developed crystalline structure with hydrogen bonded to carbon, from the results of AES (Auger electron spectroscopy), powder XRD (X-ray diffraction) method, and FTIR(Fourier transform infra-red) spectroscopy. It was shown from the cyclic voltammograms and ac-impedance spectra of carbon film electrode that a threshold overpotential was needed to overcome an activation barrier to entrance of lithium into the carbon film electrode, such as the poor crystalline structure of the carbon film electrode showing disordered carbon and the presence of residual hydrogen in its structure. The experimental results were discussed in terms of the effect of host carbon structure on the lithium intercalation capability.

• Bulletin of the Korean Chemical Society
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• 제7권5호
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• pp.331-334
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• 1986

The crystal structure of thiamin tetrahydrofurfuryl disulfide, one of the ring-opened derivatives of thiamin, has been determined by the X-ray diffraction methods. The crystal is monoclinic with cell dimensions of a = 8.704 (1), b = 11.207 (2), c = 21.260 (3) ${\AA}$ and ${\beta}$ = 92.44 (2)$^{circ}$, space group P2$_{1}$/c and Z = 4. The structure was solved by direct methods and refined to R = 0.076 for 1252 observed reflections measured on a diffractometer. The molecule assumes a folded conformation in which the pyrimidine and the tetrahydrofurfuryl rings are on the same side of the ethylenic plane. The pyrimidinyl, N-formyl and ethylenic planes are mutually perpendicular to each other and the N(3)-C(4) bond retains a single bond character. The structure is stabilized by an intramolecular N(4'${\alpha})-H{\cdots}O(2{\alpha}$) hydrogen bond. The molecules are connected via N(4'${\alpha}$)-H{\cdots}(N3')$ and O(5${\gamma})-H{\cdots}(N1')$ hydrogen bonds, forming a two-dimensional hydrogen-bonding network. The tetrahydrofurfuryl ring is dynamically disordered. The overall conformation as well as the packing mode is very similar to that of thiamin propyl disulfide.

• Macromolecular Research
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• 제17권10호
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• pp.757-762
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• 2009

The micro domain structures and crystallization behavior of the binary blends of poly(methyl methacrylate)-b-poly(pentafluorostyrene)-b-poly(methyl methacrylate) (PMMA-PPFS-PMMA) triblock copolymer with a low molecular weight poly(vinylidene fluoride) (PVDF) were investigated by small-angle X-ray scattering (SAXS), small-angle light scattering (SALS), transmission electron microscopy (TEM), optical microscopy, and differential scanning calorimetry (DSC). A symmetric, PMMA-PPFS-PMMA triblock copolymer with a PPFS weight fraction of 33% was blended with PVDF in N,N-dimethylacetamide (DMAc). In the wide range of PVDF concentration between 10.0 and 30.0 wt%, PVDF was completely incorporated within the PMMA micro domains of PMMA-PPFS-PMMA without further phase separation on a micrometer scale. The addition of PVDF altered the phase morphology of PMMA-PPFS-PMMA from well-defined lamellar to disordered. The crystallization of PVDF significantly disturbed the domain structure of PMMA-PPFS-PMMA in the blends, resulting in a poorly-ordered morphology. PVDF displayed unique crystallization behavior as a result of the space constraints imposed by the domain structure of PMMA-PPFS-PMMA. The pre-existing microdomain structures restricted the lamellar orientation and favored a random arrangement of lamellar crystallites.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.449-453
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• 2009

A mesoporous assembly of layered titanate with well-dispersed Pt cocatalysts has been synthesized via a restacking of exfoliated titanate nanosheets and a simultaneous adsorption of Pt nanoparticles. According to powder X-ray diffraction analysis, the obtained mesoporous assembly shows amorphous structure corresponding to the disordered stacking of layered titanate crystallites. Field emission-scanning electron microscopy and $N_2$ adsorption-desorption isotherm measurement clearly demonstrate the formation of mesoporous structure with expanded surface area due to the house-of-cards type stacking of the titanate crystallites. From high resolution-transmission electron microscopy and elemental mapping analyses, it is found that Pt nanoparticles with the size of ~2.5 nm are homogeneously dispersed in the mesoporous assembly of layered titanate. In comparison with the protonated titanate, the present mesoporous assembly of layered titanate exhibits better photocatalytic activity for the photodegradation of organic molecules. This finding underscores that the restacking of exfoliated nanosheets is quite useful not only in creating mesoporous structure but also in improving the photocatalytic activity of titanium oxide.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.441-444
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• 2009

The formation and structure of self-assembled monolayers (SAMs) by the adsorption of acetyl-protected octylthioacetate (OTA) on Au(111) in a catalytic tetrabutylammonium cyanide (TBACN) solution were examined by means of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Molecular-scale STM imaging revealed that OTA molecules on Au(111) in a pure solvent form disordered SAMs, whereas they form well-ordered SAMs showing a c(4 × 2) structure in a catalytic TBACN solution. XPS and CV measurements also revealed that OTA SAMs on Au(111) formed in a TBACN solution have a stronger chemisorbed peak in the S 2p region at 162 eV and a higher blocking effect compared to OTA SAMs formed in a pure solvent. In this study, we clearly demonstrate that TBACN can be used as an effective deprotecting reagent for obtaining well-ordered SAMs of thioacetyl-protected molecules on gold.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1383-1387
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• 2013

The surface structure and electrochemical behavior of self-assembled monolayers (SAMs) prepared from benzenethiol (BT), cyclohexanethiol (CHT), and cyclopentanethiol (CPT) on Au(111) surface were examined by scanning tunneling microscopy (STM) and cyclic voltammetry (CV) to understand the influence of thiol molecular backbone structure on the formation and reductive desorption behavior of SAMs. STM imaging showed that BT and CPT SAMs on Au(111) surface formed at room temperature were mainly composed of disordered domains, whereas CHT SAMs were composed of well-ordered domains with three orientations. From these STM results, we suggest that molecule-substrate interaction is a key parameter for determining the structural order and disorder of simple aromatic and alicyclic thiol SAMs on Au(111). In addition, the reductive desorption peak potential for BT SAMs with aromatic rings was observed at a less negative potential of -566 mV compared to CHT SAMs (-779 mV) or CPT SAMs (-775 mV) with aliphatic cyclic rings. This reductive desorption behavior for BT SAMs is due to the presence of p-orbitals on the aromatic rings, which promote facile electron transfer from the Au electrode to BT as compared to CHT and CPT. We also confirmed that the reductive desorption behavior for simple alicyclic thiol SAMs such as CHT and CPT SAMs on Au electrodes was not significantly influenced by the degree of structural order.

• 한국결정학회지
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• 제13권1호
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• pp.36-40
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• 2002

중성자회절법을 이용하여 여러 다른 조건으로 열처리한 (Fe/sub 0.61/Ni/sub 0.39/)₃V 합금 분말시료의 장거리 규칙도를 측정하여 규칙-불규칙 상전이의 정도를 조사하였다. 조사 결과 680℃-94 h 열처리 시료는 완전 불규칙 상태로 상전이가 발생하지 않았으며 면심입방구조를 보였다. T < 640℃의 조건에서 열처리한 시료들은 모두 장거리 규칙도 0 < S < 1으로 면심입방구조의 일부가 단순입방구조로 상전이 함을 보여주었다. 또한 Cowley의 S-T/T/sub c/ 관계식으로부터 465℃-144 h 으로 열처리한 시료가 열평형상태에 가장 근접하였음을 확인하였다

• Journal of Electrochemical Science and Technology
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• 제9권3호
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• pp.163-168
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• 2018

Biomass waste-derived carbon is an attractive alternative with environmental benignity to obtain carbon material. In this study, we prepare carbon from coffee grounds as a biomass precursor using a simple, inexpensive, and environmentally friendly method through physical activation using only steam. The coffee-derived carbon, having a micropore-rich structure and a low extent of graphitization of disordered carbon, is developed and directly applied to lithium-ion battery anode material. Compared with the introduction of the Ketjenblack (KB) conducting agent (i.e., coffee-derived carbon with KB), the coffee-derived carbon itself achieves a reversible capacity of ~200 mAh/g (0.54 lithium per 6 carbons) at a current density of 100 mA/g after 100 cycles, along with excellent cycle stability. The origin of highly reversible lithium storage is attributed to the consistent diffusion-controlled intercalation/de-intercalation reaction in cycle life, which suggests that the bulk diffusion of lithium is favorable in the coffee-derived carbon itself, in the absence of a conducting agent. This study presents the preparation of carbon material through physical activation without the use of chemical activation agents and demonstrates an application of coffee-derived carbon in energy storage devices.

• 한국조경학회지
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• 제31권4호
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• pp.25-38
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• 2003

The main problems of disordered and congested urban landscape are due to the lack of holistic management that can control various elements of forming a city. Especially, the color of urban landscape is problematic because it is related to individual and social characteristics as well as to physical characteristics. Therefore, temporary expedients that can solve only visualized problems can not be a proper solution for color problems of urban landscape. This study originated from the question about why the color of disordered and congested urban landscape has not been improved. This study aims at directly improving the urban environmental color by finding out what the actual problems related to color are, and what the solutions would be. The goal of this study is to find a holistic systematic problem-solving method. Problems of urban environmental color are identified from both literature review and questionnaires to the expert group, such as environmental planning, design group, and the landscape executive group. Through mapping of relationships among these problems, the intellectual map was made to layout the structures of problems. Based on this method, the structures of problems of urban environmental color were classified into 5 categories: 1) the items related to the administrative structure, 2) the items related to the color management goal and system, 3) the items related to the color planning and design phase, 4) the items related to the color consulting committee, and 5) the items related to the present state of color use. Thus, in order to solve the color problem in urban landscape, practical strategy is strongly required. It is not a temporary expedient but a holistic approach. The solution for the problems of urban environmental color could be divided into 6 types; ‘regulations amendment’,‘color standard amendment’,‘color management plan’,‘color education’, and ‘advertisement for the goal of color management’. Regulations amendment among these types was proposed as the most effective method due to the close relationship with problem categories. Thus, as the solution for the problems of urban environmental color, the ‘color management system’ was suggested. Detailed contents the suggested color management system were divided into three parts; 1) legislation by regulations, ordinance and acts, 2) management by controling the level of guidelines, and 3) the standards for execution of this system.

• 생명과학회지
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• 제8권6호
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• pp.681-686
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• 1998

이상의 결과로부터 spin lavel의 영향은 IASL, MSL은 이완상태 myosin head의 규칙적인 나선 배열은 흐트러진다. 특히 IASL은 효과가 크다. 적도반사의 변화로부터 myosin head는 spin label하는 것에 의해 actin filament 근방에 이동해 있다는 것을 알 수 있었다. 215 $\AA$ 반사의 감소는 spin lavel에 의한 myosin의 143 $\AA$주기성을 더욱 강하게 해 준다. 143 $\AA$, 72 $\AA$의 거동은 filament축으로부터 투영한 구조를 반영하기 때문에 IASL에는 143 $\AA$ 주기의 밀도분포가 완만하게 되어 있다는 것을 나타내고, MSL에는 143 $\AA$ 분포가 올라와 있다는 것을 나타낸다. actin 반사변화에서 MSL의 actin반사의 증가는 이동한 myosin head가 어떤 actin과 결합하였거나, spin lavel의 영향으로 actin의 구조가 변화되었다. 한편, IASL은 actin반사를 감소 시키기 때문에 myosin head의 결합을 하지 않았다. 결론적으로, 이것은 actin의 SH기에도 spin label되어 actin의 나선 구조가 크게 흐트러짐을 알 수 있었다