• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.272-272
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• 2010

The structural and electronic properties of $XAu_{16^-}$ (X = S or O) have been studied by the scalar relativistic all-electron density functional calculations, in which a particular attention is paid to the stability of various $XAu_{16^-}$ structures. We find that an X-encapsulated golden cage ($XAu_{16^-}$) represents an ionic character whereas in the other structures, adsorption characters are represented by covalent bonding. Especially, in S@$Au_{16^-}$, electrons are donated from the S atom to $Au_{16^-}$. The most stable $XAu_{16^-}$ structures exhibit a small HOMO-LUMO energy gap, indicating that they could be chemically reactive. We also calculated the activation energy barriers of the transition between the most stable exohedral and endohedral adsorption configurations as well as their reaction energies. Our results demonstrate that the activation barrier in the $OAu_{16^-}$ is lower than in $SAu_{16^-}$. This is associated with the smaller atomic radius of oxygen than that of sulfur.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.97-97
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• 2013

We present a comprehensive study on the integration of h-BN with silicon MOSFET. Temperature dependent mobility modeling is used to discern the effects of top-gate dielectric on carrier transport and identify limiting factors of the system. The result indicates that coulomb scattering and surface roughness scattering are the dominant scattering mechanisms for silicon MOSFETs at relatively low temperature. Interposing a layer of h-BN between $SiO_2$ and Si effectively weakens coulomb scattering by separating carriers in the silicon inversion layer from the charged centers as 2-dimensional h-BN is relatively inert and is expected to be free of dangling bonds or surface charge traps owing to the strong, in-plane, ionic bonding of the planar hexagonal lattice structure, thus leading to a significant improvement in mobility relative to undecorated system. Furthermore, the atomically planar surface of h-BN also suppresses surface roughness scattering in this Si MOSFET system, resulting in a monotonously increasing mobility curve along with gate voltage, which is different from the traditional one with a extremum in a certain voltage. Alternatively, high-k dielectrics can lead to enhanced transport properties through dielectric screening. Modeling indicates that we can achieve even higher mobility by using h-BN decorated $HfO_2$ as gate dielectric in silicon MOSFETs instead of h-BN decorated $SiO_2$.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.178-182
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• 1999

Simple binary $Na_2S-SiO_2$ oxysulfide glasses were prepared by a conventional melt-quench method in order to investigate the role of sulfur in glass structure and the electronic state. By X-ray photoelectron spectroscopy(XPS) measurement, S2p binding energy of the glass was observed at approximately 161eV which was close to that of ionic $S^{2-}$. The coordinating state around silicon atoms were investigated by ${29}^Si$ MAS-NMR measurement. The chemical shift observed from NMR supported that sulfur atom was joined to a silicon atom by substituting for an oxygen atom and was present as a non-bridging sulfide ion in low alkali content. On the other hand, it could be presumed that a portion of sulfur anions existed in an isolated state from the glass-network frame at high alkali content. The state of these sulfurs was also studied by Raman spectroscopy in detail.

• 폴리머
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• 제34권4호
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• pp.386-389
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• 2010

Thermal behaviors of water in the poly(acrylic acid) (PAA)/water mixtures with 0.1 M NaCl, HCl, and NaOH were investigated by DSC. It showed that adding ions in the mixtures affected the crystallization of water evidently. Compared with the PAA/water mixtures, the $T_m$ of freezable bound water in the mixtures with ions moved to lower values and varied with different cations and anions, due to the stabilization or destabilization of the hydrogen-bonding hydration between polymers and water molecules through ionic hydration. The content of non-freezable bound water in the non-crystalline phase of the PAA/water mixtures with ions was not constant, it increased with total water content gradually, owing to the more binding sites created by ions. The ions could change the distribution of different states of water in the polymer aqueous solutions evidently.

• Elastomers and Composites
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• 제54권3호
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• pp.209-219
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• 2019

It is important to analyze crosslink densities of rubber articles because the physical properties are dependent on the crosslink densities. In this paper, analytical techniques for the measurement of crosslink densities of rubber vulcanizates are described. The most widely used method to measure the crosslink density is a swelling method combined with the Flory-Rehner equation. Application of the interaction parameter (${\chi}$) of rubber and swelling solvent is critical because the crosslink density is absolutely dependent on the ${\chi}$ value. Methods for obtaining ${\chi}$ employ not only solubility parameters of the polymer and swelling solvent but also inverse gas chromatography (IGC). The solubilities of rubbers can be obtained using micro differential scanning calorimetry (${\mu}DSC$), intrinsic viscosity measurement, and UV-visible spectroscopy. Nuclear magnetic resonance (NMR) spectroscopy has been also used for the measurement of the crosslink density using the $T_2$ relaxation time, which is determined by spin-spin relaxation in solid-state NMR. For sulfur-cured rubber vulcanizates, crosslink densities according to the crosslink types of mono-, di-, and polysulfides are measured by treating the rubber samples with a chemical probe composed of thiol and amine compounds. Measurement methods of physical crosslinking by filler, crystallization, and ionic bonding have also been introduced.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.306-311
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• 1992

The stable structures of pure ethylene and mixed ethylene-ammonia cluster ions are studied using an electron impact ionization time-of-flight mass spectrometer. Investigations on the relative cluster ion distributions of $(C_2H_4)_n(NH_3)_m^+$ under various experimental conditions suggest that $(C_2H_4)_2(NH_3)_3^+$ and $(C_2H_4)_3(NH_3)_2^+$ ions have the enhanced structural stabilities, which give insight into the feasible structure of solvated ions. For the stable configurations of these ionic species, we report an experimental evidence that both $(C_2H4)_2^+(C_2H_4)_3^+$ clusters as the central cations provide three and two hydrogen-bonding sites, respectively, for the surrounding $NH_3$ molecules. This interpretation is based on the structural stability for ethylene clusters and the intracluster ion-molecular rearrangement of the complex ion under the presence of ammonia solvent molecules.

• 한국분말재료학회지
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• 제28권1호
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• pp.25-30
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• 2021

The surface of silicon dummy wafers is contaminated with metallic impurities owing to the reaction with and adhesion of chemicals during the oxidation process. These metallic impurities negatively affect the device performance, reliability, and yield. To solve this problem, a wafer-cleaning process that removes metallic impurities is essential. RCA (Radio Corporation of America) cleaning is commonly used, but there are problems such as increased surface roughness and formation of metal hydroxides. Herein, we attempt to use a chelating agent (EDTA) to reduce the surface roughness, improve the stability of cleaning solutions, and prevent the re-adsorption of impurities. The bonding between the cleaning solution and metal powder is analyzed by referring to the Pourbaix diagram. The changes in the ionic conductivity, H2O2 decomposition behavior, and degree of dissolution are checked with a conductivity meter, and the changes in the absorbance and particle size before and after the reaction are confirmed by ultraviolet-visible spectroscopy (UV-vis) and dynamic light scattering (DLS) analyses. Thus, the addition of a chelating agent prevents the decomposition of H2O2 and improves the life of the silicon wafer cleaning solution, allowing it to react smoothly with metallic impurities.

• 분석과학
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• 제20권5호
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• pp.448-451
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• 2007

A new bis(dicyclohexylammonium) chromate dihydrate complex, $[(C_6H_{11})_2NH_2]_2[CrO_4]{\cdot}2H_2O$, (I), has been synthesized and its structure analyzed by FT-IR, EDS, elemental analysis, ICP-AES, and single crystal X-ray diffraction methods. The Cr(VI) complex (I) is tetragonal system, I${\bar{4}}$2d space group with a = 12.5196(1), b = 12.5196(1), c = $17.3796(3){\AA}$, a = ${\beta}$ = ${\gamma}$ = $90^{\circ}$, V = $2724.09(6){\AA}^3$, Z = 4. The crystal structure of complex (I) consists of tetrahedral chromate $[CrO_4]^{2-}$ anion, two organic dicyclohexylammonium $[(C_6H_{11})_2NH_2]^+$ cations and two lattice water molecules. The chromate anion and protonated dicyclohexylammonium cation is mainly constructed through the ionic bond. The cyclohexylammonium rings of the dicyclohexylammonium cation take the chair form and vertical configuration with each other. The N-H${\cdot}$O and O-H${\cdot}$O hydrogen bond networks between the $N_{dicyclohexylammonium}$, $O_{water}$ and $O_{chromate}$ atom lead to self-assembled molecular conformation and stabilize the crystal structure.

• 한국의류학회지
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• 제32권6호
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• pp.928-934
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• 2008

본 연구는 염색공정의 표준화와 재현성을 확립하기 위해 흥화 황색소의 견섬유에 대한 염색성을 조사하는데 목적 이 있다. 홍화 황색소는 물로 추출한 후 농축, 동결건조하여 분말상태로 만들어 사용하였다. 염색온도 및 시간, 염료농도, 염액의 pH 등에 따른 염착성과 색상 변화에 대해 조사하였으며, 세탁 및 광견뢰도를 평가하였다. 염색온도가 증가함에 따라 염착량은 증가하였으며 $30^{\circ}C$에서 염색할 때 가장 선명한 노랑색을 얻을 수 있었다. 염료농도가 증가함에 따라 염착량이 계속 증가하여 점점 진하고 어두운 노랑색이 되었다. pH 3.5에서 최대염착량을 보였으며, 최적조건에서 색차는 1.11-2.01로서 재현성은 양호하였다. 색소와 견섬유간의 결합은 pH 5.5 부근에서는 주로 수소결합에 의해, 등전점(pH 3.8-4.0) 이하에서는 수소결합과 함께 이온결합이 관여하는 것으로 판단되었다. 세탁(드라이크리닝)견뢰도는 4/5둥급으로 좋은 편이었으나 일광견뢰도는 2/3등급이었다.

• Restorative Dentistry and Endodontics
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• 제25권2호
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• pp.272-288
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• 2000

수산화칼슘은 여러 약리작용으로 인해 근관소독제로 널리 사용되고 있는 약제이다. 근관 내에 수산화칼슘을 투약한 후 gutta-percha와 더불어 산화아연-유지놀계 근관시멘트로 근관을 충전하는 경우 근관시멘트의 물성에 변화가 있다는 보고가 있다. 따라서 본 연구에서는 수산화칼슘과 산화아연-유지놀 간의 반응에 의해 생성되는 수산화칼슘-유지놀 화합물의 반응성을 확인하기 위하여 수산화칼슘, 유지놀, 산화아연-유지놀, 수산화칼슘-유지놀 및 수산화칼슘-산화아연-유지놀 화합물을 XRD, FT-IR spectrophotometer 및 FT-NMR spectrometer로 분석하여 다음과 같은 결과를 얻었다. 1. 수산화칼슘과 산화아연-유지놀 간의 반응으로 생성된 화합물은 다음과 같았다. 2. 수산화칼슘은 유지놀과 화학결합(이온결합)을 하는 것으로 나타났다. 3. $Ca^{2+}$과 유지놀 사이의 결합은 단순 이온결합이다. 따라서 수산화칼슘-산화아연유지놀 화합물은 중화반응에서 생기거나 외부에서 유입된 물이 존재시 쉽게 이온화되어 물리적 성질이 저하될 것으로 생각된다.