• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2454-2458
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• 2007

Exploring the basic concepts for the design of CO2-philic molecules is important due to the possibility for “green” chemistry in supercritical CO2 as substitute solvent systems. The Lewis acid-base interactions and C?H…O weak hydrogen bonding were suggested as two key factors for the solubility of CO2-philic molecules. We have performed high level quantum mechanical calculations for the van der Waals complexes of CO2 with trimethylphosphate and trimethylphosphine oxide, which have long been used for metal extractants in supercritical CO2 fluid. Structures and energies were calculated using the MP2/6-31+G(d) and recently developed multilevel methods. These studies indicate that the Lewis acid-base interactions have larger impact on the stability of structure than the C?H…O weak hydrogen bonding. The weak hydrogen bonds in trimethylphosphine oxide have an important role to the large supercritical CO2 solubility when a metal is bound to the oxygen atom of the P=O group. Trimethylphosphate has many Lewis acid-base interaction sites so that it can be dissolved into supercritical CO2 easily even when it has metal ion on the oxygen atom of the P=O group, which is indispensable for a good extractant.

• 마이크로전자및패키징학회지
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• 제19권3호
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• pp.63-69
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• 2012

Adhesion and mechanical reliability of silicon/epoxy/polyimide interfaces are critical issues for flexible electronics. Bonds between these interfaces are mainly hydrogen bonds, so their adhesion is weaker than cohesive fracture toughness and vulnerable to moisture. In order to enhance adhesion and suppress moisture-assisted debonding, UV/Ozone treatment and innovative sol-gel derived hybrid layers were applied to silicon/epoxy/polyimide interfaces. The fracture energy and subcritical crack growth rate were measured by using a double cantilever beam (DCB) fracture mechanics test. Results showed that UV/Ozone treatment increased the adhesion, but was not effective for improving reliability against humidity. However, by applying sol-gel derived hybrid layers, adhesion increase as well as suppresion of moisture-assisted cracking were achieved.

• Journal of Applied Biological Chemistry
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• 제42권3호
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• pp.125-129
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• 1999

The changes in gel characteristics of soy protein and succinylated soy protein due to various specific interaction-altering reagents which affect the formation and textural properties of gels, were studied. The reagents were added to 15% soy protein solutions prior to heat treatment. Succinylated soy protein formed harder gel without the addition of reagents. Hardly no gels were formed with urea, indicating that hydrogen bonds significantly contributed to the formation and hardness of the gel and the effects of urea on the hardness of succinylated soy protein gel were more significant. Disulfide bonds were important in the formation of hard gels whether they were succinylated or not, but the contributions of hydrophobic interactions to gel hardness were relatively insignificant. The hardness reducing effects of NaCl and NaSCN were more significant in succinylated soy protein gel. As such, electrostatic interactions were important for succinylated soy protein to form hard gel but not for unmodified soy protein.

• 통합자연과학논문집
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• 제3권4호
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• pp.219-225
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• 2010

On the surface of mesoporous silica thin films (MSTF) which were fabricated by sol-gel approach there are existences of water and three different silanol types including chained, germinal and isolated silanol. Their amounts changes as a function of aging time of used sol solution, as confirmed by FT-IR. The adsorbed water generates ionic carriers such as H+ and OH- and passivates the Si dangling bonds at the interface of silicon wafer-MSTF. The ionic carriers can not only transport across the thickness of thin film to enhance the leakage current but also diffuse toward the silicon wafer-MSTF interface to depassivate Si dangling bonds. On the other hand, chained silanols or germinal silanols promote the moisture adsorption of MSTF and tend to form strongly hydrogen bonded systems with adsorbed water molecules resulting in very high dielectric constant. Isolated silanol, on the contrary, affects less on electrical properties of thin film.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.696-699
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• 1996

Silicate and borosilicate gels were prepared by the sol-gel process and thermally treated in the 150-850 ℃ temperature range. Solid-state 1H MAS and 29Si CP/MAS NMR spectroscopy were used to investigate the effects of heat treatments on the silicate gel to glass conversion process. The 1H NMR isotropic chemical shifts and the relative intensities of hydrogen bonded and isolated silanol groups have been used to access the information concerning the dehydration process on the silicate gel surface. The 29Si NMR isotropic chemical shifts affected by the local silicon environment have been used to determine the degree of crosslinking, i.e. the number of siloxane bonds. These NMR results suggest that the silicate gel to glass conversion process is occurred by two stages which are dependent on the temperature; (1) the formation of particles up to 450 ℃ and (2) the formation of large particles by aggregation of each separated single particle above 450 ℃. In addition, the effects of B atom on the formation of borosiloxane bonds in borosilicates have been discussed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.438-442
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• 2006

The degradation of Nafion membrane by hydrogen peroxide was investigated in polymer electrolyte membrane fuel cell (PEMFC). Degradation tests were carried out in a solution of $10{\sim}30%$ hydrogen peroxide containing 4ppm $Fe^{2+}$ ion which is well known as Fenton's reagent at $80^{\circ}C$ for 48hr. Characterization of degraded membranes were examined through the IR, Water-uptake, Ion exchange capacity, mechanical strength and $H_2$ permeability. After degradation, C-F, S-O and C-O chemical bonds of membrane were broken by radical formed by $H_2O_2$ decomposition. Breaking of C-F bond which is the membrane backbone reduced the mechanical strength of Nafion membrane and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Also the decomposition of C-O and S-O, side chain and terminal bond of membrane, decreased the ion exchange capacity of the membrane.

• Journal of Korean Vacuum Science & Technology
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• 제6권1호
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• pp.46-50
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• 2002

C-SiC films with different content of SiC on stainless steel substrate were prepared with ion beam mixing. It was found that hydrogen concentrations in C-SiC coatings was higher than that in stainless steel after H$\^$+/ ion implantation followed by thermal annealing. Infrared (IR) transmission measurement was used to study the mechanism of hydrogen retention by C-SiC films. The vibrational features in the range between 400 and 3200 cm$\^$-1/ in IR transmission spectra show the Si-CH$_3$, Si-CH$_2$, Si-H, CH$_2$and CH$_3$bonds, which are responsible for retaining hydrogen.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1951-1959
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• 2008

Pentamer cluster of azodicarbonamide (ADA) based on the crystalline structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties at various levels of the density functional theory. Stretching force constants of N${\cdot}{\cdot}{\cdot}$H or O${\cdot}{\cdot}{\cdot}$H, and angle-bending force constants of N-H${\cdot}{\cdot}{\cdot}$N or N-H${\cdot}{\cdot}{\cdot}$O for intermolecular hydrogen bonds in the pentamer cluster were obtained in 0.2-0.5 mdyn/$\AA$ and 1.6-2.0 mdyn$\AA$, respectively. The geometry of central ADA molecule fully hydrogen bonded with other four molecules shows good coincidence to the crystalline structure except the bond distances of N-H. Calculated Raman and infrared spectra of central ADA molecule in cluster represent well the experimental spectra of ADA obtained in the solid state compared to a single molecule. Detailed structural and vibrational properties of central ADA molecule in the pentamer cluster are presented.

• Current Photovoltaic Research
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• 제1권1호
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• pp.27-32
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• 2013

We investigated the growth mechanism of amorphous-phase Si thin films in order to improve the film characteristics and circumvent photo-degradation effects by implementation of hot-wire chemical vapor deposition. Amorphous silicon thin films grown in a silane/hydrogen mixture can be decomposed by a resistive heat filament. The structural properties were observed by Raman spectroscopy, FTIR, SEM, and TEM. The electrical properties of the films were measured by photo-conductivity, dark-conductivity, and photo-sensitivity. The contents of Si-H and $Si-H_n$ bonds were measured to be 19.79 and 9.96% respectively, at a hydrogen flow rate of 5.5 sccm, respectively. The thin film has photo-sensitivity of $2.2{\times}10^5$ without a crystalline volume fraction. The catalyst behavior of the hot-wire to decompose the chemical precursors by an electron tunneling effect depends strongly on the hydrogen mixture rate and an amorphous Si thin film is formed from atomic relaxation.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2711-2719
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• 2013

Hydrogen bonding interaction between alcohols and water molecules is an important characteristic in the aqueous solutions of alcohols. In this paper, a series of molecular dynamics simulations have been performed to investigate the aqueous solutions of low molecular weight alcohols (methanol, ethylene glycol and glycerol) at the concentrations covering a broad range from 1 to 90 mol %. The work focuses on studying the effect of the alcohols molecules on the hydrogen bonding of water molecules in binary mixtures. By analyzing the hydrogen bonding ability of the hydroxyl (-OH) groups for the three alcohols, it is found that the hydroxyl group of methanol prefers to form more hydrogen bonds than that of ethylene glycol and glycerol due to the intra-and intermolecular effects. It is also shown that concentration has significant effect on the ability of alcohol molecule to hydrogen bond water molecules. Understanding the hydrogen bonding characteristics of the aqueous solutions is helpful to reveal the cryoprotective mechanisms of methanol, ethylene glycol and glycerol in aqueous solutions.