• Journal of the Korean Chemical Society
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• v.30 no.6
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• pp.510-515
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• 1986

Spectra for the $v_3$+ Amide II combination band of thioacetamide(TA) were obtained in carbon tetrachloride solutions and in very dilute solutions of TA-N,N-dimethlylacetamide (DMA) in carbon tetrachloride in the range of 5~55$^{\circ}$C. The combination band in the three component system can be resolved into components due to monomeric TA, 1 : 1 TA-DMA complex and 1 : 2 TA-DMA complex. In the dilute solutions the experimental spectrum was resolved by using the computer into its two Lorentzian-Gaussian product components which have been identified with the monomeric TA and the 1 : 1 complex. The equilibrium constants and thermodynamic parameters of 1 : 1 complex were determined by analysis of concentration and temperature dependent spectra. The ${\Delta}H^{\circ}$ and ${\Delta}S^{\circ}$ for the 1 : 1 complex were -14.4 KJ mol$^{-1}$ and -15.6 J mol$^{-1}deg^{-1}$, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.901-909
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• 2012

This paper describes characteristics of solid-state $NaBH_4$ hydrogen generation and supply system for fuel cell UAV. Flow rate and pressure of the generated hydrogen were dramatically changed during $NaBH_4$ decomposition using acid. Hydrogen supply was stabilized by a self-pressurized reactor, and hydrogen stabilization method was introduced. For hydrogen generation in below zero-temperature, hydrochloric acid was diluted by propylene glycol-water mixtures. Solid-state $NaBH_4$hydrogen generation and supply system was designed. Basic operation experiments was performed to reveal the characteristics of this hydrogen generation system.

• Journal of the Korean Applied Science and Technology
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• v.12 no.2
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• pp.21-28
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• 1995

N-아실 아미도에틸 N-아미도 카르복시산 유도체들의 물리적 특성과 계면성이 연구되었다. 묽은 용액의 표면장력은 $22{\sim}32dyne/cm$의 값을 나타냈으며 이들 cmc의 범위는 $0.8{\sim}6.0mmol/L$이었다. 표면장력 저하능은 소수성의 알칼사슬이 길어질수록 그리고 카르복시기와 아미드기 사이의 메틸렌기의 수가 감소할수록 증가하였다. 반응생성물의 구조와 계면성의 관계를 비교 ${\cdot}$ 검토한 바 온화한 Krafft point와 뛰어난 습윤성, 낮은 기포력을 나타내었다.

• Resources Recycling
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• v.7 no.3
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• pp.17-26
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• 1998

A study on the recovery of silver and nitric acid in the liquid waste resulted from the mediated electrochemical oxidation(MEO) process was conducted. The removal of silver in the concentrated nitric acid solutions was carried out by the electrodeposition. The removal efficiency more than 98% could be obtained in nitric acid concentrations less than 3 M with the current efficiency of nearly 100%. The experimonts on the evaporation for the recovery of nitric acid were performed as well. At the evaporation factor of 25., the degree of nitric acid recovery in 3.5 M nitric acid solution containing 0.5 to 1.0 mol% NaNO, was 80~90% resulting in 2.8~3.1 M nitric acid. The design factors and operating conditions of the distillation tower were analyzed by using MEH model derived by Maphtali-Sandholm with the throughput of 4 kg/hr for the enrichment of dilute nitric acid solution recovered by evaporation to reuse in the MEO process. The distillation column composed of eleven theoretical stages having the overall tray efficiency of 70% are needed to obtain 1.03 kg/h of 12M nitric acid and 2.97 kg/h of water with feed being introduced to the column at tray 6 from the bottom at the reflux ratio of 0.25, the reboiler with the heat load of 2.7 kW, and the condenser with the cooling load of 0.5 kW.

• Journal of the Korean Electrochemical Society
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• v.5 no.3
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• pp.111-116
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• 2002

Electrochemical scanning tunneling microscopy was employed to study the evolution of surface morphology during electrochemical preparation of Si(111)-H from Si(111) oxide. Anodic dark current of cyclic voltammogram in 0.2M $NH_4F$ solution (pH 4.7) decreased as the number of cycles increased and remained nearly constant after the second cycle. Then, the Si(111) oxide was entirely stripped, which was followed by H termination on the Si(111) surface. Hydrides at kink and step sites were etched more rapidly than on the terrace, which remained triangle pits with [112] oriented steps where existed stable monohydride. Then, triangle pits deepened. During chronomamperometry at 0.4V anodic dark current shoulder appeared and decreased slowly, indicated the stripping of Si(111) oxide and the formation of stable (112) oriented steps with monohydride. Additionally, the etching mechanism of Si(111)-H in 0.2M $NH_4F(pH 4.7)$ solution at +0.4V was discussed.

• Polymer(Korea)
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• v.39 no.3
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• pp.370-381
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• 2015

In the system of poly(vinyl alcohol) (PVA)/dimethyl sulfoxide, the refractive index of polymer was very well matched to that of solvent and thus its scattered intensity could be minimized. After adding small amount of polystyrene latex particle (nominal diameter 200 nm), diffusion behavior of only probe particle was investigated against the concentration of polymer matrix by means of dynamic light scattering. The polymer concentration dependence of its reduced diffusion coefficient was able to be analysed with the stretched exponential function of the reduced concentration $C[{\eta}]$. In very dilute concentration regime, the depletion layer kept constant but at the early semi-dilute regime of $1{\leq}C[{\eta}]{\leq}2.5$, the concentration-dependent exponent of depletion layer ${\delta}$ was appeared to be -0.8 which was very close to theoretical one of -0.85. However it was also observed at the higher concentration that its layer thickness decreased more abruptly than theoretical expectation and this phenomenon was ascribed to Oosawa type attractive interaction between adjacent latex particles.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1092-1095
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• 1999

The well-known mixed-acid process for the aromatic nitration requires subsequent separation of spent acid, mainly dilute sulfuric acid. A novel nitration process using $HNO_3-NO_2-O_3$ was tested in a small pilot scale with 3 mol of p-nitrotoluene. Nitrogen dioxide(14.3 mol) was added three times in parts into the solution of p-nitrotoluene and $HNO_3$(6 mol) in dichloroethane. The nitration proceeded to more than 97% conversion within 5.5 h using 0.871 mol/h of ozone. As a clean process of aromatic nitration, this method is expected to replace the present process which causes the environmental problems.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.226-230
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• 2009

Rice straw was pretreated using dilute sulfuric acid at reaction conditions covering two levels of reaction temperature (140, $150^{\circ}C$) and five levels of acid concentrations ($1.0{\sim}3.0%wt$). The production and decomposition rates of major components of rice straw indicating glucose, xylose, galactose and arabinose were investigated. The production rate of arabinose and the decomposition rate of xylose were greatest among them. The maximum attainable hemicellulose (xylose+galactose+arabinose) yield was about 80%. High acid concentration appears to favor the maximum yield but high temperature does not. The optimum condition was found to be $140^{\circ}C$, 2.5% and 20 minutes. The maximum glucose yields were almost same, around $16{\sim}18%$, regardless of reaction conditions.

• Journal of the Korean Chemical Society
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• v.38 no.4
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• pp.265-270
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• 1994

The aquation and base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ were studied by UV spectroscopic method in various SDS aqueous solution. The base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ with the addition of 0, 0.05, 0.1 mol dm$^{-3}$ sodium chloride was studied. For the aquation of the complex, the rate constant in the micellar phase(kH$^M$) was a little larger than that in the aqueous phase(kH$^W$). With the increase of SDS concentration, the second order rate constant(kOH) for the base hydrolysis unchanged below the CMC and sharply decreased down to a limiting value after the CMC was reached. The effect of added NaCl on the rate behavior of the complexes in the micellar solution were investigated by using an ion-exchanged model.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.141-141
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• 1999

전기화학과 초고진공(ultra-high vacuum, UHV) 분광법을 이용하여 고체/액체의 계면에서 일어나는 현상을 분자단위에서 이해하고 조절하기 위한 연구를 수행하였다. 이들 중 전기화학으로 형성된 구리 및 은 금속(sub)monlayer 박막을 그 예로 선택하여 소개한다. 초박막 금속의 흡착량은 cyclic voltammogram과 새로 개발된 Auger electron spectroscopy (AES) 정량법을 통해 얻어졌고, 이 값들은 low energy electron diffraction (LEED) 및 in-situ atomic force microscopy (AFM)법을 이용한 구조 분석결과와 비교되어졌다. 또한 화학상태를 확인하기 위하여 core-level electron energyy loss spectroscopy (CEELS)를 사용하였다. 먼저 황산 전해질에서 금(111) 단결정 전극상에 전기화학적으로 형성된 굴의 계면특성을 조사하였다. 특정 전위값에서 2/3 ML의 구리와 1/3 ML의 음이온이 상호 흡착하여 ({{{{ SQRT { 3} }}$\times${{{{ SQRT { 3} }}) 격자 구조를 보였고, 전위값이 커지거나 줄어들면, 이 구조가 사라지는 현상이 관찰되었다. 즉 이 ({{{{ SQRT { 3} }}}}$\times${{{{ SQRT { 3} }}}}) 흡착구조는 첫 번째 UPD underpotential deposition) 피크에 특이하게 관련되어 있음을 알 수 있었다. 금속 초박막 형성에 미치는 음이온의 영향을 좀 더 확인하기 위해 초박막 은이 증착된 금 단결정 전극상의 황산 음이온에 관하여 연구하였다. 은의 증착이 일어날 수 없는 양전위값 영역에서 ({{{{ SQRT { 3} }}}}$\times${{{{ SQRT { 3} }}}})의 규칙적인 음이온의 구조를 보였다. 그리고 은의 장착은 세척 과정과 용액의 농도에 따라 p(3$\times$3)과 p(5$\times$5)의 규칙적인 두가지 구조를 가졌다. in-situ AFM에서는 p(3$\times$3)의 은 증착 구조만 나타났고, 음 전위값으로 옮겨가면 p(1$\times$1) 구조로 바뀌었다. ex-situ 초고진공 결과와 이 AFM의 in-situ 결과를 상호 비교 논의할 것이다. 음이온의 흡착이 없는 묽은 플로르산(HF) 전해질에서 은은 전위값을 음전위 쪽으로 이동해 감에 따라 p(3$\times$3), p(5$\times$5), (5$\times$5), (6$\times$6), 그리고 (1$\times$1)의 연속적 구조 변화를 보였다. 이 다양한 구조들을 AES로부터 얻어진 표면 흡착량과 연결시켰더니 정량적으로 잘 일치되는 결과를 보였다. 전기화학적인 증착에서는 기존의 진공 증착과 비교할 때 음이온의 공흡착이 금속 초박막 형성 메카니즘에 큰 영향을 미침을 알 수 있었다. 또한 은의 전기화학적 다층박막 성장은 MSM (monolayer-simultaneous-multilayer) 메카니즘을 따름을 확인하였다. 마지막으로 구조 및 양이 규칙적으로 조절되는 전극의 응용가능성이 간단히 논의될 것이다.