• 산업기술연구
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• 제20권A호
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• pp.39-44
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• 2000

Highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its solution properties were investigated. The intrinsic viscosities for crude biopolymer and biopolymers purified by dialysis or CPC(cetylpyridinium chloride) treatment were 58.24, 73.60 and 42.18 dL/g, respectively. The intrinsic viscosity of biopolymer showed the maximum value at the neutral pH but it was decreased remarkably at the alkaline or acidic pH. Biopolymer exhibited the property of polyelectrolyte, showing the sharp decrease of intrinsic viscosity by the addition of NaCl. Intrinsic viscosity of dilute solution at the low NaCl concentration was exponentially dependent on temperature and its temperature dependency was increased with NaCl concentrations. The chain stiffness, coil overlap parameter, and critical concentration were 0.09, 5.25 and 0.07g/dL, respectively. Temperature dependency on intrinsic viscosity of biopolymer solution was different each other at $45^{\circ}C$. Flow activation energies at temperatures above $45^{\circ}C$ were constant, while those at temperatures below $45^{\circ}C$ increased with increase of added NaCl concentration.

• 한국세라믹학회지
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• 제24권6호
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• pp.543-552
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• 1987

The effects of deposition variables on SnO2 CVD were investigated for SnCl4＋O2 reaction at 300∼700$^{\circ}C$, Psncl4=1${\times}$10-5∼1${\times}$10-3 atm, and Po2=5${\times}$10-4∼1 atm. A thermodynamic equilibrium study on Sn-Cl-O system has been performed with the computer calculation. The calculation indicates that major species participating the reaction in SnCl4 and not intermediate species, SnCl2. Good uniformity of the film thickness was obtained at the flow rate of 11cm/sec, which resulted from the stable gas flow in our cold wall reactor. The experimental results showed that apparent activation energy of the deposition was about 13.5Kcal/mole below the temperature of 500$^{\circ}C$ and the deposition mechanism was controlled by surface reation. The behavior of deposition rate on the reactant partial pressures could be explained with the Langmuri-Hinshelwood mechanism. X-ray study demonstrated that SnO2 film deposited at temperatures above 400$^{\circ}C$ were polycrystalline with tetragonal rutile structure and grew with (211) and (301) preferred orientations.

• Molecules and Cells
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• 제37권3호
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• pp.202-212
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• 2014

ClC-1 is a member of a large family of voltage-gated chloride channels, abundantly expressed in human skeletal muscle. Mutations in ClC-1 are associated with myotonia congenita (MC) and result in loss of regulation of membrane excitability in skeletal muscle. We studied the electrophysiological characteristics of six mutants found among Korean MC patients, using patch clamp methods in HEK293 cells. Here, we found that the autosomal dominant mutants S189C and P480S displayed reduced chloride conductances compared to WT. Autosomal recessive mutant M128I did not show a typical rapid deactivation of Cl- currents. While sporadic mutant G523D displayed sustained activation of $Cl^-$ currents in the whole cell traces, the other sporadic mutants, M373L and M609K, demonstrated rapid deactivations. $V_{1/2}$ of these mutants was shifted to more depolarizing potentials. In order to identify potential effects on gating processes, slow and fast gating was analyzed for each mutant. We show that slow gating of the mutants tends to be shifted toward more positive potentials in comparison to WT. Collectively, these six mutants found among Korean patients demonstrated modifications of channel gating behaviors and reduced chloride conductances that likely contribute to the physiologic changes of MC.

• 한국세라믹학회지
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• 제27권7호
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• pp.916-924
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• 1990

The preparatin of the fine TiN powders by reduction-nitridation of TiCl3-Al-N2 system was attempted in the temperature range from 350$^{\circ}$to 100$0^{\circ}C$. The formation mechanism and kinetics of TiN were examined, and the resultant TiN powder was characterized by means of XRD, PSA and SEM-EPMA methods. TiN was formed at temperatrue higher than $600^{\circ}C$. As an intermediate phase, AlTi was obtained. The apparent activation energy for the formation of TiN was approximately 4.2kcal/mole(600$^{\circ}$~90$0^{\circ}C$). The crystallite size and lattice constnat of TiN powder obtained in the temperature range from 600$^{\circ}$to 100$0^{\circ}C$ for 2h at the Al/TiCl3 molar ratio of 1.0 were 160~255A and 4.231~4.239A, respectively. According to PSA measurement, the mean particle size ranged from 14.0 to 14.8${\mu}{\textrm}{m}$.

• Carbon letters
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• 제22권
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• pp.70-80
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• 2017

Activated carbons (ACs) have been used as electrode materials of electric double-layer capacitors (EDLC) due to their high specific surface areas (SSA), stability, and ecological advantages. In order to make high-energy-density ACs for EDLC, petroleum pitch (PP) pre-carbonized at $500-1000^{\circ}C$ in $N_2$ gas for 1 h was used as the electrode material of the EDLC after KOH activation. As the pre-carbonization temperature increased, the SSA, pore volume and gravimetric capacitance tended to decrease, but the crystallinity and electrode density tended to increase, showing a maximum volumetric capacitance at a medium carbonization temperature. Therefore, it was possible to control the crystalline structure, SSA, and pore structure of AC by changing the pre-carbonization temperature. Because the electrode density increased with increasing of the pre-carbonization temperature, the highest volumetric capacitance of 28.4 F/cc was obtained from the PP pre-carbonized at $700^{\circ}C$, exhibiting a value over 150% of that of a commercial AC (MSP-20) for EDLC. Electrochemical activation was observed from the electrodes of PP as they were pre-carbonized at high temperatures above $700^{\circ}C$ and then activated by KOH. This process was found to have a significant effect on the specific capacitance and it was demonstrated that the higher charging voltage of EDLC was, the greater the electrochemical activation effect was.

• Carbon letters
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• 제8권2호
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• pp.95-100
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• 2007

A series of activated carbons (ACs) were derived from sugarcane bagasse under two activation schemes: steam-pyrolysis at $600-800^{\circ}C$ and chemical activation with $H_3PO_4$ at $500^{\circ}C$. Some carbons were treated at 400, $600^{\circ}C$, or for 1-3 h, and/or in flowing air during pyrolysis of acid-impregnated mass. XRD profiles displayed two broad diffuse bands centered around $2{\theta}=23$ and $43^{\circ}$, currently associated with diffraction from the 002 and 100/101 set of planes in graphite, respectively. These correspond to the interlayer spacing, Lc, and microcrystallite lateral dimensions, La, of the turbostratic (fully disordered) graphene layers. Steam pyrolysis-activated carbons exhibit only the two mentioned broad bands with enhancement in number of layers, with temperature, and small decrease in microcrystallite diameter, La. XRD patterns of $H_3PO_4$-ACs display more developed and separated peaks in the early region with maxima at $2{\theta}=23$, 26 and $29^{\circ}$, possibly ascribed to fragmented microcrystallites (or partially organized structures). Diffraction within the $2{\theta}=43^{\circ}$ is still broad although depressed and diffuse, suggesting that the intragraphitic layers are less developed. Varying the conditions of chemical activation inflicts insignificant structural alterations. Circulating air during pyrolysis leads to enhancement of the basic graphitic structure with destruction and degradation in the lateral dimensions.

• Nuclear Engineering and Technology
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• 제5권4호
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• pp.321-333
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• 1973

브롬화벤젠썰포닐류 (R-C$_{6}$H$_4$SO$_2$Br, R=p-MeO, p-$CH_3$, p-H, p-NO$_2$등)의 할로겐 교환반응을 무수 아세톤 중에서 행하고 두 온도에서의 반응속도항수를 구함으로써 활성화 파라메타들을 아울러 결정하였다. 친핵자의 강도는 강한 전자흡인 치환기를 가졌거나 약한 전자공여 치환기를 가진 유도체에 대하여는 Cl->I-$\geq$Br-의 순위였으며, 강한 전자공여 치환기의 유도체에 대하여는 I-$\geq$Cl->Br-의 순위임을 보았다. 하메트(Harnmett)점시는 치환기를 가진 염화벤젠쎌포닐류에서와 유사하게 약간 위로 볼록한 특징을 보였는데 이것은 치환기를 가진 염화벤질류의 할로겐 교환반응의 그것이 아래로 오목함을 보이는 것과는 대조적이었다. 한편 브롬화벤젠썰포닐과 브롬화리티움 사이의 할로겐 교환반응 속도를 여러용매에서 측정한 결과 반응속도가 큰 순서는 ($CH_3$)$_2$CO>$CH_3$CN》MeOH이었다. 속도항수와 활성화파라메타들을 염화벤젠쎌포닐류에 대한 것과 비교하였으며 치환기효과, 용매효과 등에서 얻은 결과들을 전이상태의 구조적 특징으로 설명하고 반응기구를 논의하였다.

• 대한화학회지
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• 제33권4호
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• pp.371-378
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• 1989

분광광도법을 이용하여 [pt[dien]X]$^+$(X = $Cl^-$, $Br^-$, $I^-$) 와 ${NO_2}^-$와의 치환반응을 $20{\sim}35^{\circ}C,\;1{\sim}1500$ bar 범위에서 조사했다. 이들 반응의 속도는 모두 온도와 압력이 증가함에 따라 증가하였고, 치환 용이성은 $Cl^-$ > $Br^-$ > $I^-$였다. 활성화 부피변화(│${\Delta}V^{\neq}$│)는 모두 큰 음(-)의 값을 가졌고 온도가 증가함에 따라 감소하였다. $25^{\circ}C$에서 구한 일차속도상수($k_1$)와 이차속도상수 ($k_2$)는 압력이 증가함에 따라 다같이 증가하였고, $k_1$ 경로와 $k_2$ 경로에 대한 활성화부피(${\Delta}{V_1}^{\neq}$ 와 ${\Delta}{V_2}^{\neq}$)는 모두 큰 음(-)의 값을 가졌다. 또한 1 bar에서 $k_1$과 $k_2$를 구했고 온도가 증가함에 따라 모두 증가하였다. 각 반응경로에 대한 활성화파라미터를 결정했고, 모든 실험적 결과로부터 이 반응은 이탈기의 성질과 반응경로에 관계없이 회합(A)메카니즘을 가질 것으로 생각된다.

• 콘크리트학회논문집
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• 제26권1호
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• pp.71-78
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• 2014

사용후핵연료의 중간저장시설인 콘크리트 캐스크(cask)는 해안부근에 입지할 가능성이 크기 때문에 염해에 대한 문제가 크게 우려된다. 그리고 염해에 의한 철근의 부식 및 균열발생은 철근콘크리트구조물의 방사선 차폐기능뿐 아니라 구조성능 저하의 주요 원인이기 때문에 염해에 대한 평가는 매우 중요한 사항이다. 특히 염해환경과 함께 콘크리트 캐스크 내부에서는 사용후핵연료의 발열에 의해 $60^{\circ}C$정도의 고온 환경이 예상되기 때문에 고온에서의 염해에 대한 검토가 요구되지만, 기존 콘크리트 구조물의 염해평가에서는 온도에 대한 영향이 전혀 고려되어 있지 않아 고온에서 염해에 노출된 철근콘크리트구조물들의 내구설계 및 수명예측을 위해 참고할 만한 자료가 거의 없다. 이 연구에서는 다양한 온도환경에서의 염수(NaCl)침지시험을 통해 콘크리트의 염화물이온 확산계수를 측정하고 염화물이온 확산계수와 온도의 관계를 규명하고자 하였다. 실험 결과, 콘크리트의 염화물이온 확산계수는 온도의 증가에 따라 현저히 증대하여 고온환경에서의 염해 발생가능성이 매우 큰 것으로 조사되었다. 또한 크리트의 염화물이온 확산계수는 물시멘트(W/C)비가 낮아질수록 감소하였고, 이 경향은 온도가 증가(고온환경)하여도 동일하게 나타났다. 염화물이온 확산계수의 온도의존성은 아레니우스식(Arrhenius equation)으로 나타내어졌고 회귀분석 결과, 확산계수의 대수 값은 절대온도의 역수와 선형관계를 나타내었다. 또한 온도의존성을 나타내는 활성화에너지(activation energy)는 물시멘트(W/C)비가 낮을수록 높게 나타났다.

• 대한환경공학회지
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• 제22권1호
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• pp.133-139
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• 2000

리그닌의 열분해반응 후 발생하는 잔류고형물을 활용해보고자 $ZnCl_2$로 활성화하여 활성탄을 제조하였다. 공정변수로 설정한 활성화 온도, 활성화 시간 및 활성화제의 첨가량 등이 활성탄의 세공구조와 비표면적에 미치는 영향을 조사하여 최적 활성화 조건을 구하였다. 리그닌의 열분해 잔류고형물에 활성화제인 염화아연을 300wt% 첨가한 것을 질소분위기에서 $1000^{\circ}C$로 1시간 동안 활성화시켰을 때 비교적 높은 비표면적과 흡착능을 가지면서 세공구조가 잘 발달된 활성탄을 제조할 수 있었다.