• Composites Research
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• 제22권5호
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• pp.37-42
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• 2009

온도, 수분 및 자외선과 같은 자연환경을 모사할 수 있는 가속노화시험장치를 적용하여 복합적인 환경인자에 노출된 탄소섬유/에폭시 복합재의 열분석 특성과 화학구조분석을 수행하였다. 복합적인 환경인자의 최대 노출시간은 3000시간으로 노출시간에 따른 복합재의 열분석 특성과 화학구조는 Modulated DSE와 FTIR을 통해 조사하였다. Modulated DSC 시험을 통한 연우-결과에 따르면 노출시간이 증가할수록 복합재 내에 치밀한 망사 구조가 형성되어 유리전이온도는 증가함을 알 수 있었다. 또한 노출시간이 증가할수록 복합재의 특성에 영향을 미치는 물리시효가 발생하여 엔탈피 완화현상을 나타내는 흡열 피크가 관찰되었다. 아울러 FTIR 시험을 통해 관찰된 피크의 위치는 노출시간에 큰 영향을 받지 않지만 피크의 세기는 노출시간이 증가할수록 에폭시기에 발생되는 경화 반응으로 인해 점차 감소함을 알 수 있었다.

• 한국세라믹학회지
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• 제50권1호
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• pp.25-30
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• 2013

The pore volume of hardened cement with waterproofing materials is lower compared to that of hardened cement without waterproofing materials. Thus, fewer gaps will appear by means of chemical reactions between $Ca^{2+}$ ions in hardened cement and water, solutes, and other ions. Due to the selective permeability, the osmotic pressure of hardened cement can change due to physical effects such as the reduction of the pore volume and the reduction in the number of pores, as well as by the electrochemical reaction between water, solutes, other ions and $Ca^{2+}$ ions in hardened cement. Of course, these factors do not have independent effects but instead a combined complex effect. Accordingly, we studied changes in the osmotic pressure due to the difference in the pore structure of hardened cement. A pore size smaller than 1 nm in hardened cement had only a slight effect on the osmotic pressure, whereas a pore size larger than 1 nm had a direct effect on the osmotic pressure.

• KSBB Journal
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• 제27권4호
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• pp.207-214
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• 2012

Emulsions are mixture of immiscible liquids in which one is dispersed in all over the other. They have been applied to many applications including cosmetics, foods, drug delivery system (DDS), fine chemicals, and chemical separations. Especially, emulsion technology is one of the most useful technique to formulate cosmetics such as eye cream, foundation, and foam cleansing. In general, the emulsions can be generated by mechanical agitation of two immiscible fluids. However, the emulsions obtained by conventional method have limited in stability, monodispersity, and complicate process. We describe here preparation techniques of representative cosmetic emulsions such as liposome, liquid crystal emulsion, nanoemulsion, multiple emulsion, and pickering emulsion. Furthermore, various factors which can control the physical properties of each cosmetic emulsions are briefly discussed.

• 멤브레인
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• 제17권2호
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• pp.93-98
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• 2007

The reliability of innovative membrane contactors technology (i.e. Gas/Liquid Membrane Contactors, Membrane Distillation/Crystallization) is today increasing for seawater desalination processes, where traditional pressure-driven membrane separation units are routinely operated. Furthermore, conventional membrane operations can be integrated with membrane contactors in order to promote possible improvements in process efficiency, operational stability, environmental impact, water quality and cost. Seawater is the most abundant aqueous solution on the earth: the amount of dissolved salts covers about 3% of its composition, and six elements (Na, Mg, Ca, K, Cl, S) account for more than 90% of ionic species. Recent investigations on Membrane Distillation-Crystallization have shown the possibility to achieve significant overall water recovery factors, to limit the brine disposal problem, and to recover valuable salts (i.e. calcium sulphate, sodium chloride, magnesium sulphate) by combining this technology with conventional RO trains. In this work, the kinetics of $CaSO_4{\cdot}2H_2O,\;NaCl\;and\;MgSO_4{\cdot}7H_2O$ crystallization is experimentally investigated in order to improve the design of the membrane-based crystallization unit.

• 대한의생명과학회지
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• 제13권4호
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• pp.361-368
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• 2007

Biological samples can be fixed either by chemical method by using chemical solution or physical methods by using heat treatment. The problem in traditional heat fixation is unsatisfactory quality due to uneven heat conduction in specimen and loss of inner cell contents. Chemical fixation method also bears several intrinsic problems like the limit in specimen size, time consumption in fixative impregnation, and loss of low molecular weight cell components. These factors deteriorate the quality of fixed specimen, thus limit the magnification and contrast of tissue pictures. Microwave heat has been reported to be a good alternative to current chemical methods to overcome these problem. In this study, we tried to introduce the microwave energy method to routine fixation work in hospital. We replaced chemical fixative with saline to provide moderate reaction condition, and used frozen section to reduce time for sample preparation. Temperature was measured at each experiment. The fixation of rat kidney tissue with 2.45 GHz electromagnetic wave and saline showed similar result to the control group fixed with traditional chemical method. Human tumor tissue fixed with 2.45 GHz electromagnetic in frozen section was improved in terms of histochemistry of PAS and immunohistochemistry of tumor marker like cytokeratin. Total turnaround time was reduced from $24\sim38$ h to to $2\sim4$ h. In conclusion, the quality of samples prepared by microwave heating method was at least as good as that of traditional method. If the condition for the fixation of different specimens is standardized, this new method could be applied to routine work in hospital, and could save working time as well.

• 대한화학회지
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• 제33권5호
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• pp.538-544
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• 1989

1-(phenoxymethyl)benzotriazole(1)과 1-(thiophenoxymethyl)benzotriazole(2) 유도체중의 X 치환기가 전자를 끄는 세기(${\rho}<0$)와 methylene group의 인접 Y원자에 의한 local diamagnetic effect(Y=O(1)>S(2)), 그리고 용매의 극성파라미터($E_T$=Kcal/mol:acetone;42.2>chloroform;39.0)가 클수록 methylene group의 수소원자($H_m$)와 용매사이에 B-형의 수소결합성이 증가되었으며 (1)의 methylene group 에 대한 substituent chemical shift($CH_2-SCS$)에 미치는 자유 에너지 직선관계(LFER)의 조성은 아세톤 용액 중에서 장(F)(또는 유발(I))-효과 보다 공명(R)-효과가 더 크게 나타나는 용매 의존적인 경향이었다.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.3039-3045
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• 2013

Dual-frequency ultrasound assisted photocatalysis (DUAP) method was proposed to degrade a stable organic model effluent, cresol red (CR), using the prepared $Fe^{3+}$-doped $TiO_2$ with active carbon fiber loading ($Fe^{3+}-TiO_2/ACF$) as photocatalyst. The influence of key factors, including Fe doping amount and power density of dual-frequency ultrasounds (20/40 kHz), on the degradation efficiency was investigated. The degradation efficiency rises to 98.7% in 60 min accompanied by the color removal of CR liquid samples from yellow to colorless transparent at optimal conditions. A synergy index of 1.40 was yielded by comparison with single ultrasound assisted photocatalysis (SUAP) and the photocatalysis without ultrasound assisted (UV/$TiO_2$), indicating that a clear synergistic effect exists for the DUAP process. Obvious enhancement of degradation efficiency for the DUAP process should be attributed to production of large amount of free radicals by strong cavitational effects of dual ultrasounds.

• Membrane and Water Treatment
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• 제5권3호
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• pp.207-219
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• 2014

Fouling is one of the critical factors associated with the application of membrane technology in treating palm oil mill effluent (POME), due to the presence of high concentration of solid organic matter, oil, and grease. In order to overcome this, chemical cleaning is needed to enhance the effectiveness of membranes for filtration. The potential use of sodium hydroxide (NaOH), sodium chloride (NaCl), hydrochloric acid (HCl), ethylenediaminetetraacetic acid (EDTA), and ultrapure water (UPW) as cleaning agents have been investigated in this study. It was found that sodium hydroxide is the most powerful cleaning agent, the optimum conditions that apply are as follows: 3% for the concentration of NaOH, $45^{\circ}C$ for temperature solution, 5 bar operating pressure, and solution pH 11.64. Overall, flux recovery reached 99.5%. SEM images demonstrated that the membrane surface after cleaning demonstrated similar performance to fresh membranes. This is indicative of the fact that NaOH solution is capable of removing almost all of the foulants from PES membranes.

• 한국표면공학회지
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• 제50권5호
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• pp.315-321
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• 2017

Antireflective pyramid arrays can be readily obtained via anisotropic etching in alkaline solution (KOH, NaOH), which is widely used in crystalline-Si (c-Si) solar cells. The periodic inverted pyramid arrays show even lower light reflectivity because of their superior light-trapping characteristics. Since this inverted pyramidal structures are mostly achieved using very complex techniques such as photolithograpy and laser processes requiring extra costs, here, we demonstrate the Cu-nanoparticle assisted chemical etching processes to make the inverted pyramidal arrays without the need of photolithography. We have mainly controlled the concentration of $Cu(NO_3)_2$, HF, $H_2O_2$ and temperature as well as time factors that affecting the reaction. Optimal inverted pyramid structure was obtained through reaction parameters control. The reflectance of inverted pyramid arrays showed < 10% over 400 to 1100 nm wavelength range while showing 15~20% in random pyramid arrays.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.886-889
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• 2018

This article presented two-staged chemical precipitation for radioactive wastewater decontamination by using chemical agents. The total amount of radioactive wastewater was $35m^3$, and main radionuclides were Cs-137, Cs-134, and Co-60. Initial radioactivity concentration of the liquid waste was 2264, 17, and 9 Bq/L for Cs-137, Cs-134 and Co-60, respectively. Potassium ferrocyanide, nickel nitrate, and ferrum nitrate were selected as chemical agents at high pH levels 8-10 according to the laboratory jar tests. After the process, radioactivity was precipitated as sludge at the bottom of the tank and decontaminated clean liquid was evaluated depending on discharge limits. By this precipitation method decontamination factors were determined as 66.5, 8.6, and 9 for Cs-137, Cs-134, and Co-60, respectively. By using the potassium ferrocyanide, about 98% of the Cs-137 was removed at pH 9. At the bottom of the tank, radioactive sludge amount from both stages was totally $0.98m^3$. It was transferred by sludge pumps to cementation unit for solidification. By chemical processing, 97.2% of volume reduction was achieved. The potassium ferrocyanide in two-staged precipitation method could be used successfully in large-scale applications for removal of Cs-137, Cs-134, and Co-60.