• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.119-120
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• 2023

Corrosion of the steel rebar in coastal environment caused huge economical loss of the globe. Therefore, coating on the steel rebar being used to mitigate the corrosion. In the present study, we have applied epoxy coating on arc thermal sprayed Al coating (a dual metal/polymeric coating) vis-à-vis compared with as coated one (Al coating). The corrosion studies were performed in simulated concrete pore solution with 3.5 wt. % NaCl solution. The morphology of the dual epoxy/Al coating is smooth while Al coating shows rankle and defects. Due to defects, Al coating is susceptible to corrosion while dual epoxy/Al coating has performed excellent compared to as coated one at extended period of immersion.

• 멤브레인
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• 제14권2호
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• pp.108-116
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• 2004

본 연구에서는 비대칭 polyvinylidene fluoride (PVDF)막을 기질막으로 하여 Pore-filled 이온교환막을 제조하였다. 먼저 다공성 PVDF막의 기공에 80%의 chloromethylate aryl ring을 가지고 있는 poly(vinylbenzyl chloride) (PVBCI)과 1,4- diaminobicyclo［2,2,2］octane (DABCO)을 tetrahydrofuran (THF)와 dimethylforamide (DMF)가 8:2로 혼합된 용액에 녹여서 채워 넣고 겔화시킨 후, 남아 있는 chloromethyl group에 trirnethylamine (TMA, 40 wt% in water)을 이용하여 양이온 암모니움 site를 형성시키면 pore-filled 음이온교환막이 형성된다. 이와 같이 2단계의 제조 방식으로 제조된 pore-filled 막은 크기의 변화가 없으며, 가교도의 조절로써 최종 막의 특성이 간단하게 조절되는 것을 보여주었다. SEM과 AFM의 표면촬영의 결과로부터 기질막의 기공 내에 고분자겔의 존재를 확인하였다. 투과도와 배제율에 많은 영향을 미치는 용매를 조사한 결과 tetrahydrofuran (THF)만을 사용하여 제조한 막보다 THF와 DMF를 함께 사용할 때 더 우수한 막이 제조되었다. 제조된 최종 막의 수투과도 조사결과, 가교도 10% 막의 경우 아주 낮은 압력에서(100 Kpa) 전형적인 한외여과막의 투과도(8∼10 kg/$m^2$hr)를 보여주었으며 배제율 또한 우수한 결과(55∼60%)를 보여주었다. 압력에 대한 pore-filled 이온교환막의 성능을 관찰한 결과 압력이 증가할수록 투과도와 배제율은 함께 증가하였다.

• 멤브레인
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• 제26권1호
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• pp.26-31
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• 2016

폴리카프로락톤(PCL)에 NaCl을 혼합한 용액을 블레이드법에 의하여 막형태로 제조한 후 NaCl을 추출하는 염출법을 이용하여 조직공학적으로 사용할 3차원 다공망을 갖는 멤브레인 형태의 지지체를 제조하였다. 본 연구에서는 성형된 멤브레인의 건조조건과, NaCl 입자의 크기, NaCl의 혼합량을 각각 다르게 하여 제조하였다. 별도로 제작한 고분자용액 공급장치를 이용하여 PCL/클로로포름($CHCl_3$) 용액에 NaCl 입자가 균일하게 혼합된 용액을 유리판에 분주하여 필름 어플리케이터를 사용하여 블레이드법에 의한 멤브레인을 제조하였다. 멤브레인 지지체에는 NaCl 입자에 의한 거대기공과 거대기공을 이루는 구조벽에서는 $CHCl_3$의 증발에 의한 미세기공이 함께 복합적으로 상호 연결되어 형성되었다.

• Fibers and Polymers
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• 제6권2호
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• pp.121-126
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• 2005

Semicrystalline poly(ethylene terephthalate) (cPET)/amorphous poly(ethylene terephthalate) with isophthalic acid (aPET) blends with 100/0, 75/25, 50/50, 25/75, and 0/100 by weight ratios were dissolved in a mixture of trifluoroacetic acid (TFA)/methylene chloride (MC) (50/50, v/v) and electrospun via the electrospinning technique. Solution properties such as solution viscosity, surface tension and electric conductivity were determined. The solution viscosity slightly decreased as aPET content increased, while there was no difference in surface tension with respect to aPET composition. The characteristics of the electro spun cPET/aPET blend nonwovens were investigated in terms of their morphology, pore size and gas permeability. All these measurements were carried out before and after heat treatment for various blend weight ratios. The average diameter of the fibers decreased with increasing aPET composition due to the decrease in viscosity. Also, the morphology of the electrospun cPET/aPET blend nonwovens was changed by heat treatment. The pore size and pore size distribution varied greatly from a few nanometers to a few microns. The gas permeability after heat treatment was lower than that before heat treatment because of the change of the morphology.

• Corrosion Science and Technology
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• 제8권4호
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• pp.143-147
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• 2009

In biomedical implants and dental fields, titanium has been widely utilized for excellent corrosion resistance and biocompatibility. However, Ti and its alloys are nonbioactive after being implanted in bone. In this study, for the purpose of improvement in biocompatibility the anodic $TiO_2$ layer on Ti-xNb alloys were fabricated by electrochemical method in phosphate solution, and the effect of Nb content on the pore size, the morphology and crystallinity of Ti oxide layer formed by the anodic oxidation method was investigated. The Ti containing Nb up to 3 wt%, 20 wt% and 40 wt% were melted by using a vacuum furnace. The sample were cut, polished, and homogenized for 24 hr at $1050^{\circ}C$ for surface roughness test and anodizing. Titanium anodic layer was formed on the specimen surface in an electrolytic solution of 1 M phosphoric acid at constant current densities ($30mA/cm^2$) by anodizing method. Microstructural morphology, crystallinity, composition, and surface roughness of oxide layer were observed by FE-SEM, XRD, EDS, and roughness tester, respectively. The structure of alloy was changed from $\alpha$-phase to $\beta$-phase with increase of Nb content. From XRD results, the structure of $TiO_2$ formed on the Ti-xNb surface was anatase, and no peaks of $Nb_2O_5$ or other Nb oxide were detected suggesting that Nb atoms are dispersed in $TiO_2$-based solid solution. Surface roughness test and SEM results, pore size formed on surface and surface roughness decreased as Nb content increased. From the line analysis results, intensity of Ti peak was high in the center of pore, whereas, intensity of O peak was high in the outside of pore center.

• 대한토목학회논문집
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• 제28권1C호
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• pp.9-17
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• 2008

본 연구에서는 압밀 중에 위치별 간극수압의 측정을 통하여 시료 내 여러 위치에서 투수계수를 산정할 수 있는 이론해를 제시하였으며, 이를 바탕으로 간극비 및 체적압축계수를 산정할 수 있는 방법을 제안하였다. 또한 여러 위치에서 간극수압을 측정할 수 있는 방사내측배수가 가능한 대형압밀시험기를 제작하고 카올리나이트를 이용하여 압밀시험을 실시하였다. 시험결과로부터 압밀 중 투수계수, 간극비, 체적압축계수의 변화 및 시료 내 위치별 분포를 평가하였으며, 압밀완료 후 시료의 함수비 측정으로 평가된 값들과의 비교를 통하여 실험결과의 신뢰성을 검증하였다. 실험결과 투수계수, 체적압축계수, 간극비는 압밀 중 감소하며, 재하단계에 따라서도 감소함을 확인하였다. 또한 그 분포형태는 배수면 근처에서 가장 작고 배수거리에 따라 증가하며 비배수 경계면 근처에서는 오히려 약간 작은 것으로 나타났다.

• Corrosion Science and Technology
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• 제16권4호
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• pp.175-182
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• 2017

Galvanic current measurement, polarization curves, electrochemical impedance spectroscopy and weight loss test were used to study the corrosion behavior of carbon steel before and after carbon fibers coupling to the carbon steel in simulated concrete pore solutions, and the film composition on the steel surface was analyzed using XPS method. The results indicate that passive film on steel surface had excellent protective property in pore solutions with different pH values (13.3, 12.5 and 11.6). After coupling with carbon fibers (the area ratio of carbon steel to carbon fiber was 12.31), charge transfer resistance $R_{ct}$ of the steel surface decreased and the $Fe^{3+}/Fe^{2+}$ value in passive film decreased. As a result, stability of the film decreased and the corrosion rate of steel increased. Decreasing of the area ratio of steel to carbon fiber from 12.3 to 6.15 resulted in the decrease in $R_{ct}$ and the increase in corrosion rate. Especially in the pore solution with pH 11.6, the coupling leads the carbon steel to corrode easily.

• 멤브레인
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• 제15권4호
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• pp.338-348
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• 2005

정밀여과 모세관 막을 이용한 무기 콜로이드 현탁액의 투과유속 감소특성을 검토하였다. 무기 현탁입자의 종류에 따른 투과거동은 알루미나 현탁액의 투과유속이 벤토나이트 현탁액보다 평균 2배정도 컸으며, 운전시간 경과에 따른 투과유속의 감소도 알루미나 현탁액이 벤토나이트 현탁액에 비하여 전체적으로 서서히 감소하는 경향을 보였다. 운전 시간 10분까지의 투과유속 감소율을 나타내는 초기투과유속 감소율은 벤토나이트 현탁액이 알루미나 현탁액보다 더 컸다. 막 투과유속 감소는 케익오염과 세공막힘오염에 기인하며, 막오염 형태에 있어 벤토나이트 현탁액의 세공막힘오염이 알루미나 현탁액 보다 현저히 크게 나타났다. 운전압력 $1.0\;kg_f/cm^2$에서 총 막오염에 대한 성분오염의 비율은 알루미나 현탁액의 경우 완전세공막힘 $9.35\%$, 표준세공막힘 $6.82\%$, 케익여과 $83.832\%$이었다. 순환흐름속도의 증가로 인해 투과유속은 증가하였고, 알루미나 현탁액은 $6.5\%$, 벤토나이트 현탁액은 $13.5\%$ 증가하였다. 세공크기가 $0.34\;{\mu}m$인 막의 투과유속은 세공의 크기가 $0.24\;{\mu}m$인 막보다 컸으며, 세공크기의 증가에 따른 투과유속은 알루미나 현탁액이 1.61배, 벤토나이트 현탁액이 1.76배 증가하였다.

• Computers and Concrete
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• 제7권5호
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• pp.421-435
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• 2010

This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test, have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

• 한국표면공학회지
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• 제28권3호
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• pp.182-191
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• 1995

A highly porous silicon layer was fabricated by anodizing single crystalline silicon in a dilute solution of hydrofluoric acid. The color of the porous silicon changed from red and blue to yellow gold during the anodizing process. The current-voltage (I-V) curve of the anodizing process showed a typical Schottky diode rectification form. The cell voltage decreased with the increase of HF concentration in the solution at high current range. However, the voltage was independent on HF concentration in the solution at low current range. The pore size was dependant on anodizing condition (HF concentration, current and anodizing time). The pore size and wall width of porous silicon layer were 4~6 and 1~3 nm, respectively. Surface of the porous silicon was covered with silicon compound ($SiH_x$etc.) according to IR spectrum analysis. The peak wavelength and width of photoluminescence (PL) spectrum of porous silicon were 650~850 nm (1.5~1.9 eV) and 250 nm, respectively. The photoluminescence intensity and peak wavelength, and porosity of porous silicon increased with increasing anodizing current and decreased with increasing HF concentration in the anodizing solution.