• 멤브레인
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• 제27권2호
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• pp.182-188
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• 2017

본 연구에서는 고분자 전해질 연료전지(PEFC)의 전해질막의 화학적 안정성의 향상을 위하여 3-mercaptopropyl silica gel (3MPTSG)과 poly(arylene ether sulfone)(SPAES)을 이용하여 복합막을 제조하였다. 일반적으로 방향족 탄화수소계 고분자막은 전극 부분에서 발생한 라디컬에 의한 고분자 산화가 일어나 내구성이 감소하게 되는데 이는 대부분 주쇄에 포함된 에테르 기 부분의 취약성으로 발생한다. 본 연구에서는 이러한 라디칼에 의한 고분자 주쇄의 산화를 방지하기 위해 친수성의 무기물 입자를 도입하여 이온전도도 감소율을 최소화하고 산화안정성을 높이고자 하였다. 복합막들의 물성 및 전기화학적 특성을 평가하기 위해 접촉각, FT-IR, 이온전도도, 이온교환용량(IEC), 함수율, 열안정성 등을 수행하였다. 실리카의 함량이 0에서 0.5%까지 증가함에 따라 이온전도도 및 함수율은 각각 10% 감소한 0.076 S cm-1 및 16% 감소한 24.6 wt%이었으나, 산화안정성은 10% 향상되었다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.23-23
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• 2018

In this study, new titanium alloys were prepared by adding elements such as tantalum (Ta), zirconium (Zr) and the like to complement the biological, chemical and mechanical properties of titanium alloys. The Ti-40Ta-xZr ternary alloy was formed on the basis of Ti-40Ta alloy with the contents of Zr in the contents of 0, 3, 7 and 15 wt. %. Plasma electrolytic oxidation (PEO), which combines high-voltage sparks and electrochemical oxidation, is a novel method to form ceramic coatings on light metals such as Ti and its alloys. These oxide film produced by the electrochemical surface treatment is a thick and uniform porous form. It is also composed of hydroxyapatite and calcium phosphate-based phases, so it has the characteristics of bone inorganic, non-toxic and very high bioactivity and biocompatibility. Ti-40Ta-xZr alloys were homogenized in an Ar atmosphere at $1050^{\circ}C$ for 1 hour and then quenched in ice water. The electrochemical oxide film was applied by using a power supply of 280 V for 3 minutes in 0.15 M calcium acetate monohydrate ($Ca(CH_3COO)_2{\cdot}H_2O$) and 0.02 M calcium glycerophosphate ($C_3H_7CaO_6P$) electrolyte. A small amount of 0.0075M zinc acetate and magnesium acetate were added to the electrolyte to enhance the bioactivity. The mechanical properties of the coated surface of Ti-40Ta-xZr alloys were evaluated by Vickers hardness, roughness test, and elastic modulus using nano-indentation, and the surface wettability was evaluated by measuring the contact angle of the coated surface. In addition, cell activation and differentiation were examined by cell culture of HEK 293 (Human embryonic kidney 293) cell proliferation. Surface properties of the alloys were analyzed by scanning electron microscopy(FE-SEM), EDS, and X-ray diffraction analysis (XRD).

• 한국자동차공학회논문집
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• 제15권4호
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• pp.10-16
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• 2007

A rubber seal for wheel bearing which has been mainly applied to car wheel supporting device is required to have both high sealing performance and drag torque. Because of severe operational conditions like infiltration of mud or splashed water, the importance of rubber seal which is aimed for leakage prevention of grease and effective blocking of foreign substances has been increasing continuously. The sealing performance of this seal depends on several factors such as materials of seal, friction conditions of contact regions and geometry of seals and so on. We have focused on the effects of geometric characteristics such as the angle of main lip, interference between lip edge and inner metallic ring. In this study, the optimization of geometric variables was performed using the finite element analysis. For the sake of finite element analysis, uniaxial tensile tests were conducted and several constants for Mooney-Rivlin's equation were obtained. According to the results of this study, mock-up bearing was made. To verify this study, drag torque and mud spray test were preformed.

• Korean Chemical Engineering Research
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• 제55권6호
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• pp.778-784
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• 2017

Poly(acrylic acid) (PAA)로 가교된 Poly(vinyl alcohol) (PVA)에 Na-Y 제올라이트 입자를 첨가하여 투과증발막을 제조하였다. 적외선 분광 분석(FT-IR), 팽윤 실험, 접촉각 측정, SEM 및 XRD 분석을 통해 분리막의 특성을 연구하였으며, 제조된 분리막은 물/아세트산 혼합물의 투과증발 분리에 적용하였다. 연구결과 분리막에 첨가된 Na-Y 제올라이트의 함량이 증가함에 따라 분리막의 친수성이 증가하였으며, 제올라이트가 첨가된 PVA/PAA분리막은 제올라이트가 첨가되지 않은 분리막에 비해 높은 투과도를 나타내었다. 10 wt% 아세트산 수용액에서 8 wt%의 제올라이트가 포함된 PVA/PAA 분리막이 가장 높은 선택도와 투과도를 나타내었다.

• 대한치과보철학회지
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• 제45권6호
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• pp.795-804
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• 2007

Statement of problem. Nano-scale calcium-phosphate coating on the anodizing titanium surface using ion beam-assisted deposition (IBAD) has been recently introduced to improve the early osseointegration. However, not much is known about their surface characteristics that have influence on tissue-implant interaction. Purpose. This study was aimed to investigate microtopography, surface roughness, surface composition, and wettability of the titanium surface modified by the anodic oxidation and calcium phosphate coating using IBAD. Material and methods. Commercially pure titanium disks were used as substrates. The experiment was composed of four groups. Group MA surfaces represented machined surface. Group AN was anodized surface. Group CaP/AN was anodic oxidized and calcium phosphate coated surfaces. Group SLA surfaces were sandblasted and acid etched surfaces. The prepared titanium discs were examined as follows. The surface morphology of the discs was examined using SEM. The surface roughness was measured by a confocal laser scanning microscope. Phase components were analyzed using thin-film x-ray diffraction. Wettability analyses were performed by contact angle measurement with distilled water, formamide, bromonaphtalene and surface free energy calculation. Results. (1) The four groups showed specific microtopography respectively. Anodized and calcium phosphate coated specimens showed multiple micropores and tiny homogeneously distributed crystalline particles. (2) The order of surface roughness values were, from the lowest to the highest, machined group, anodized group, anodized and calcium phosphate deposited group, and sandblasted and acid etched group. (3) Anodized and calcium phosphate deposited group was found to have titanium and titanium anatase oxides and exhibited calcium phosphorous crystalline structures. (4) Surface wettability was increased in the order of calcium phosphate deposited group, machined group, anodized group, sandblasted and acid etched group. Conclusion. After ion beam-assisted deposition on anodized titanium, the microporous structure remained on the surface and many small calcium phosphorous crystals were formed on the porous surface. Nanoscale calcium phosphorous deposition induced roughness on the microporous surface but hydrophobicity was increased.

• Corrosion Science and Technology
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• 제19권1호
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• pp.16-22
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• 2020

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.

• 청정기술
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• 제14권1호
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• pp.35-39
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• 2008

본 연구에서는 용매에 따른 고분자의 용해도 차이를 이용하여 슬라이드글라스 표면위에 초소수성 고분자막을 성공적으로 제조하였다. 폴리스타이렌 (PS)을 tetrahydrofuran (THF)에 녹인 후 다시 에탄올(EtOH)을 첨가하여 두 용매의 용해도 차이로 표면에 초소수성 성질을 갖게 제조하였다. 한편, EtOH 첨가, 코팅방법, 용액혼합 시간과 속도 및 다른 알콜들이 형성된 표면의 소수성에 미치는 영향들을 각각 조사하였다. 접촉 각 측정기를 사용하여 측정한 결과 $150^{\circ}$ 이상의 물 접촉각을 확인하였고, 광학현미경(optical microscopy)과 주사전자현미경(scanning electron microscope, SEM)으로 관찰한 표면 구조는 $5\;{\mu}m$ 이하의 입자들로 구성된 미세다공성 구조임이 확인되었다.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.85-92
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• 2015

PURPOSE. This study aimed to investigate the efficacy of cleaning solutions on saliva-contaminated zirconia in comparison to air-abrasion in terms of resin bonding. MATERIALS AND METHODS. For saliva-contaminated air-abraded zirconia, seven cleaning methods)-no contamination (NC), water-spray rinsing (WS), additional air-abrasion (AA), and cleaning with four solutions (Ivoclean [IC]; 1.0 wt% sodium dodecyl sulfate [SDS], 1.0 wt% hydrogen peroxide [HP], and 1.0 wt% sodium hypochlorite [SHC])-were tested. The zirconia surfaces for each group were characterized using various analytical techniques. Three bonded resin (Panavia F 2.0) cylinders (bonding area: $4.5mm^2$) were made on one zirconia disk specimen using the Ultradent jig method [four disks (12 cylinders)/group; a total of 28 disks]. After 5,000 thermocycling, all specimens were subjected to a shear bond strength test with a crosshead speed of 1.0 mm/minute. The fractured surfaces were observed using an optical and scanning electron microscope (SEM). RESULTS. Contact angle measurements showed that groups NC, AA, IC, and SHC had hydrophilic surfaces. The X-ray photoelectron spectroscopy (XPS) analysis showed similar elemental distributions between group AA and groups IC and SHC. Groups IC and SHC showed statistically similar bond strengths to groups NC and AA (P>.05), but not groups SDS and HP (P<.05). For groups WS, SDS, and HP, blister-like bubble formations were observed on the surfaces under SEM. CONCLUSION. Within the limitations of this in vitro study, some of the cleaning solutions (IC or SHC) were effective in removing saliva contamination and enhancing the resin bond strength.

• 마이크로전자및패키징학회지
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• 제17권1호
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• pp.75-80
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• 2010

다공성 탄소전극기지 위의 무전해 니켈도금에 관한 연구를 하였다. 다공성 탄소전극기지로는 다공도가 20 ${\mu}m$ 이상인 것과 16~20 ${\mu}m$ 인 것을 사용하였다. 소수성인 탄소 표면은 $60^{\circ}C$ 이상의 암모니아 용액에 침적함으로써 그 표면 성질이 친수성으로 변화 되었고, 40분 이상 침적 시 접촉각이 $20^{\circ}$ 이하까지 측정 되었다. 도금욕의 pH가 증가됨에 따라 탄소기지 위에 도금된 니켈 도금층의 인의 석출량은 감소하였으며 니켈 도금층이 결정질 구조를 갖는 현상이 관찰되었다. 도금층의 두께는 pH가 증가함에 따라 증가하였다. 활성화 처리를 위한 $PdCl_2$의 농도에 따른 도금층의 두께 변화는 없었으나, 도금에 필요한 $PdCl_2$의 최소농도는 5 ppm 이상인 것으로 나타났다.

• 한국의류학회지
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• 제32권9호
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• pp.1461-1466
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• 2008

This study provides effects of mixed activators on enzymatic activation and determines optimum mixture ratio for enzymatic treatment. Wool 80% and polyester 20% blend fabric and papain from carica papaya are used in this experiment. L-cysteine and sodium sulfite are used as activators for papain treatment process. The treatment condition is pH 7.5, $70^{\circ}$, papain concentration 10%(o.w.f), 60 minutes. L-cysteine and sodium sulfite are added in enzyme solution with various concentrations($0{\sim}50mM$). The optimum treatment condition is determined by measuring weight loss, tensile strength, whiteness, water contact angle(WCA), dyeability and surface micrographs. The results are as follow; The optimum mixture ratio of activators is L-cysteine 2mM and sodium sulfite 10mM. Mixed activators assists in improving the activation of papain. WCA of papain treated fabrics is decreased since papain treatment with activator mixture makes wool polyester blend fabrics more hydrophilic. Dyeing property of papain-treated fabrics more improves by the treatment with mixed activators than with single activator. It means that this method can save time and lower cost. After papain treatment in the presence of mixed activator, the surface of fabrics is modified. The surface of wool fiber shows to be descaled and hydrolyzed, and that of polyester fiber shows to be cracked.