• 한국결정성장학회지
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• 제29권5호
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• pp.215-221
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• 2019

건축용 내외장재로 사용되는 도자타일은 최근에 오염 방지 기능에 대한 시장의 수요에 따라, $TiO_2$ 코팅을 통한 친수성(hydrophilic property) 표면개발 연구와 더불어 표면에서 물방울의 흐름성을 향상시켜 오염물질을 제거하는 소수성(hydrophobic property) 표면을 갖는 도자타일에 대한 연구가 진행되고 있다. 특히 추가적인 코팅 공정 적용 없이 $1000^{\circ}C$ 이상의 소결 과정을 통해서 소수성을 갖으며, 기존 도자타일의 기계적 물성의 저하가 나타나지 않는 표면유약의 개발이 매우 중요하다. 본 연구에서는 상용화 도자타일의 표면유약에 조성에 구리 분말을 첨가하여 기존 소결 공정을 적용하고, 추가 코팅 공정 없이 소수성 도자타일을 제작하고 표면유약의 두께에 따른 접촉각 특성 변화를 관찰하였다. 구리 분말이 첨가되지 않은 도자타일의 표면 접촉각은 $25^{\circ}$로 친수성을 보이는 반면에 구리 분말이 첨가된 표면유약이 $150{\mu}m$ 두께인 경우에 접촉각이 $109^{\circ}$까지 증가하는 것을 확인하였다. 이와 같은 구리 분말이 첨가된 표면유약의 우수한 소수성 발현은 유약 표면에서 구리 입자의 세포 구조(cellular structure) 분포에 의한 것으로 확인되었다. 또한 개발된 소수성 도자타일의 기계적 물성(꺽임강도, 내화학성, 내마모성, 내동해성)은 기존 도자타일과 거의 동일하고 'KS L 1001 도자타일'의 기준을 만족하는 결과를 얻을 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.47.2-47.2
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• 2010

텍스쳐링은 태양전지 표면에 어떠한 "요철"을 만들거나 거칠게 만들어 빛이 반사되는 면을 최대한 늘리는 구조를 만드는 공정으로 anti-reflection coating과 같이 태양전지에 입사되는 빛의 반사를 최소화 시키는데 그 목적이 있다. 단결정 실리콘 웨이퍼의 경우 표면에 피라미드 구조를 형성하는 것이 텍스쳐링 공정인데, 수산화칼륨과 이소프로필 알콜의 혼합용액으로 인해 식각되는 웨이퍼 표면이 작은 "pellet"으로 시작하여 그 크기와 수가 점점 증가하여 피라미드의 형태를 갖춰가는 방법으로 진행된다. 이와 같은 텍스쳐링 공정의 성패를 좌우하는 가장 큰 이슈는 "식각률"이다. 이 식각률에 영향을 주는 인자는 그 종류가 많으나 온도, 시간, KOH 농도(비율) 세 가지로 압축할 수 있다. 또 다른 요소인 Bath 내 chemical flow 및 Bubbling은 정량화하기 어렵고, 이용 장비가 변경되면 공정 조건 또한 변경되기 때문이다. 본 논문에서는 단결정 실리콘 웨이퍼에 적용하는 최적의 텍스쳐링 조건을 수립하기 위해 주요 공정변수를 온도, 시간, KOH 농도로 정하고, 다구치 방법을 사용하여 주요공정변수의 범위를 정하였으며, 보다 완벽한 강건설계를 위하여 3인자 3수준의 망소특성으로 설계하였다. 그 결과 반사율과 식각률의 경향성을 파악하여 주요 변수들 간 최적의 조건을 찾을 수 있었다.

• 대한한방내과학회지
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• 제35권4호
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• pp.483-497
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• 2014

Objectives: The aims of study were developing cut-off value of Yin-deficiency questionnaire (YDQ) for diagnosis of Yin-deficiency (YD) and compare diagnostic ability between YDQ and Yin-deficiency scale score (YDS) in xerostomia patients. Methods: We recruited 58 xerostomia patients. They were diagnosed YD or non-YD by 3 Korean medicine doctors (KMD). We assessed YD using YDQ and YDS. We evaluated xerostomia using VAS, Dry Mouth Symptom Questionnaire (DMSQ), Salivary Flow Rate (SFR), oral moisture on buccal mucosa and tongue surface (OMB and OMT). We surveyed tongue coatings using Winkel Tongue Coating Index (WTCI). Results: We diagnosed 23 patients YD and 35 patients non-YD. There were no significant differences of age, sex and body mass index between the YD and non-YD groups. Using receiver operating characteristic curve analysis, the optimal cut-off value of YDQ was defined as 304. Sensitivity, specificity and Youden index of YDQ were 86.96%, 71.43% and 1.5839 respectively. Using Cohen's coefficient of agreement, we found that degree of agreement between KMD and YDQ diagnosis was moderate (${\kappa}$=0.524, p<0.001). Using Pearson's correlation analysis, we found concurrent validity of YDQ and YDS were significant correlated. Using area under curve value, we found diagnostic ability between YDQ and YDS were not significantly different (p=0.505), but there were more strong correlations between DMSQ-symptoms and YDQ (r=0.731, p<0.001) than correlations between DMSQ-symptoms and YDS (r=0.418, p<0.01). Conclusions: The cut-off value of YDQ can diagnose YD in xerostomia and diagnostic ability of YDQ in xerostomia is better than YDS.

• 한국지반환경공학회 논문집
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• 제15권8호
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• pp.39-44
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• 2014

초임계 조건에서 제조된 망간산화물이 코팅된 활성탄($Mn_3O_4$/AC)에 의한 납 흡착특성을 규명하기 위해 칼럼실험을 통해 파과특성에 미치는 운전변수의 영향에 관해 실험하였다. 활성탄에 망간산화물을 코팅시킴으로써 물질전달대와 평형흡착량은 대략 2.8배 증가하는 것으로 나타났다. 흡착층 높이의 증가는 수용액이 흡착대에 체류하는 시간을 증가시켜 파과시간, 물질전달대와 평형흡착량을 증가시키는 것으로 나타났다. 칼럼으로 공급되는 유량이 증가함에 따라 수용액으로부터 흡착제로 납이 빠르게 전달되어 접촉되므로 파과시간과 물질전달대가 감소하였다. 유량 증가는 흡착대에서 납의 체류시간을 감소시켜 흡착경계면에서의 확산현상을 감소시키므로 평형흡착량을 감소시키는 것으로 나타났다. 칼럼으로 유입되는 납 농도가 증가하면 흡착제로 전달되는 납의 양이 증가하여 물질전달이 빠르게 완료되므로 파과시간과 물질전달대가 감소하는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1105-1113
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• 2004

Disinfection of a waterborne pathogenic protozoa, Giardia lamblia, by the conventional chlorine method has been known to be difficult. An alternative disinfection has been carried out by using a UV -light illuminating optical­fiber photoreactor. Light intensity diffused from one piece of a clad-removed optical-fiber was $1- 1.5{\mu}Em^{-2}s^{-1}$. Disinfection capability in a UV -light irradiated optical-fiber reactor suspended with 0.01 g $TiO_{2}\;dm^{-3}$ was 1.4 times that in the same reactor without $TiO_{2}$ photocatalysts. To resolve the absorption and scattering of UV light by the particles themselves as well as the difficulty of recycling particles in the slurry­type reactor, $TiO_{2}$ which was obtained by a hydrothermal method, was immobilized on clad-removed optical fibers. Such pretreatment of fiber surface resulted in an excellent transparency, which enhanced the UV light to diffuse laterally from a fiber surface. Coating time of the prepared solution by the hydrothermal method was not effective after more than two times. Disinfection capability in the $TiO_{2}$-immobilized optical-fiber reactor was $83\%$ in 1 h at $40^{\circ}C$, which was slightly higher than $76\%$ at $22^{\circ}C$ and $68\%$ at $10^{\circ}C$. Disinfection capability at $22^{\circ}C$ increased from $74\%$ at an initial pH of 3.4, through $76\%$ at pH 6.5, to $87\%$ at an initial pH of 10. Oxygen supply with air-flow rate of 5 $cm^3\;min^{-1}$ did not seem to increase the disinfection capability with UV /immobilized $TiO_2$.

• 대한환경공학회지
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• 제27권9호
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• pp.939-945
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• 2005

입상형/비드형(직경 = 5 mm) 광촉매가 충진된 고정상 반응기에서 유량별 광산화 반응속도를 고찰한 결과 유량이 400 mL/min 이상에서 페놀의 분해속도가 더 이상 증가하지 않았다. 비드형 광촉매의 경우에는 부식율과 코팅량의 증가에 따른 뚜렷한 광산화 반응속도의 차이가 나타나지 않았다. 광촉매의 종류별 페놀의 분해능을 비교한 결과 Degussa P25가 STS-02(Ishihaha사)와 $TiO_2$(N사)에 비해 높은 광산화 활성을 나타내 주었다. 유체의 전단력에 의한 표면의 마모가 쉽게 일어날 수 있는 입상형 광촉매보다 $TiO_2$가 코팅된 비드형 광촉매를 사용함으로써 광촉매 활성을 오래 동안 유지할 수 있는 광산화 시스템의 개발이 가능하다.

• Journal of Microbiology and Biotechnology
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• 제19권9호
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• pp.1019-1027
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• 2009

A noncompartmented microbial fuel cell (NCMFC) composed of a Mn(IV)-carbon plate and a Fe(III)-carbon plate was used for electricity generation from organic wastewater without consumption of external energy. The Fe(III)-carbon plate, coated with a porous ceramic membrane and a semipermeable cellulose acetate film, was used as a cathode, which substituted for the catholyte and cathode. The Mn(IV)-carbon plate was used as an anode without a membrane or film coating. A solar cell connected to the NCMFC activated electricity generation and bacterial consumption of organic matter contained in the wastewater. More than 99% of the organic matter was biochemically oxidized during wastewater flow through the four NCMFC units. A predominant bacterium isolated from the anode surface in both the conventional and the solar cell-linked NCMFC was found to be more than 99% similar to a Mn(II)-oxidizing bacterium and Burkeholderia sp., based on 16S rDNA sequence analysis. The isolate reacted electrochemically with the Mn(IV)-modified anode and produced electricity in the NCMFC. After 90 days of incubation, a bacterial species that was enriched on the Mn(IV)-modified anode surface in all of the NCMFC units was found to be very similar to the initially isolated predominant species by comparing 16S rDNA sequences.

• 한국안전학회지
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• 제33권3호
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• pp.15-20
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• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.14-14
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• 2001

Nitride films such as TiN, CrN etc. deposited on glass by PVD processes have been developed for many industrial applications. These nitride films deposited on glass were widely used for not only decorative and optical coatings but also wear and corrosion resistance coatings employed as dies and molds made of glass for the example of lens forming molds. However, the major problem of nitride coatings on glass by PVD process is non-uniform film owing to pin-hole and micro crack. It is estimated that nonuniform coating is influenced by a different surface energy between metal nitrides and glass due to binding states. In this work, therefore, for the evaluation of nucleation and growth mechanism of nitride films on glass TiN and CrN film were synthesized on glass with various nitrogen partial pressure by unbalanced magnetron sputtering. Prior to deposition, for the examination of relationship between surface energy and film microstructure plasma pre-treatment process was carried out with various argon to hydrogen flow rate and substrate bias voltage, duty cycle and frequency by using pulsed DC power supply. Surface energy owing to the different plasma pre-treatment was calculated by the measurement of wetting angle and surface conditions of glass were investigated by X-ray Photoelectron Spectroscopy(XPS) and Atomic Force Microscope(AFM). The microstructure change of nitride films on glass with increase of film thickness were analyzed by X-Ray Diffraction(XRD) and Scanning Electron Microscopy(SEM).