• 한국재료학회지
• /
• 제24권8호
• /
• pp.434-442
• /
• 2014

Serious environmental problems have been caused by the greenhouse effect due to carbon dioxide($CO_2$) or nitrogen oxides($NO_x$) generated by the use of fossil fuels, including oil and liquefied natural gas. Many countries, including our own, the United States, those of the European Union and other developed countries around the world; have shown growing interest in clean energy, and have been concentrating on the development of new energy-saving materials and devices. Typical non-fossil-fuel sources include solar cells, wind power, tidal power, nuclear power, and fuel cells. In particular, organic solar cells(OSCs) have relatively low power-conversion efficiency(PCE) in comparison with inorganic(silicon) based solar cells, compound semiconductor solar cells and the CIGS [$Cu(In_{1-x}Ga_x)Se_2$] thin film solar cells. Recently, organic cell efficiencies greater than 10 % have been obtained by means of the development of new organic semiconducting materials, which feature improvements in crystalline properties, as well as in the quantum-dot nano-structure of the active layers. In this paper, a brief overview of solar cells in general is presented. In particular, the current development status of the next-generation OSCs including their operation principle, device-manufacturing processes, and improvements in the PCE are described.

• 한국결정성장학회지
• /
• 제24권1호
• /
• pp.33-40
• /
• 2014

전기방사법(Electrospinning technique)을 이용하여 PVdF-HFP(Poly vinylidene fluoride-co-hexafluoropropylene) 멤브레인을 제조하고, 그 멤브레인 표면위에 DLC(Diamond-like carbon) 코팅공정을 적용하여 멤브레인의 표면변화 및 접촉각 변화를 조사하였다. Ar 플라즈마 처리시간 및 처리조건에 따라 PVdF-HFP 멤브레인 파이버 표면이 주름(wrinkles)형태로 변화 하였다. 이러한 Ar 플라즈마 처리가 된 PVdF-HFP 멤브레인은 초친수성(super-hydrophilic) 특성으로 변했지만, 초친수성 PVdF-HFP 멤브레인에 DLC 코팅공정을 적용하면 반대로 초소수성(super-hydrophobic) 특성으로 변화되었다. 이러한 특성을 가진 표면을 접촉각 측정과 XPS, FE-SEM 측정으로 분석하였다. 따라서 화학적 조성과 표면 형상에 의해 접촉각 특성을 가지는 것으로 확인하였다.

• 한국지반환경공학회 논문집
• /
• 제18권11호
• /
• pp.35-40
• /
• 2017

한랭지역에 건설된 터널은 낮은 기온으로 인하여 콘크리트 라이닝 배면의 동결이 발생하게 되며, 콘크리트 라이닝의 손상을 발생시켜 터널구조물의 내구성을 감소시킨다. 터널 라이닝 배면 지반의 동결을 억제시키기 위하여 터널 라이닝 표면에 발열체를 부착하고 일정시간 동안 발열시켜 콘크리트 라이닝 내부의 온도변화를 측정하였다. 냉동챔버를 제작하여 현장현황을 모사하고 발열체는 탄소나노튜브(CNT, Carbon Nano Tube) 재료를 플레이트로 제작하여 표면에 부착하고 전기공급을 통해 발열시켰다. 발열체를 발열시킴에 따라 콘크리트 라이닝의 내부 위치별 온도변화 분포를 측정하였으며, 외기온도 및 발열온도의 유지시간에 따른 영향을 분석하였다.

• Elastomers and Composites
• /
• 제42권3호
• /
• pp.143-150
• /
• 2007

본 연구에서는 고무제품의 수치 안정성과 성능유지에 직접적으로 영향을 미치는 중요한 특성 중 하나인 온도변화에 따른 고무재료의 경도변화를 고찰하였다. 새롭게 제작된 Inter-national Rubber Hardness Degree(IRHD, Normal type) 경도측정 시험기를 사용하여 미충전된 NR과 SBR 시편의 여러 온도에서 경도변화를 측정하였으며 Young's modulus 값과 비교하였다. NR과 SBR 모두 유리전이온도 근처에서 경도와 Young's modulus의 급격한 변화를 보였다. 온도가 증가함에 따라 경도와 Young's modulus 값이 증가하는 경향을 보였으며 이는 분자의 운동성과 엔트로피 영향으로 해석할 수 있다. 카본블랙과 실리카가 충전된 NR과 SBR의 경우 충전제의 함량이 증가함에 따라 경도에 미치는 온도의 영향이 감소함을 관찰하였다.

• 한국컴퓨터정보학회논문지
• /
• 제15권12호
• /
• pp.175-180
• /
• 2010

본 논문에서는 고전적인 분자 동역학 시뮬레이션을 통해서 다양한 길이를 가진 이중벽 탄소나노 튜브로 만들어진 초고주파 나노 기계 공진기의 주파수 변동 특성을 분석한다. 분석의 목적은 이중벽 탄소나노 튜브 벽의 길이에 따라 변동하는 공진기의 주파수 분석이다. 실험 결과, 주파수 변동이 여러 가지 외벽 길이 값 L10에 대해서는 내벽/외벽 길이 비율 L5/L10의 함수로 최대 주파수로 정규화된 공진 주파수가 Pearson VII 함수에 잘 맞고, 여러 가지 내벽 길이 값에 대해서는 외벽/내벽 길이 비율의 함수로 최대 주파수로 정규화된 공진 주파수가 Gauss 분산 함수에 잘 맞는 것을 보여준다.

• 멤브레인
• /
• 제21권1호
• /
• pp.98-105
• /
• 2011

본 연구에서는 셀룰로오스 트리아세테이트(CTA) 고분자를 이용한 중공사형 분리막을 상분리법에 의해 제조하였으며, 제조된 중공사 분리막의 기체분리 성능을 평가하였다. 제조된 중공사형 분리막의 기체분리 특성을 부여하기 위해서 1,4-dioxane을 10 wt.% 내외로 첨가하였다. 1,4-dioxane의 첨가에 의해 중공사 표면에 치밀층 형성을 위해서는 1,4-dioxane이 표면에서 증발되는 것이 필수적이며, 이를 위해 air-gap의 조절에 의해 중공사 표면에 치밀층이 생성되도록 하였다. 제조된 CTA 중공사형 기체분리막의 표면 및 단면의 모폴로지 측정을 위하여 전자주사현미경을 사용하였다. 또한 CTA 중공사형 기체분리막의 산소, 질소, 이산화탄소에 대한 기체투과도를 측정하였으며, 이 때 $P_{CO2}$ = 17 GPU, ${\alpha}_{CO2/N2}$ = 48을 나타내었다.

• 한국수소및신에너지학회논문집
• /
• 제25권4호
• /
• pp.436-442
• /
• 2014

$LaCoO_3$ powders synthesized by Pechini process were pulverized by planetary ball-milling to decrease particle size and characterized as a catalyst in alkaline solution for oxygen reduction and evolution reaction (ORR & OER). The changes of physical properties, such as particle size distribution, surface area and electric conductivity, were analyzed as a function of ball-milling time. Also, the variations of the crystal structure and surface morphology of ball-milled powders were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemically catalytic activities of the intrinsic $LaCoO_3$ powders decreased with increasing ball-milling time, but their electrochemical performance as an electrode improved by the increase of the surface area of the powder.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제11권6호
• /
• pp.530-537
• /
• 2006

Recently isolated, Pseudomonas putida SN1 grows on styrene as its sole carbon and energy source through successive oxidation of styrene by styrene monooxygenase (SMO), styrene oxide isomerase (SOI), and phenylacetaldehyde dehydrogenase. For the production of (S)-styrene oxide, two knockout mutants of SN1 were constructed, one lacking SOI and another lacking both SMO and SOI. These mutants were developed into whole-cell biocatalysts by transformation with a multicopy plasmid vector containing SMO genes (styAB) of the SN1. Neither of these self-cloned recombinants could grow on styrene, but both converted styrene into an enantiopure (S)-styrene oxide (e.e. > 99%). Whole-cell SMO activity was higher in the recombinant constructed from the SOI-deleted mutant (130 U/g cdw) than in the other one (35 U/g cdw). However, the SMO activity of the former was about the same as that of the SOI-deleted SN1 possessing a single copy of the styAB gene that was used as host. This indicates that the copy number of styAB genes is not rate-limiting on SMO catalysis by whole-cell SN1.

• Journal of Electrical Engineering and Technology
• /
• 제13권5호
• /
• pp.2059-2066
• /
• 2018

This study explored the feasibility of utilizing an SWCNT-coated fabric sensor for the development of a wearable motion sensing device. The extent of variation in electric resistance of the sensor material was evaluated by varying the fiber composition of the SWCNT-coated base fabrics, attachment methods, number of layers, and sensor width and length. 32 sensors were fabricated by employing different combinations of these variables. Using a custom-built experimental jig, the amount of voltage change in a fabric sensor as a function of the length was measured as the fabric sensors underwent loading-unloading test with induced strains of 30 %, 40 %, and 50 % at a frequency of 0.5 Hz. First-step analysis revealed the following: characteristics of the strain-voltage curves of the fabric sensors confirmed that 14 out of 32 sensors were evaluated as more suitable for measuring human joint movement, as they yield stable resistance values under tension-release conditions; furthermore, significantly stable resistance values were observed at each level of strain. Secondly, we analyzed the averaged maximum, minimum, and standard deviations at various strain levels. From this analysis, it was determined that the two-layer sensor structure and welding attachment method contributed to the improvement of sensing accuracy.

• 한국분말재료학회지
• /
• 제17권6호
• /
• pp.456-463
• /
• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.