• 한국화재소방학회논문지
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• 제24권4호
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• pp.41-46
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• 2010

고강도 콘크리트는 대형 사회기반 구조물로서 많이 활용되고 있다. 고강도 콘크리트는 우수한 재료적 성능과 내구성을 확보하고 있지만 반면에 화재에 대한 급작스러운 폭렬현상으로 인하여 구조적인 문제를 야기시키기도 한다. 따라서 본 연구에서는 콘크리트 피복두께에 추가하여 내화피복재를 사용함으로써 내화피복두께에 따른 콘크리트의 내화성능을 평가하고 최적의 내화피복두께를 산정하는 실험적 연구를 수행하였다. 내화피복재를 10mm 간격으로 증가시키면서 실험을 수행한 결과 콘크리트의 내화성능이 크게 향상됨을 볼 수 있었으며, 최적의 내화피복두께는 약 1~3mm로 산정되었다. 또한 폭렬에 의하여 급작스러운 콘크리트 내부의 온도상승 이후 기화열에 의한 열손실로 완만하게 온도가 상승되는 현상이 실험적으로 관측되었다. PP 섬유는 약 $200^{\circ}C$ 부근에서 용해되어 고온에서는 빈 채널만 남게 되므로 내부 증기압을 저감시켜주는 역할도 관측되었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 춘계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.6-6
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• 1994

Har dmaterials such as cemented carbides with or without coated layer, cermets, ceramics and diamond or c-BN high pressure sintered compact are used for cutting tools, wear -resistant parts, rock drilling bits and/or high pressure vessels. These hardmaterials contain not only hard phase, but also second consituent as the element for forming ductile phase and/or sintering aid, and the mechanical properties of each material depend on (1) the amount of the second constituent as well as (2) the grain size of the hard phase. The hardness of each material mainly depends on these two factors. The fracture strength, however, largely depends on other microstructur a1 factors as well as the above two factors. For all hardmaterials, the fracture strength is consider ably affected by (3) the size of microstructur a1 defect which acts as the fracture source. In cemented carbides, the following factors which are generated mainly due to the addition of the second constituent are also important; (4) the variation of the carbon content in the normal phase region free from V-phase and graphite phase, (5) the precipitation of $Co_3$ during heating at about $800^{\circ}C$,(6) the domain size of binder phase, and (7) the formation of ${\beta}$-free layer or Co-rich layer near the surface of sintered compacts. For cemented carbides coated with thin hard substance, the important factors are as follows; (8) the kind of coated substance, (9) the formation of ${\eta}$-phase layer at the interface between coated layer and substrate, (10) the type of residual stress (tension or compression) in the coated layer which depends on the kind of coating method (CVD or PVD), and (11) the properties of the substrate, and (12) the combination, coherency and periodicity of multi-layers. In the lecture, the details of these factors and their effect on the strength will be explained.

• 반도체디스플레이기술학회지
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• 제15권1호
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• pp.65-69
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• 2016

We have investigated the possibility of recycling of an organic material that is wasted during thermal evaporation. To this end, we have collected a wasted organic material (N,N'-diphenly-N,N'-bis(1,1'-biphenyl)-4,4'-diamine(NPB)) from a vacuum chamber, purified it by recrystallization, and fabricated bilayer organic light-emitting diodes (OLEDs) with the recycled NPB. It is found that the surface roughness of thin films coated with the purified NPB is much enhanced. OLEDs fabricated by thermal evaporation of the purified NPB show lower device efficiency than OLEDs with the original NPB. However, the power efficiency of OLED fabricated by spin coating of the purified NPB is comparable with that of OLED with the original NPB. Therefore, such a recycling method by recrystallization would be more suitable for solution-processed OLEDs.

• 한국환경과학회지
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• 제25권5호
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• pp.737-744
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• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.396-399
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• 2003

In this paper, the purpose is to develop imaging technique of synchrotron radiation using CMOS image sensor. The detector using hybrid method to be research in this lab was used, in order to increase image signal. We made experiments with 1B2 Whitebeam/microprobe beamline in PAL (Pohang Accelerator Laboratory). Phosphor materials such as ZnS:(Ag,Li), ZnS:(Cu,Al), $Y_2O_2S:Eu$ were produced by spin coating on glass. Synchrotron radiation images were acquired and evaluated from monochromatic light from monochromoator in PAL 1B2line. From obtained object and phantom, MTF was 0.15 in ZnS:(Ag,Li) phosphor, and 0.178 in ZnS:( Cu,Al) at 151p/mm. MTFs were unsystematic because thickness of phosphor and uniformity of surface were not optimized. It's expected to improve MTF and the qualify of images as uniformity's optimized.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.324-327
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• 2005

An electrophoretic display using $TiO_2$ particles is the most promising candidate because it offers various advantages such as ink-on-paper appearance, good contrast ratio, wide viewing angle, image stability in the off-state and extremely low power consumption. The core technology of electrophoretic display is the dispersion controlling of $TiO_2$ nano particles in nonaqueous solution. To prepare an ink for electronic paper using electrophoretic properties of $TiO_2$ nano particles, cyclohexane with low dielectric constant and transparency, polyethylene for producing polymer coating layer which reduces apparent gravity of $TiO_2$, and $TiO_2$ powders were mixed together by planetary-mill. The zeta-potential value of $TiO_2$ particles in cyclohexane was measured about -40mV, but was measured over -110mV by dispersant attached to polyethylene-coated $TiO_2$ surface. Prepared electronic ink was filled in cross patterned micro-wall with $200{\mu}m$ in width and $40{\mu}m$ in height on ITO glass designed by photolithography. The response time of electronic paper evaluated by mobility of $TiO_2$ particle between micro-walls was measured 0.067sec, but the drift velocity from reflectance wave form during reverse from of electronic ink was measured 0.07cm/sec.

• Journal of Welding and Joining
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• 제25권4호
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• pp.28-34
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• 2007

The heating unit of direct heating method manufactured as the plasma spray coating of $TiO_2/NiCr$ conductive heating material on the surface of heating unit in order to improve the disadvantages of indirect heating method. $TiO_2$ and NiCr (80wt.%Ni-20wt.%Cr) that had the properties of conduction and heating was chosen for the conductive heating material. The compositions of the composite powders were studied $TiO_2-30wt.%NiCr\;and\;TiO_2-10wt.%NiCr$. As the heating temperature was increased, the hardness of heating layer was increased because of the fine microstructure and the decrease of porosity. The adhesion strength was decreased for coarsening and connection of voids in the insulation layer, and the electrical resistivity of heating layer was increased for fine crack formation and growth. In this study, the best efficient sprayed coatings with heating unit was concluded as the plasma sprayed $TiO_2-10wt.%NiCr$ coatings that was heat treated at $300^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.276-279
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• 2004

Plasma enhanced chemical vapor deposition (PECVD) of silicon nitride (SiN) is a proven technique for obtaining layers that meet the needs of surface passivation and anti-reflection coating. In addition, the deposition process appears to provoke bulk passivation as well due to diffusion of atomic hydrogen. This bulk passivation is an important advantage of PECVD deposition when compared to the conventional CVD techniques. A further advantage of PECVD is that the process takes place at a relatively low temperature of 300t, keeping the total thermal budget of the cell processing to a minimum. In this work SiN deposition was performed using a horizontal PECVD reactor system consisting of a long horizontal quartz tube that was radiantly heated. Special and long rectangular graphite plates served as both the electrodes to establish the plasma and holders of the wafers. The electrode configuration was designed to provide a uniform plasma environment for each wafer and to ensure the film uniformity. These horizontally oriented graphite electrodes were stacked parallel to one another, side by side, with alternating plates serving as power and ground electrodes for the RF power supply. The plasma was formed in the space between each pair of plates. Also this paper deals with the fabrication of multicrystalline silicon solar cells with PECVD SiN layers combined with high-throughput screen printing and RTP firing. Using this sequence we were able to obtain solar cells with an efficiency of 14% for polished multi crystalline Si wafers of size 125 m square.

• 한국염색가공학회지
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• 제31권3호
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• pp.165-176
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• 2019

Polyurethane-ureas(PUUs) were prepared from 4,4'-methylenebis(cyclohexyl isocyanate) and various diols including isosorbide. Isosorbide is starch-derived monomer that exhibit a wide range of glass transition temperature and are therefore able to be used in many applications. PUU was synthesized by a pre-polymer polymerization using a catalyst. Successful synthesis of the PUU was characterized by fourier transform-infrared spectroscopy. Thermal properties were determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. It was found that by tuning isosorbide content in the resin, their glass transition temperature(Tg) slightly decreased. Physical properties were also determined by tensile strength and X-ray diffraction. There is no significant differences between petroleum-derived diol and isosorbide in XRD analysis. Moreover, their physical and optical properties were determined. The result showed that the poly(tetramethylene ether glycol)/isosorbide-based PUU exhibited enhanced tensile strength, transmittance, transparency and biodegradability compared to the existing diols. After 11 weeks composting, the biodegradability of blends increased in ISB-PUU. The morphology of the fractured surface of blend films were investigated by scanning electron microscopy.

• 접착 및 계면
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• 제20권3호
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• pp.102-109
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• 2019

PET기재 필름 위에 코팅된 다층박막 필름의 층별성분을 ATR FT-IR과 Pyro GC/MS(Gas Chromatography/Mass Spectroscopy)를 이용하여 분석을 시도하였다. 필름의 단면은 액체질소에 담근 후 파괴시켜 얻었으며 광학 현미경을 이용하여 관찰하였다. 이 결과 코팅층의 총 두께는 $70{\mu}m$였으며 3개의 층으로 관찰되었다. 각 층의 두께는 너무 얇기 때문에 표면층을 제외하고는 직접분석이 어려워 적절한 용매로서 각 층을 드러나게 한 후 ATR FT-IR과 pyro-GC/MS를 이용하여 분석을 시도하였다. 이 결과 3개 층은 공통적으로 우레탄-아크릴레이트 공중합체로 밝혀졌다. 또한 무기 혹은 금속성분의 첨가여부는 XPS와 SEM-EDAX를 이용하여 분석하였으며 도장층 (1)에는 나노크기의 실리카 입자가 도장층 (2)에서는 알루미늄 박편이 존재함을 알게 되었다.