• 한국결정성장학회지
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• 제22권1호
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• pp.57-63
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• 2012

$Al_2TiO_5$에 LAS(${\beta}$-spodumene)와 $Fe_2O_3$를 첨가하여 고상법으로 세라믹 소결체를 제조하였다. $Al_2TiO_5$에 첨가된 LAS는 액상을 형성하고, $Fe_2O_3$는 입자 성장을 억제시켜 소결체를 치밀화하였다. 첨가제의 양을 변화시켜 소결특성, 기계적 특성 및 열충격 특성에 대하여 조사하였다. $Fe_2O_3$가 20 wt% 첨가된 LAS를 $Al_2TiO_5$에 20 wt% 첨가하였을 때, 꺽임 강도는 120 MPa 이상이었고, 열충격에 대한 저항성은 $1200^{\circ}C$ 이상으로 우수함을 확인하였다.

• 한국결정성장학회지
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• 제21권1호
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• pp.47-53
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• 2011

미연탄소가 과량 함유된 석탄 바닥재와 준설토가 30 wt% 혼합된 모분말(parent batch powders)로 부터 인공골재를 제조하고 그 물성을 평가하였다. 특히 폐유리 또는 폐유리에 $Na_2O$를 5 wt% 첨가하여 제조된 프리트(NWG)의 혼합이 인공골재의 발포 특성에 미치는 영향을 고찰하였다. 모분말로 제조된 골재는 과량의 미연탄소가 소결을 방해하여 부피비중이낮았다. 그러나 모분말에 폐유리를 첨가하면 소결이 촉진되어 치밀화가 일어나고 부피 비중이 증가하였다. 한편 모분말에 NWG를 5 wt% 첨가하여 인공골재를 제조하면, 단순히 폐유리만 첨가한 경우에 비하여 부피비중 값이 감소하였다. 이는 고온에서 융제의 점도가 $Na_2O$ 영향으로 낮아짐에 따라 골재표면에 다량의 액상이 생성되었고 이로 인해 표면 액상에 가스가 포집되어 표피가 다공성을 나타내기 때문이다. 본 연구에서 $1100^{\circ}C$ 이상으로 소성된 시편은 부피 비중 1.15~1.34 및 흡수율 11~19 %을 갖는 경량골재의 특성을 나타내었으며, 발포 현상은 내부가 아닌 표피에서 발생되는 특징을 보였다.

• 한국결정성장학회지
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• 제21권1호
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• pp.41-46
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• 2011

폐기물인 석탄바닥재와 준설토가 70 : 30(wt%)으로 혼합된 배치분말에 적니를 0~30 wt% 첨가하고 $1050{\sim}1250^{\circ}C$에서 10분 직화 소성하여 인공골재를 제조하고 그 물성을 평가하였다. 특히 인공골재의 발포특성에 미치는 적니 첨가량 효과를 분석하기 위해 비중 및 흡수율을 측정하고, 그 결과를 미세구조 결과와 연계하여 고찰하였다. 제조된 인공골재는 소성온도 및 적니 첨가량이 증가할수록 발포성이 향상되어 경량화 되는 특징을 나타내었다. $1050{\sim}1150^{\circ}C$ 범위로 소결된 대부분의 인공골재는 잘 형성된 블랙코어 구조를 가졌으나, 적니가 첨가되고 $1200^{\circ}C$ 이상으로 소결된 시편들은 $Fe_2O_3$의 환원에 의한 과량의 가스 방출 및 액상 형성으로 인하여 블랙코어 부분이 시편 표피를 뚫고 나오는 현상이 나타났다. 특히 적니 30 wt%를 함유한 시편은 $1100^{\circ}C$ 이상으로 소결하면 폭발되어 여러 조각으로 흩어졌다. 본 연구에서 $1200^{\circ}C$에서 소결된 시편의 부피비중은 적니가 첨가되지 않은 것은 1.2, 적니가 20 wt% 첨가된 것은 1.0 이하의 경량골재 특성을 나타내었다.

• 공업화학
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• 제25권1호
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• pp.116-120
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• 2014

접촉분해 가솔린 제조공정의 부산물의 하나인 접촉분해경유(LCO)는 많은 유용 방향족 성분을 함유하고 있다. 그 중에서도 특히 2,6-dimethylnaphthalene (2,6-DMN)은 PEN 수지, 고분자 액정 등의 기초 원료로서 주목된다. 지금까지 중유에 혼합되어 연료로서만 사용되고 있는 LCO로부터 2,6-DMN 등과 같은 유용 방향족 탄화수소를 분리, 정제하는 것이 가능하게 되면 자원의 유용이용이라는 관점에서 그 의미는 매우 크다. 본 연구는 melt crystallization (MC)과 solute crystallization (SC)의 조합에 의해 2,6-DMN의 고순도 정제를 검토했다. MC와 SC의 원료로서는 증류-추출 조합에 의해 LCO로부터 회수한 DMN 이성체 혼합물(2,6-DMN의 농도: 10.43%)과 MC로부터 회수한 결정을 각각 사용했다. SC의 용매는 메탄올과 아세톤 혼합물(60 : 40 wt%)을 사용했다. MC-SC의 조합에 의해 99.5%의 2,6-DMN 결정을 회수할 수 있었다. MC-SC는 DMN 이성체 혼합물에 함유된 2,6-DMN의 고순도 정제에 매우 유용한 조합의 하나임을 확인했다.

• 산업경영시스템학회지
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• 제40권1호
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• pp.114-123
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• 2017

The global small and mid-sized display market is changing from thin film transistor-liquid crystal display to organic light emitting diode (OLED). Reflecting these market conditions, the domestic and overseas display panel industry is making great effort to innovate OLED technology and incease productivity. However, current OLED production technology has not been able to satisfy the quality requirement levels by customers, as the market demand for OLED is becoming more and more diversified. In addition, as OLED panel production technology levels to satisfy customers' requirement become higher, product quality problems are persistently generated in OLED deposition process. These problems not only decrease the production yield but also cause a second problem of deteriorating productivity. Based on these observations, in this study, we suggest TRIZ-based improvement of defects caused by glass pixel position deformation, which is one of quality deterioration problems in small and medium OLED deposition process. Specifically, we derive various factors affecting the glass pixel position shift by using cause and effect diagram and identify radical reasons by using XY-matrix. As a result, it is confirmed that glass heat distortion due to the high temperature of the OLED deposition process is the most influential factor in the glass pixel position shift. In order to solve the identified factors, we analyzed the cause and mechanism of glass thermal deformation. We suggest an efficient method to minimize glass thermal deformation by applying the improvement plan of facilities using contradiction matrix in TRIZ. We show that the suggested method can decrease the glass temperature change by about 23% through an experiment.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.65-65
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• 2011

Single-well carbon nanotubes (SWNT) have been proposed as a promising candidate for various applications owing to their excellent properties. In particular, their fascinating electrical and mechanical properties could provide a new area for the development of advanced engineering materials. A transparent conductive thin film (TCF) has increased for applications such as liquid crystal displays, touch panels, and flexible displays. Indium tin oxide (ITO) thin films, which have been traditionally used as the TCFs, have a serious obstacle in TCFs applications. SWNTs are the most appropriate materials for conductive films for displays due to their excellent high mechanical strength and electrical conductivity. But, a bundle of CNTs has different electrical properties than their individual counterparts. In this work, the fabrication by the spraying process of transparent SWNT films and reduction of its sheet resistance on PET substrates is researched. Arc-discharge SWNTs were dispersed in deionized water by adding sodum dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWNT was spray-coated on PET substrate and dried on a hotplate at $100^{\circ}C$. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then treated with ionic doping treatment, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. Results, we show that 97 ${\Omega}$/> sheet resistance can be achieved with 81% transmittance at the wavelength of 550 nm. The changes in electrical and optical conductivity of SWNT film before and after ionic doping treatments were discussed.

• Journal of Information Display
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• 제10권1호
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• pp.33-36
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• 2009

A new hybrid silicon thin-film transistor (TFT) fabrication process using the DPSS laser crystallization technique was developed in this study to realize low-temperature poly-Si (LTPS) and a-Si:H TFTs on the same substrate as a backplane of the active-matrix liquid crystal flat-panel display (AMLCD). LTPS TFTs were integrated into the peripheral area of the activematrix LCD panel for the gate driver circuit, and a-Si:H TFTs were used as a switching device of the pixel electrode in the active area. The technology was developed based on the current a-Si:H TFT fabrication process in the bottom-gate, back-channel etch-type configuration. The ion-doping and activation processes, which are required in the conventional LTPS technology, were thus not introduced, and the field effect mobility values of $4\sim5cm^2/V{\cdot}s$ and $0.5cm^2/V{\cdot}s$ for the LTPS and a-Si:H TFTs, respectively, were obtained. The application of this technology was demonstrated on the 14.1" WXGA+(1440$\times$900) AMLCD panel, and a smaller area, lower power consumption, higher reliability, and lower photosensitivity were realized in the gate driver circuit that was fabricated in this process compared with the a-Si:H TFT gate driver integration circuit

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.75-76
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• 2006

LCD-BLU (Liquid Crystal Display - Back Light Unit) is one of kernel parts of LCD unit and it consists of several optical sheets(such as prism, diffuser and protector sheets), LCP (Light Guide Plate), light source (CCFL or LED) and mold frame. The LGP of LCD-BLU is usually manufactured by forming numerous dots with $50{\sim}200{\mu}m$ in diameter on it by erosion method. But the surface of the erosion dots of LGP is very rough due to the characteristics of the erosion process during the mold fabrication, so that its light loss is high along with the dispersion of light into the surface. Accordingly, there is a limit in raising the luminance of LCD-BLU. In order to overcome the limit of current dot patterned LGP, optical pattern design with $50{\mu}m$ micro-lens was applied in the present study. Especially, the negative and positive micro-lens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP. The attention was paid to the effects of different pattern conditions to the brightness distribution of BLU with micro-lens patterned LGP. Finally, negative micro-lens patterned LGP showed superior results to the one made by positive in average luminance.

• 센서학회지
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• 제30권6호
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• pp.369-375
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• 2021

In this study, heterogeneous ZnO/CNTF composites were developed to improve the NO₂-sensing response, facilitated by the self-heating property. Highly conductive and mechanically stable CNTFs were prepared by a wet-spinning process assisted by the liquid crystal (LC) behavior of CNTs. Metal-organic frameworks (MOFs) of ZIF-8 were precipitated on the surface of the CNTF (ZIF-8/CNTF) via one-pot synthesis in solution. The subsequent calcination process resulted in the formation of the ZnO/CNTF composites. The calcination temperatures were controlled at 400, 500, and 600 ℃ in an N₂ atmosphere to confirm the evolution of the microstructures and NO₂-sensing properties. Gas sensor characterization was performed at 100 ℃ by applying a DC voltage to induce Joule heating through the CNTF. The results revealed that the ZnO/CNTF composite after calcination at 500 ℃ (ZnO/CNTF-500) exhibited an improved response (R_air/R_gas = 1.086) toward 20 ppm NO₂ as compared to the pristine CNTF (R_air/R_gas = 1.063). Selective NO₂-sensing properties were demonstrated with negligible responses toward interfering gas species such as H₂S, NH₃, CO, and toluene. Our approach for the synthesis of MOF-driven ZnO/CNTF composites can provide a new strategy for the fabrication of wearable gas sensors integrated with textile materials.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.421-421
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• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency