• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.542-547
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• 2010

n-Paraffin and saturated fatty acid methyl esters in the diesel and bio-diesel fuel crystallize at low temperature. Many articles have addressed various solutions for the low temperature crystallization problem and one of them is the use of methacrylate copolymers. In this work, we synthesized a series of copolymers in the reaction condition of 70 : 30 molar ratio of lauryl methacrylate (LMA) (or stearyl methacrylate (SMA)) and alkyl methacrylates. The structures of the copolymers were characterized by $^1H$-NMR and FT-IR spectroscopy, and the molecular weight of copolymers were obtained from Gel Permeation Chromatography (GPC) method. The concentrations of additives were 500~1000 ppm and 1000~10000 ppm in diesel fuels and bio-diesel fuel (BD5 and BD20), respectively. The addition of copolymers changes the many properties of fuel such as the pour point (PP), cloud point (CP) and cold filtering plugging point (CFPP). For example, the low temperature properties of the copolymers containing SMA ($PSMAmR_2n$) were excellently improved about 15, 7, and $10^{\circ}C$ for PP, CP and CFPP, respectively.

• Membrane Journal
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• v.33 no.3
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• pp.94-109
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• 2023

1,3-Dioxolane is an exciting material that has attracted widespread interest in the chemical, paint, and pharmaceutical industries as a solvent, electrolyte, and reagent because 1,3-dioxolane is not toxic, carcinogenic, explosive, auto-flammable, and multifunctional, and due to their excellent miscibility in most organic and aqueous solvent conditions. Recently, this material has received increasing attention as a CO₂-selective polymer precursor to separating CO₂ from flue gas and natural gas mixtures. Poly(1,3-dioxolane) (PDXL) possesses higher ether oxygen content than polyethylene oxide (PEO), which demonstrates superior membrane CO₂/N₂ separation properties owing to their polar ether oxygen groups exhibiting strong affinity toward CO₂. Thus, PDXL-based membranes displayed an outstanding CO₂ solubility selectivity over non-polar (N₂, H₂, and CH₄) gases. However, the polar groups of PDXL, like PEO, promote chain packing efficiency and cause polymer crystallization, thereby reducing its gas permeability, which should be improved. In this short review, we discuss the recent advancement and limitations of PDXL membranes in gas separation applications. To conclude, we provide future perspectives for inhibiting the limits of 1,3-dioxolane-based polymers in the CO₂ separation process.

• Polymer(Korea)
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• v.34 no.3
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• pp.237-241
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• 2010

Mechanical characteristics and chemical resistance have been investigated for PC/PBT blends. The changes in mechanical performance of PC/PBT blends was monitored during the treatment with both the PC thinner and general-purpose thinner to figure out the chemical resistance. The PC thinner greatly affected the mechanical properties of PC/PBT blends compared with general-purpose thinner. In the case of PC thinner treatment, the mechanical performance was improved with increased PC content at lower PC content ranges, say below 50%. However the mechanical performance was dropped rapidly at higher PC content ranges due to poor chemical resistance of PC. Transparent pure PC specimen became opaque after chemical treatment with PC thinner, and this can be interpreted by solvent-induced crystallization.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2131-2134
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• 2015

In this study, It has been demonstrated a new and realizable possibility of the ferroelectric random access memory devices by all solution processing method with paper substrates. Organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films were formed on paper substrate with Al electrode for the bottom gate structure using spin-coating technique. Then, they were subjected to annealing process for crystallization. The fabricated PVDF-TrFE thin films were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found from polarization versus electric field (P-E) measurement that a PVDF-TrFE thin film on paper substrate showed very good ferroelectric property. This result agree well with that of a PVDF-TrFE thin film fabricated on the rigid Si substrate. It anticipated that these results will lead to the emergence of printable electron devices on paper. Furthermore, it could be fabricated by a solution processing method for ferroelectric random access memory device, which is reliable and very inexpensive, has a high density, and can be also fabricated easily.

• Fibers and Polymers
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• v.7 no.1
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• pp.12-19
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• 2006

For thermal adaptable fabrics, the polyurethane-urea microcapsules containing phase-change materials (PCMs: hexadecane, octadecane and eicosane) were successfully synthesized by interfacial polycondensation using 2,4-toluene diisocyanate (TDI)/poly(ethylene glycol) (PEG400)/ethylene diamine (EDA) as shell monomers and nonionic surfactant NP-12 in an emulsion system under stirring rates of $3,000{\sim}13,000$ rpm. The mean particle size of microcapsule decreased significantly with increasing the stirring rate up to 11,000 rpm, and then leveled off. The mean particle size increased with increasing the content and molecular weight (eicosane > octadecane > hexadecane) of PCMs at the same stirring rate. The mean particle sizes of microcapsules were found to decrease with increasing the NP-12 content up to 1.5 wt%, and thereafter increased a little. It was found that the melting temperature ($T_m$) and crystallization temperature ($T_c$) of three kinds of encapsulated PCMs and their enthalpy changes (${\Delta}H_m,{\Delta}H_c$) increased with increasing PCM contents. The encapsulation efficiencies (Ee) of hexadecane microcapsule linearly increased with increasing the content of hexadecane. It was found that the stable microcapsule containing 50 wt% of hexadecane could be obtained in this study. However, Ee of octadecane and eicosane microcapsules increased with increasing PCM's contents up to 40 wt%, and then decreased a little. By considering the encapsulation efficiency, it was found that the maximum/optimum contents of octadecane and eicosane microcapsules were about 40 wt%. By the dynamic thermal performance test, it was found that the maximum buffering levels of Nylon fabrics coated with hexadecane, octadecane, and eicosane microcapsules were about $-2.4/+2.9^{\circ}C,\;-3.6/+3.6^{\circ}C\;and\;-4.0/+4.7^{\circ}C$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.647-650
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• 2006

Low temperature polycrystalline silicon (LTPS) technology using a high power laser have been widely applied to thin film transistors (TFTs) for liquid crystal, organic light emitting diode (OLED) display, driver circuit for system on glass (SOG) and static random access memory (SRAM). Recently, the semiconductor industry is continuing its quest to create even more powerful CPU and memory chips. This requires increasing of individual device speed through the continual reduction of the minimum size of device features and increasing of device density on the chip. Moreover, the flat panel display industry also need to be brighter, with richer more vivid color, wider viewing angle, have faster video capability and be more durable at lower cost. Kornic Systems Co., Ltd. developed the $KORONA^{TM}$ LTP/GLTP series - an innovative production tool for fabricating flat panel displays and semiconductor devices - to meet these growing market demands and advance the volume production capabilities of flat panel displays and semiconductor industry. The $KORONA^{TM}\;LTP/GLTP$ series using DPSS laser and XeCl excimer laser is designed for the new generation of the wafer & FPD glass annealing processing equipment combining advanced low temperature poly-silicon (LTPS) crystallization technology and object-oriented software architecture with a semistandard graphical user interface (GUI). These leading edge systems show the superior annealing ability to the conventional other method. The $KORONA^{TM}\;LTP/GLTP$ series provides technical and economical benefits of advanced annealing solution to semiconductor and FPD production performance with an exceptional level of productivity. High throughput, low cost of ownership and optimized system efficiency brings the highest yield and lowest cost per wafer/glass on the annealing market.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.144-144
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• 2012

최근 폴리머를 기판으로 하는 고속 Flexible TFT (Thin film transistor)나 고효율의 박막 태양전지(Thin film solar cell)를 실현시키기 위해 낮은 비저항(resistivity)을 가지며, 높은 홀 속도(carrier hall mobility)와 긴 이동거리를 가지는 다결정 반도체 박막(poly-crystalline semiconductor thin film)을 만들고자 하고 있다. 지금까지 다결정 박막 반도체를 만들기 위해서는 비교적 높은 온도에서 장시간의 열처리가 필요했으며, 이는 폴리머 기판의 문제점을 야기시킬 뿐 아니라 공정시간이 길다는 단점이 있었다. 이에 반도체 박막의 재결정화 온도를 낮추어 주는 metal (Al, Ni, Co, Cu, Ag, Pd, etc.)을 이용하여 결정화시키는 방법(MIC)이 많이 연구되어지고 있지만, 이 또한 재결정화가 이루어진 반도체 박막 안에 잔류 금속(residual metal)이 존재하게 되어 비저항을 높이고, 홀 속도와 이동거리를 감소시키는 단점이 있다. 이에 본 실험은, 종래의 MIC 결정화 방법에서 이용되어진 금속 증착막을 이용하는 대신, HIPIMS (High power impulse magnetron sputtering)와 PIII&D (Plasma immersion ion implantation and deposition) 공정을 복합시킨 방법으로 적은 양의 알루미늄을 이온주입함으로써 재결정화 온도를 낮추었을 뿐 아니라, 잔류하는 금속의 양도 매우 적은 다결정 반도체 박막을 만들 수 있었다. 분석 장비로는 박막의 결정화도를 측정하기 위해 GIXRD (Glazing incident x-ray diffraction analysis)와 Raman 분광분석법을 사용하였고, 잔류하는 금속의 양과 화학적 결합 상태를 알아보기 위해 XPS (X-ray photoelectron spectroscopy)를 통한 분석을 하였다. 또한, 표면 상태와 막의 성장 상태를 확인하기 위하여 HRTEM(High resolution transmission electron microscopy)를 통하여 관찰하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.81-81
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• 2010

유리기판위에 큰 결정입자를 갖는 실리콘 (폴리 실리콘) 박막을 제조하는 것은 가격저가화 및 대면적화 측면 같은 산업화의 높은 잠재성을 가지고 있기 때문에 그동안 많은 관심을 가지고 연구되어 오고 있다. 다양한 방법을 이용하여 다결정 실리콘 박막을 만들기 위해 노력해 오고 있으며, 태양전지에 응용하기 위하여 연속적이면서 10um이상의 큰 입자를 갖는 다결정 실리콘 씨앗층이 필요하며, 고속증착을 위해서는 (100)의 결정성장방향 등 다양한 조건이 제시될 수 있다. 다결정 실리콘 흡수층의 품질은 고품질의 다결정 실리콘 씨앗층에서 얻어질 수 있다. 이러한 다결정 실리콘의 에피막 성장을 위해서는 유리기판의 연화점이 저압 화학기상증착법 및 아크 플라즈마 등과 같은 고온기반의 공정 적용의 어려움이 있기 때문에 제약 사항으로 항상 문제가 제기되고 있다. 이러한 관점에서 볼때 유리기판위에 에피막을 성장시키는 방법으로 많지 않은 방법들이 사용될 수 있는데 전자 공명 화학기상증착법(ECR-CVD), 이온빔 증착법(IBAD), 레이저 결정화법(LC) 및 펄스 자석 스퍼터링법 등이 에피 실리콘 성장을 위해 제안되는 대표적인 방법으로 볼 수 있다. 이중에서 효율적인 관점에서 볼때 IBAD는 산업화측면에서 좀더 많은 이점을 가지고 있으나, 박막을 형성하는 과정에서 큰 에너지 및 이온크기의 빔 사이즈 등으로 인한 표면으로의 damages가 일어날 수 있어 쉽지 않는 방법이 될 수 있다. 여기에서는 이러한 damage를 획기적으로 줄이면서 저온에서 결정화 시킬 수 있는 cold annealing법을 소개하고자 한다. 이온빔에 비해서 전자빔의 에너지와 크기는 그리드 형태의 렌즈를 통해 전체면적에 조사하는 것을 쉽게 제어할 수 있으며 이러한 전자빔의 생성은 금속 필라멘트의 열전자가 아닌 Ar플라즈마에서 전자의 분리를 통해 발생된다. 유리기판위에 흡수층 제조연구를 위해 DC 및 RF 스퍼터링법을 이용한 비정질실리콘의 박막에 대하여 두께별에 따른 밴드갭, 캐리어농도 등의 변화에 대하여 조사한다. 최적의 조건에서 비정질 실리콘을 2um이하로 증착을 한 후, 전자빔 조사를 위해 1.4~3.2keV의 다양한 에너지세기 및 조사시간을 변수로 하여 실험진행을 한 후 단면의 이미지 및 결정화 정도에 대한 관찰을 위해 SEM과 TEM을 이용하고, 라만, XRD를 이용하여 결정화 정도를 조사한다. 또한 Hall효과 측정시스템을 이용하여 캐리어농도, 이동도 등을 각 변수별로 전기적 특성변화에 대하여 분석한다. 또한, 태양전지용 흡수층으로 응용을 위하여 dark전도도 및 photo전도도를 측정하여 광감도에 대한 결과가 포함된다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.601-608
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• 2014

In this paper, we have characterized the electrical properties related to gate leakage current in AlGaN/GaN MISHFETs with varying the thickness (0 to 10 nm) of $Al_2O_3$ gate insulator which also serves as a surface protection layer during high-temperature RTP. The sheet resistance of the unprotected TLM pattern after RTP was rapidly increased to $1323{\Omega}/{\square}$ from the value of $400{\Omega}/{\square}$ of the as-grown sample due to thermal damage during high temperature RTP. On the other hand, the sheet resistances of the TLM pattern protected with thin $Al_2O_3$ layer (when its thickness is larger than 5 nm) were slightly decreased after high-temperature RTP since the deposited $Al_2O_3$ layer effectively neutralizes the acceptor-like states on the surface of AlGaN layer which in turn increases the 2DEG density. AlGaN/GaN MISHFET with 8 nm-thick $Al_2O_3$ gate insulator exhibited extremely low gate leakage current of $10^{-9}A/mm$, which led to superior device performances such as a very low subthreshold swing (SS) of 80 mV/dec and high $I_{on}/I_{off}$ ratio of ${\sim}10^{10}$. The PF emission and FN tunneling models were used to characterize the gate leakage currents of the devices. The device with 5 nm-thick $Al_2O_3$ layer exhibited both PF emission and FN tunneling at relatively lower gate voltages compared to that with 8 nm-thick $Al_2O_3$ layer due to thinner $Al_2O_3$ layer, as expected. The device with 10 nm-thick $Al_2O_3$ layer, however, showed very high gate leakage current of $5.5{\times}10^{-4}A/mm$ due to poly-crystallization of the $Al_2O_3$ layer during the high-temperature RTP, which led to very poor performances.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.174-181
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• 2007

In this study, $SiO_2/poly(ethylene-co-vinyl$ alcohol)(EVOH) hybrid coating materials with gas barrier property could be produced using sol-gel method. The biaxially oriented polypropylene (BOPP) substrate with surface pretreatment was coated with the prepared hybrid sols containing various inorganic silicate component by a spin coating method. Crystallization behavior of the hybrids was investigated in terms of analysis of X-ray diffraction and cooling thermogram from DSC experiment. From the morphological observation of the $SiO_2/EVOH$ hybrid gel, it was confirmed that there existed an optimum content of inorganic silicate precursor, Tetraethylorthosilicate (TEOS), to produce hybrid materials with dense microstructure, exhibiting uniformly dispersed silica particles with average size below 100 nm. When TEOS was added at below or above the optimum content, particle clusters with large domain were observed, resulting in phase separation. This morphological result was found to be in good agreement with that of oxygen permeability of the hybrid coated films. In the case of film coated with hybrid prepared from addition of 0.01 - 0.02mol of TEOS, a remarkable improvement in barrier property could be obtained, however, with the addition of TEOS more than 0.04 mol, the barrier property was dramatically reduced because of phase separation and micro-crack formation on the film surface.