벗김전압전류법을 이용한 카본나노튜브 전극에서의 카드뮴 분석

차재민,최정식,국원준,사봉준,이승재,방유섭,오영빈,곽정희 한국환경교육학회 2012 한국환경교육학회 학술대회 자료집 Vol.2012 No.12

Femto Second Laser Pulse에 의한 유리의 결정화 및 기계적 특성

차재민,문필용,김동현,박성제,조성학,류봉기,Cha, Jae-Min,Moon, Pil-Yong,Kim, Dong-Hyun,Park, Sung-Je,Cho, Sung-Rak,Ryu, Bong-Ki 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.6

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5$ glasses were irradiated to strengthen by the crystallization using Femto second laser Pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed. Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360 nm. Especially, samples irradiated by 140 mW laser with XYZ stage having at the rate of 100$\~$l000 $\mu$m/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90 mW laser irradiated samples. Moreover, samples irradiated by laser had higher values ($4.4\~4.56{\times}10^{-3}(Pa)$) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2$\~$1 .5 times higher values than them of mother glass.

Femto Second Laser Pulse에 의한 유리의 결정화 기계적 특성

차재민,류봉기,문필용,김동현,박성제,조성학 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.6

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals.In this study, Ag-doped 45SiO224CaO24Na2O4P2O5 glasses were irradiated to strengthen by the crystallization using Femto second laser pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed.Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360nm. Especially, samples irradiated by 140mW laser with XYZ stage having at the rate of 100~1000㎛/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90mW laser irradiated samples.Moreover, samples irradiated by laser had higher values (4.4 ~ 4.56 x 10-3(Pa)) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2 ~ 1.5 times higher values than them of mother glass.

Large-scale Production and Therapeutic Compound Regulation of Extracellular Vesicles via 3D Stem Cell Bioprocess Using Biopolymers

차재민,정선영,김태희,배호재,김진석,방오영 한국고분자학회 2018 한국고분자학회 학술대회 연구논문 초록집 Vol.43 No.1

Effect of Nano-NiO Additive on Adhesion Strength and Bubble Structure of Vitreous Enamels

차재민,김주형,신재영,류봉기 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.7

The effect of NiO nanopowder on the adhesion strength and formation of fish-scales in vitreous enamels has been investigated. The results of a ball drop test indicated that the adhesion strength was greatly increased by a mill addition of NiO nanopowder. The adhesion strength and bubbling microstructure of the enamel were studied using optical and scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS) analysis. The results showed that, as a mill additive, NiO nanopowder changes the composition and structure at the enamel-steel interface and enables interdiffusion. In addition, as the amount of mill addition was increased, the size of the gas bubbles increased and the cracks of the enamel layer, generally referred to as fish-scaling, were reduced.

기능기화 된 그래핀 나노플레이틀릿이 첨가 된 탄소섬유 강화 고분자 복합소재의 제조 및 기계적 특성 연구

차재민,김준희,류호진,홍순형,Cha, Jaemin,Kim, Jun Hui,Ryu, Ho Jin,Hong, Soon H. 한국복합재료학회 2017 Composites research Vol.30 No.5

탄소섬유는 매우 우수한 기계적, 전기적, 열적 특성을 가진 소재로써, 고분자를 매트릭스로 하는 복합재료로써 산업적으로 널리 쓰이고 있다. 하지만 이 복합재료는 높은 강도 및 탄성을 가진 탄소섬유에 비해, 약한 고분자 매트릭스로 인한 분리 형상이 약점으로 지적되고 있다. 이를 해결하기 위해 강화재의 첨가가 필수적이다. 그래핀은 매우 우수한 기계적 물성을 지닌 강화재로써, 첨가 시에 높은 물성 향상을 기대할 수 있다. 하지만 그래핀 자체의 응집현상과 고분자 기지와의 약한 결합이 강화효과를 제대로 구현해내지 못하는 결과를 초래하고 있다. 이러한 문제점을 해결하기 위한 핵심 기술로 제시된 것이 기능기화 방법이며, 이를 통해 분산성을 향상시킬 수 있다. 본 연구에서는 멜라민을 이용하여 그래핀 나노플레이틀릿의 기능기화를 진행하고, 이를 에폭시 고분자 기지와 혼합하였다. 제조된 그래핀 나노플레이틀릿/에폭시을 이용하여 탄소섬유 강화 고분자 복합재료를 제조하고 굽힘 특성과 층간전단강도를 측정하였다. 그 결과 복합재료의 기계적 물성이 증가되었으며, 그래핀 나노플레이틀릿의 분산성이 향상됨을 확인하였다. Carbon fiber is a material with excellent mechanical, electrical and thermal properties, which is widely used as a composite material made of a polymer matrix. However, this composite material has a weak point of interlaminar delamination due to weak interfacial bond with polymer matrix compared with high strength and elasticity of carbon fiber. In order to solve this problem, it is essential to use reinforcements. Due to excellent mechanical properties, graphene have been expected to have large improvement in physical properties as a reinforcing material. However, the aggregation of graphene and the weak interfacial bonding have resulted in failure to properly implement reinforcement effect. In order to solve this problems, dispersibility will be improved. In this study, functionalization of graphene nanoplatelet was proceeded with melamine and mixed with epoxy polymer matrix. The carbon fiber reinforced polymer composites were fabricated using the prepared graphene nanoplatelet/epoxy and flexural properties and interlaminar shear strength were measured. As a result, it was confirmed that the dispersibility of graphene nanoplatelet was improved and the mechanical properties of the composite material were increased.

Development and validation of a UPLC-MS/MS method for the quantification of aceta-minophen in human plasma and its application to pharmacokinetic studies

차재민,김보경,권미리,이주미,옥보람,강우열,임미선,성숙진,김현주,이혜원,윤영란 대한임상약리학회 2016 Translational and Clinical Pharmacology Vol.24 No.1

We developed an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of acetaminophen concentration in human plasma. Fol-lowing protein precipitated extraction, the analytes were separated and analyzed using an UPLC-MS/MS in the multiple reaction monitoring (MRM) mode with the respective [M+H]+ ions, m/z 152.06 → 110.16 for acetaminophen and m/z 180.18 → 138.12 for phenacetin (internal standard, IS). The method showed a linear response from 1 to 100 μg/mL (r > 0.9982). The limit of quantitation for acetaminophen in plasma was 1 μg/mL. The intra- and inter-day accuracy ranged in the ranges of 94.40–99.56% and 90.00–99.20%, respectively. The intra- and inter-day precision ranged in the ranges of 2.64–10.76% and 6.84–15.83%, respectively. This method was simple, reliable, precise and accurate and can be used to determine the concentration of acetaminophen in human plasma. Fi¬nally, this fully validated method was successfully applied to a pharmacokinetic study of acetamino¬phen in healthy volunteers following oral administration.

Embryoid Body Size-Mediated Differential Endodermal and Mesodermal Differentiation Using Polyethylene Glycol (PEG) Microwell Array

차재민,황유식,배호재,Nasser Sadr,Sam Manoucheri,Faramarz Edalat,김기영,김상복,권일근,ALI KHADEMHOSSEINI 한국고분자학회 2015 Macromolecular Research Vol.23 No.3

Embryoid bodies have a number of similarities with cells in gastrulation, which provides useful biologicalinformation about embryonic stem cell differentiation. Extensive research has been done to study the control ofembryoid body-mediated embryonic stem cell differentiation in various research fields. Recently, microengineeringtechnology has been used to control the size of embryoid bodies and to direct lineage specific differentiation ofembryonic stem cells. However, the underlying biology of developmental events in the embryoid bodies of differentsizes has not been well elucidated. In this study, embryoid bodies with different sizes were generated within microfabricatedPEG microwell arrays, and a series of gene and molecular expressions related to early developmentalevents was investigated to further elucidate the size-mediated differentiation. The gene and molecular expressionprofile suggested preferential visceral endoderm formation in 450 μm embryoid bodies and preferential lateral platemesoderm formation in 150 μm embryoid bodies. These aggregates resulted in higher cardiac differentiation in 450 μmembryoid bodies and higher endothelial differentiation in 150 μm embryoid bodies, respectively. Our findings mayprovide further insight for understanding embryoid body size-mediated developmental progress.

Changes in the Electrical Conductivity and Catalytic Property of Vanadium Iron Borophosphate Glasses with Crystallization

차재민,정화진,류봉기 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.10

Glasses were prepared in the V2O5−P2O5−B2O3 system containing Fe2O3 and were crystallized to examine the changes in the structure, as well as the catalytic and the electrical properties. The glasses were annealed in a graphite mold at a temperature above the glass transition temperature for 1 h and were heat-treated at the crystallization temperature for 1 h, 6 h and 12 h, respectively. Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the structural changes of the V−O bonds after crystallization while the X-ray photoelectron spectroscopy (XPS) analysis indicated a decrease in V5+ and an increase in V4+ amounts. The X-ray diffraction (XRD) analysis indicated that a new crystalline phase of non-stoichiometric Fe0.12V2O5 was formed after 1 h of heat treatment. Structural changes induced by the crystallization were analyzed by determining the molecular volume from the sample density. The conductivity and the catalytic property were examined based on the migration of V and Fe ions exhibiting different valence states with crystallization. Both the conductivity and the catalytic property improved after the samples had been crystallized at the crystallization peak temperature (Tp). Furthermore, as compared to the sample heat treated for 1 h, the conductance and catalytic properties were improved for samples crystallized at Tp for 6 h and 12 h.

PbO-SiO_2계 유리에서의 유동 특성

차재민,김웅식,송현진,이병철,류봉기 釜山大學校生産技術硏究所 2002 生産技術硏究所論文集 Vol.61 No.-

유리에 관한 연구에 있어 점도는 가장 중요한 특성중의 하나로 여겨지며, 용융 상태, 작업 온도, 서냉 온도 또는 결정화 속도에 등과 같은 인자와도 크게 관계가 있다. 특히 각기 다른 조성을 가진 유리에서도 점도는 매우 다양하며, 온도에 크게 영향을 받는다. PbO-SiO_2 이성분계 유리에서는 PbO가 첨가됨에 따라 점도의 온도의존성이 커지고 표면장력이 감소하였다. 온도와 시간에 따른 spreading ratio를 비교한 결과 PbO의 함량이 증가함에 따라 유동성이 증가하였고 온도에 따른 유동성의 증가율도 크게 증가하였다. 그리고 일정한 온도에서 시간의 경과에 따른 유동성의 증가율은 감소하였다. The viscosity of a glass is one of the most important properties. It determines the melting conditions, the temperatures of working and annealing, fining behavior and devitrification rate. The viscosities of different glasses vary enormously with composition and are strong functions of temperature. On adding PbO in the PbO-SiO_2 binary system, the temperature dependence of the viscosity was large, the surface tension decreased. In the temperature and time dependence of spreading ratio, the spreading ratios of glass increased with increase PbO content and the rate in its increase decreased with time at constant temperature.