• 대한소아치과학회지
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• 제41권1호
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• pp.1-7
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• 2014

가정에서 유치가 탈락하였을 경우 쉽게 구할 수 있는 저장 용액에 보관한 후, 보관되었던 유치에서 세포를 배양할 수 있다면 지금보다 더 많은 유치로부터 줄기 세포를 추출할 수 있을 것이다. 본 연구는 유치의 치수 세포가 다양한 보관 용액의 종류와 기간에 영향을 받는지 확인해 보고자 하였다. 330개의 탈락 유치를 신선군, 건조군, 세포배양액 2, 4, 7일 보관군, 우유 2, 4, 7일 보관군, 생리식염수 2, 4, 7일 보관군으로 각각 30개씩 무작위로 나누었다. 각 군 간의 유치 치수 조직 세포의 일차 배양을 시행하여 성공한 개수와 실패한 개수를 계산하여 생존 성공률을 비교하였다. 일차 배양 결과 보관 기간이 늘어날수록 일차 배양 시 세포의 생존 성공률이 낮아지는 것으로 나타났다. 2일 보관군과 4일 보관군까지 세포배양액, 우유, 생리식염수 간의 보관 용액에 따른 성공률의 유의할 만한 차이는 없었다. 그러나 7일 보관군에서는 세포배양액에 비해 우유와 생리식염수에 보관한 유치에서 성공률이 유의하게 떨어지는 것으로 나타났다. 유치 발거 후 우유나 생리식염수 등의 보관용액에 일정 기간 보관 후 그 치수 조직을 세포 배양에 사용하는 것이 가능하지만 보관 기간이 길어질수록 세포 획득 가능성이 줄어든다.

• 한국산업융합학회 논문집
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• 제17권1호
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• pp.1-6
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• 2014

Styrene-butadiene-styrene copolymer(SBS)/Clay nanocomposites were prepared by melt mixing method with organic clay modified with dimethyl dihydrogenated-tallow amine(Cloisite 15A) and methyl tallow bis (2-hydroxy-ethyl) amine(Cloisite 30A), respectively. From the results of XRD, we found that mono layered silicates were dispersed in SBS matrix and they were exfoliated nanocomposites. Mechanical properties of exfoliated SBS nanocomposites were more improvedl than those of SBS. Especially, it was found that the addition of small amount of organoclay was enough to improve mechanical properties without increasing hardness.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.85-88
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• 2012

Studies on the effects of layered silicate content on the AC electrical treeing and breakdown behaviors of epoxy/layered silicate nanocomposites were carried out in needle-plate electrode geometry. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that 1 wt% of the multilayered silicate was fully exfoliated into nano-sized monolayers in the epoxy matrix however, over 3 wt% of the silicate was in an intercalated state. When 1 wt% layered silicates were incorporated, an electrical tree was initiated in 439 min and propagated at a speed of 2.3 ${\mu}m$/min after applying 781.4 kV/mm, representing a decreased in starting initiation time by a factor of 11.0 and increase in propagation speed by a factor 8.2 in comparison with neat epoxy resin. These values were in great decline after the layered silicate content was increased to 3wt% which implies that the exfoliated silicate blocked the tree initiation and propagation processes effectively. However the effect was largely decreased in the intercalated state.

• 한국응용과학기술학회지
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• 제20권3호
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• pp.243-250
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• 2003

Poly(methyl methacrylate)/clay nanocomposite particles with particle size of 275${\sim}$292 nm range were successfully prepared using emulsion polymerization. The content of montmorillonite based on the methyl methacrylate monomer was chosen as 30 wt.%. 2,2-azobis(isobuthylamidine hydrochloride) and n-dodecyltrimethylammonium chloride were used as an initiator and a surfactant in cationic emulsion system. Potassium persulfate and sodium lauryl sulfate were used as an initiator and a surfactant in anionic emulsion system. The evidence of intercalated /exfoliated structure of montmorillonite in the nanocomposite prepared in our experiment was confirmed by wide angle x-ray diffraction patterns of $d_{001}$ plane. Thermal behavior of nanocomposite was traced using DSC and TGA. It was found that the nanocomposite particle prepared by cationic emulsion system showed intercalated structured. We also found that the nanocomposite particle obtained from anionic emulsion system resulted in the fully exfoliated structure.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.11-15
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• 2003

In order to suppress a repulsive interfacial energy between hydrophilic clay and hydrophobic polymer matrix in preparing a polymer/clay nanocomposite, a third component of amphiphilic nature such as poly($\varepsilon$-caprolactone) (PCL) was introduced into the model system of styrene-acrylonitrile copolymers (SAN)/Na-montmorillonite. Once $\varepsilon$-caprolactone was polymerized in the presence of Na-rnontmorillonite, the successful ring-opening polymerization of $\varepsilon$-caprolactone and the well-developed exfoliated structure of PCL/Na-montmorillonite mixture were confirmed, Thereafter, SAN was melt-mixed with PCL/Na-montmorillonite nanocomposite, which resulted in that SAN matrix and PCL fraction were completely miscible to form homogeneous mixture with retention of the exfoliated state of Na-montmorillonite, exhibiting that PCL effectively stabilizes the repulsive polymer/clay interface and contributes the improvement of mechanical properties of the nanocomposites.

• Fibers and Polymers
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• 제6권4호
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• pp.289-296
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• 2005

Biodegradable nanocomposites were prepared by mixing a polymer resin and layered silicates by the melt intercalation method. Internal structure of the nanocomposite was characterized by using the small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). Nanocomposites having exfoliated and intercalated structures were obtained by employing two different organically modified nanoclays. Rheological properties in shear and extensional flows and biodegradability of nanocomposites were measured. In shear flow, shear thinning behavior and increased storage modulus were observed as the clay loading increased. In extensional flow, strain hardening behavior was observed in well dispersed system. Nanocomposites with the exfoliated structure had better biodegradability than nanocomposites with the intercalated structure or pure polymer.

• Macromolecular Research
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• 제15권2호
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• pp.178-184
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• 2007

A poly(ethylene terephthalate) (PET)/organosilicate nanocomposite, with enhanced mechanical properties, has been prepared using the melt intercalation method. For this purpose, a new organic modifier has been synthesized for the preparation of organosilicate, which is thermally stable and compatible with PET. The use of the new organosilicate yielded almost exfoliated PET nanocomposite; whereas, the PET nanocomposites prepared by use of commercial organoclays (Cloisite 15A and 30B) show only an intercalated morphology. Particularly, the use of the new organosilicate showed an enhanced tensile modulus, and without sacrifice of the tensile strength and elongation on breaking, while the use of commercial organoclays only exhibit a trade-off between those mechanical properties.

• 한국결정성장학회지
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• 제22권2호
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• pp.84-91
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• 2012

Single and few-layer graphene nanosheets (GNs) have successfully synthesized by a modified Hummer's method followed by chemical reduction of exfoliated graphene oxide (GO) in the presence of hydrazine monohydrate. GO and GNs were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Atomic force microscopy (AFM), Optical microscopy (OM) and by electrical conductivity measurements. The result showed that electrical conductivity of GNs was significantly improved, from $4.2{\times}10^{-4}$ S/m for GO to 12 S/m for GNs, possibly due to the removal of oxygen-containing functional group during chemical reduction. In addition, the $NO_2$ gas sensing characteristics of GNs are also discussed.

• 한국표면공학회지
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• 제55권2호
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• pp.84-90
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• 2022

With the growing interest in energy storage and conversion systems including secondary batteries, capacitors, and water electrolysis, various electrode materials are being developed to improve the energy efficiency. Among them, graphene is regarded as one of the promising candidates owing to its exceptional properties - large surface area, and excellent electrical conductivity. Herein, we report a facile one-step electrochemical approach to synthesize exfoliated graphene/Fe oxide compound. The effect of experimental conditions - the types of applied voltage, kinds of counter electrodes, acidity of electrolyte on the synthesis of graphene/Fe oxide compound is investigated.

• Composites Research
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• 제26권4호
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• pp.254-258
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• 2013

본 연구에서는 폴리프로필렌과 다양한 탄소나노소재를 사용하여 제조한 복합재의 압출방향 및 권취속도에 따른 기계적 물성과 결정화도에 대한 연구를 수행하였다. 폴리프로필렌에 탄소나노소재를 균일하게 분산시키기 위해 미분쇄기에 폴리프로필렌 분말(<700 ${\mu}m$)과 탄소나노소재를 혼합한 후 나노복합재 필름 제조를 위해 압출기를 사용하였다. 나노복합재 필름의 결정화도를 분석하기 위해 differential scanning calorimetry를 이용하였다. 기계적 물성을 인장시험을 통해서 측정한 후 순수 폴리프로필렌 물성과 비교하였고, 압출 시 필름 권취속도에 대한 나노복합재 결정화도의 차이를 확인하였다. 탄소나노소재를 첨가함으로써 고분자 필름의 기계적 물성이 향상됨을 확인하였고, 그에 따른 결정화도 역시 증가하는 것을 확인하였다. 반면, 권취속도가 증가 할수록 압출물의 냉각속도도 역시 증가함으로써 결정화도가 오히려 감소함을 확인하였다.