• 접착 및 계면
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• 제14권1호
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• pp.1-12
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• 2013

Core 입자로 methyl methacrylate (MMA), ethyl methacrylate (EMA)를 사용하고 shell 입자로 MMA, EMA, 2-hydroxyl ethyl methacrylate (2-HEMA), glycidyl methacrylate (GMA) 및 methacrylic acid (MAA)를 각각 사용하여 개시제 ammonium persulfate (APS), 유화제로 sodium dodecyl benzene sulfonate (SDBS)의 농도(0.01~0.03 wt%), 단량체의 종류와 조성을 변화시켜 수용성 유화중합으로 다중 core-shell복합입자를 제조하여 전환율, 입자경 및 입도분포, 평균분자량, 분자구조, 유리전이온도, 플라즈마 처리후의 접촉각, 등온열분해속도 및 인장강도를 각각 측정하여 다음과 같은 결론을 얻었다. SDBS 농도 0.02 wt%에서 MMA core-(EMA/GMA) shell 복합입자의 전환율이 98.5%로 우수하였고, 입자직경은 SDBS 농도 0.03 wt%에서 EMA core-(MMA/GMA) shell의 복합입자가 $0.48{\mu}m$로 높게 나왔다. 유리전이온도 측정으로부터 공중합체는 1~2개의 전이곡선 그리고 다중 core-shell 복합입자는 3개의 전이곡선을 얻었다. 전체적으로 접착박리강도의 크기는 shell 단량체가 MMA core인 경우 EMA/MAA > EMA/2-HEMA > EMA/GMA의 순으로 되었다.

• 센서학회지
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• 제27권2호
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• pp.76-81
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• 2018

Au@ZnO core-shell nanoparticles (NPs) were prepared by a simple method followed by heat-treatment for gas sensor applications. The advantage of the core-shell morphology was investigated by comparing the gas sensing performances of Au@ZnO core-shell NPs with pure ZnO NPs and different wt% of Au-loaded ZnO NPs. The crystal structures, shapes, sizes, and morphologies of all sensing materials were characterized by XRD, TEM, and HAADF-STEM. Au@ZnO core-shell NPs were nearly spherical in shape and Au NPs were encapsulated in the center with a 40-45 nm ZnO shell outside. The gas sensing operating temperature for Au@ZnO core-shell NPs was $300^{\circ}C$, whereas it was $350^{\circ}C$ for pure ZnO NPs and Au-loaded ZnO NPs. The maximum response of Au@ZnO core-shell NPs to 1000 ppm CO at $300^{\circ}C$ was 77.3, which was three-fold higher than that of 2 wt% Au-loaded ZnO NPs. Electronic and chemical effects were the primary reasons for the improved sensitivity of Au@ZnO core-shell NPs. It was confirmed that Au@ZnO core-shell NPs had better sensitivity and stability than Au-loaded ZnO NPs.

• 한국가구학회지
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• 제24권4호
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• pp.379-388
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• 2013

In this study, the effect of various glass fiber (GF) contents in a shell layer and shell thickness changes on the flexural property of coextruded wood plastic composites (WPCs) in combination with three core systems (weak, moderate, and strong) was investigated. GF behaved as an effective reinforcement for the whole coextruded WPCs and GF alignments in the shell layer played an important role in determining the flexural property of the coextruded WPCs. At a given shell thickness, the flexural property of the whole coextruded WPCs was improved with the increase of GF content in shell. For core quality, when the core is weak, increase of GF content in shell led to improved flexural property of the whole composites and increase of shell thickness helped it. On the other hand, when the core is strong, the flexural property of the whole composites showed reduced features at low GF content in shell and increase of shell thickness aggravated it. This approach provides a method for optimizing performance of the coextruded WPCs with various combinations of core-shell structure and properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.47-47
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• 2009

The formation of variable one-dimensional structures including core/shell structure is of particular significance with respect to potential applications for thermoelectric devices with the enhanced figure of merit ($ZT=S2{\sigma}T/{\kappa}$). We report the fabrication of Bi-Te core/shell nanowire based on a novel stress induced method. Fig. 1 schematically shows the nanowire fabrication process. Bi nanowires are grown on the Si substrate by the stress-induced method, and then Te is evaporated on the Bi nanowires. Fig. 2 is a transmission electron microscopy image clearly showing a core/shell structure for which effective phonon scattering and quantum confinement effect are expected. Electrical conductivity of the core/shell nanowire was measured at the temperatures from 4K to 300K, respectively. Our results demonstrate that Bi-Te core/shell nanowire can be grown successfully by the stress-induced method. Based on the result of electrical transport measurement and characteristic morphology of rough surface, Seebeck coefficient and thermal conductivity of Bi-Te core/shell nanowires are presented.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.366-366
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• 2011

이성분 산화물인 ZnO/$TiO_2$ core-shell 나노입자는 core-shell 구조의 특성과 이성분 산화물의 상호작용에 의해서 염료감응형 태양전지의 효율향상을 기대할 수 있다. Znic acetate($Zn_2(CH_3COO)$)와 Titanium(IV) butoxide($Ti(OBu)_4$)를 이용하여 ZnO 나노입자를 수열합성하고 그 주의에 $TiO_2$을 가수분해 반응을 이용하여 둘러싸는 core-shell형태의 물질을 합성하였다. 그 이후 결정성 및 유기물 제거를 위해서 4시간 동안 고온에서 소성하였다. SEM 결과에 따르면 소성 온도를 600도까지 증가시키면 ZnO의 경우 나노입자의 크기가 증가하는 경향을 확인하였다. 하지만 core-shell의 경우는 ZnO의 뭉침현상을 $TiO_2$이 방해하여 초기합성된 크기와 동일한 크기를 유지하는 것을 확인하였다. 또한 XRD 결과에 따르면 주변에 형성된 $TiO_2$ 이외에 $Zn_2TiO_4$의 spinel 구조를 가지는 물질이 합성되는 것을 확인할 수 있었다. 합성된 core-shell 구조의 나노입자는 약 40~50 nm의 크기를 가지고 600도에서 소성된 입자의 경우 산소 정공이 거의 없는 약 3 eV의 밴드갭을 가지는 물질로 합성이 되었다. Core-shell 나노입자의 경우 염료 감응형 태양전지의 반도체 물질로 응용 가능할 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.872-879
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• 2002

One of the improtant characteristics of core-shell type nanoparticles is the long-term storage and reuse as an aqueous injection solution when required. For this reason, reconstruction of lyophilized core-shell type nanoparticles is considered to be essential . BAB type triblock copolymers differ from AB type diblock copolymers, which contain the A block as a hydrophilic part and the B block as a hydrophobic part. by not being easily redistributed into phosphate-buffered saline (PBS, pH 7.4, 0.1 M). Therefore, lyophilized core-shell type nanoparticles of CEC triblock copolymer were reconstituted using a somication process with a bar-type sonicator in combination with a freezing-thawing process. Soncation for 30s only resuspended CEC nanoparticles in PBS; their particle size distribution showed a monomodal pattern with narrow size distribution. The bimodal size distribution pattern and the aggregates were reduced by further sonication for 120 s but these nanoparticles showed a wide size distribution. The initial burst of drug release was increased by reconstitution process. The reconstitution of CEC core-shell type nanoparticles by freezing-thawing resulted in trimodal distribution pattern and formed aggregates, although freezing-thawing process was easier than sonication . Drug release form CEC nanoparticles prepared by freezing-thawing was slower than from the original dialysis solution. Although core-shell typenanoparticles of CEC triblock copolymers were not easily performed. Cytotoxicity testing of core-shell type nanoparticles of CEC-2 triblock copolymers containing clonazepam (CNZ) was performed using L929 cells. Cytotoxicity of CNZ was decreased by incorporation into nanoparticles.

• 한국주조공학회지
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• 제18권5호
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• pp.481-487
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• 1998

Shell sand is widely used to make a complex shape castings due to its good collapsibility. When molten metal is poured into the mold, various gases are generated by the thermal decomposition of binder in the shell core. Casting defects such as blow hole and blister come from these gases. If it is possible to predict the evolution of gas quantitatively, it may provide effective solutions for minimizing the casting defects. To examine the gas evolution by shell core quantitatively, casting experiment and calculation were carried out. Gas pressure and gas volume evolved by shell core were measured in the experiment, and temperature distribution in the shell core was obtained by heat transfer analysis. From the result above, prediction on the gas volume evolved during pouring was tried. As forming pressure of the shell core increased and forming temperature decreased, the gas evolution increased. There was a close relationship between the calculated gas volume evolved and the measured one.

• 한국응용과학기술학회지
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• 제26권1호
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• pp.74-79
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• 2009

The inorganic-organic composite particles with core-shell structure were polymerized by using styrene and potassium persulfate (KPS) as a shell monomer and an initiator, respectively. We studied the effect of surfactants on the core-shell structure of silicone dioxide/styrene composite particles polymerized in the presence of sodium dodecyl sulfate(SDS), polyoxyethylene alkylether sulfate (EU-S133D), and at none surfactant condition. We found that $SiO_2$ core / polystyrene(PS) shell structure was formed when polymerization of styrene was conducted on the surface of $SiO_2$ particles, and the concentration SDS and EU-Sl33D was $8.34{\times}10^{-2}mole/L$. The core-shell structure was confirmed by measuring the thermal decomposition of the polymer composite using thermogravimetric analyzer (TGA), and the morphology of the composite particles was characterized by transmission electron microscope (TEM).

• 센서학회지
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• 제21권6호
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• pp.456-460
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• 2012

Au/$SnO_2$ core-shell structure nanoparticles (NPs) were synthesized by microwave hydrothermal method, and the effect of working temperature on sensitivity of Au/$SnO_2$ core-shell NPs for CO gas was investigated. The $SnO_2$ shell layer was consisted of $SnO_2$ primary particles with 4.5 nm diameter. The response of Au/$SnO_2$ core-shell NPs for CO gas was maximized at the working temperature of $350^{\circ}C$ while the sensitivity increased with decreasing the working temperature due to the low grain size effect of $SnO_2$ NPs on the response of CO gas.

• 한국세라믹학회지
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• 제40권9호
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• pp.902-908
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• 2003

Au/TiO$_2$ core-shell 구조 나노 미립자가 졸-겔법에 의해서 제조되었고, TiO$_2$ shell의 형상과 결정성이 TEM과 UV-Vis. absorption spectrometer에 의해서 조사되었다. Au/TiO$_2$ core-shell 나노 미립자는 Au 콜로이드 에탄올 수용액 중에서 TOAA(Titanium Oxide Acethylacetonate)의 가수분해에 의해 합성될 수 있었다. Au 나노 미립자의 표면에 형성된 TiO$_2$ shell의 두께는 약 1 nm이었다. TiO$_2$ shell의 결정성을 조사하기 위하여. TiO$_2$가 피복된 Au 콜로이드 에탄올 용액에 254 nm의 자외선과 $^{60}$Co의 방사선을 조사하였다. Au 나노 미립자의 surface plasmon 현상은 방사선이 조사되었을 때만 나타났고, 이 결과로부터 TiO$_2$ shell은 비정질 상태임을 알 수 있었으며, Au의 분산성 향상을 위해 표면에 처리된 MUA(Mercaptoundecanoic Acid)층은 전자의 이동을 방해하는 장애물로 작용하지 않음을 확인할 수 있었다.