• Composites Research
• /
• 제31권3호
• /
• pp.94-98
• /
• 2018

Well-defined, monodispersed hollow ZnO nanoparticles were successfully synthesized by a facile one-pot solution method at room temperature. Hollow ZnO nanoparticles were fabricated using polystyrene nanoparticles as seed particles. The removal of core particles via solvent extraction yields hollow nanoparticles. The structures and morphologies of the obtained products were characterized with Fourier transform infrared (FT-IR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction pattern (XRD) and Scanning electron microscopy (SEM). The formation mechanism of the hollow structure of the ZnO nanoparticles was also investigated. The technique developed here is expected to be useful in the preparation other metal oxides and hollow architectures.

• 대한금속재료학회지
• /
• 제49권12호
• /
• pp.950-955
• /
• 2011

In the present study, the formation of hollow Cu oxide nanoparticles through the oxidation process at temperatures from 200 to $300^{\circ}C$ has been studied by transmission electron microscopy with Cu nanoparticles produced by the plasma arc discharge method. The Cu nanoparticles had a thin oxide layer on the surface at room temperature and the thickness of this oxide layer increased during oxidation in atmosphere at $200-300^{\circ}C$ However, the oxide layer consisted of $Cu_2O$ and CuO after oxidation at $200^{\circ}C$ whereas this layer was comprised of only CuO after oxidation at $300^{\circ}C$ On the other hand, hollow Cu oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process.

• 전기화학회지
• /
• 제11권3호
• /
• pp.154-158
• /
• 2008

The synthesis of hollow ${Sb_93}{Pt_7}$ nanospheres smaller than 30 nm with a shell consisting of smaller nanoparticles, with an average particle size of ${\sim}$ 3 nm is reported. The formation of this alloy is driven by galvanic replacement reaction involving Sb nanoparticles and ${H_2}{PtCl_6} $ without need for any additional reductants. Further, the reaction proceeds selectively as long as the redox potential between two metals is favorable. The capacities of the hollow samples are 669 and 587mAh/g at rates of 1 and 7C, respectively, while those values for the nanoparticles are 647 and 480mAh/g at rates of 1, 7C, respectively. This result shows the significantly improved capacity retention of the hollow sample at higher C rates, indicating that high surface area of the hollow nanospheres makes the current density more effective than that for the solid counterpart.

• Bulletin of the Korean Chemical Society
• /
• 제30권5호
• /
• pp.1135-1138
• /
• 2009

Hollow Sn and Pb nanoparticles have been prepared by a rapid injection of an aqueous solution of $SnCl_2$- poly(vinylpyrrolidone) (PVP, surfactant) and $Pb(OAc)_2${\cdot}$3H_2O-PVP$ into an aqueous solution of sodium borohydride (reducing agent) in simple, one-pot reaction at room temperature under an argon atmosphere, respectively. The two hollow nanoparticles have been fully characterized by TEM, HRTEM, SAED, XRD, and EDX analyses. Upon exposure to air, the black Pb hollow nanoparticles are gradually transformed into a mixture of Pb, litharge (tetragonal PbO), massicot (orthorhombic PbO), and $Pb_5O_8$. The order and speed of mixing of the reactants between the metal precursor-PVP and the reductant solutions and stoichiometry of all the reactants are crucial factors for the formation of the two hollow nanocrystals. The Sn and Pb hollow nanoparticles were produced only when 1:(1.5-2) and 1:3 ratios of the Sn and Pb precursors to $NaBH_4$ were employed with a rapid injection, respectively.

• Bulletin of the Korean Chemical Society
• /
• 제34권6호
• /
• pp.1853-1856
• /
• 2013

$TiO_2$ hollow nanoparticles (HNPs) and their light scattering effect which influences on the photoelectric conversion efficiency of a dye-sensitized solar cell (DSSC) were investigated. When only HNPs were employed in DSSC as the anode layer material, the conversion efficiency (e.g., 0.96%) was the lowest, possibly due to scattering loss of incident light. However, DSSC fabricated by using HNPs as a scattering overlayer on the $TiO_2$ nanoparticles (P-25), showed higher conversion efficiency (4.02%) than that without using HNPs (3.36%).

• 청정기술
• /
• 제28권1호
• /
• pp.18-23
• /
• 2022

에너지 절약을 위한 연구 중 단열 기술 분야에서는 공기의 낮은 열전도도를 활용한 연구가 이뤄지고 있으며 널리 상용화 되고 있다. 본 연구에서는 입자 내부에 공기층을 갖는 중공형(hollow) 형태의 실리카 나노 입자를 제조하여 공기층 크기가 단열 성능에 미치는 영향에 대해 고찰하였다. Polystyrene 주형법을 이용하여 졸-겔공정을 통해 속이 빈 중공형 실리카 나노 입자(Hollow silica nanoparticles)를 제조하였고, 입자를 5 wt %로 도료에 첨가한 후 열전달 실험을 통해 단열 성능을 확인하였다. 기존 페인트에 입자를 혼합하여 약 15 %이상의 단열효율을 나타냈으며, 내부 공기층의 크기가 큰 입자가 작은 입자에 비해 5% 높은 단열 성능을 나타냈다. 이번 연구를 통해 내부 크기에 따른 단열효과의 차이를 보여줌으로써, 중공형 형태의 입자를 첨가제나 도료 제조에 사용하는 경우 단열효과를 높이기 위해 매질 내에서 입자가 공기층을 최대로 이룰 수 있도록 입자의 크기를 고려해야함을 제시한다.

• Bulletin of the Korean Chemical Society
• /
• 제33권3호
• /
• pp.906-910
• /
• 2012

Hollow gold-silver bimetallic nanoparticles (AuAg-HNPs) have been synthesized and their optical and structural properties were characterized. Initially Ag nanoparticles (Ag-NPs) were prepared using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. AuAg-HNPs could then be synthesized via galvanic replacement reaction in a PEI aqueous solution by reacting sacrificial Ag template with a precursor compound of Au, i.e., $HAuCl_4$. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of $Ag^+$ in the presence of Cl from $HAuCl_4$ salt was avoided. On this basis, the relatively high concentrations of $HAuCl_4$ and PEI-stabilized Ag nanoparticles could be used for the fabrication of AuAg-HNPs. Because of their increased surface areas and reduced densities, the AuAg-HNPs were expected and confirmed to outperform their solid counterparts in applications such as catalysis for the reduction of 4-nitrophenol in the presence of $NaBH_4$.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1158-1161
• /
• 2004

Shell shaped hollow carbon nanoparticles are synthesized in the oxygen-hydrogen diffusion flame with $C_{2}H_{2}$ as precursor when it is irradiated with $CO_{2}$ laser of certain power. Below this power of laser, we couldn't get any other but amorphous soot. This shell shaped hollow carbon nanoparticles shows outer wall of high degree of crystallinity with void space inside of itself. And size distribution of these nanoparticles is measured with TEM image analysis. Also the structural comparison between this carbon nanoparticle and soot is done by Raman and XRD measurement. These results show this carbon nanoparticles are of grapheme structure, which means it has good crystallinity when compared with soot.

• 한국수소및신에너지학회논문집
• /
• 제24권6호
• /
• pp.550-557
• /
• 2013

A glucose hydrothermal method is described for preparing hollow carbon spheres (HCS), which have a regular morphology and a high Brunauer-Emmett-Teller surface area of 28.6 m2/g. Scanning electron microscopy shows that they have thin shells and diameter between 2 and 8 ${\mu}m$. The HCSs were modified for the enhanced room temperature hydrogen storage by employing Ni nanoparticles on their surface. The Ni-decorated HCSs were characterized by X-ray diffraction, transmission electron microscopy coupled with an energy dispersive spectroscope, and an inductively coupled plasma spectrometer, indicating that fine and well-distributed Ni nanoparticles can be accomplished on the HCSs. The hydrogen uptake capacity in HCSs with and without Ni loading was evaluated using a high-pressure microbalance at room temperature under a hydrogen pressure upto 9 MPa. As much as 1.23wt.% of hydrogen can be stored when uniformly distributed Ni nanoparticles are formed on the HCSs, while the hydrogen uptake capacity of as-received HCSs was 0.41 wt.%. For Ni nanoparticle-loaded HCSs, hydrogen molecules could be easily dissociated into atomic hydrogen and then chemically adsorbed by the sorbents, leading to an enhanced capacity for storing hydrogen.

• 폴리머
• /
• 제35권5호
• /
• pp.390-394
• /
• 2011

현탁중합에 의한 폴리(비닐 아세테이트)((poly(vinyl acetate)(PVAc))/은 미세입자 제조시 사용된 은 나노입자가 중합속도 및 PVAc 미세입자의 형태에 미치는 영향을 고찰하였다. 주사전자현미경, 투과전자현미경, X선 회절, 원자흡수분광분석법을 이용하여 제조된 미세입자의 형태와 특성을 분석한 결과, 사용된 은 나노입자 표면의 친수성 정도와 계면활성제의 농도에 따라 미세입자의 표면이 골프공 표면처럼 오목해지거나 다양한 형태의 중공 구조를 가지는 PVAc/은 미세입자가 제조됨이 관찰되었다. 계면활성제로 개질된 은 나노입자를 이용하여 중합한 경우에 중합속도가 약간 증가하였으며, 80% 이상의 전환율을 가지는 PVAc/은 미세입자를 제조할 수 있었다.