Eun Gyeong Han

Bio: Eun Gyeong Han is an academic researcher from Yonsei University. The author has contributed to research in topics: Copper plating & Copper. The author has an hindex of 2, co-authored 2 publications receiving 178 citations.

Effects of catalyst accelerator on electromagnetic shielding in nonelectrolytic Cu-plated fabrics

Abstract: The effects of etching and catalyst accelerating conditions on microstructures of copper films and electromagnetic interference (EMI) shielding effectiveness (SE) of nonelectrolytic copper-plated fabrics were investigated. Copper films were coated onto polyester fabrics by a conventional nonelectrolytic copper plating process. Comparison of two etchants had the result where uniform deposition of Cu particles in the smaller size was observed using acidic etchant, which provided the better EMI SE than alkaline etchant. We found that KCl was the better catalyst accelerator than commonly used SnCl2. EMI SEs and conductivities of copper-plated fabrics increased as the concentration of KCl increased up to 0.1 mole/l and then decreased with further addition.

Ordered Mesoporous Carbon/Fused Silica Composites

Abstract: A series of novel, dense, and interesting ordered mesoporous carbon (OMC)/fused silica composites with different carbon contents has been prepared by a controllable but simple sol-gel method followed by hot-pressing. In the as-sintered OMC/fused silica composites the carbon particles still exist in the form of perfectly ordered carbon nanowires. Conductivity measurements on the composites indicate that these novel composites are electrically conductive and have a typical percolation threshold of 3.5-5 vol% OMC. The electromagnetic interference (EMI) shielding efficiency (SE) of an OMC/fused silica composite containing 10 vol% OMC is as high as 40 dB in the X band which is higher than that of a carbon nanotube (CNT)/ fused silica composite with the same carbon content (∼30 dB). This indicates that these conductive OMC/fused silica composites are very suitable for an application as EMI shielding materials. Upon increasing the volume content of OMC in the composite the overall contribution as well as the increase rate of the microwave absorption are larger than those of the microwave reflection, which suggest that OMC/ fused silica composites may also be promising electromagnetic (EM) wave absorbing materials. Based on the promising properties of these composites this work will hopefully lead to the development of new low-cost and highly efficient EMI shielding or EM wave absorbing materials.

Towards cost-efficient EMI shielding materials using carbon nanostructure-based nanocomposites

Abstract: Using a combination of dispersing low-cost carbon nanofibers and a small quantity of carbon nanotubes within the polystyrene matrix, we have demonstrated the formation of a novel nanocomposite with superior microstructure and improved electromagnetic interference (EMI) shielding characteristic. This nanocomposite is very promising for use as an effective and practical EMI shielding material owing to its high shielding effectiveness, light weight, low cost, and easy processability.

Synthesis and microwave absorption of uniform hematite nanoparticles and their core-shell mesoporous silica nanocomposites

Abstract: Single-crystal α-iron oxide (denoted as FO) particles with uniform sub-micrometer size and polyhedron-like shape have been successfully fabricated by using polyvinylpyrrolidone (PVP) capping agent-mediated hydrolysis of iron nitrate under mild hydrothermal conditions (200 °C). The hematite products were characterized via combined techniques including scanning electronic microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The single-crystal hematite particles have relatively uniform sizes of 180–360 nm and octahedron-shaped structures with comparatively smooth surfaces. Furthermore, the as-made hematite particles can be used as cores to prepare core-shell mesoporous silica composites. The intermediate nonporous silica layer was coated first via a sol-gel process, and then the mesoporous silica structure was coated as the outer shell layer by a surfactant-assembly method, resulting in uniform core-shell mesoporous silica FO@nSiO2@mSiO2 composites. TEM images show that the FO@nSiO2@mSiO2 composites possess distinct two-layer coating core-shell structures with ordered hexagonal mesostructure in the outer silica shell layer. N2 sorption measurements show that the uniform accessible mesochannel size for the FO@nSiO2@mSiO2 nanocomposites is ∼2.10 nm, the surface area is as high as ∼445 m2/g, and the pore volume is as large as ∼0.29 cm3/g. Furthermore, the reflection loss (dB) spectra measured in the frequency range 2–18 GHz showed that the FO@nSiO2@ mSiO2 composites have improved electromagnetic interference (EMI) shielding effectiveness (SE) compared to that of pure hematite materials. This is mainly attributed to the better impedance match and multiple-interfacial polarization among the FO@nSiO2@mSiO2 nanocomposites.