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EMI shielding properties of nanoparticle/CNF composites
강근원,허훈,표성규,김희진,소대섭 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
On the basis of EMI(electromagnetic interference) shielding mechanism, the effective materials for EMI should absorb electromagnetic waves as well as reflect them. Absorbing materials require electric or magnetic dipoles intrinsically. Otherwise reflecting materials have to possess their own electrical conductivity and need larger surface area based on skin effect. Furthermore, EMI shielding materials need to be light-weight and flexible nowadays. In this work we added BaTiO<sub>3</sub>, Fe<sub>3</sub>O<sub>4</sub> nanoparticles having both electric and magnetic dipoles according to weight fraction into the carbon nanofiber as the light-weight and flexible EMI materials that are able to effectively block electromagnetic waves. We measured electrical conductivity by using 4-point probe. The structure was investigated by XRD. The morphology of the nanofiber web was confirmed by SEM and TEM. EMI shielding capability of the carbon nanofiber web was measured by network analyzer.
EMI Shielding Properties of electrospun carbon fiber web
강근원,김희진,표성규,허훈 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Recently, a lot of research on EMI shielding materials has been being done in fields of electronic industries. For effective electromagnetic shielding, materials are required to have both large surface area and absorbing or reflecting capability of electro magnetic waves. In case of electromagnetic waves absorbing materials, they have to have both electric dipoles and magnetic dipoles simultaneously. Generally, the electric dipoles and the magnetic dipoles are related to a dielectric constant and a magnetic permeability, respectively. In this research, BaTiO3 with a high dielectric constant and Fe3O4 with high magnetic permeability were used to fabricate the high surface area carbon nanofiber in order to enhance the EMI shielding properties. Carbon nanowebs were prepared from PAN precursor/filler solutions by electrospinning and following carbonization process. We investigated EMI shielding properties of prepared carbon nanoweb. We measured electrical conductivity by using 4-point probe. Morphology of nanoweb was confirmed by SEM and TEM. Structure was investigated by using XRD and XPS.
김희진,황태연,강근원,Jeanine Pichler-Nagl,소대섭,박성진,허훈 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.50 No.-
Carbon materials such as graphite have been widely used as the anode materials of secondary batteries. Inspite of good stability, they are limited by low capacity. Silicon has a 4 times higher capacity than anyother carbon material. But it cannot be used, because it has a low stability caused by the volume expansion. In this study, we fabricated a silicon nanoball encapsulated with graphene (Si-GB) to overcome thementioned problems. In order to form a core/shell structured graphene encapsulated silicon nanoball,nickel was coated on the surface of a silicon nanoball by electroless plating method. Then, a graphene layerwas synthesized on the surface of the nickel shell by a CVD process. We were able to make a Si-GB byetching the nickel layer. The Si-GBs were formed with a spherical void between the silicon particle and thegraphene layer, by which it has a better safety against to volumetric change of anode during lithiation/delitiation of repeated charging–discharging in secondary batteries. Morphology of the grapheneencapsulated silicon nanoball was observed by thefield emission scanning electron microscope (FESEM)and thefield emission transmission electron microscope (FETEM) tofind core–shell structured nanoball. Spherical structure of graphene encapsulated silicon nanoball was investigated by the Raman, the X-rayPhotoelectron Spectroscopy to identify graphene layer on the surface of the inner silicon core. The charge–discharge performance of the Li-ion battery using Si-GB was investigated by the battery cycler system.
김희진,황태연,강근원,허훈 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
In this study, we prepared a silicon nanoball encapsulated with graphene shell(Si-GB) for the anode material to get a lithium ion battery with high stability and capacity. For preparing Si-GB, electroless plating and CVD method were used. The Si-GB has a gap between the inner silicon core and the graphene shell, so that there is enough room for the volume change of silicon during charge and discharge. The morphology of Si-GB was observed by field emission scanning electron microscope (FESEM) and field emission transmission electron microscope (FETEM). Si-GB was investigated by Raman and X-ray Photoelectron Spectroscopy to identify graphene layer on the surface of the inner silicon core. The electrochemical performance of the Li-ion battery using Si-GB was investigated by battery cycler system and galvanostat system.
Charge/Discharge performance of Carbonaceous Anode Material from Waste Tire
김희진,황태연,강근원,허훈 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
This study is intended to recycle the carbonaceous materials from waste tire and estimate its high added value for anode material of lithium ion battery. We gained carbons by heat-treatment of waste tire in argon atmosphere at 500°C~1500°C. The morphology of the obtained carbon was observed by field emission scanning electron microscope (FESEM) and field emission transmission electron microscope (FETEM). The chemical structure of the carbon was investigated by Raman, X-ray Photoelectron Spectroscopy. The electrochemical performance of the Li-ion battery using the obtained carbon was investigated by battery cycler system and galvanostat system.