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이온주입에 의한 PET(polyethylene teraphthalate)의 표면결합상태 변화와 표면전기전도도 특성
이재형,길재근 대한전기학회 2004 전기학회논문지C Vol.53 No.7(C)
A study has been made of surface modification of organic materials by ion implantation to increase the surface electrical properties. The substrate used were PET(polyethylene teraphthalate). N+, Ar+ implantation was performed at energies of 40 keV and 50 keV with fluences from 5×1015, 1×1016, 7×1016, 1×1017 ions/㎠. UV/Vis, FT-IR and XPS spectroscopy measured for surface structure changes. Surface resistance decrease of implanted polymers was affected by ion implantation energy, ion species and ion dose rate. Surface conductivity of PET increased 2×109 ~2×1010Ω/sq by ion implantation. Result of various spectroscopy analysis, the cause of increasing PET surface conductivity was expected to breaking C=O bonds. It was formation carbon network structure by promote cross-linking and create C-C, C=C bonds.
Fabrication and Surface Deformation of Boron Nitride Nanotubes by RF Plasma and Ion Beam
홍성민,길재근 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.4
Boron Nitride Nanotubes (BNNT) are one of the candidate materials for storing hydrogen by physical adsorption. It has been reported that this hydrogen storage capacity increases as the crystallinity of the nanostructures decreases. Here, BNNT was synthesized using an RF plasma torch system, and the surface of the BNNT was irradiated with nitrogen ions using an ion beam device, and changes in the surface microstructure were subsequently investigated. A multi-walled BNNT with a wall thickness of about 5 nm was synthesized using a 60 kW RF plasma torch. Amorphous impurities generated during the synthesis process were removed by heat treatment and membrane filtering. Then nitrogen ions were irradiated for 40 minutes at energies of 40 keV and 50 keV, respectively, using an ion beam irradiation device. The changes in the microstructure of the BNNT surface following ion beam irradiation were confirmed by HR-TEM, Raman spectrometer and FT-IR spectrometer. The tube walls of the BNNT were disordered by the nitrogen ions irradiation. At 50 keV, the tube walls located in the middle became disordered, which was attributed to an increase in penetration depth due to the higher irradiation energy. The maximum peak in the Raman spectra and FT-IR spectra of the ion irradiated BNNT were also shifted to a lower frequency. Ion irradiation reduced the crystallinity of the nanostructures. The potential improvement in hydrogen storage capacity by nitrogen ion irradiation of BNNT was confirmed.
Radio-activation Effect on a Polymer by Proton Beam Irradiation
라세진,정명환,길재근,김계령 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.22
In irradiation experiments using proton beams of more than a few MeV in energy, radio-activation of samples can essentially be caused by proton-induced nuclear reactions. Highly radioactive samples occasionally cause some problems or inconvenience concerning the sample handling and posttreatment because we have to wait for the samples to cool to the safe value for radiation protection. The activity mainly depends on the constituent atoms of the sample and the container if the proton energy is constant. If the radioactivity of samples is to be reduced, there are two alternatives, one is to change the sample’s constituents and the other is to change the sample case material. We were concerned about the general case material, a polymer, because the sample’s constituents are almost impossible in most experiments. Polymers, such as PP (polypropylene), PS (polystyrene), PET (polyethylene terephthalate), and PMMA (poly methyl methacrylate), are representative materials for sample cases. PET and PMMA are composed of C, H, and O, and PP and PS are composed of C and H. In this experiment, we used a proton beam with an energy of 45-MeV and a current of 10-nA. To verify the effect of oxygen on the radioactivity, we used a radiation survey meter and a HPGe spectroscopy system to measure the gamma equivalent dose rate and the gamma-ray spectroscopy.
이재형,이찬영,길재근 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.11
A study has been made of surface modification of various organic materials by ion implantation to increase the surface electrical properties. The substrate used were PP(polypropylene), PET(polyethylene teraphthalate), ECOP(ethylene copolyester), PS(polystyrene). N$_2$, Ar ion implantation was performed at energies of 40 and 50keV with fluences from 5${\times}$ 10$\^$15/ to 7${\times}$10$\^$16/ ions/$\textrm{cm}^2$ with and without H$_2$O gas environment. Surface resistance decrease of implanted polymers was affected by ion implantation energy, ion species, atmosphere of chamber and kind of polymer. In result, surface conductivity of polymers irradiated with atmosphere gas H$_2$O was 10 times more higher than normal vacuum atmosphere, but after 90 hours, surface conductivity returned to the without H$_2$O gas atmosphere condition caused by aging effect. After vacuum forming, surface resistance value was changed to over 10$\^$16/$\Omega$/$\square$, because creation of surface cracks.
Comparison of the Effects of Cell Death between Pulsed and Continuous-wave Proton Beams
정명환,라세진,길재근,최병호,김계령 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.22
Most proton therapy machines are cyclotrons that can produce continuous wave-type proton beams. The Proton Engineering Frontier Project (PEFP) has been developing a 100-MeV proton linear accelerator since 2002, and recently, we have been trying to design a compact synchrotron as a proton therapy machine. These two kinds of accelerators are pulsed machines that have a high peak current that can deliver higher doses for a few microseconds compared to the cyclotron. To utilize a 100-MeV proton linear accelerator for basic studies of proton therapy, we studied the effect of a pulsed proton beam on biological organisms and compared it to the case of a continuouswave beam. To measure the apoptosis, we used 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) and a colony formation assay for lung and prostate cancer cells. As a result, the lung and prostate cancer cell killing effects caused by pulsed and continuous-wave protons were similar for the same absorbed dose levels. In conclusion, the killing effect on the tumor cell of a proton beam is determined by the total absorbed dose, not by dose rate.