Investigation of the Effects of High-energy Proton-beam Irradiation on Metal-oxide Surfaces by Using Methane Adsorption Isotherms

Euikwoun Kim,이정길,김재용,김계령 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.2

The creation of possible local defects on metal-oxide surfaces due to irradiation with a high-energy proton beam was investigated by using a series of gas adsorption isotherms for methane (CH₄) on a MgO powder surface. After a MgO powder surface having only a (100) surface had been irradiated with a 35-MeV proton beam, the second atomic layer of methane had completely disappeared while two distinct atomic layers were found in a layer-by-layer fashion on the surfaces of unirradiated samples. This subtle modification of the surface is evidenced by a change of the contrasts in the morphologies measured a using a transmission electron microscopy. Combined results obtained from an electron microscopy and methane adsorption isotherms strongly suggest that the high-energy proton-beam irradiation induced a local surface modification by imparting kinetic energy to the sample. The calculation of the 2-dimensional compressibility values, which are responsible for the formation of the atomic layers, confirmed the surface modification after irradiating surface-clean MgO powders with a proton beam.

Adsorption and capillary condensation behavior of Ar and N₂ on Ti doped SBA-15

Euikwoun KIM,Jaeyong KIM 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Adsorption behaviors of nitrogen on Ti doped SBA-15.

Kim, Euikwoun,Kim, Jae Yong American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.9

<P>Thermodynamic properties of nitrogen on Ti doped santa barbara amorphous No. 15 samples having large pore sizes in an order of a few micrometers were studied by analyzing the adsorption isotherm data obtained near the triple point (63.15 K). A series of adsorption data as a function of the normalized pressure revealed that nitrogen forms two distinctive isotherm steps. The first step represents the adsorption behavior on surface while the second step is believed to be responsible for the interaction of gas molecules in a capillary, so called a 'capillary condensation.' The existence of a hysteresis measured between adsorption and desorption isotherms at 77.3 K evidenced that gas molecules fill the pores in the sample. Plots of 2-dimensional compressibility values that were calculated in terms of change of adsorbed molecules with respect to the change of measured pressure exhibit a prominent peak near the second isotherm step supporting that the pores are filled with adsorbed molecules. A careful examination of the second isotherm step revealed that the amount of adsorbed molecules increased at temperatures below the triple point while it decreased above the triple point, and such a phenomenon is responsible for the geometrical confinement of gas molecules in porous materials.</P>

Studies on formation of carborane film prepared by using a deuterium glow discharge method.

Shin, Hongsik,Kim, Euikwoun,Lee, Sang Yong,Lee, Sang-Hwa,Park, Sang-Joon,Chung, Kyu-Sun,Hong, Suk-Ho,Kim, Jaeyong American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.11

<P>Carborane powders (C2B10H12) were deposited on silicon substrates and the physical properties of the films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma-pulse. To obtain the optimum thickness of the films, three silicon substrates were positioned at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using XRD, TEM, and SEM. For the deposition, the carborane powder was warmed to 80 degrees C in 10 minutes and was applied a DC-power pulse of 900 W (150 volts, 6 amps) for 2 hours. The mass of carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 A was achieved from the samples placed closest to the carborane inlet and the thickness became thinner as farther from the source suggesting that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet.</P>

Proton Irradiation and Hydrogen Diusion in Quasicrystals

Jae-Kyun Jeon,Jeonggil Lee,Euikwoun Kim,Yun-Man Lee,Sang-Hwa Lee,신혜민,Soo-Bin Choi,Sang-Pil Youn,Kyeryung Kim,Jae-Yong Kim 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.5

Ti-Zr-Ni quasicrystals are new candidates for hydrogen storage applications due to their capabil- ity of loading a large amount of hydrogen at reasonable temperature and hydrogen pressure. The technical applications, however, have been limited because of the presence of a thick oxygen layer, which must be eliminated prior to introducing hydrogen into a sample. To effectively remove the oxygen barrier and to enhance the capability of hydrogen absorption, we irradiated Ti39.5Zr39.5Ni21 quasicrystal ingots by using a proton beam at energy of 20 MeV, 15 mA for 30 minutes. The proton-beam-treated samples were exposed to a hydrogen pressure of 650 psi at 200℃ and the results were analyzed by monitoring the pressure change of the chamber. The main concerns were a careful measurement of the weight gain after hydrogenation and an estimate of the peak shifts in X-ray diffraction. An absorption of hydrogen was observed for the proton-beam-irradiated samples while little hydrogen loading was noticed for unirradiated ones. Our results demonstrate that proton irradiation may be used as a new technique that can effectively eliminate the oxygen barrier and enhance the rates of hydrogen diffusion. However, more systematic investigations regarding the role of the proton are required before applying the technique for practical applications. Ti-Zr-Ni quasicrystals are new candidates for hydrogen storage applications due to their capabil- ity of loading a large amount of hydrogen at reasonable temperature and hydrogen pressure. The technical applications, however, have been limited because of the presence of a thick oxygen layer, which must be eliminated prior to introducing hydrogen into a sample. To effectively remove the oxygen barrier and to enhance the capability of hydrogen absorption, we irradiated Ti39.5Zr39.5Ni21 quasicrystal ingots by using a proton beam at energy of 20 MeV, 15 mA for 30 minutes. The proton-beam-treated samples were exposed to a hydrogen pressure of 650 psi at 200℃ and the results were analyzed by monitoring the pressure change of the chamber. The main concerns were a careful measurement of the weight gain after hydrogenation and an estimate of the peak shifts in X-ray diffraction. An absorption of hydrogen was observed for the proton-beam-irradiated samples while little hydrogen loading was noticed for unirradiated ones. Our results demonstrate that proton irradiation may be used as a new technique that can effectively eliminate the oxygen barrier and enhance the rates of hydrogen diffusion. However, more systematic investigations regarding the role of the proton are required before applying the technique for practical applications.

Physical and Magnetic Characteristics of Carbon Nanotubes Radiated by Proton Beams

Chung-Jong Yu,Jae yong Kim,Euikwoun Kim,Kyoohyun Han,Suil Suh,Yoon man Lee 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I

Single-walled carbon nanotubes were radiated by proton beams with energy of 35.7 MeV at the Bragg peaks, and magnetic force gradient images and topography were simultaneously measured by using a Nanoscope IV scanning probe microscope while changing the tip distance from the sample. The results show that the magnetic force gradient images become unclear as the scan height increases from 10 nm from the surface of the specimen and completely disappear at 50 nm. When the CNTs were radiated by proton beams, however, clear magnetic force gradient images were observed even at higher scan heights (100 nm) while very little change was noticed in the physical properties, including the tube shapes. It is interesting to note that magnetic force gradient images were not changed by reversing the magnetization of the tip, which reflects an induction of magnetism on the carbon nanotubes.