Papers by Author: Young Seak Lee

Abstract: This research involved the deposition of chitosan on the surface of activated carbon(AC) to get an adsorbent(CS-AC) to removal Cr(VI) from aqueous solution. Each adsorbent used in this study was characterized using BET specific surface analyzer, FT-IR and elemental analyzer. Batch experiments were conducted to determine the removal efficiency of Cr(VI). Chitosan was physically adsorbed on the surface of the AC and the removal efficiency of CS-AC was greater than that of raw activated carbon(RAC), suggesting that the surface modification of AC by chitosan provides more adsorption sites on their solid surface for Cr(VI) adsorption.

Abstract: In this work, carbon nanofibers(CNFs) were prepared by using electrospinning method. Phosphoric acid and sodium carbonate activation of CNFs were conducted to increase surface area and pore volume. Pore structures of activated CNFs were developed with increasing surface area and pore volume through activation. Specific surface area increased about 60 times and total pore volume developed around 120 times. Activated CNFs have different pore distribution with different chemical agent.

Abstract: In this work, nano-sized nickel particles were dispersed on multi-walled carbon nanotubes using multi-step impregnation method, to use them as hydrogen storage media. The dispersion degree of nickel particles on multi-walled carbon nanotubes is inversely proportional to the nickel concentration of solution. It was observed that the low nickel concentration is efficient to decorate nickel particles into the inner space. Multi-step impregnation method of MWNTs through several times with low nickel concentration is more efficient to manufacture Ni-MWNTs having well dispersed metallic nickel particles.

Abstract: In this study, methane gas absorption ability of activated carbon (AC) with surface functional group effect, was evaluated after nitric acid and urea treatment of AC surface. Specific surface area and pore distribution of AC were studied through nitrogen absorption isotherm at 77 K. Micro pore volume was calculated through H-K method. Absorbed methane amount was evaluated through volumetric method at room temperature by using auto absorption apparatus. Absorbed methane amount of AC was found to increase with specific surface area increase. Correlation proposed between the methane absorption amount and surface nature indicates that the surface nature plays an important role on the absorption amount at a given temperature.

Abstract: The rheological behaviors of mesophase pitch containing different contents (0, 1.0, 2.0 wt%) of multi-wall carbon nanotubes (MWNTs) were studied by using ARES cone-plate rheometer. The dynamic response of mesophase pitch containing MWNTs was different from that of pure mesophase pitch due to the MWNTs as a suspension in viscous pitch. The dynamic viscosity increased with increasing the amount of MWNTs, which is a clear evidence of the interruption of MWNTs in mesophase pitch. Also, the phase angle result indicates that mesophase pitch containing MWNT had less elastic nature than pure mesophase pitch.

Abstract: Graphite nanofibers (GNFs)–supported platinum (Pt) catalysts had been prepared by an electrochemical deposition by controlling an applied potential to a potential of Pt reduction. Pt nanoparticles were successfully deposited by using potential sweep methods. The catalyst prepared by 18 sweep times showed the lowest resistance and the highest electroactivity. These electrochemical properties were dependent on the size, loading level, and morphology of catalysts. The influences of electrochemical condition on the sizes and loading level of catalysts were also investigated.

Abstract: In this work, to introduce polar functional groups on carbon surfaces, activated carbon fibers (ACFs) were treated by nitric acid in order to enhance the adsorption capacity of propylamine which was one of toxic gases in cigarette smoke. It was found that the polar functional groups were predominantly increased up to 2.0 M of nitric acid, resulting in the increase of total surface acidity. It was found that the adsorption amount of propylamine of the modified ACFs was increased around 17% after a nitric acid treatment. From the XPS results, it was observed that propylamine was reacted with strong or weak polar (acidic) groups, such as COOH, -COO or OH existed on the ACF surfaces.

Abstract: Electrochemical double layer capacitors (EDLCs) are promising high power energy sources for many different applications where high power density, high cycle efficiency and long cycle life are needed. However, because the energy density of EDLCs is small compared to that of rechargeable batteries one needs to increase the capacitance of EDLCs. The nanofiber diameters range from 50 nm to 400 nm, depending on the concentration of polymer solution types, tip-to-collector distance, applied voltage, and viscosity of the solution. The main advantage of the electrospinning process is that it is a simple means to prepare continuous fibers with unusually large surface to volume ratios and pore structure surfaces. So, feature of nanofiber webs are the high specific surface area developed by creating pores on the nanofiber surface. In this work, the multiwalled carbon nanotubes embedded polyacrylonitrile solutions in N,N-dimethylformamide (DMF) were electrospun to be webs consisting of 350 nm ultrafine nanofibers, which were used to produce a series of activated carbon nanofibers with developed mesoporosity and high electrical conductivity through stabilization, carbonization-activation processes.

Abstract: In this work, we prepared porous graphite nanofibers (PCNFs) from herringbone-type graphite nanofibers, and nano-sized transition metals such as copper metal, were loaded on the PCNFs by a metal electroplating in order to prepare novel catalysts for the control of toxic gases, such as hydrogen chloride. From experimental results, PCNFs had around 2000 m2/g of a specific surface area, and it was decreased slightly after metal loading. In case of metal content, we could control them from less 3 to over 30 wt% by means of the plating time and current density applied. After the metal loading, all samples having transition metal nanoclusters showed higher efficiency of HCl removal than that of samples without metals. However we also found that some samples having excessive metal content showed a decrease in the efficiency of HCl removal. This result meant that one of key technologies was both to find optimal metal content and to remain high specific surface area of substrates.