• Electronic Materials Letters
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• v.14 no.6
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• pp.755-765
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• 2018

In situ nitrogen doped hard carbon nanotubes (NHCNT) were fabricated by pyrolyzing tubular nitrogen doped conjugated microporous polymer. KOH activated NHCNT (K-NHCNT) were also prepared to improve their porous structure. XRD, SEM, TEM, EDS, XPS, Raman spectra, $N_2$ adsorption-desorption, galvanostatic charging-discharge, cyclic voltammetry and EIS were used to characterize the structure and performance of NHCNT and K-NHCNT. XRD and Raman spectra reveal K-NHCNT own a more disorder carbon. SEM indicate that the diameters of K-NHCNT are smaller than that of NHCNT. TEM and EDS further indicate that K-NHCNT are hollow carbon nanotubes with nitrogen uniformly distributed. $N_2$ adsorption-desorption analysis reveals that K-NHCNT have an ultra high specific surface area of $1787.37m^2g^{-1}$, which is much larger than that of NHCNT ($531.98m^2g^{-1}$). K-NHCNT delivers a high reversible capacity of $918mAh\;g^{-1}$ at $0.6A\;g^{-1}$. Even after 350 times cycling, the capacity of K-NHCNT cycled after 350 cycles at $0.6A\;g^{-1}$ is still as high as $591.6mAh\;g^{-1}$. Such outstanding electrochemical performance of the K-NHCNT are clearly attributed by its superior characters, which have great advantages over those commercial available carbon nanotubes ($200-450mAh\;g^{-1}$) not only for its desired electrochemical performance but also for its easily and scaling-up preparation.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.159-159
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• 2009

In this work, nitrogen and oxygen functionalities was introduced to the graphite nanofibers (GNFs) and their effect on electrocatalytic performance of the GNF supports for direct methanol fuel cells (DMFCs) was invesigated. The nitrogen and oxygen groups were introduced through the urea treatments and acid treatment, respectively. And, PtRu catalysts deposited on modified GNFs were prepared by a chemical reduction method. The catalysts were characterized by means of elemental analysis, nitrogen adsorption, and X-ray photoelectron spetroscopy (XPS). The structure and morphological characteristics of the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). As a result, the Pt-Ru nanoparticles were impregnated on GNFs with good formation in 3-5 nm. And, the cyclic voltammograms for methanol oxidation revealed that the methanol oxidation peak varied depending on changes of surface functional groups. It was thus considered that the PtRu deposition was related to the reduction of PtRu and surface characteristics of the carbon supports. The changes of surface functional groups were related to PtRu reduction, significantly affect the methanol oxidation activity of anode electrocatalysts in DMFCs.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1185-1188
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• 1998

Layered nanocomposite, SiO2/TiO2 sol pillared clay, has been prepared by the ion exchange reaction of Na' ion in montmorillonite with positively charged mixed SiO2/TiO2 sol. The nanosized sol particles were synthesized by mixing SiO2 sol solution with TiO2 one, which is obtained by acidic hydrolysis of TEOS and TiCl4, respectively. From powder XRD, the basal spacing (d001) of the sample calcined at 400 ℃ was found to be ca. 60 Å, due to the multistacking of nanosized SiO2 and TiO2 sol particles, which was confirmed by the pore size analysis from 129Xe NMR and micropore analysis calculated from nitrogen adsorption. The BET specific surface area shows the value of 684 m2g-1 (Langmuir 1115 m2g-1), which is the highest among various pillared clays ever reported previously, and the total porosity is found to be 0.51 mlg-1, and the pores are mainly composed of micropore with a size of ca. 11.8 Å. This result agrees with the adsorption capacity obtained from water adsorption. According to diffuse reflectance ultraviolet-visible spectroscopy, it is found that the TiO2 particles stabilized in the interlayer space of montmorillonite are quantum-sized of ca. 20 Å.

• Carbon letters
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• v.28
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• pp.111-115
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• 2018

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.727-736
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• 2006

Granular activated carbon (GAC) has been identified as a best available technology (BAT) by the United States Environmental Protection Agency (USEPA) for removal disinfection by-product (DBP) precursors, such as dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). Rapid small-scale column test (RSSCT) were used to investigate four types of carbon (F400, Norit1240, Norit40S, and Aquasorb1500) for their affinity to absorb natural organic matter (NOM). DOC, $UV_{254}$, and Total dissolved nitrogen (TON) concentrations were measured in the column effluent to track GAC breakthrough. DOC and $UV_{254}$ breakthrough occurred at around 3500 bed volumes (BVs) of operation for all GACs investigated. The $UV_{254}$ breakthrough curves showed 33% to 48% at 8000 BVs, when the DOC was 48% to 65%. All GACs showed greater removal in DOC than $UV_{254}$. The NORIT1240 GAC was determined to have the highest adsorption capacity for DOC and $UV_{254}$. The removal of nitrate (NOTN) had not broken through over BVs. The initial TON breakthrough curves were started around 50%, when the DOC breakthrough was only 10 % at 500 BVs. The curves were gradually increased after 3500 BVs and approximately 69% through 81% of TON breakthrough occurred at 8000 BVs. All of the GACs were able to remove TON, in the case of this investigation the majority of the TON was present as DON. Because nitrate nitrogen was seldom removed and ammonium nitrogen ($NH_3-N$) was not detected in the effluent from RSSCTs even though raw water. The carbon usage rate of DOC was from 2 to 6 times less than that of TON. The NORIT1240 GAC demonstrated the best performance in terms of DOC removal, while the F400 GAC was best in terms of TON removal. Excitation emission matrix(EEM) analysis was used to show that GAC adsorption successfully removed most of Humic-like DOC and Fulvic-like DOCs. However, soluble microbial product(SMP)-like DOC in the absence of raw water were detected in the NORIT40S and Aquasorb1500 GAC. The authors assumed that this results is due probably to the part of GAC in the RSSCT which was converted into biological activated carbon(BAC). To compare with organics removal by GAC according to preloading, the virgin GACs had readily accessible sites that were adsorbed DOC more rapidly than preloaded GACs, but the TDN removal had not showed differences between those GACs.

• Advances in nano research
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• v.15 no.1
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• pp.35-48
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• 2023

Nanoparticles are known for their outstanding properties such as particle size, surface area, optical and electrical properties. These properties have significantly boasted their applications in various surface phenomena. In this work, calcium oxide nanoparticles were synthesized from periwinkle shells as an approach towards waste management through resource recovery. The sol gel method was used for the synthesis. The nanoparticles were characterized using X-Ray diffractometer (XRD), Fourier Transformed Infra-Red Spectrophotometer (FTIR), Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra violet visible spectrophotometer (UV-visible). While DLS and SEM underestimate the particle diameter, the BET analysis reveals surface area of 138.998 m²/g, pore volume = 0.167 m³/g and pore diameter of 2.47 nm. The nanoparticles were also employed as an adsorbent for the purification of dye (methyl orange) contaminated water. The adsorbent showed excellent removal efficiency (up to 97 %) for the dye through the mechanism of physical adsorption. The adsorption of the dye fitted the Langmuir and Temkin models. Analysis of FTIR spectrum after adsorption complemented with computational chemistry modelling to reveal the imine nitrogen group as the site for the adsorption of the dye unto the nanomaterials. The synthesized nanomaterials have an average particle size of 24 nm, showed a unique XRD peak and is thermally and mechanically stable within the investigated temperature range (30 to 70 ℃).

• Analytical Science and Technology
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• v.13 no.1
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• pp.89-95
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• 2000

Three grades of activated carbon fibers (ACFs) were prepared from various precursors of plantic, synthetic, and mixed fabrics of viscose rayon and cotton. The ACFs an exhibited type I isotherms on the adsorption of nitrogen or argon. Micropore analysis revealed that the ACFs have uniform micropore size distribution in which their peak diameters were in the range of $5.6{\pm}0.3{\AA}$. The BET surface area of ACFs up to $1600m^2g^{-1}$ was proportional to the adsorption capacity of iodine. The BET values of the ACFs prepared were proportional to the burn-off degree of the products.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.658-662
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• 2009

In this work, the amine-treated activated carbon nanotubes (A-MWNTs) were used to investigate the $CO_2$ adsorption behaviors. A-MWNTs were prepared by impregnation with amine in methanol after chemical activation methods using a KOH. The characteristics of amine-treated A-MWNTs were studied by X-ray photoelectron spectroscopy (XPS), $N_2$ adsorption, desorption isotherms at 77 K. The specific surface area and pore volume of the A-MWNTs were analyzed by BET equation, BJH method, and t-plot method. $CO_2$ capture capacity as a function of temperature was measured by temperature programmed desorption (TPD). From the results, the amine treatment increased the basicity and nitrogen content of the A-MWNTs. The $CO_2$ adsorption capacity of the amine-nontreated A-MWNTs showed the highest value at room temperature and then greatly decreased with increasing the temperature. However, the amine-treated A-MWNTs presented a softer slope with temperature compared to the amine-nontreated ones. It was due to the strong interactions between $CO_2$ and amino groups presented on the carbon surfaces studied.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.2
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• pp.63-71
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• 2023

Increased nitrogen in the water system has become an important environmental problem around the world, as it causes eutrophication, algae bloom, and red tide, destroys the water system, and undermines water's self-purification. The most common form of nitrogen in the water system is ammonium ion (NH₄⁺), and the largest portion of ammonium ions comes from wastewater. NH₄⁺ is a major contributor to eutrophication, which calls for appropriate treatment and measures for ammonium removal. This study produced biochar by applying Sorghum × drummondii, a type of biomass with a great growth profile, analyzed the adsorption capacity of Sorghum × drummondii biochar produced from the changing carbonization temperature condition of 200 to 400℃ in the ammonium ion range of 10 to 100 ppm, and used the results to evaluate its potential as an adsorbent. Carbonization decomposed the chemical structure of Sorghum × drummondii and increased the content of carbon and fixed carbon in the biochar. The biochar's pH and electrical conductivity showed high adsorption potential for cations due to electrical conductivity as its pH and electrical conductivity increased along with higher carbonization temperature. Based on the results of an adsorption experiment, the biochar showed 54.5% and 17.4% in the maximum and minimum NH₄-N removal efficiency as the concentration of NH₄-N increased, and higher carbonization temperature facilitated the adsorption of pollutants due to the biochar's increased pores and specific surface area and subsequently improved NH₄-N removal efficiency. FT-IR analysis showed that the overall surface functional groups decreased due to high temperature from carbonization.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.10-20
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• 2023

Because of its inexpensive cost, mild steel is frequently employed as a construction material in different industries. Unfortunately, because of its limited resistance to corrosion, a protective layer must be applied to keep it from decaying in acidic or basic environments. The presence of heteroatoms, such as nitrogen, oxygen, and pi-electrons in the Schiff base could cause effective adsorption on the mild steel surface, preventing corrosion. The weight loss method and scanning electron microscopy (SEM) were used to investigate the inhibitory effects of APIDO on mild steel in a 1 M hydrochloric acid environment. The efficiency of inhibition increased as the inhibitor concentration increased and decreased as the temperature increased. The SEM analysis confirmed that the corrosion inhibition of APIDO proceeded by the formation of an organic protective layer over the mild steel surface by the adsorption process. Simulations based on the density functional theory are used to associate inhibitory efficacy with basic molecular characteristics. The findings acquired were compatible with the experimental information provided in the research.