Structural properties of water around uncharged and charged carbon nanotubes

Mozaffar Ali Mehrabian,Amir Reza Ansari Dezfoli,Hassan Hashemipour Rafsanjani 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3

Studying the structural properties of water molecules around the carbon nanotubes is very important in a wide variety of carbon nanotubes applications. We studied the number of hydrogen bonds, oxygen and hydrogen density distributions, and water orientation around carbon nanotubes. The water density distribution for all carbon nanotubes was observed to have the same feature. In water-carbon nanotubes interface, a high-density region of water molecules exists around carbon nanotubes. The results reveal that the water orientation around carbon nanotubes is roughly dependent on carbon nanotubes surface charge. The water molecules in close distances to carbon nanotubes were found to make an HOH plane nearly perpendicular to the water-carbon nanotubes interface for carbon nanotubes with negative surface charge. For uncharged carbon nanotubes and carbon nanotubes with positive surface charge, the HOH plane was in tangential orientation with water-carbon nanotubes interface. There was also a significant reduction in hydrogen bond of water region around carbon nanotubes as compared with hydrogen bond in bulk water. This reduction was very obvious for carbon nanotubes with positive surface charge. In addition, the calculation of dynamic properties of water molecules in water-CNT interface revealed that there is a direct relation between the number of Hbonds and selfdiffusion coefficient of water molecules.

Carbon-Coated Magnetite Embedded on Carbon Nanotubes for Rechargeable Lithium and Sodium Batteries

Park, Dae-Yeop,Myung, Seung-Taek American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.14

<P>Fe<SUB>3</SUB>O<SUB>4</SUB>, carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB>, and carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> embedded on carbon nanotubes are synthesized via hydrothermal reaction. Scanning electron microscopic analysis reveals that particle size of the as-synthesized Fe<SUB>3</SUB>O<SUB>4</SUB> ranges 100–250 nm, whereas carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> ranges 10–15 nm in diameter and is surrounded by a thin carbon layer derived from sucrose. The surface modification by carbon is effective in prohibiting crystal growth during hydrothermal reaction. The carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> is loaded on conductive carbon nanotubes during a hydrothermal reaction where the carbon nanotubes are added prior to the reaction. Li and Na cell tests indicate that the carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB> embedded on carbon nanotubes exhibits excellent capacity retention and a good rate capability compared to those of Fe<SUB>3</SUB>O<SUB>4</SUB> and carbon-coated Fe<SUB>3</SUB>O<SUB>4</SUB>. For both cases, the presence of conductive carbon nanotubes provides a conduction path of electrons and is thereby responsible for good capacity retention. These results demonstrate the feasibility of dual alkali ions (Li<SUP>+</SUP> and Na<SUP>+</SUP>) storage in inexpensive magnetite.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-14/am502424j/production/images/medium/am-2014-02424j_0011.gif'></P>

Characterization of hybrid carbon nanotubes/carbon fibers-reinforced composites: effect of carbon nanotube content on electromagnetic interference properties of the composites

함은광,최웅기,김영근,서민강 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

In recent years, the metal has used commonly for electromagnetic wave shielding, but there has disadvantages such as expensive and heavy. Carbon nanotubes/carbon fibers-reinforced composites have attracted attention due to benefit such as stiffness, flexibility, and low weight. In this work, the effect of electroless plating and anodizing treated carbon nanotube on electromagnetic interference (EMI) properties of carbon nanotubes/carbon fibers-reinforced composites was studied. The tensile and flexural properties of the composites were also investigated. Carbon nanotube content was varied with 0.3wt%, 0.7wt%, and 1.0wt% in carbon fibers-reinforced composites.

Singlewall carbon nanotubes covered with polystyrene nanoparticles by in-situ miniemulsion polymerization

Ham, Hyeong Taek,Choi, Yeong Suk,Chee, Mu Guen,Chung, In Jae Wiley Subscription Services, Inc., A Wiley Company 2006 Journal of polymer science Part A, Polymer chemist Vol.44 No.1

<P>This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene-singlewall carbon nanotube (PS-SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS-SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS-SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle-SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006</P> <B>Graphic Abstract</B> <P>Singlewall carbon nanotubes covered with polystyrene nanoparticles were prepared via in-situ miniemulsion polymerization. Polystyrene nanoparticles were attached on the surface of singlewall carbon nanotubes. The nanoparticles partially covered the sidewall of carbon nanotubes. The bare surface of singlewall carbon nanotubes and polystyrene nanoparticle attached singlewall carbon nanotubes were coexisted. Polystyrene-singlewall carbon nanotube composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. Their structural difference and properties were examined. <img src='wiley_img/0887624X-2006-44-1-POLA21185-gra001.gif' alt='wiley_img/0887624X-2006-44-1-POLA21185-gra001'> </P>

TiO₂ nanotubes/carbon nanotubes for indoor CO₂ gas reduction

김현,양비룡 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

A manned spacecraft environmental control and life support system (ECLSS) is a group of systems that allow human to live in space for long term exploration. Generally ECLSS consists of several main components such as, atmosphere, water recovery and managements. In this study twisted TiO₂ nanotubes/carbon nanotubes were prepared and tested for different parts of the ECLSS. In first step photocatalytic oxygen generation using twisted TiO₂ nanotubes/carbon nanotubes with IrO₂ nanoparticles coated optical fibers will be performed. In second and third step CO₂ photoreduction and water purification systems using twisted TiO₂ nanotubes coated optical fibers will be developed and tested, respectively. In fourth step, air purification systems will be developed. In final step twisted TiO₂ nanotubes/carbon nanotubes coated optical fibers in cylinder type reactor will be employed to develop anti-contaminant and antibacterial systems.

Practical Preparation of Carbon Black/Carbon Nitride Compounds and Their Photocatalytic Performance

Shaozheng Hu,Haoying Wang,Fei Wang,Jin Bai,Lei Zhang,Xiaoxue Kang,GuangWu 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.10

Here we report a carbon-black-modified g-C3N4 nanocomposite prepared by a convenient method and its photocatalytic performance, which was compared with other carbon-material-, carbon nanotube (CNT)-, C60-, and graphene (GR)-modified g-C3N4 nanocomposites. X-ray diffraction, N2 adsorption, UV–vis spectroscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and photoluminescence were used to characterize the prepared composite material. The results reveal that incorporating g-C3N4 with carbon materials decreases the bandgap and the electron–hole recombination rate of the prepared catalysts. No significant difference was observed in the structural and optical properties among these four series of carbon-material-modified g-C3N4 nanocomposites. Carbon-based materials cannot act as visible-light sensitizers but they can facilitate the separation and transport of photogenerated carriers. These composites obey a tentative reaction mechanism similar to rhodamine B (RhB) photocatalytic degradation. Carbon-black-modified g-C3N4 exhibits comparable activity and stability as those of GR-modified g-C3N4 , which is better than the modification by C60 and CNTs. Compared to CNTs, GR, and C60 , carbon black is a cheap and effective carbon source with excellent photocatalytic performance for the preparation of carbon material/g-C3N4 nanocomposites.

Theoretical Investigation of Lithium-Atom Insertion into Ultra-Small Diameter Carbon Nanotubes

Anurak Udomvech,Teerakiat Kerdcharoen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Computations of Li intercalation into ultra-small single-walled carbon nanotubes have been car- ried out within the framework of the rst-principles density functional calculation. The energy and the structural properties of two Li atoms as a function of distance along the longitudinal axis of (3,3), (4,2) and (5,0) nanotubes have been calculated. We found that Li atoms could be easily pulled into the interior of (3,3) and (4,2) nanotubes whereas a small energy barrier existed at the open-mount of (5,0) tube. The zigzag (5,0) nanotube allows Li-Li to localize near the tube center, forming a Li2 cluster inside the nanotube. In contrast, Li atoms prefer to locate near the open mounts of the armchair (3,3) tube. In case of a (4,2) nanotube, no preferential location is found, as described by the at potential energy prole. The intercalated atoms aect the geometric pa- rameters at the central region more than the rest of the nanotube. These results provide evidence that chirality plays a crucial role in Li-tube interactions, especially for ultra-small nanotubes, which suggests that appropriate tubule chiralities are needed if ecient anode materials are to be used in Li batteries. Computations of Li intercalation into ultra-small single-walled carbon nanotubes have been car- ried out within the framework of the rst-principles density functional calculation. The energy and the structural properties of two Li atoms as a function of distance along the longitudinal axis of (3,3), (4,2) and (5,0) nanotubes have been calculated. We found that Li atoms could be easily pulled into the interior of (3,3) and (4,2) nanotubes whereas a small energy barrier existed at the open-mount of (5,0) tube. The zigzag (5,0) nanotube allows Li-Li to localize near the tube center, forming a Li2 cluster inside the nanotube. In contrast, Li atoms prefer to locate near the open mounts of the armchair (3,3) tube. In case of a (4,2) nanotube, no preferential location is found, as described by the at potential energy prole. The intercalated atoms aect the geometric pa- rameters at the central region more than the rest of the nanotube. These results provide evidence that chirality plays a crucial role in Li-tube interactions, especially for ultra-small nanotubes, which suggests that appropriate tubule chiralities are needed if ecient anode materials are to be used in Li batteries.

Electrochemical Capacitors Based on Aligned Carbon Nanotubes Directly Synthesized on Tantalum Substrates

Kim, Byung-Woo,Chung, Hae-Geun,Min, Byoung-Koun,Kim, Hong-Gon,Kim, Woong Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.12

We demonstrate that vertically aligned carbon nanotubes can be synthesized directly on tantalum substrate via water-assisted chemical vapor deposition and evaluate their properties as electrochemical capacitors. The mean diameter of the carbon nanotubes was $7.1{\pm}1.5\;nm$, and 70% of them had double walls. The intensity ratio of G-band to D-band in Raman spectra was as high as 5, indicating good quality of the carbon nanotubes. Owing to the alignment and low equivalent series resistance, the carbon nanotube based supercapacitors showed good rate performance. Rectangular shape of cyclic voltammogram was maintained even at the scan rate of > 1 V/s in 1 M sulfuric acid aqueous solution. Specific capacitance was well-retained (~94%) even when the discharging current density dramatically increased up to 145 A/g. Consequently, specific power as high as 60 kW/kg was obtained from as-grown carbon nanotubes in aqueous solution. Maximum specific energy of ~20 Wh/kg was obtained when carbon nanotubes were electrochemically oxidized and operated in organic solution. Demonstration of direct synthesis of carbon nanotubes on tantalum current collectors and their applications as supercapacitors could be an invaluable basis for fabrication of high performance carbon nanotube supercapacitors.

Purification of Multi Walled Carbon Nanotubes (Mwcnts) Synthesized by Arc Discharge Set Up

Y. Malathi,Balaji Padya,K.V.P. Prabhakar,P.K. Jain 한국탄소학회 2010 Carbon Letters Vol.11 No.3

Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ~0.34 nm. Multiwalled carbon nanotubes were synthesized by arc-discharge technique. MWCNTs were formed at the cathode deposit along with other carbonaceous materials like amorphous carbon, graphite etc. However, to get the best advantage of carbon nanotubes in various advanced applications, these undesired carbonaceous materials to be removed which is a challenging task. In the present study, various techniques were tried out for purifying MWCNTs such as physical filtration, chemical treatment and thermal annealing. SEM, FTIR, TGA and BET techniques were used to characterize the CNTs at various stages. Results shows that suitable chemical treatment followed by thermal annealing under controlled flow of oxygen gives the better route for purification of carbon nanotubes.

CNT를 첨가한 Silicon/Carbon 음극소재의 전기화학적 특성

정민지 ( Min Zy Jung ),박지용 ( Ji Yong Park ),이종대 ( Jong Dae Lee ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.1

Silicon/Carbon/CNT, Anode material, Carbon nanotube, Magnesiothermic re실리콘의 부피팽창과 낮은 전기전도도를 개선하기 위하여 Silicon/Carbon/CNT 복합체를 제조하였다. Silicon/Carbon/CNT 합성물은 SBA-15를 합성한 후, 마그네슘 열 환원 반응으로 Silicon/MgO를 제조하여 Phenolic resin과 CNT를 첨가하여 탄화하는 과정을 통해 합성하였다. 제조된 Silicon/Carbon/CNT 합성물은 XRD, SEM, BET, EDS를 통해 특성을 분석하였다. 본 연구에서는 충방전, 사이클, 순환전압전류, 임피던스 테스트를 통해 CNT 첨가량에 따른 전기화학적 효과를 조사하였다. LiPF6 (EC:DMC:EMC=1 :1 :1 vol%) 전해액에서 Silicon/Carbon/CNT 음극활물질을 사용하여 제조한 코인셀은 CNT 함량이 7 wt% 일 때 1,718 mAh/g으로 높은 용량을 나타내었다. 코인셀의 사이클 성능은 CNT첨가량이 증가할수록 개선되었다. 11 wt%의 CNT를 첨가한 Silicon/Carbon/CNT 음극은 두 번째 사이클 이후 83%의 높은 용량 보존율을 나타냄을 알 수 있었다.duction, Lithium ion battery Silicon/Carbon/CNT composites as anode materials for lithium-ion batteries were synthesized to overcome the large volume change during lithium alloying-de alloying process and low electrical conductivity. Silicon/Carbon/CNT composites were prepared by the fabrication processes including the synthesis of SBA-15, magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling, carbonization of phenolic resin with CNT and HCl etching. The prepared Silicon/ Carbon/CNT composites were analysed by XRD, SEM, BET and EDS. In this study, the electrochemical effect of CNT content to improve the capacity and cycle performance was investigated by charge/discharge, cycle, cyclic voltammetry and impedance tests. The coin cell using Silicon/Carbon/CNT composite (Si:CNT=93:7 in weight) in the electrolyte of LiPF6 dissolved in organic solvents (EC:DMC:EMC=1:1:1 vol%) has better capacity (1718 mAh/g) than those of other composition coin cells. The cycle performance of coin cell was improved as CNT content was increased. It is found that the coin cell (Si:CNT=89:11 in weight) has best capacity retension (83%) after 2nd cycle.