• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.426-438
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• 2023

Lithium-sulfur batteries, recently attracting attention as next-generation batteries, have high energy density but are limited in application due to sulfur's insulating properties, shuttle phenomenon, and volume expansion. This study used an economical and simple vacuum filtration method to prepare a freestanding electrode without a binder and collector. Carbon nanotubes (CNTs) are used to improve the electrical conductivity of sulfur, where CNT also acts as both collector and conductor. In addition, metal oxides (MO_x, M=Ni, Mg), which are easy to adsorb lithium polysulfide, are added to the CNT/S electrode to suppress the shuttle reaction in lithium-sulfur batteries, which is a result of suppressing the loss of active sulfur material due to the excellent adsorption of lithium polysulfide by metal oxides. The MO_x@CNT/S electrode exhibited higher capacity characteristics and cycle stability than the CNT/S electrode without metal oxides. Among the MO_x@CNT/S electrodes, the NiO@CNT/S electrode displayed a high discharge capacity of 780 mAh g^-1 at 1 C and an extreme capacity decrease to 134 mAh g^-1 after 200 cycles. Although the MgO@CNT/S electrode exhibited a low discharge rate of 544 mAh g^-1 in the initial cycle, it showed good cycle stability with 90% of capacity retention up to 200 cycles. Further, to achieve high capacity and cycle stability, the Ni_0.7Mg_0.3O@CNT/S electrode, mixed with Ni:Mg in the ratio of 0.7:0.3, manifested an initial discharge rate of 755 mAh g^-1 (1 C) and a capacity retention rate of more than 90% after 200 cycles. Therefore, applying binary metal oxides to CNT/S provides a freestanding electrode for developing economical and high-performance Li-S batteries, effectively improving lithium polysulfide's high capacity characteristics and dissolution.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.184-192
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• 2022

Porous NiO synthesized via hydrothermal synthesis was used in the electrodes of lithium-sulfur batteries to inhibit the elution of lithium polysulfide. The electrode of the lithium-sulfur battery was manufactured as a freestanding flexible electrode using an economical and simple vacuum filtration method without a current collector and a binder. The porous NiO-added S/CNT/NiO electrode exhibited a high initial discharge capacity of 877 mA h g^-1 (0.2 C), which was 125 mA h g^-1 higher than that of S/CNT, and also showed excellent retention of 84% (S/CNT: 66%). This is the result of suppressing the dissolution of lithium polysulfide into the electrolyte by the strong chemical bond between NiO and lithium polysulfide during the charging and discharging process. In addition, for the flexibility test of the S/CNT/NiO electrode, the 1.6 × 4 cm² pouch cell was prepared and exhibited stable cycle characteristics of 620 mA h g^-1 in both the unfolded and folded state.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.468-468
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• 2011

Carbon nanotubes (CNTs) have been considered as one of the promising candidate for next-generation field emitters because of their unique properties, such as high field enhancement factor, good mechanical strength, and excellent chemical stability. So far, a lot of researchers have been interested in field emission properties of CNT itself. However, it is necessary to study proper field emitter shapes, as well as the fundamental properties of CNTs, to apply CNTs to real devices. For example, specific applications, such as x-ray sources, e-beam sources, and microwave amplifiers, need to get a focused electron beam from the field emitters. If we use planar-typed CNT emitters, it will need several focal lenses to reduce a size of electron beam. On the other hand, the point-typed CNT emitters can be an effective way to get a focused electron beam using a simple technique. Here, we introduce a fabrication of CNT fibers with nanoscale point tips which can be used as a point-typed emitter. The emitter made by the CNT fibers showed very low turn-on electric field, high current density, and large enhancement factor. In addition, it showed stable emission current during long operation period. The high performance of CNT point emitter indicated the potential e-beam source candidate for the applications requiring small electron beam size.

• Polymer(Korea)
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• v.38 no.5
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• pp.573-579
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• 2014

The effect of synthesis conditions such as carbon nanotube (CNT), 2,2,2-trifluoroethylmethacrylate (3FMA), and composition of organic-inorganic material in ozone resistance and surface characteristics of ultraviolet cured organic-inorganic hybrid coating film has been investigated. Coating solution was prepared using tetraethoxysilane (TEOS), silane coupling agent methacryloyloxypropyltrimethoxysilane (MPTMS), 3FMA, various organic materials with acrylate group, and CNT, then bar-coated on substrates using applicator, and densified by UV-curing. It was found that ozone resistance and adhesion of the coating film were strongly dependent upon contents of TEOS, 3FMA, and CNT. Especially, ozone resistance, adhesion, and surface hardness of coating film with CNT were improved, relatively. Ozone resistance of coating film with a high TEOS content was increased, but adhesion was decreased. In addition, it was also found that ozone resistance of coating film was increased with contents of 3FMA. On the other hand, surface hardness was decreased with increase of 3FMA.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.360-365
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• 2006

Carbon nanotubes (CNTs) have been the subject of intensive studies for applications in the fields of nano technologies in recent years due to their superior mechanical, electric, optical and electronic properties. Because of their exceptionally small diameters (${\appros}\;several\;nm$) as well as their high Young's modulus (${\appros}1\;TPa$), tensile strength (${\appros}\;200\;GPa$) and high elongation (10-30%) in addition to a high chemical stability, CNTs are attractive reinforcement materials for light weight and high strength metal matrix composites. Although extensive researches have been performed on the electrical, mechanical and functional properties of CNTs, there are not many successful results on the mechanical properties of CNT dispersed nanocomposites. In this paper, we applied equal channel angular pressing for consolidation of CNT/Cu powder mixtures. We also investigated the hardness and microstructures of CNT/Cu nanocomposites used experimental for metal matrix composites.

• Carbon letters
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• v.25
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• pp.55-59
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• 2018

Carbon chain inserted carbon nanotubes (CNTs) have been experimentally proven having undergone pronounced property change in terms of electrical conductivity compared with pure CNTs. This paper simulates the geometry of carbon chain inserted CNTs and analyzes the mechanism for conductivity change after insertion of carbon chain. The geometric simulation of Pt doped CNT was also implemented for comparison with the inserted one. The results indicate that both modification by Pt atom on the surface of CNT and addition of carbon chain in the channel of the tube are effective methods for transforming the electrical properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations. All the calculations were obtained based on density functional theory method.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1081-1086
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• 2005

Dynamic behavior of carbon nanotubes (CNTs) in an electric field is directly observed by in-situ transmission electron microscopy (TEM). The CNT field emitters examined by in-situ TEM are multiwalled, double-walled and single walled CNTs. Threshold fields for electron emission and sustainable emission currents depending on the structure of CNTs are presented, and degradation mechanism of the CNT field emitters is discussed. In addition to the microscopy studies on individual CNTs, our recent development in surface treatment of CNT layers grown by chemical vapor deposition, which brings about high density of emission current and high uniformity, is also presented.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1536-1537
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• 2005

We have made point electron sources using carbon nanotubes (CNTs). For the fabrication of point electron sources, CNTs were dispersed in a solution and attached on electrochemically etched W tips using electrophoresis. In our study, we have utilized various CNTs such as single-walled CNT (SWCNT), multiwalled CNT (MWCNT), and thin-MWCNT and threshold current, turn-on voltage, filed enhancement factor of each emitter have been studied upon a tube/bundle diameter and length. In addition, fieldemitted electron energy distribution of various CNT emitters is characterized.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.229-230
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• 2012

Platinum (Pt) has been commonly used as a counter electrode material in dye-sensitized solar cells, because it has high catalytic activity and electric conductivity as well as chemical inertness with iodide electrolyte. However, Pt is too expensive to be commercialized. Therefore, in the present study, carbon black counter electrode with Pt and carbon nano tube (CNT) was investigated. The power conversion efficiency with Pt added carbon black electrode was lower than hat of pure Pt electrode which was 6.47 %. By adding 3 wt% Pt to the carbon black counter electrode, the power conversion efficiency was maximized at 5.88 %. On them, additional adding of 1 wt % CNT, the power conversion efficiency (${\eta}$)wasincreasedupto6.21%. The reason of power conversion efficiency improvement with a proper amount of Pt and CNT was examined by comparing the impedance properties measured using EIS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.47-48
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• 2006

Carbon nanotubes (CNTs)-doped homogeneously aligned nematic liquid crystal (LC) cells driven by in-plane field were fabricated and their electro-optic characteristics were investigated. Effective cell retardation values in an absence of an electric field between doped and undoped LC were the same each other. In the presence of an electric field, however, measured effective cell retardation value was smaller in the CNT-doped cell than in the undoped cell so that the transmittance was slightly smaller in the CNT-doped cell than in the undoped cell. In addition, the CNT-doped cell exhibited slight increase in driving voltage and decrease in response time compared to the undoped cell. The CNT effects on electro-optic characteristics of the cell were discussed.