• Journal of Powder Materials
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• v.17 no.4
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• pp.281-288
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• 2010

A carbon doped $TiO_2$ (C-$TiO_2$) photocatalyst, which shows good photocatalytic activity to Ultraviolet irradiation and visible irradiation, was successfully prepared by co-grinding of $TiO_2$ with ethanol or Activated Carbon(C), followed by heat treatment at $200^{\circ}C$ in air for 60 min. Ethanol and C were used as a representative agent of liquid and solid for carbon doping. Their influence on improving photocatalytic ability and carbon doping degree was studied with degradation of methyl orange and XPS analysis. The product prepared by co-grinding of $TiO_2$ with Ethanol had Ti-C and C-O chemical bonds and showed higher photocatalytic activity than the product prepared by co-grinding of $TiO_2$ with C, where just C-O chemical bond existed. As a result, mechanochemical route is useful to prepare a carbon doped $TiO_2$ photocatalyst activating to visible irradiation, where the solid-liquid operation is more effective than solid-solid operation to obtain a carbon doped $TiO_2$.

• Journal of Powder Materials
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• v.23 no.6
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• pp.420-425
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• 2016

N-doped carbon nanofibers as catalysts for oxygen-reduction reactions are synthesized using electrospinning and carbonization. Their morphologies, structures, chemical bonding states, and electrochemical performance are characterized. The optimized N-doped carbon nanofibers exhibit graphitization of carbon nanofibers and an increased nitrogen doping as well as a uniform network structure. In particular, the optimized N-doped carbon nanofibers show outstanding catalytic activity for oxygen-reduction reactions, such as a half-wave potential ($E_{1/2}$) of 0.43 V, kinetic limiting current density of $6.2mAcm^{-2}$, electron reduction pathways (n = 3.1), and excellent long-term stability after 2000 cycles, resulting in a lower $E_{1/2}$ potential degradation of 13 mV. The improvement in the electrochemical performance results from the synergistic effect of the graphitization of carbon nanofibers and the increased amount of nitrogen doping.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.303-306
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• 2007

Recent studies in the literature have shown that it is possible to overcome the limitations of the physical properties of liquid crystals by the doping of carbon nanotubes. Although still in its infancy, the potential of such a new approach for opportunities in display applications should not go unnoticed.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.12-15
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• 2013

The pure and carbon (C)-doped $MgB_2$ thin films were fabricated on $Al_2O_3$ (0001) substrates at a temperature of $650^{\circ}C$ by using hot-filament-assisted hybrid physical-chemical vapor deposition technique. The $T_c$ value for pure $MgB_2$ film is 38.5 K, while it is between 30 and 35 K for carbon-doped $MgB_2$ films. Expansion in c-axis lattice parameter was observed with increase in carbon doping concentration which is in contrast to carbon-doped $MgB_2$ single crystals. Significant enhancement in the critical current density was obtained for C-doped $MgB_2$ films as compared to the undoped $MgB_2$ film. This enhancement is most probably due to the incorporation of C into $MgB_2$ and the high density of grain boundaries, both help in the pinning of vortices and result in improved superconducting performance.

• Carbon letters
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• v.14 no.3
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• pp.175-179
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• 2013

Isolated single wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition (CVD) using a liquid precursor (xylene) as a carbon source. Transmission electron microscopy (TEM) and atomic force microscopy confirmed the isolated structure of the SWCNTs. Micro-Raman measurements showed a tangential G-band peak ($1590cm^{-1}$) and radial breathing mode (RBM) peaks ($150-240cm^{-1}$). The tube diameters determined from the RBM frequencies are in good agreement with those obtained from TEM. The chirality of the isolated SWCNTs could be determined based on the energy of the laser and their diameter. A further preliminary study on the nitrogen doping of isolated SWCNTs was carried out by the simple use of acetonitrile dissolved in the precusor.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.13-13
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• 2008

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.148-149
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• 2012

This paper reports doping of carbon atoms in GaN layer, which based on dimethylhydrazine (DMHy) and growth temperature. It is well known that dislocations can act as non-radiative recombination center in light emitting diode (LED). Recently, many researchers have tried to reduce the dislocation density by using various techniques such as lateral epitaxial overgrowth (LEO) [1] and patterned sapphire substrate (PSS) [2], and etc. However, LEO and PSS techniques require additional complicated steps to make masks or patterns on the substrate. Some reports also showed insertion of carbon doped layer may have good effect on crystal quality of GaN layer [3]. Here we report the growth of GaN epitaxial layer by inserting carbon doped GaN layer into GaN epitaxial layer. GaN:C layer growth was performed in metal-organic chemical vapor deposition (MOCVD) reactor, and DMHy was used as a carbon doping source. We elucidated the role of DMHy in various GaN:C growth temperature. When growth temperature of GaN decreases, the concentration of carbon increases. Hence, we also checked the carbon concentration with DMHy depending on growth temperature. Carbon concentration of conventional GaN is $1.15{\times}1016$. Carbon concentration can be achieved up to $4.68{\times}1,018$. GaN epilayer quality measured by XRD rocking curve get better with GaN:C layer insertion. FWHM of (002) was decreased from 245 arcsec to 234 arcsec and FWHM of (102) decreased from 338 arcsec to 302 arcsec. By comparing the quality of GaN:C layer inserted GaN with conventional GaN, we confirmed that GaN:C interlayer can block dislocations.

• Carbon letters
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• v.17 no.1
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• pp.29-32
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• 2016

This paper addresses the effect of dopants on the electronic properties of zigzag (8, 0) semiconducting single walled carbon nanotubes (SWCNTs), using extended Hückel theory combined with nonequilibrium Green’s function formalism. Through appropriate dopant concentrations, the electronic properties of SWCNTs can be modified. Within this context, we present our ongoing investigation on (8, 0) SWCNTs doped with nitrogen. Quantum confinement effects on the electronic properties of the SWCNTs have also been investigated. The obtained results reveal that the electronic properties of SWCNTs are strongly dependent on the dopant concentration and modification of electronic structures by hydrogen confinement.

• Composites Research
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• v.29 no.4
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• pp.132-137
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• 2016

Based on mussel-inspired polydopamine (PDA), a novel technique to fabricate carbon nanowire (CNW) arrays is presented for a possible use of porous carbon electrode in electrochemical energy storage applications. PDA can give more porosity and nitrogen-doping effect to carbon electrodes, since it has high graphitic carbon yield characteristic and rich amine functionalities. Using such outstanding properties, the applicability of PDA for electrochemical energy storage devices was investigated. To achieve this, the decoration of the CNW arrays on carbon fiber surface was performed to increase the surface area for storage of electrical charge and the chemical active sites. Here, zinc oxide (ZnO) nanowire (NW) arrays were hydrothermally grown on the carbon fiber surface and then, PDA was coated on ZnO NWs. Finally, high temperature annealing was performed to carbonize PDA coating layers. For higher energy density, manganese oxide ($MnO_x$) nanoparticles (NPs), were deposited on the carbonized PDA NW arrays. The enlarged surface area induced by carbon nanowire arrays led to a 4.7-fold enhancement in areal capacitance compared to that of bare carbon fibers. The capacitance of nanowire-decorated electrodes reached up to $105.7mF/cm^2$, which is 59 times higher than that of pristine carbon fibers.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.607-612
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• 2009

We investigated the effects of Co doping on the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with ZnO using pulsed laser deposition. Structural examinations clearly confirmed a distinct nanostructure of the CNTs coated with ZnO nanoparticles of an average diameter as small as 10 nm and showed little influence of doping 1 at.% Co into ZnO on the morphology of the ZnO-CNT composites. It was found from the gas sensing measurements that 1 at.% Co doping into ZnO gave rise to a significant improvement in the response of the ZnO-CNT composite sensor to NO gas exposure. In particular, the Co-doped ZnO-CNT composite sensor shows a highly sensitive and fast response to NO gas at relatively low temperatures and even at low NO concentrations. The observed significant improvement of the NO gas sensing properties is attributed to an increase in the specific surface area and the role as a catalyst of the doped Co elements. These results suggest that Co-doped ZnOCNT composites are suitable for use as practical high-performance NO gas sensors.