• ALGAE
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• v.17 no.3
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• pp.195-199
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• 2002

We investigated the association of Chlorella vulgaris and E. coli W9110 in removal of total organic carbon with the lab-scaled continuous river water flow system (CRWFS). Artificial wastewater was applied at two levels of organic carbon concentration; 1,335 $mg{\cdot}l^{-1}$ in the treatment (T)-1 and 267 $mg{\cdot}l^{-1}$ in T-2. The highest densities of C. vulgaris were $8.3{\times10^6\;cells{\cdot}ml^{-1}$ in T-1 and $6.9{\times}10^6\;cells{\cdot}ml^{-1}$ in T-2. The maximum densities of E. coli W3110 were $2.0{\times}10^8$ clony forming unit (CFU)${\cdot}ml^{-1}$ in T-1 and $3.9{\times}10^8\;CFU{\cdot}ml^{-1}$ in T-2. The densities increased during the first 11 days in T-q and 4 days in T-2, and decreased rapidly till 35th day, then increased slightly afterwards. This trend was prominent in T-2. It was inplied that wider range of nutrients was required in the growth of heterotrophic bacteria in T-2 than in T-1. The algal biomass should be increased effectively for the successful removal of organic carbon.

• Journal of the Korean institute of surface engineering
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• v.28 no.3
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• pp.133-141
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• 1995

The deposition characteristics of diamond films were investigated for three different substrates : Si, Inconel 600 and steel. Diamond films were prepared by microwave plasma CVD method using $CH_4$, $H_2$ and $O_2$ as reaction gases. The deposited films were analyzed with SEM, Raman spectroscopy and ellipsometer. For Si substrate, diamond films were successfully obtained for most of the deposition conditions used in this study. As the $CH_4$ flow rate decreased and the $O_2$ flow rate increased, the quality of the film was improved due to the reduced non-diamond phase in the film. For Inconel 600 substrate, the surface pretreatment with diamond powders was required to deposit a continuous diamond film. The films deposited at temperatures of $600^{\circ}C$ and $700^{\circ}C$ had mainly diamond phase, but they were peeled off locally due to the difference in the thermal expansion coefficient between the substrate and the deposited films. The films deposited at $500^{\circ}C$ and $850^{\circ}C$ had only the graphitic carbon phase. For steel substrate, all of the films deposited had only the graphitie carbon phase. We speculated that the formation of diamond nuclei on the steel substrate was inhibited due to the diffusion of carbon atoms into the steel substrate which has a large amount of carbon solubility.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.42-48
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• 2020

Given the increasing interest in air pollution, several technologies to measure black carbon (BC) aerosol particles have been developed. As most BC aerosol particles are smaller than 1 ㎛, it is necessary to pre-separate the particles by size before a BC measuring instrument samples the aerosol particles. In this study, a miniature cyclone separator for portable BC measuring instruments was developed. A numerical approach was used to design the miniature cyclone separator with operating flow rates of 50, 100, or 150 mLPM, and then a prototype cyclone separator was manufactured for experimental validation. The numerical results of the cut-off size and pressure drop of the miniature cyclone separator agreed well with the experimental data. The cut-off sizes of the miniature cyclone separator were determined to be 2.9, 0.94, and 0.63 ㎛ for operating flow rates of 50, 100, and 150 mLPM, respectively. Thus, the miniature cyclone separator is suitable for use as a sampling inlet for the portable black carbon measuring instrument to sample BC aerosol or PM2.5 aerosol.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1331-1335
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• 2010

A novel spherical carbon composite material, in which nanosized disordered carbons are dispersed in a soft carbon matrix, has been prepared and investigated for use as a potential anode material for lithium ion batteries. Disordered carbons were synthesized by ball milling natural graphite in air. The composite was prepared by mixing the ball-milled graphite with petroleum pitch powder, pelletizing the mixture, and pyrolyzing the pellets at $1200^{\circ}C$ in an argon flow. The ballmilled graphite consists of distorted nanocrystallites and amorphous phases. In the composite particle, nanosized flakes are uniformly distributed in a soft carbon matrix, as revealed by X-ray diffractometer (XRD) and transmission electron microscopy (TEM) experiments. The composite is compatible with a pure propylene carbonate (PC) electrolyte and shows high rate capability and excellent cycling performance. The electrochemical properties are comparable to those of hard carbon.

• Carbon letters
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• v.3 no.1
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• pp.25-32
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• 2002

Aligned multi-wall carbon nanotubes (MWNTs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. In this study, we investigated the influence of reaction parameters such as gas flow rate, ferrocene-xylene ratio and partial pressure, and reaction time on the yield and structure of vertically aligned carbon nanotubes produced by the floating catalyst method. The MWNTs produced had diameters in the range of 20~l00 nm, length around $100{\mu}m$ and bulk density about $0.51g/cm^3$ at a pressure of l0000 psi. It was possible to produce MWNTs with much faster growth rate of $12{\mu}m/min$ than that reported previously by the increase of ferrocene-xylene partial pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.274-286
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• 2003

Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.37-41
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• 2008

The effects of carbon-coated silicon anode on the electrochemical properties and structural change were investigated. The carbon-coated silicon powders have been prepared by thermal decomposition under argon/10wt% propylene mixed gas flow at $700^{\circ}C$. The surface and crystal structure of the synthesized materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Lithium cells with electrodes made from the uncoated and the carbon coated silicon anode were assembled and tested. The carbon-coated silicon particles merged together well after the insertion/extraction of lithium ions, and showed a relatively low irreversible capacity compared with the uncoated silicon particle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.473-474
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• 2006

Aligned carbon nanotubes(CNTs) array were synthesized using direct current plasma-enhanced chemical vapor deposition. The nickel microgrids catalyzed the growth of carbon nanotubes which take on the area of the nickel microgrids. Selective growth of areas of nanotubes was achieved by patterning the nickel film. CNTs were grown on the pretreated substrates at 30% $C_2H_2:NH_3$ flow ratios for 10min. Carbon nanotubes with diameters about 20 nanometers and lengths approximately 720 nanometers were obtained. Morphologies of carbon nanotubes were observed by FE-SEM and TEM.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.568-572
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• 2009

The adsorption characteristics of tartrazine by granular activated carbon were experimentaly investigated in the batch adsorber and the packed column. The adsorptivity of activated carbon for tartrazine was largely improved by pH control, and 98 percent of initial concentration could be removed at pH 3. It was estabilished that the adsorption equilibrium of tartrazine on granular activated carbon was sucessfully fitted by Freundlich isotherm equation in the concentration range from 50 mg/L to 1,000 mg/L. The characteristics of breakthrough curve of activated carbon packed column, which depend on the design variables such as initial concentration, bed height, and flow rate, were studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.116-123
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• 2009

Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5nm Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission electron microscopy (TEM), Energy-dispersive spectra (EDS) and X-ray diffraction (XRD). Crystalinity and surface bonding groups of carbon are investigated through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.