• Journal of the Korean Chemical Society
• /
• v.57 no.6
• /
• pp.691-696
• /
• 2013

Black carbon contributes to global warming and melting of polar ice as well as causing respiratory diseases. However, it is also an inexpensive, easily available carbon nano material for elementary chemistry experiments. In this study, black carbon samples collected from candle light and automobile exhaust pipes have been investigated to examine their compositions and surface characteristics. The observed broad G and D bands and amorphous $sp^3$ band in their Raman spectra as well as the high intensity of the D (defect) band reveal that black carbon is principally made of amorphous graphite. The black carbon deposits in automobile exhaust pipes are apparently more amorphous, probably due to the shorter time allowed for formation of the carbonaceous matter. An exceptionally large water contact angle ($159.7^{\circ}$) is observed on black carbon, confirming its superhydrophobicity. The surface roughness evidently plays an important role for the contact angle much larger than that of crystalline graphite ($98.3^{\circ}$). According to the Sassie-Baxter equation, less than 1% the area actually in contact with the water drop.

• Journal of the Korean institute of surface engineering
• /
• v.41 no.2
• /
• pp.63-68
• /
• 2008

Traditionally and generally used calcined clay was carburized, and its characteristics were studied. Carburization treatment was performed by the thermally decomposed carbon and the deposit carbon which occur in a so called 'Boudouard reaction $(2CO{\rightarrow}CO_2+C)'$ at fuel combustion process in a closed-type furnace. The color of the carburized calcine clay changed from yellow to black, and the carbon component revealed as crystalline graphite by the X-ray diffraction test. The weight of the carburized calcine clay decreased to about 4 wt.% by the 1st heating to $1400^{\circ}C$ in air but it does not decreased by the 2nd heating of the same conditions. By the carburization treatment, the water absorption changed from 13 wt.% to 6 wt.%, and the contact angle for water drop changed, too, from 0 to $87^{\circ}$ which was tested by the photograph of one minute after a water drop contact. It means the carburized calcine clay does not absorb water drop so it has a hydrophobic characteristic.

• Journal of Korea Foundry Society
• /
• v.25 no.3
• /
• pp.115-122
• /
• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.

• Resources Recycling
• /
• v.15 no.2 s.70
• /
• pp.37-44
• /
• 2006

The total amount of graphite reserves in Korea is about 260 thousand tons. Graphite larks international competitiveness it is mined in only few mines, but recently the demand of portable electronic has increased. Therefore a research for manufacturing domestic high purity graphite is necessary because all of high purity graphite used electrode of 2nd batter depends on expensive importation. A preprocessing level for producing high purity graphite, flotation was conducted using microbubble column machine. In this research $D_{50}=10.314{\mu}m$ sample was used which was produced after grinding 29.50% F.C. primary crushing sample($D_{50}=69.393{\mu}m$) for 20 minutes through attrition mill. As a result using this sample, product above 95% F.C. with recovery over 90% was obtained with only after first stage process through the microbubble column.

• Korean Journal of Materials Research
• /
• v.11 no.8
• /
• pp.679-684
• /
• 2001

The surface of natural graphite has not only good electrical conductivities and lubrication properties but also has strong hydrophobicity. There are no functional groups and chemical properties on it. It is difficult to join with any other ions and to disperse in aqueous system. In order to increase dispersion ability throughout modification of surface property, it is necessary to let graphite have some function on its surface by the adsorption of surfactant molecules. In this study, using zeta potential adsorbed surfactant molecules(ABDM) on graphite surface and its surface Properties turn hydrophobic into hydrophilic. The dispersing mechanism of graphite particles in aqueous system has been explained using the DLVO theory, It is concluded that the high dispersable graphite suspension of which dispersing stability$(T_{1/2})$ is 44.5 hours at pH 10 and 22.5mV zeta potential can be produced.

• Elastomers and Composites
• /
• v.49 no.1
• /
• pp.66-72
• /
• 2014

Carbon coating on silica particles is done by grafting expanded graphite on the silica aggregates. Successful coating of carbon is corroborated using FT-IR, TGA, XPS and TEM. Crystalline nature of coated graphite is corroborated using XRD. Influence of carbon coated silica particles on rheometric and mechanical properties of SBR composites are investigated. Carbon coated silica particles showed significant improvement in rheometric and mechanical properties, when compared to pristine silica filled system corroborating higher polymer-filler adhesion. This fact was further supported by bound rubber content and equilibrium swelling ratios of unvulcanized and vulcanized SBR composites.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.10
• /
• pp.1965-1968
• /
• 2008

The effects of carbon-coated silicon/graphite (Si/Gr.) composite anode on the electrochemical properties were investigated. The nanosized silicon particle shows a good cycling performance with a reasonable value of the first reversible capacity as compared with microsized silicon particle. The carbon-coated silicon/graphite composite powders have been prepared by pyrolysis method under argon/10 wt% propylene gas flow at $700{^{\circ}C}$ for 7 h. Transmission electron microscopy (TEM) analysis indicates that the carbon layer thickness of 5 nm was coated uniformly onto the surface silicon powder. It is confirmed that the insertion of lithium ions change the crystalline silicon phase into the amorphous phase by X-ray diffraction (XRD) analysis. The carbon-coated composite silicon/graphite anode shows excellent cycling performance with a reversible value of 700 mAh/g. The superior electrochemical characteristics are attributed to the enhanced electronic conductivity and low volume change of silicon powder during cycling by carbon coating.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.4
• /
• pp.11-15
• /
• 2008

Metrology tools with the ability to measure spindle motion error on the order of a nanometer are required due to recent advances in nanotechnology. We propose a direct measurement method for the radial motion error of a precision spindle using a regular crystalline lattice and a scanning tunneling microscope (STM). A highly oriented pyrolytic graphite (HOPG) crystal combined with an STM is used as a two-dimensional reference scale. The measurement principle and the preliminary experimental results are discussed in this article. The preliminary experimental results demonstrated that the proposed method has the capability to incorporate a two-dimensional encoder to measure the spindle motion error.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.5
• /
• pp.3627-3632
• /
• 2015

We investigated mechanical, rheological and electrical properties of graphite/PP/LCP composites for a bipolar plate of the polymer electrolyte membrane fuel cell. The composites containing very low molecular weighted PP showed much higher electrical conductivity compared with other thermoplastics. This was attributed to the enhanced dispersion of graphite particles due to the low viscosity of the PP. The conductivity of the composites was increased in a great extent by incorporation of small amount of carbon nano tube (CNT). However, the acid treated CNT which contains oxygen atoms did not increase the conductivity of the composite. From this result, it is concluded that the CNT has higher affinity with non polar polymer. The composite with low molecular weighted PP provided good processability so that the composites can be processed by an injection molding while the mechanical strength is deficient compared to other polymers. In order to reinforce the low mechanical property, LCP/PP was used as a binder and the graphite/PP/LCP composite showed the higher conductivity and moderate mechanical strength maintaining suitable processability.

• Journal of the Korean Ceramic Society
• /
• v.32 no.10
• /
• pp.1103-1110
• /
• 1995

Silicon carbide (SiC) films have been deposited on the isotropic graphite by chemical vapor deposition. Change of deposition parameters affected significantly the microstructure and preferred orientation of SiC films. Preferred orientation of SiC films was (111) or (220), and microstructure showed the startified structure consisting of small crystallite or faceted columnar structure depending on the deposition parameters. For microhardness, (111) oriented film and stratified structure were superior to (220) oriented film and faceted columnar structure, respectively. Surface of (111) oriented films was less rough than that of (220) oriented films. Adhesion force between graphite substrate and SiC films was above 100N for crystalline films and 49N for amorphous film.