• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.57-63
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• 2017

High-purity ${\beta}-SiC$ powders for SiC single-crystal growth were synthesized by direct carbonization. The use of high-purity raw materials to improve the quality of a SiC single crystal is important. To grow SiC single crystals by the PVT method, both the particle size and the packing density of the SiC powder are crucial factors that determine the sublimation rate. In this study, we tried to produce high-purity ${\beta}-SiC$ powder with large particle sizes and containing low silicon by introducing a milling step during the direct carbonization process. Controlled heating improved the purity of the ${\beta}-SiC$ powders to more than 99 % and increased the particle size to as much as ${\sim}100{\mu}m$. The ${\beta}-SiC$ powders were characterized by SEM, XRD, PSA, and chemical analysis to assess their purity. Then, we conducted single-crystal growth experiments, and the grown 4H-SiC crystals showed high structural perfection with a FWHM of about 25-48 arcsec.

• Fire Science and Engineering
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• v.34 no.4
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• pp.101-106
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• 2020

This study analyzed flame growth characteristics and carbonization patterns when floor materials were burned vertically using a needle flame produced for this study. It was found that PVC flooring was fire retardant and the area under direct flame contracted inward. Vertical combustion causes solidification in the form of a lump at the bottom and also generates soot in a pattern that progresses upwards. This study found that laminated flooring exhibited no fire retarding characteristics and that the laminated layer of its upper surface was destroyed by fire, causing irregular delamination. The carbonization ranges at the left and right sides were determined to be symmetrical. A vertical combustion test of a sample carpet showed that it exhibited no fire-retarding characteristics. It was observed that if heat accumulated in the carpet, the flame formed an ascending air current, and that when flammable materials were present around the flame, they further accelerated the diffusion of the flame. The carbonization pattern at the carpet surface exposed to direct flame revealed that the carpet surface had melted and had flown downwards and that many tiny holes formed on it.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.35-40
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• 2018

Nd:YAG laser was used to carbonize polyimide films to produce carbon films. This is a simple manufacturing process to fabricate low cost sensors. By applying this method, we studied characteristics of flexible and low-cost piezoresistive. Previously, many studies focused on carbonization of polyimide using $CO_2$ laser with wavelength of $10.6{\mu}m$. In this paper, carbonization (carbonization process) was performed on polyimide films using an Nd:YAG laser with a wavelength of $1.064{\mu}m$. In order to increase the resolution, we optimized the laser conditions of the power density ($W/cm^2$) and the beam scan rate. In previous studies using $CO_2$ laser, the minimum line width was $140{\sim}220{\mu}m$ but in this study, carbon line width was reduced to $35{\sim}40{\mu}m$. The initial sheet resistance of the carbon sensor was $100{\sim}300{\Omega}/{\square}$. The resistance decreased by 30% under stretched with a curvature radius of 21 R. The calculated gauge factor was 56.6. This work offers a simple, highly flexible, and low-cost process to fabricate piezoresistive sensors.

• Carbon letters
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• v.22
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• pp.25-35
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• 2017

The aim of the work was to investigate the thermo-electrical properties of low cost and rapidly produced randomly oriented carbon/carbon (C/C) composite. The composite body was fabricated by combining the high-pressure hot-pressing (HP) method with the low-pressure impregnation thermosetting carbonization (ITC) method. After the ITC method step selected samples were graphitized at $3000^{\circ}C$. Detailed characterization of the samples' physical properties and thermal properties, including thermal diffusivity, thermal conductivity, specific heat and coefficient of thermal expansion, was carried out. Additionally, direct current (DC) electrical conductivity in both the in-plane and through-plane directions was evaluated. The results indicated that after graphitization the specimens had excellent carbon purity (99.9 %) as compared to that after carbonization (98.1). The results further showed an increasing trend in thermal conductivity with temperature for the carbonized samples and a decreasing trend in thermal conductivity with temperature for graphitized samples. The influence of the thickness of the test specimen on the thermal conductivity was found to be negligible. Further, all of the specimens after graphitization displayed an enormous increase in electrical conductivity (from 190 to 565 and 595 to 1180 S/cm in the through-plane and in-plane directions, respectively).

• Carbon letters
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• v.15 no.1
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• pp.15-24
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• 2014

As a part of the electromagnetic spectrum, microwaves heat materials fast and efficiently via direct energy transfer, while conventional heating methods rely on conduction and convection. To date, the use of microwave heating in the research of carbon-based materials has been mainly limited to liquid solutions. However, more rapid and efficient heating is possible in electron-rich solid materials, because the target materials absorb the energy of microwaves effectively and exclusively. Carbon-based solid materials are suitable for microwave-heating due to the delocalized pi electrons from sp2-hybridized carbon networks. In this perspective review, research on the microwave heating of carbon-based solid materials is extensively investigated. This review includes basic theories of microwave heating, and applications in carbon nanotubes, graphite and other carbon-based materials. Finally, priority issues are discussed for the advanced use of microwave heating, which have been poorly understood so far: heating mechanism, temperature control, and penetration depth.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.539-543
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• 2014

Foam type porous silicon carbide ceramics were fabricated by a polymer replica method using polyurethane foam, carbon black, phenol resin, and silicon powder as raw materials. The influence of the C/Si mole ratio of the ceramic slurry and heat treatment temperature on the porous silicon carbide microstructure was investigated. To characterize the microstructure of porous silicon carbide ceramics, BET, bulk density, X-ray Powder Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were employed. The results revealed that the surface area of the porous silicon carbide ceramics decreases with increased heat treatment temperature and carbon content at the $2^{nd}$ heat treatment stage. The addition of carbon to the ceramic slurry, which was composed of phenol resin and silicon powder, enhanced the direct carbonization reaction of silicon. This is ascribed to a consequent decrease of the wetting angles of carbon to silicon with increasing heat treatment temperature.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.113-118
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• 2015

To improve the methanol electro-oxidation in direct methanol fuel cells(DMFCs), Pt electrocatalysts embedded on porous carbon nanofibers(CNFs) were synthesized by electrospinning followed by a reduction method. To fabricate the porous CNFs, we prepared three types of porous CNFs using three different amount of a styrene-co-acrylonitrile(SAN) polymer: 0.2 wt%, 0.5 wt%, and 1 wt%, respectively. A SAN polymer, which provides vacant spaces in porous CNFs, was decomposed and burn out during the carbonization. The structure and morphology of the samples were examined using field emission scanning electron microscopy and transmission electron microscopy and their surface area were measured using the Brunauer-Emmett-Teller(BET). The crystallinities and chemical compositions of the samples were examined using X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties on the methanol electro-oxidation were characterized using cyclic voltammetry and chronoamperometry. Pt electrocatalysts embedded on porous CNFs containing 0.5 wt% SAN polymer exhibited the improved methanol oxidation and electrocatalytic stability compared to Pt/conventional CNFs and commercial Pt/C(40 wt% Pt on Vulcan carbon, E-TEK).

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3576-3582
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• 2014

Zeolite-templated carbons (ZTCs), which have high specific surface area, were prepared by a conventional templating method using microporous zeolite-Y for catalyst supports in direct methanol fuel cells. The ZTCs were synthesized at different temperatures to investigate the characteristics of the surface produced and their electrochemical properties. Thereafter, Pt-Ru was deposited at different carbonization temperatures by a chemical reduction method. The crystalline and structural features were investigated using X-ray diffraction and scanning electron microscopy. The textural properties of the ZTCs were investigated by analyzing $N_2$/77 K adsorption isotherms using the Brunauer-Emmett-Teller equation, while the micro- and meso-pore size distributions were analyzed using the Barrett-Joyner-Halenda and Harvarth-Kawazoe methods, respectively. The surface morphology was characterized using transmission electron microscopy and inductively coupled plasma-mass spectrometry. The electrochemical properties of the Pt-Ru/ZTCs catalysts were also analyzed by cyclic voltammetry measurements. From the results, the ZTCs carbonized at $900^{\circ}C$ show the highest specific surface areas. In addition, ZTC900-PR led to uniform dispersion of Pt-Ru on the ZTCs, which enhanced the electro-catalytic activity of the Pt-Ru catalysts. The particle size of ZTC900-PR catalyst is about 3.4 nm, also peak current density from the CV plot is $12.5mA/cm^2$. Therefore, electro-catalytic activity of the ZTC900-PR catalyst is higher than those of ZTC1000-PR catalyst.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.64-69
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• 2013

The various promotion countermeasures such as solidification, carbonization, and the creation of cement materials have been considered to existing treatment methods such as incineration and the creation of composts, since direct landfill was prohibited for encouraging the recycling based on the sludge treatment on land. The Main objective of this study is to investigate the feasibility of co-incineration for MSW (municipal solid waste) and SS (sewage sludge) through the quantitative supply of sewage sludge. In this study, optimum water content to operate normally incinerator is 85%. In order to increase the workability of sewage sludge, it is necessary to supply properly water. In the case study of sites, optimum water content is 87% due to the water evaporation. Therefore, it was found that the water content up to 87% would be reached the stable operation of co-incinerator on the mixture of municipal waste solid and sewage sludge.

• Journal of Adhesion and Interface
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• v.14 no.2
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• pp.82-87
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• 2013

Preliminary studies on the synthesis of magnetic nanoparticles including nanoporous carbon materials have been done via a direct carbonization process from resol, ferric nitrate and triblock copolymer F127. The results show that the nanoporous magnetite/carbon ($Fe_3O_4$/carbon) with a low $Fe_3O_4$ content (1 wt%) possesses an ordered 2-D hexagonal (p6mm) structure, uniform nanopores (3.6 nm), high surface areas (up to 635 $m^2/g$) and pore volumes (up to 0.48 $cm^3/g$). Magnetite nanoparticles with a small particle size (10.2 nm) were confined in the matrix of amorphous carbon frameworks with superparamagnetic property (7.7 emu/g). The nanoporous magnetite/carbon showed maximum adsorption amount (995 mg/g) of ibuprofen after 24 h at room temperature. The nanoporous magnetite/carbon was separated from solution easily by using a magnet. The nanoporous magnetite/carbon material is a good adsorbent for hydrophobic organic drug molecules, i.e. ibuprofen.