• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.974-980
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• 1998

This study is concerned with the production of carbon fiber reinforced carbon(C/C) with polyaromatic mesophase pitch as matrix precursor and with the investigation of friction-wear characteristics in ambient air using a constant speed type of friction tester. The main problem in using the polyaromatic mesophase as the matrix precursor is the high viscosity which may limit the complete impregnation of the fiber preform in the vacuum. To solve these problems two dimensional carbon fiber fabrics were infiltrated with meso-phase pitch in the pitch impregnator. After the impregnation and the heat treatment process. C/C com-posites were characterized by density porosity to monitor the influence of high pressure and temperature. It showed that the bulk density was increased and the apparent porosity and the density increasing rate was reduced as repeating the impregnation the carbonization and the heat treatment. The friction-wear charac-teristics of C/C composites were investigated by measuring the average friction coefficient and the specific wear rate as functions friction speed and friction pressure using a constant speed type of friction tester. C/C composite4s showed the average friction coefficient to be reduced as increasing the friction speed and the friction pressure.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.706-713
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• 2015

Graphite foams (GFs) were prepared by adding different amounts of mesophase pitch (MP) into polyvinyl alcohol-acrylic acid (PVA-AAc) solution followed by the heat treatment. It was confirmed that the pore diameters of GFs were controlled by the slurry concentration, which was the mesophase content added in polymer solution, and their thermal conductivity and compressive strength were also controlled by porosities of GFs formed at different conditions. The resulting GFs in this study had the highest thermal conductivity of $53.414{\pm}0.002W/mK$ and compressive strength of $1.348{\pm}0.864MPa$ at 0.69 in porosity. The thermal conductivity of MP based GFs increased approximately 23 times higher than that of using isotropic pitch based GFs due to the developed graphitic structure.

• Carbon letters
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• v.11 no.4
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• pp.304-310
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• 2010

To manufacture a carbon/carbon composite the coal tar pitch was used as the matrix precursor and the PAN (polyacrylonitrile)-based carbon fiber was used as the reinforcing material to weave 3-directional preform. For pressure carbonization HIP equipment was used to produce a maximum temperature of $1000^{\circ}C$ and a maximum pressure of 100 MPa. The carbonization was induced by altering the dwell temperature between $250^{\circ}C$ and $420^{\circ}C$, which is an ideal temperature for the moderate growth of the mesophase nucleus that forms within the molten pitch during the pressure carbonization process. The application of high pressure during the carbonization process inhibits the mesophase growth and leads to the formation of spherical carbon particles that are approximately 30 nm in size. Most particles were spherical, but some particles were irregularly shaped. The spread of the carbon particles was larger on the surface of the carbon fiber than in the interior of the matrix pocket.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.985-990
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• 2003

By heat treating coal tar pitch between 450∼500$^{\circ}C$, mesophase pitch could be obtained. Subsequently, this pitch was oxi-stabilized between 160∼240$^{\circ}C$ in air for the purpose of reducing swelling and distortion. The mechanism of stabilization was analysed using the thermo-gravity and FT-IR. To investigate the effect of oxi-stabilization, the shore hardness and bending stress were measured with carbonized green body which was made from oxi-stabilized coal tar pitch.

• Carbon letters
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• v.2 no.3_4
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• pp.182-191
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• 2001

Quinoline insoluble formed by the heat treatment was hot-pressed near its softening point. The green body was stabilized in the temperature range of $300{\sim}400^{\circ}C$ and subsequently carbonized below $1300^{\circ}C$ in an argon atmosphere. The behaviors of QI formation was examined with varying the heat treatment temperature and the lapse of time of the sample carbonized at various temperatures. And the mechanical property, corrosion resistance, and friction behavior were also measured optimum content of mesophase pitch ensured a dense structure and high $LC_{(002)}$ value, which resulted in high mechanical properties, good corrosion resistance, and low-stable friction behavior.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.908-916
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• 1991

The characteristics of the carbonized and calcined products made from coal tar pitch coke and coal tar pitch, were investigated in the aspect of the manufacture of isotropic graphite with high density. The mesophase from the pitch was rapidly formed at higher heat-treatment temperature between 410$^{\circ}C$ and 450$^{\circ}C$, where the insolubes in the pitch accelerated the rate of nucleation and growth of the mesophase. The benzene insolubles and the quinoline insolubes were increased as the heat treatment temperature and the heat-treatment time increased. The ratio of benzene insolubles and quinoline solubles (BI/QS) was decreased as the heat-treatment temperature was higher and maintained to be nearly constant regardless of heat-treatment time at fixed heat treatment temperature. The bulk density of the calcined carbon was linearly proportional to the ratio of quinoline solubes to volatile matter in the green coke. Anisotropic ratio of electrical resistance was measured to be between 0.98 and 1.10.

• Carbon letters
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• v.19
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• pp.89-98
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• 2016

Taguchi’s experimental design was employed in the melt spinning of molten mesophase pitch to produce carbon fibers. The textures of the obtained carbon fibers were radial with varied crack angles, as observed by scanning electron microscopy and polarized optical imaging. The diameter, crack angle, preferred orientation, and tensile modulus of the produced samples were examined to investigate the influence of four spinning variables. The relative importance of the variables has been emphasized for each characteristic. The results show that thicker carbon fiber can be obtained with a smaller entry angle, a higher spinning temperature, a reduced winding speed, and an increased extrusion pressure. The winding speed was found to be the most significant factor in relation to the fiber diameter. While it was observed that thicker carbon fiber generally shows improved preferred orientation, the most important variable affecting the preferred orientation was found to be the entry angle. As the entry angle decreased from 120° to 60°, the shear flow was enhanced to induce more ordered radial alignment of crystallite planes so as to obtain carbon fibers with a higher degree of preferred orientation. As a consequence, the crack angle was increased, and the tensile modulus was improved.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.421-430
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• 2016

To prepare mesophase pitches through low energy process, pyrolysis fuel oil with $AlCl_3$ has been modified using two-step heat treatment which is heat-treated at $330^{\circ}C$ for 3~5 h after pre-treatment at $250^{\circ}C$. The result of polarized optical microscope observation, mesophase is not observed in pitches carried out only pre-heat treatment. While mesophase content is significantly increased from 9% to 100% according to increasing secondary heat treatment time from 3 h to 5 h. Synthesizing of the mesophase pitch at low temperature of $330^{\circ}C$ is attributed to decrease of viscosity of the pitches carried out first heat treatment with $AlCl_3$. The result of Fourier-transform infrared spectroscopic analysis, it is expected that aromatization of aliphatic compounds is dominant at early secondary heat treatment, on the other hand, polycondensation reaction becomes dominant as secondary heat treatment time increases. Aromaticity and stacking height of the pitches secondary heat treated for 5 hours are more increased about 25% and 107%, respectively, than that of pitches carried out only first heat treatment.

• 한국기계연구소 소보
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• s.15
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• pp.37-46
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• 1985

Properties of Precursor pitch derived from petroleum residue were studied physical and chemical analysis method for investigation of production of pitch fiber. For preparing of those precursor pitches it was carried out a temperature and time variation experiment i reactor. It was demonstrated the precursor pitch prepared in this study to have a similar properties to Ashland precursor pitch capable of bulk mesophase formation from the results of the basic analysis, that is, molecular weight distribution, coking yield, carbon content, chemical composition, etc.

• Proceedings of the Korean Fiber Society Conference
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• 1991.06b
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• pp.27-28
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• 1991