• Fibers and Polymers
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• 제1권2호
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• pp.97-102
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• 2000

Pitch precursors were synthesized from coal tar(CT) and pyrolysis fuel oil(PFO, petroleum residue oil) at relatively low temperature of $250^{\circ}$, in the presence of horontrifluorideidiethyletherate complex(BFDE) as a catalyst and nitrobenzene(NB) as a co-catalyst. The softening point, nitrogen content and carbon yield increased with an increase of concentration of NB. The pitch precursors with good spinnability were prepared by removing the volatile components through $N_2$ blowing. The precursor pitches were spun through a circular nozzle, stabilized at $310^{\circ}$ and finally carbonized at $1000^{\circ}$. The optically anisotropic structure formed at the absence of NB was changed into isotropic structure, showing a decrease in size of the flow domain. The hollow carbon fiber could be prepared in the process of stabilization. The results proposed that the morphology of carbon materials could be controlled by changing the concentration of catalyst and/or co-catalyst and/or stabilization condition that affect on the mobility of molecules during carbonization.

• 한국응용과학기술학회지
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• 제22권2호
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• pp.91-95
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• 2005

Carbon composites were prepared with pitch-based round, C, hollow-type carbon fibers and pitch matrix. The thermal conductivities parallel and perpendicular to the fiber axis were measured by steady-state method. It was found that the thermal conductivities depended on the cross-sectional forms of the reinforcing fibers as well as the reinforcing orientation and carbon fiber precusors. Especially, mesophase pitch-based hollow carbon fiber-carbon composites had the most excellent thermal anisotropy, which was above 100.

• Carbon letters
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• 제10권3호
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• pp.202-207
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• 2009

Pitch-based carbon fiber tows were prepared from naphtha cracking bottom oil by reforming and carbonization. The relationship between exothermic heat and carbon contents of the fiber was investigated by changing the carbonization conditions. The carbon contents and the crystallinities of isotropic pitch-based carbon fibers were 86.8~93.8 wt% and 33.7~40.1%, respectively, which were linearly proportional to the increase of carbonization temperature from 700 to $1000^{\circ}C$. The exothermic heat (temperature increase) of fiber tows was measured in a short time, which was also linearly proportional to the increase of carbon contents due to the increase of crystallinity, even though the crystallinity was low. Therefore, the carbon contents or carbonization degree of fibers can rapidly and indirectly be estimated by measuring the surface temperature increase of fibers.

• 공업화학
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• 제31권1호
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• pp.36-42
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• 2020

산화 공정이 피치의 열거동 특성에 미치는 영향을 규명하기 위하여 다양한 공정 온도에서 산화된 피치를 제조하였다. 피치의 열거동 특성은 thermogravimetric analysis (TGA)를 이용하여 분석하였으며, derivative thermogravimetry (DTG) 그래프 거동 변화에 따라 A (25~100 ℃), B (250~550 ℃), C (550~800 ℃) 세 구간으로 분석하였다. A 구간에서는 피치에 함유되어 있던 수분이 제거되면서 중량 감소가 발생하였다. B 구간에서 산화에 의하여 피치의 열적 안정성이 향상되었다. 이는 산화 온도가 증가할수록 피치의 방향족화도 및 분자량이 증가하였기 때문으로 판단된다. 반면, C 구간에서는 B 구간과 반대의 결과를 보였다. C 구간에서 열적 안정성이 저해된 것은 산화 공정에 의하여 피치에 도입된 C-OH, C-O-C, C=O 결합이 분해되고, 이에 의하여 발생한 산소 화합물이 피치의 연소 반응을 유도하였기 때문으로 사료된다.

• Carbon letters
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• 제1권3_4호
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• pp.165-169
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• 2001

The C-type mesophase pitch-based carbon fiber (C-MPCF) was prepared throuch C-type spinnerette and compared the mechanical properties to those of round type mesophase pitch fiber (R-MPCF) and C-type isotropic pitch fiber (C-iPCF). The tensile strength and modulus of C-MPCF were about 18.6% and 35.7% higher than those of R-MPCF. The tensile strength of C-MPCF was 62% higher than that of C-iPCF of the same $8{\mu}m$ thickness because of more linear transverse texture, which could be easily converted to graphitic crystallinity during heat treatment. The torsional rigidity of C-MPCF was 2.37 times higher than that of R-MPCF. The electrical resistivity of C-MPCF was $8{\mu}{\Omega}{\cdot}m$. The C-iPCF shows far lower electrical resistivity than R-iPCF as well as the mesophase carbon fiber because of better alignment of texture to the fiber axis.

• Carbon letters
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• 제1권1호
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• pp.6-11
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• 2000

Coal tar pitch was chemically modified with 10 wt% benzoquinone (BQ) to raise the softening point of isotropic pitch precursor and the precursor was melt-spun into pitch fibers, stabilized, carbonized and activated with steam at $900^{\circ}C$. The weight loss of carbon fiber-benzoquinone (CF-BQ) increased with the increase of activation time like other fibers, but was lower than those of Kureha fiber at the same activation time in spite of larger geometric surface area. Those adsorption isotherms fitted into 'Type I' according to Brunauer, Deming, Deming and Teller classification. However, there was very thin low-pressure hysteresis that lower closure points of the hysteresis are about 0.42-0.45. From the pore size distribution curves, there might be some micropores having narrow-necked bottle; a series of interconnected pore is more likely than discrete bottles. FT-IR studies showed that the functional groups such as carboxyl, quinone, and phenol were introduced to ACFs-BQ surface after steam activation. Methylene blue decolorization and iodine adsorption capacity of ACF-BQ increased linearly with the increase of specific surface area and was larger than that of ACF-Kureha at the same specific surface area.

• Carbon letters
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• 제6권1호
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• pp.1-5
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• 2005

Isotropic pitch based carbon fibers were exposed to isothermal oxidation in carbon dioxide gas to study the activation kinetics under the temperature of 800~$1100^{\circ}C$. The kinetic equation $f=1-{\exp}(-at^b)$ was introduced and the constant b was obtained in the range of 0.92~1.25. It was shown that the activated carbon fiber shows the highly specific surface area (SSA) when the constant b comes close to 1. The activation kinetics were evaluated by the reaction-controlling regime (RCR) according to changes of the apparent activation energy with changes of the conversion. It was observed that the activation energies increase from 47.6 to 51.2 kcal/mole with the conversion increasing from 0.2 to 0.8. It was found that the pores of the activated carbon fiber under the chemical reaction were developed well through the fiber.

• Carbon letters
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• 제15권4호
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• pp.247-254
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• 2014

In this work, thermal treatment accompanied with different acid treatments was applied to a commercial coal tar pitch (CTP) to obtain a spinnable precursor pitch for carbon fiber. In the case of thermal treatment only, a relatively high reaction temperature of between $380^{\circ}C$ and $400^{\circ}C$ was required to obtain a softening point (SP) range of $220^{\circ}C-260^{\circ}C$ and many meso-phase particles were created during the application of high reaction temperature. When nitric acid or sulfuric acid treatment was conducted before the thermal treatment, the precursor pitch with a proper SP range could be obtained at reaction temperatures of $280^{\circ}C-300^{\circ}C$, which were about $100^{\circ}C$ lower than those for the case of thermal treatment only. With the acid treatments, the yield and SP of the precursor pitch increased dramatically and the formation of meso-phase was suppressed due to the lower reaction temperatures. Since the precursor pitches with acid and thermal treatment were not spinnable due to the inhomogeneity of properties such as molecular weight distribution and viscosity, the CTP was mixed with ethanol before the consecutive nitric acid and thermal treatments. The precursor pitches with ethanol, nitric acid, and thermal treatments were easily spinnable, and their spinning and carbon fiber properties were compared to those of air blowing and thermal treated CTP.

• Carbon letters
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• 제3권2호
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• pp.80-84
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• 2002

The surface treatment of C-type isotropic pitch-based carbon fiber was carried out by anodic oxidation in 5 wt% $NH_4NO_3$ electrolyte. The changes of fiber surface and carbon fiber/ABS resin composites were characterized by SEM, XPS and mechanical properties test. The oxygen functional groups on the surface, such as hydroxyl (-C-OH), carboxyl (-COOH) groups etc., increased after oxidation. Tensile strength, flexural strength and modulus of carbon fiber/ABS composites were also enhanced. However, the impact strength decreased with the improvement of the surface adhesion between CF and matrix.

• 한국기계연구소 소보
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• 통권13호
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• pp.15-25
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• 1984

The infrared spectra were determined to discover the characteristics and properties of poff-, PV-, and cc-samples, and studied influence on the formation of mesophase or liquid crystal. The experimental results were as follows; a) Samples with long aliphatic side chain appear cracking texture on temperature forming liquid crystal. b) The fine isotropic microstructure appears in a heterogeneous material containing sulfur, 7.18 w%. c) In the size of molecular weight the lighter than 500 form liquid crystal. d) When poff-sample was treated at $400^{\circ}C$ aliphatic hydrocabon compounds decrease, presented well-oriented bulk liquid crystal.