• The Korean Journal of Ceramics
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• 제4권3호
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• pp.240-244
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• 1998

The analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composites using coal tar pitch as a matrix precursor at each cyle. Three factors were defined in analyzing the densification process: impregnation efficiency, retention efficiency, and overall densification efficiency. The relationships developed were applied to the experimental results for three densification cycles of C/C composites with pitches as an impregnant to evaluate the factors which may depend on the impregnant and on the route of carbonization. The impregnation efficiency increased with the repeated process cycles whereas the retention efficiency decreased irrespective of the impregnant and carbonization route. Carbonization route P+A+G, in which pressure carbonizationl (P) and graphitization (G) were done before after atmospheric pressure carboniztion (A) respectively, using impregnant of high carbon yields was the most effective method in densifying C/C composites.

• Carbon letters
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• 제6권3호
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• pp.173-180
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• 2005

In this study, AR (aromatic resin) pitch was employed as the matrix-precursor for carbon/carbon composite because it exhibits much higher coke yield than coal tar pitch. As a result, a fabrication process of carbon/carbon composites can be shortened. It has been known that the pitches may cause swolling problem during the carbonization process. In order to restrain the swelling occurrence, a small quantity of carbon black was added to the AR pitch. Due to addition of carbon black the swelling was decreased largely and the perform can be infiltrated with the AR pitch. The densification efficiency of the performs was compared with various matrix-precursors. The coke yield of matrixprecursors, the morphology and the degree of graphitization of carbon matrix were analyzed.

• Carbon letters
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• 제14권3호
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• pp.152-161
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• 2013

Needle coke is an important material for graphite electrodes. Delayed coking is used to produce needle coke. Producing good quality needle coke is not simple because it is a multi-parameter controlled process. Apart from that, it is important to understand the mechanism responsible for the delayed coking process, which involves mesophase formation and uniaxial rearrangement. Temperature and pressure need to be optimized for the different substances in every feedstock. Saturate hydrocarbon, aromatic, resin and asphaltene compounds are the main components in the delayed coking process for a low Coefficient Thermal Expansion value. In addition, heteroatoms, such as sulphur, oxygen, nitrogen and metal impurities, must be considered for a better graphitization process that prevents the puffing effect and produces better mesophase formation.

• 한국주조공학회지
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• 제6권4호
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• pp.290-297
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• 1986

Austempered ductile cast iron has been well known for their good toughness and strength. Generally these properties were improved by the various heat treatments and alloying elements. In this study, the effects of prior heat treatment history(near ferrite, near pearlite, near martensite) on the toughness and strength of the austempered ductile cast iron were studied experimentally and theoretically. All of the test specimens was austenitized at $900^{\circ}C$ for 1 h and austempered at $300^{\circ}C$, $350^{\circ}C$, $400^{\circ}C$, $450^{\circ}C$, respectively. The prior structure of near martensite in austempered ductile cast iron was not good in term of toughness and strength because the carbon content was apt to high in austenite during ausnitizing. It was found, on the other hand, that the ferrite matrix as prior structure had good combination of toughness and strenght. The best tensile strength and good toughness were obtained at $300^{\circ}C$, austemper in the prior structure of near ferrite, while $400^{\circ}C$ austemper in that of near pearlite and martensite.

• 한국광물학회지
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• 제1권1호
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• pp.48-62
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• 1988

The high aluminous meta-claystones are thinly bedded to metasedimentary rocks which belong to Chununsan Formation. Major high aluminous minerals in the ores ae andalusite, kaolinite and pyrophyllite. The other significant constituents are sericite, chloritoid and carbonaceous material, etc. Ores can be classified into 4 types according to mineral compositions; andalusite- kolinite-sericite, andalusite-kaolinite-chloritoid, kaolinite-sericite-pyrophyllite, and kaolinite-chloritoid-sericite ore. The formation of ore minerals are resulted from sedimentary, diagenetic, metamorphic and hydrothermal processes. Andalusite are formed by low-grade metamorphism under the conditions of $400~500^{\circ}C$ and below 4kb, from the view-point of mineral stability field, illite-mica crystallinity and graphitization degree of the carbonaceous material. Andalusites are partly altered to kaolinite, forming major mineral phase in the ores.

• Carbon letters
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• 제1권2호
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• pp.64-68
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• 2000

This paper describes the mechanical properties and oxidation resistance of carbon fibers with and without additions of boron oxide additives, and describes the changes in the properties resulting from increased heat treatment temperature (HTT) of the fibers. Carbon fibers in this experiment were heat treated up to $2800^{\circ}C$ each with and without boron oxide treated on the surface of fibers. In the case of boron oxide added carbon fibers, they do not show the improvement of tensile strength and modulus compared to those of no treated carbon fibers below $2200^{\circ}C$ since they are doped substitutionally with boron above $2600^{\circ}C$, which accelerate the graphitization of carbon fibers. Boron oxide implanted carbon fibers showed high resistance to oxidation, however, when carbon fibers were heat treated below $2200^{\circ}C$, they showed almost the same trend of air oxidation.

• 대한화학회지
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• 제13권4호
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• pp.395-399
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• 1969

On the soft carbon made from petroleum coke, it was found that the graphitization began at around 2,000$^{\circ}C and crystallite diameters were almost saturated at 2,400$^{\circ}C., and that the molecular planes were difficult to arrange into an ideal graphite lattice in spite of the saturation of crystallinity by heat treatment temperature. On the hard carbon made from cross-linked thermosetting plastics, phenol-formaldehyde filler and phenol-benzaldehyde binder, it was very difficult to rotate the molecular planes into a regular directional arrangement and into a consecutive order corresponding to the large graphite crystals. In addition to the above mentioned crystallinity, it was also determined in relation to electric conductivity, resistivity, hardness and apparent density of carbons.

• 한국주조공학회지
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• 제1권2호
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• pp.2-9
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• 1981

Graphite spheroidization and scaling resistance of cast iron containing 5-10% Al were investigated. It is impossible to obtain spheroidal graphite in cast iron containing Al with 8 % and over, but possible to obtain spheroidal graphite even in cast iron with an Al content of about 10 % by increasing Si content. In the scaling test carried out under the heating condition of $950^{\circ}C$ in air for total of 50 hours, the scaling resistance of cast iron containing Al with 8 % and over was remarkably superior, and also spheroidal graphite cast iron was superior to flake graphite cast iron. The scale became thinner more compacts and more protective with increasing Al content.

• 한국결정성장학회지
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• 제10권1호
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• pp.55-61
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• 2000

리튬이온전지의 음극재료로서 hard carbon에 PVC를 이용한 탄소를 코팅함으로써 비가역용량 감소와 가역용량 증가 등 전기화학적 특성이 향상되었다. 이러한 특성 향상은 PVC코팅에 의한 표면개질로 대기와의 반응을 억제함에 기인한 것으로 생각되며, 또한 Ni 첨가에 의해 PVC 탄소의 흑연화 정도를 조절할 수 있었으며, 이들과 관련된 전기화학적 특성을 비교 고찰하였다.

• 한국전기전자재료학회논문지
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• 제13권10호
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• pp.817-821
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• 2000

In this work, we have investigated the dependence of annealing temperature(T$\_$a/) on optical and electrical properties of amorphous hydrogenated SiC(a-SiC:H) films. The a-SiC:H films were deposited on corning glass and p-type Si(100) wafer by PECVD (plasma enhanced vapor deposition) using SiH$_4$+CH$_4$+N$_2$ gas mixture. The experimental results have shown that the optical energy band gap(E$\_$opt/)of the thin films annealed at high temperatures have shown that the graphitization of carbon clusters and micro-crystalline silicon occurs. The current-voltage characteristics have shown good electrical properties at the annealed films.