• Carbon letters
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• 제6권4호
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• pp.234-242
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• 2005

Bending and tensile properties of 2D cross-ply C/C composites with processing heat treatment temperature (HTT) are evaluated. C/C composites used are made from two types of PAN based T700 and M40 carbon fibers with phenolic resin as carbon matrix precursor. Both the types of composites are heat treated at different temperatures (ranging from 750 to $2800^{\circ}C$) and characterized for bending and tensile properties. It is observed that, real density and open porosity increases with HTT, however, bulk density does show remarkable change. The real density and open porosity are higher in case T-700 carbon fiber composites at $2800^{\circ}C$, even though the density of M40 carbon fiber is higher. Bending strength is considerably greater than tensile strength through out the processing HTT due to the different mode of fracture. The bending and tensile strength decreases in both composites on $1000^{\circ}C$ which attributed to decrease in bulk density, thereafter with increase in HTT, bending and tensile strength increases. The maximum strength is in T700 fiber based composites at HTT $1500^{\circ}C$ and in M40 fiber based composites at HTT $2500^{\circ}C$. After attending the maximum value of strength in both types of composite at deflection HTT, after that strength decreases continuously. Decrease in strength is due to the degradation of fiber properties and in-situ fiber damages in the composite. The maximum carbon fiber strength realization in C/C composites is possible at a temperature that is same of fiber HTT. It has been found first time that the bending strength more or less 1.55 times higher in T700 fiber composites and in M40 fiber composites bending strength is 1.2 times higher than that of tensile strength of C/C composites.

• 대한수학회논문집
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• 제23권2호
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• pp.257-268
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• 2008

Let G and K be compact subgroups of orthogonal groups and $0{\leq}r<x<{\infty}$. We prove that every topological fiber bundle over a definable $C^r$ manifold whose structure group is K admits a unique strongly definable $C^r$ fiber bundle structure up to definable $C^r$ fiber bundle isomorphism. We prove that every G vector bundle over an affine definable $C^rG$ manifold admits a unique strongly definable $C^rG$ vector bundle structure up to definable $C^rG$ vector bundle isomorphism.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.31-41
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• 1998

Single fiber fragmentation technique was used to evaluate the change of interfacial properties by degradation of fiber tensile strength in the fiber reinforced composites. The influences of fiber tensile strength on the interfacial properties have been evaluated by the fragmentation specimens(weak fiber samples) of glass fiber/epoxy resin that was made using the pre-degraded glass fiber in distilled water at $80^{circ}C$ for specified periods. The effects of the immersion time on the interfacial properties in the distilled water at $80^{circ}C$ also have been evaluated by the fragmentation specimens(original fiber samples) of glass fiber/epoxy resin that was made using the received glass fiber. As the result, the tensile strength of glass fiber was decreased with the increasing of the treatment time in the distilled water at $80^{circ}C$ and the interfacial shear strength was independent of the change of the glass fiber strength in the single fiber fragmentation test. But in the durability test using the single fiber fragmentation specimen, interfacial shear strength decreased with the increasing of the immersion time in distilled water ar $80^{circ}C$. And it turned out that the evaluating of interfacial shear strength using original fiber tensile strength was valuable in the durability test for the water environment by the single fiber fragmentation technique.

• 한국염색가공학회지
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• 제12권5호
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• pp.308-314
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• 2000

The dyeability of C. I. Disperse Violet 1 on polyester fiber in alkance including a small amount of water was investigated. Up to 1% of water in alkanes the dye uptakes were increased rapidly. The dyeing transition temperature of the polyester fiber in alkanes with 1% of water was $86.5^\circ{C}$ that is lower by $11^\circ{C}$ than $97.5^\circ{C}$ in alkanes only. This means that water plasticizes the polyester fiber, and that dyes begin to penetrate the polyester fiber at lower temperature. Addition of trichloromethane which is known as a strong plasticizer on polyester fiber, in alkanes, increased the dye uptakes of C. I. Disperse Violet 1 on polyester fiber at $100^\circ{C}$, but the dyeing transition temperature was lower by $3^\circ{C}$ than in alkanes only.

• 한국세라믹학회지
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• 제45권4호
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• pp.204-207
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• 2008

This paper presents a new process for producing SiC fiber-SiC matrix(SiC/SiC) composites by reaction sintering. The processing strategy for the fabrication of the SiC/SiC composites involves the following: (1) infiltration of the SiC fiber fabric using a slurry consisting of Si and C precursors, (2) stacking the slurry-infiltrated SiC fiber fabric at room temperature, (3) cross-linking the stacked composites, (4) pyrolysis of the stacked composites, and (5) hot-pressing of the pyrolyzed composites. It was possible to obtain dense SiC/SiC composites with relative densities of >96% and a typical flexural strength of ${\sim}400$ MPa.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.158-161
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• 2006

SiC materials have been extensively studied for high temperature components in advanced energy conversion system and advanced gas turbine. However, the brittle characteristics of SiC such as law fracture toughness and law strain-to fracture impose a severe limitation on the practical applications of SiC materials. SiC/SiC composites can be considered as a promising candidate in various structural materials, because of their good fracture toughness. In this composite system, the direction of SiC fiber will give an effect to the mechanical properties. It is therefore important to control a properdirection of SiC fiber for the fabrication of high performance SiC/SiC composites. In this study, unidirection and two dimension woven structures of SiC/SiC composites were prepared starting from Tyranno SA fiber. SiC matrix was obtained by nano-powder infiltration and transient eutectoid (NITE) process. Effect of microstructure and density on the sintering temperature in NITE-SiC/SiC composites are described and discussed with the fiber direction of unidirection and two dimension woven structures.

• Carbon letters
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• 제1권1호
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• pp.12-16
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• 2000

Carbon fiber was reacted with gaseous silicon monoxide which is produced from pack-powder mixture at elevated temperature. As a result of the reaction, two kinds of SiC fiber were obtained. The first one was SiC fibers which were converted from carbon fiber. The fiber is constituted with polycrystal like fine grains or monolithic crystals that have a size from sub-micron to $10\;{\mu}m$. Their size depends on the temperature during the conversion reaction. The second one was ultra-fine SiC fibers that were found on the surface of the converted SiC fibers. The ultra-fine fibers have diameters from 0.08 to $0.2\;{\mu}m$ and their aspect ratio were larger than 100. The chemical composit ion of the ultra-fine fibers was analyzed using an Auger electron spectroscopy. In result, the fibers consist of 51% silicon, 38% carbon and 11% oxygen by weight.

• Korean Chemical Engineering Research
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• 제60권3호
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• pp.439-445
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• 2022

본 연구에서는 전기방사를 이용해 제조한 Si/C Fiber 표면에 실리콘과 석유계 피치를 코팅하여 전지의 용량 안정성을 개선하고자 하였다. TEOS와 PAN을 전기방사 Fiber의 전구체로 사용하여 DMF에 용해해 방사하였다. 전기 방사된 Fiber는 탄화, 환원, 피치 코팅 공정의 특성을 분석하여 최적 공정을 조사하였으며, TEOS와 PAN의 비율에 따라 제조한 음극 소재의 성능을 평가하였다. 탄화/환원 공정 후의 TEOS : PAN = 4 : 6 (CR-46)로 제조된 음극 복합 소재는 657 mAh/g의 용량을 보여주었다. 전기화학적 성능을 개선하기 위하여, CR-46 표면에 실리콘과 석유계 피치를 코팅하였다. 피치의 조성을 10 wt%로 고정하였을 때, 실리콘의 함량이 증가할수록 용량은 개선되지만, 안정성은 저하됨을 알 수 있었다. 실리콘의 조성을 10 wt%로 제조한 음극 복합 소재는 982.4 mAh/g의 높은 용량과 86.1%의 용량 안정성을 확인할 수 있었다. 고속 충·방전 특성을 분석하기 위한 율속 테스트에서는 80.2%의 용량비(5C/0.1C)를 나타내었다.

• 한국세라믹학회지
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• 제49권4호
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• pp.287-294
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• 2012

Ceramic Matrix Composites (CMCs) represent a class of non-brittle refractory materials for harsh and extreme environments in aerospace and other applications. The quasi-ductility of these structural materials depends on the quality of the interface between the matrix and the fiber surface. In this study, a manufacture route is described where in contrast to most other processes no additional fiber coating is used to adjust the fiber/matrix interfaces in order to obtain damage tolerance and fracture toughness. Adapted microstructures of uncoated carbon fiber preforms were developed to permit the rapid infiltration of molten alloys and the subsequent reaction with the carbon matrix. Furthermore, any direct reaction between the melt and fibers was minimized. Using pure silicon as the reactive melt, C/SiC composites were manufactured with an aim of employing the resulting composite for friction applications. This paper describes the formation of the microstructure inside the C/C preform and resulting C/C-SiC composite, in addition to the MAX phases.

• Advances in materials Research
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• 제1권3호
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• pp.221-231
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• 2012

In this study, the physical and mechanical properties of bamboo fiber reinforced epoxy composites were studied. Composites were fabricated using short bamboo fiber at four different fiber loading (0 wt%, 15 wt%, 30 wt% and 45 wt%). It has been observed that few properties increases significantly with respect to fiber loading, however properties like void fraction increases from 1.71% to 5.69% with the increase in fiber loading. Hence, in order to reduce the void fraction, improve hardness and other mechanical properties silicon carbide (SiC) filler is added in bamboo fiber reinforced epoxy composites at four different weight percentages (0 wt%, 5 wt%, 10 wt% and 15 wt%) by keeping fiber loading constant (45 wt%). The significant improvement of hardness (from 46 to 57 Hv) at 15 wt%SiC, tensile strength (from 10.48 to 13.44 MPa) at 10 wt% SiC, flexural strength (from 19.93 to 29.53 MPa) at 5 wt%SiC and reduction of void fraction (from 5.69 to 3.91%) at 5 wt%SiC is observed. The results of this study indicate that using particulate filled bamboo fiber reinforced epoxy composites could successfully develop a composite material in terms of high strength and rigidity for light weight applications compared to conventional bamboo composites. Finally, SEM studies were carried out to evaluate fibre/matrix interactions.