• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.56-60
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• 2014

The polyimide composite membranes were prepared with polyimide composite solutions including graphenes by using the phase inversion method. The morphologies of these membranes were significantly changed according to the graphene loadings in composite solutions and the solvent systems of the composite solutions. The finger-like macro-voids were formed in the hollow fiber membranes which were prepared in the NMP solvent system with a small amount of ethanol. As increasing the content of the viscous alcohols such as glycerol or 1,3-propanediol in the composite solution, however, the morphologies of the hollow fiber membranes were changed to sponge-like types. In case of flat membranes, the increase of graphene content in polyimide composites causes that their membranes change from the finger-like macro-porous to sponge-like morphologies.

• Carbon letters
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• v.5 no.3
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• pp.108-112
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• 2004

Effect of silicon infiltration on the bend and tensile strength of 2D cross-ply carbon-carbon composites are studied. It is observed that bend strength higher than tensile strength in both types of composite is due to the different mode of fracture and loading direction. After silicon infiltrations bend and tensile strength suddenly decreases of carbon-carbon composites. This is due to the fact that, after silicon infiltration, silicon in the immediate vicinity of carbon forms the strong bond between carbon and silicon by formation silicon carbide and un-reacted silicon as free silicon. Therefore, these composites consist of three components carbon, silicon carbide and silicon. Due to mismatch between these three components secondary cracks developed and these cracks propagate from $90^{\circ}$ oriented plies to $0^{\circ}$ oriented plies by damaging the fibers (i.e., in-situ fiber damages). Hence, secondary cracks and in-situ fiber damages are responsible for degradation of mechanical properties of carbon-carbon composites after silicon infiltration which is revealed by microstructure investigation study by scanning electron microscope.

• Carbon letters
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• v.5 no.1
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• pp.12-17
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• 2004

In this study, the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence of oxyfluorination on properties was investigated. The surface characteristics of the modified fiber were determined by using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer. The oxyfluorination of carbon fibers was one of the more effective methods to increase surface wettability by the formation of semicovalent C-F bond and C-O bond depending on reaction conditions. When oxygen mole fraction is increased from 0.5 to 0.9, it is probable that attached fluorine atoms at the surface of the fibers reacted with other components. As increased oxyfluorination time and decreased its pressures, semi-covalent peak is increased at 0.5 of oxygen mole fraction. The total surface free energy of oxyfluorinated carbon fibers decreased with increasing oxygen mole fraction over 0.5. These results indicate that the surface of carbon fibers became much more hydrophilic after the short oxyfluorination. The surface free energy of oxyfluorinated carbon fibers progressively decreased after 10 min treatment. The polar components of surface free energies were however, significantly higher for all oxyfluorinated samples than that for the untreated carbon fiber.

• Journal of the Korean Wood Science and Technology
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• v.50 no.5
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• pp.315-324
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• 2022

The termicidal activity and chemical components of wood vinegar from two sources of biomass, nipah fruit shells (NFS) and a mixture of shells and fiber (MSF), were evaluated against Coptotermes curvignathus. A no-choice test was carried out to evaluate their termicidal activity using filter paper samples treated with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% NFS or MSF vinegar. Both wood vinegars exhibited antitermitic activity against C. curvignathus. The results show that increased concentrations of NFS and MSF vinegar significantly increased termite mortality. In particular, the NFS vinegar caused complete mortality and the lowest filter paper mass losses at 2.18% when treated with 12.5% wood vinegar. The most abundant chemical compounds of NFS vinegar were cyclopropanecarbonyl chloride, 2,5-dichlorophenol, 2-propanone, acetic acid, propanoic acid, benzenesulfonic acid, 3,7-dimethyl-6-octenal, and trans-geraniol. Meanwhile, the main compounds in the MSF vinegar were 1,2-ethanediol, formic acid, acetic acid, ethanoic acid, 2-furancarboxaldehyde, phenol, 2-methoxy phenol, and 4-methyl phenol.

• Korean Journal of Food Science and Technology
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• v.40 no.6
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• pp.680-685
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• 2008

In this study, we assessed the functional characteristics of Aralia continentalis Kitagawa (AcK) and Aralia continentalis Kitagawa leaf (AcK-leaf), including crude saponin contents, antioxidant activity, nutritive elements, dietary fiber, and chlorophyll contents. The results of our analysis of nutritive elements in AcK, the contents of the general components, inorganic components, and vitamins were all relatively high. The contents of inorganic components were also high in the following order: K>Ca>P>Na>Mg. Among vitamins, $\beta$-carotene and vitamin C contents were all high. The crude saponin content was 63.7 mg/g in the AcK and 63.5 mg/g in the AcK leaf, and the antioxidant activity was determined to be relatively high. With regard to the dietary fiber content, the total dietary fiber content was 2.13% (soluble 0.40, insoluble 1.72) in the AcK and 5.98% (soluble 1.06, insoluble 4.89) in the AcK leaf, and the total chlorophyll content was 92.58 mg in the AcK and 147.25 mg/100 g in the AcK-leaf.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.1
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• pp.52-58
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• 2013

The effets of the pretreatments of tropical kapok fibers were evaluated in this study in terms of water sorption capacity and oil sorption capacity. The alkali treatments with NaOH resulted in the reduction of lignin, oil and hemicellulose, which were detected with FT-IR spectrum. The reduction of the lyphophilic components such as fat on kapok fiber by the ozone treatments were also measured with FT-IR spectrum. The oil sorption capacity of kapok fiber was decreased by the alkali treatments and the ozone treatments, while the water sorption capacity was increased. The liquid sorption capacity were greatly affected by the mechanical cutting of kapok fiber which exposed the big lumen of kapok fiber. The hydrophilic property of kapok fiber could be controlled by the pretreatments, which would increase the applicability of kapok fiber for preparation of various functional paper products.

• Journal of the Korean Wood Science and Technology
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• v.46 no.4
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• pp.393-401
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• 2018

Natural fibers derived from lignocellulosic materials are considered to be more environment-friendly than petroleum-based synthetic fibers. Several natural fibers, such as seedpod fibers, have a potential for development, including kapok and balsa fibers. The characteristics of both fibers were evaluated to determine their suitability for specific valuable applications. The purpose of this study was to analyze some important fundamental properties of kapok and balsa fibers, including their dimensions, morphology, chemical components, and wettability. The results showed that the average fiber lengths for kapok and balsa were 1.63 and 1.30 cm, respectively. Kapok and balsa fibers had thin cell walls and large lumens filled with air. The kapok fiber was composed of 38.09% ${\alpha}-cellulose$, 14.09% lignin, and 2.34% wax content, whereas the balsa fiber was composed 44.62% ${\alpha}-cellulose$, 16.60% lignin, and 2.29% wax content. The characteristics of kapok and balsa fibers were examined by X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry analyses. The contact angle of the distilled water on kapok and balsa fibers was more than $90^{\circ}$, indicating that both fibers are hydrophobic with low wettability properties because of to the presence of wax on the fiber surface.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.157-163
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• 2008

This paper presents a novel fiber optic tiltmeter system for the health monitoring of large-size structures. The system is composed of a sensor head, a light control unit and a signal processing unit. The sensing mechanism of the sensor head is based on a novel integration of the moire fringe phenomenon with fiber optics to achieve a robust performance in addition to its immunity to EM interference, easy ratting, and low cost. In this paper, a prototype of the fiber optic tiltmeter system has been developed successfully. A low-cost light control unit has been developed to drive the system's optic and electronic components. From an experimental test, the fiber optic tiltmeter is proven to be a prospective sensor for the monitoring of the tilting angle of civil structure with a good linearity. Finally, the test also successfully demonstrates the performance and the potential of the novel fiber optic tiltmeter system to monitor the health of civil infrastructures.

• Design & Manufacturing
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• v.17 no.3
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• pp.55-60
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• 2023

The fiber-reinforced plastics and cellular injection molding process can be used to efficiently reduce the weight of battery housing components of mild hybrid electronic vehicles(MHEV) made of metal. However, the fiber orientation of fiber-reinforced plastics and the growth of foaming cells are intertwined during the injection molding process, so it is difficult to predict the mechanical properties of products in the design process. Therefore, it is necessary to evaluate the mechanical properties of the materials prior to the efficient stiffness design of the target product. In this study, a study was conducted to evaluated the mechanical properties of fiber reinforced cellular injection-molded specimens. Two types of fiber-reinforced plastics that can be used in the target product were evaluated for changes in tensile properties of cellular injection-molded specimens depending on the foaming ratio and position from the injection gate. The PP and PA66 specimens showed a decrease of tensile modulus and strength of approximately 30% and 17% depending on the foaming ratio, respectively. Also, the tensile strength decreased approximately 26% and 17% depending on the position from the injection gate, respectively. As a result, it was confirmed that the PP specimens have a significantly mechanical property degradation compared to the PA66 specimens depending on the foaming ratio and position.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.138-141
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• 2001

The evolution of lectures and microstructure during the warm-rolling and subsequent annealing in aluminum 3004 alloy sheets was investigated by employing X-ray texture measurements and microstructure observations. Whereas the typical $\beta$-fiber orientations with the strong Bs-orientation $\{112\}<110>$ formed in the normally cold-rolled specimen, the warm-rolling at $250^{\circ}C$ led to the development of a strong through thickness texture gradient which was characterized by shear texture at the surface layer and rolling textures at the center layer After warm rolling, ultra-fine grains formed in the thickness layer with shear texture components. Upon recrystallization annealing, the $\{001\}<100>$ Cube-texture developed at the expense of normal rolling texture components the rise to the formation of corase recrystallized grains. However, in the layer with shear texture components the continuous recrystallization took place and the fine grain size persisted even after recrystallization annealing.