• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.102-102
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• 2003

TLCP/polyester composite fibers (TPCFs) based on melt blends of PEN, PET, and TLCP were prepared by melt blending and spinning process to achieve high performance fibers. Reinforcement effect and TLCP fibrillar structure resulted in improvement of mechanical properties for TPCFs. The increase in the apparent crystallite size was attributed to the development of larger crystallites and more ordered crystalline structures in the annealed TPCFs. Molecular orientation was an important factor to determine mechanical property of TPCFs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.3
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• pp.124-128
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• 2011

Electrospun webs have been widely investigated for applying to drug delivery system (DDS) because of their high specific surface area and high porosity. In this study, the composite webs of PLA (poly(lactic acid)) and $TiO_2$ were fabricated by melt-electro-spinning method for applying to drug delivery system. The morphologies of PLA/$TiO_2$, webs were observed using scanning electron microscope (SEM) and field emission transmission electron microscope (FE-TEM). The crystal structures of PLA/$TiO_2$ composite webs were confirmed by X-ray diffractometer (XRD).

• International Journal of Industrial Entomology and Biomaterials
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• v.40 no.1
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• pp.28-32
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• 2020

Recently, many studies have been undertaken on the wet spinning and electrospinning of silk because wet-spun fibers and electrospun webs of silk can be applied in the biomedical and cosmetic fields owing to the good biocompatibility of silk. The rheological properties of silk solution are important because they strongly affect the spinning performance of the silk solution and the structures of resultant fibrous materials. Therefore, as a preliminary study on the effect of solvent composition on the rheological properties of silk fibroin (SF) solution and structure of the resultant film, in the reported work, methanol was added to the SF formic acid solution. A small amount of methanol (i.e. 2%) added to the SF formic acid solution significantly altered the rheological properties of the solution: its shear viscosity increased by 10 folds at low shear and decreased on increasing the shear rate, demonstrating shear thinning behavior of the SF solution. Dynamic tests for the SF solution indicated that the addition of 2% methanol altered the viscous state of the SF formic acid solution to elastic. However, the molecular conformation (i.e. β-sheet conformation) of the regenerated SF film cast from formic acid remained unchanged on the addition of 2% methanol.

• Journal of Korea Foundry Society
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• v.28 no.1
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• pp.31-36
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• 2008

Ti-Ni-Cu alloys are very attractive shape memory alloys for applications as actuators because of a large transformation elongation and a small transformation hysteresis. Rapidly solidified Ti-Ni alloy ribbons have been known to have the shape memory effect and superelasticity superior to the alloy ingots fabricated by conventional casting. In this study, solidification structures and shape memory characteristics of $Ti-Ni_{30}-Cu_{20}$ alloy ribbons prepared by melt spinning were investigated by means of DSC and XRD. Operating parameters to fabricate the amorphous ribbons were the wheel velocity of 55 m/s and the melt spinning temperature of $1500^{\circ}C$. The crystallization temperature was measured to be $440^{\circ}C$. The crystallized ribbons exhibited very fine microstructure after annealing at $440^{\circ}C$ for 10 minutes and $460^{\circ}C$ for 5 minutes and was deformed up to about 6.8% and 6.23% in ductile manner, respectively. Stress-strain curve of the ribbon exhibited a flat stress-plateau at 64 MPa and this is associated with the stress-induced a B2-B19 martensitic transformation. During cycle deformation with the applied stress of 220 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $4.3^{\circ}C$ and 3.6%.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.459-468
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• 1995

For high performance aerospace structures, the properties of highest priority are low density, high strength, and high stiffness(modulus of elasticity). Addition of beryllium decrease the density of the aluminum alloy and increase the strength and the stiffness of the alloy. However it is very difficult to produce the Al-Be alloy having useful engineering properties by conventional ingot casting, because of the extremely limited solid solubility of beryllium in aluminum. So, rapid solidification processing is necessary to obtain extended solid solubility. In this study, rapidly solidified Al-6 at% Be alloy were prepared by twin roll melt spinning process and single roll melt spinning process. Twin roll melt spun ribbons were extruded at $450^{\circ}C$ with reduction in area of 25 : 1 after vacuum hot pressing at $550^{\circ}C and 375^{\circ}C$. The microstructure of melt spun ribbon exhibited a refined cellular microstructure with dispersed Be particles. As advance velocity of liquid/solid interface increase, the morphology of Be particle vary from rod-like type to spherical type and the crystal structure of Be particle from HCP to BCC. These microstructural characteristics of rapidly solidified Al-6at.%Be alloy were described on the basis of metastable phase diagram proposed by Perepezko and Boettinger. The extruded ribbon consisted of recrystallized grains dispersed with Be particles and exhibited improved tensile property compared with that of extruded ingot.

• Macromolecular Research
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• v.11 no.1
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• pp.62-68
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• 2003

Thermotropic liquid crystalline polymer (TLCP)/poly(ethylene 2,6-naphthalate) (PEN)/poly(ethylene terephthalate) (PET) ternary blends were prepared by melt blending, and were melt-spun to fibers at various spinning speeds in an effort to improve fiber performance and processability. Structure and property relationship of TLCP/PEN/PET ternary blend fibers and effects of annealing on those were investigated. The mechanical properties of ternary blend fibers could be significantly improved by annealing, which were attributed to the development of more ordered crystallites and the formation of more perfect crystalline structures. TLCP/PEN/PET ternary blend fibers that annealed at 18$0^{\circ}C$ for 2 h, exhibited the highest values of tensile strength and modulus. The double melting behaviors observed in the annealed ternary blend fibers depended on annealing temperature and time, which might be caused by different lamellae thickness distribution as a result of the melting-reorganization process during the DSC scans.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.128-135
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• 2007

Micro-channels for a wave micropump have been fabricated using the Stereolithography and UV Photolithography. The micro-channel with a channel height of $500\;{\mu}m$ was fabricated with stereolithography. UV photolithography was used for producing micro-channels with a channel length less than $100\;{\mu}m$. The fabrication process data including spinning rpm, pre-bake and post-bake time, and develop time for single layer and multiple layer 3D micro-structures using SU-8 photo resist are experimentally found. A film mask printed with a 40,000 dpi laser printer was used for UV lithography and micro-structures in the order of tens of micrometers in dimension were successfully fabricated.

• Journal of the Korean Magnetic Resonance Society
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• v.9 no.1
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• pp.67-73
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• 2005

$^{27}AI$ triple quantum magic angle spinning (3QMAS) NMR spectra of several mordenite (MOR) sample were simulated with the point charge model method and compared with experimental 3QMAS spectra. Signal positions from different tetrahedral (T) sites in 3QMAS spectra are mainly governed by local structures of T sites such as T-O-T angles and T-O bond lengths. When preparation methods, cations in addition to Si/Al rations vary, the local structures of T sites in MOR change enough to alter signal patterns in 3QMAS of MOR. This inhibits to study the of Al distribution variation over 4 different T sites in mordenite during process such as dealumination by 3QMAS spectra.

• Composites Research
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• v.37 no.4
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• pp.330-336
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• 2024

Silicon carbide (SiC) fibers exhibit excellent heat and chemical resistance at high temperatures. In this study, polycarbosilane melt spinning, oxidation curing, and pyrolysis were performed to fabricate amorphous SiC fibers, and their resistance heating characteristics were evaluated. A stick-type amorphous silicon carbide fiber heating element was manufactured, and the resistance was measured using the two-point probe method. The structural, electrical, and heating characteristics were evaluated at different pyrolysis temperatures. The fiber produced at 1300℃ displayed the highest conductivity and the maximum heating compared to the fibers produced at 1200℃ and 1400℃. This may be attributed to difference in the structures of the fibers, particularly the SiC and graphitic carbon structures.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.608-612
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• 2009

The local structures of the boron and vanadium sites in the ternary glass $xV_2O_5-B_2O_3-yNa_2O$ were studied by $^{11}B\;and\;^{51}V$ magic angle spinning (MAS) nuclear magnetic resonance (NMR). With increasing x, the mole ratios of the $BO_3\;and\;BO_4$ structures were enhanced, as were the quadrupole asymmetry parameters for the $BO_3$ structures, while the quadrupole coupling constants for the sites were reduced. However, the opposite trends were observed with increasing y, implying that $V_2O_5$ and $Na_2O$ play opposite roles. The $VO_4,\;VO_5\;and\;VO_6$ structures with all oxygens bonded to the vanadium neighbors were identified. Vanadiums bonded to the greater number of oxygens were more populated at higher contents of $Na_2O\;and\;V_2O_5$. In addition, the $VO_4$ structures with at least one oxygen bonded to boron instead of vanadium were detected at low $Na_2O$ contents. The electron densities of various vanadium oxide structures were affected by the weight densities and vanadium ion densities. The $VO_4$ structures were more likely to be vanadium oxide structures right next to $V4^{+}$ ions.