• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.59-60
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• 2003

The undrawn monofilament of poly (trimethylene terephthalate) (PTT) was obtained by melt-spinning. After being annealed at 40 C it was analyzed by the measurements of DSC, DMA, WAXD and ATR FT-IR. Tg of PTT fiber after annealing for more than 96 hours was 20 C higher than that before annealing as determined by the DSC and DMA measurements. The WAXD analysis showed very weak diffraction peaks at 2$\theta$=17$^{\circ}$ and 2$\theta$=24$^{\circ}$ for the annealing time of more than 96 hours. The ATR FT-IR measurements made clear the conformational change of methylene chains of PTT glycol residue from random to gauche-gauche conformation.

• Korean Journal of Materials Research
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• v.13 no.11
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• pp.721-724
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• 2003

A Fe-Si-B-Ni amorphous alloy manufactured by one roll melt-spinning method showed the crystallization temperature difference of a maximum $10^{\circ}C$ according to each lot. This temperature difference had a considerable influence on the annealing process to be conducted for obtaining the proper inductance of the alloy. The proper annealing temperature of the alloy was $480^{\circ}C$ and the annealing time increased as the crystallization temperature increased. The activation energy measured by Kissinger method increased as the crystallization temperature increased. Therefore, the annealing process must be adjusted by the crystallization temperature difference of the amorphous alloy.

• Journal of Powder Materials
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• v.3 no.4
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• pp.253-259
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• 1996

The efficiency of thermoelectric devices for different applications is known to depend on the thermoelectric effectiveness of the material which tends to grow with the increase of its chemical homogeneity. Thus an important goal for thermal devices is to obtain chemically homogeneous solid solutions. In this work, the new process with rapid solidification (melt spinning method) followed by hot pressing was investigated to produce homogeneous material. Characteristics of the material were examined with HRD, SEM, EPMA-line scan and bending test. Property variations of the materials were investigated as a function of variables, such as dopant ${CdCl}_{2}$ quantity and hot pressing temperature. Quenched ribbons are very brittle and consist of homogeneous $Bi_2Te_3$, ${Bi}_{2}{Se}_{3}$ solid solutions. When the process parameters were optimized, the maximum figure of merit was 2.038$\times$$10^{-3}K^{-4}. The bending strength of the material hot pressed at 50$0^{\circ}C$ was 8.2 kgf/${mm}^2$.

• Journal of Korea Foundry Society
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• v.26 no.2
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• pp.92-97
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• 2006

Contact material is widely used as electrical parts. Ag-Cd alloy has a good wear resistance and stable contact resistance. But the disadvantages of Ag-Cd alloy are coarse Cd oxides and harmful metal, Cd. To solve the disadvantages of that, Ag-Sn alloy that has stable and fine Sn oxide at high temperature has been developed. In order to optimize Sn amount that affects the formation of the oxide layer on the surface, we worked for the microstructures and properties of Ag-Sn material fabricated by rapid solidification process. The experimental procedure were melting using high frequency induction, melt spinning, and internal oxidation. We have shown that the optimized Sn amount for high hardness is 7.09 wt%Sn. Surface oxide layer forms when Sn amount is over 9.45 wt%. The size of Sn oxide is 20 nm.

• The Korean Journal of Rheology
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• v.4 no.2
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• pp.148-160
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• 1992

폴리프로필렌(PP)과 폴리에틸렌(PE)혼합물의 용융방사에 있어서 불안정성을 연구하 였으며 혼합물의 유변학적 성질, 혼합물의 형태학적 특성과 연신공명과의 관계를 고찰한 것 이다. 신장점도는 spinline rheometer를 사용하여 측정하여 섬유직경은 광센서를 이용하여 방사공정에서 on-line 측정하였고 연신공명의 주기는 Fourier 변환을 이용하여 분석하였다. PP와 PE혼합물의 용융방사에 있어서 PP 함유량이 많을수록 연신공명이 발생하는 임계연신 비가 줄어들고 그 주기는 길어진다. 정상상태에서 구한 유변학적 성질을 이용하여 Shah와 Pearson의 이론식과 Fisher와 Denn의 이론식으로부터 구한 임계연신비값이 실험치와 많은 차이를 보여주었다. 연신공명에 의하여 형성된 섬유의 가는 부분의 배향도는 굵은 부분에 비하여 크게 향상되었으며 PP 함유량이 많을수록 배향도가 크게 증가하였다.

• Fibers and Polymers
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• v.5 no.1
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• pp.59-67
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• 2004

The development of high tenacity, high modulus monofilaments from Polypropylene/Clay nanocomposite has been investigated. Pure sodium montmorillonite nanoclay was modified using hexadecyl trimethyl ammonium bromide (HTAB) via an ion exchange reaction. Pure and modified clay were characterized through X-ray diffraction, FTIR and TGA. The modified clay was melt blended with polypropylene (PP) in presence of a swelling agent. Composite filaments from PP/Clay nanocomposite were prepared at different weight percentages of nanoclay and the spinning and drawing conditions were optimized. The filaments were characterized for their mechanical, morphological and thermal properties. The composite PP filaments with modified clay showed improved tensile strength, modulus and reduced elongation at break. The composite filaments with unmodified clay did not show any improvement in tensile strength but the modulus improved. The sharp and narrow X-ray diffraction peaks of PP/nanoclay composite filaments indicate increase in crystallinity in presence of modified clay at small loadings (0.5 %). The improved thermal stability was observed in filaments with modified as well as unmodified clays.

• Particle and aerosol research
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• v.5 no.2
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• pp.71-81
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• 2009

In this study, Nylon 6,6 electrospun (ES) nanofiber filter media were prepared at various spinning conditions. The ES filters tested had no intrinsic electrical charges. The ES filters were triboelectrically charged in the course of filter sample handling, and the charge was drastically decayed in a few hours. On the other hand, the corona charged melt blown filter media showed a permanent electrical charge. The electrical charge state of the ES filters was also examined by comparing collection efficiencies of ES filters for uncharged and charged aerosol particles.

• Korea-Australia Rheology Journal
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• v.20 no.3
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• pp.153-164
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• 2008

Modeling and experiments of three electrospinning systems have been presented and they are i) axisymmetric instabilities in electrospinning of various polymeric solutions, ii) non-isothermal modeling of polymer melt electrospinning, and iii) control of nanoparticle distribution and location via confined self-assembly of block copolymers during electrospinning. It has been demonstrated that predicted simulations are in good agreement with corresponding electro spinning experiments, and theoretical analysis provides fundamental understanding of phenomena that take place during electrospinning of various polymeric liquids.

• Journal of Korea Foundry Society
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• v.11 no.5
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• pp.398-405
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• 1991

Al-Li alloy has a high strength with low density. Practically this alloy should use by the material which made from the rapid solidification. Therefore we examine the solidification structures of alloy with cooling rate. According to cooling rate increased, grain size and secondary dendrite arm spacing were smaller. Also grain size was further smaller by Zr added. To obtain more fine solidification structure, rapid solidification by single roll melt spinning was performed. According to higher wheel speed, cooling rate increased and cell size was smaller. Because of locally different cooling rate, different cell size was obtained in same specimen. More than cooling rate $10^6^{\circ}C$ /sec, zone A(insensible zone to corrosion)was obtained.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.304-308
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• 2002

The new Cu-Zr-Ti-Ni-Pd amorphous alloy system has been introduced and manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties of the alloys were examined. The reduced glass transition temperature(Trg = Tg/Tm) and the supercooled liquid region(${\Delta}$Tx = Tx-Tg) of $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ alloy were 0.620 and 57 K respectively. $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ amorphous alloy was produced in the rod shape with 2mm diameter using the Cu-mold die casting. The hardness value of the amorphous bulk alloy was 432 DPN.