• Journal of the Korean Society for Heat Treatment
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• v.13 no.4
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• pp.265-271
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• 2000

The microstructural change and transformation characteristics with cooling rate i.e. wheel speed were investigated in 82.8wt%Cu-12.8wt%Al-4.3wt%Ni SMA ribbons fabricated by melt-spinning. The thickness and width of ribbon were decreased with increasing wheel speed, while the uniformity of it was improved. At same wheel speed, the grain size of the contact surface of ribbon was smaller than that of free surface. The mean grain size was decreased with increasing wheel speed, resulted in obtaining grains with $3{\mu}m$ in mean diameter in the wheel speed of 30 m/s. However, micro-voids and cracks at grain boundary could be observed at higher wheel speed. $M_s$ and $A_s$ temperatures were decreased, and $M_s{\sim}M_f$ and $A_s{\sim}A_f$ temperature ranges were broadened with increasing wheel speed. All the ribbons were retained the ordered $D0_3$ due to rapid cooling, the volume fraction of it was increased with increasing wheel speed.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.408-415
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• 1995

Polycrystalline Al-Cu ribbons were produced by planar flow casting(PFC). Solidification behavior and microstructual changes of the ribbons have been investigated as a function of ribbon thickness and processing parameters. The solidification front velocity, V varies within the ribbon, decreasing with increasing the distance, S from the wheel-contact surface, as $V=17.6S^{-1}$. In Al-4.5wt%Cu alloy, rapid decrease in solidification velocity toward the free surface causes a change in solidification morphology from planar to cellular, and finally, to dendritic. The length and inclination of columnar grains solidified with planar front were related to the wheel velocity. The transition from particulate degenerate eutectic structure to regular lamellar eutectic structure was observed to be caused by a difference of the relative growth velocites of ${\alpha}-Al$ and ${\theta}$ during solidification in the Al-Cu eutectic alloy.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1190-1190
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• 2006

• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.233-238
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• 1992

Melt-spun $Nd_{14}Fe_{76}Co_4B_6$ and $Nd_{10.5}Fe_{79}Co_2Zr_{1.5}B_7$ ribbons were prepared under an externally applied magnetic field. Magnetic properties in terms of anisotropy were evaluated by discussing the effect of textured structure of the ribbon samples as well as its powders. About 32 % increase in $(B{\cdot}H)_{max}$ and 18.8 % increase in $B_r$ were observed along the perpendicular direction of the ribbon plane which is more prominent for the Nd-Fe-Co-Zr-B than for the Nd-Fe-Co-B alloy. The enhancement of magnetic anisotropy was monitored by measuring the anisotropy constant of each alloy as a function of quenching rate of the ribbon. It was found that for the melt-spun ribbon quenched at slow rate(less than 7 m/s) the magnetic field effect was overwhelmed by the heat gradient effect through the ribbon thickness while the field effect was prominent at intermediate quenching rate (more than 7~11 m/s). The reproducible maximum energy product, $(B{\cdot}H)_{max}$=16.4 MGOe can be obtained from the Nd-Fe-Co-Zr-B alloy.

• Applied Microscopy
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• v.26 no.2
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• pp.235-241
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• 1996

Amophization and decomposition behaviour in $Mg_{62}Cu_{26}Y_{12}$ alloy prepared by melt spinning method and wedge type metal mold casting method have been investigated by a detailed transmission electron microscopy. Amorphous phase has formed in melt-spun ribbon. In the case of the wedge type specimen, however, the amorphous phase has formed only around the tip area within about 2 mm thickness. The remaining part of the wedge type specimen consists of crystalline phases, $Mg_{2}Cu\;and\;Cu_{2}Y$. The supercooling for crystallization behaviour of the amorphous $Mg_{62}Cu_{26}Y_{12}$ alloy, ${\Delta}T_x$ has been measured to be about 60 K. Such a large undercooling of the crystallization bahaviour enables formation of the amorphous phase in the $Mg_{62}Cu_{26}Y_{12}$ alloy under the cooling rate of $10^{2}K/s$. The amorphous $Mg_{62}Cu_{26}Y_{12}$ has decomposed into crystalline phases, $Mg_{2}Cu\;and\;Cu_{2}Y$ after heat treatment at $170^{\circ}C\;and\;250^{\circ}C$.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.554-554
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• 2000

To improve mechanical properties of Cu-Al-Ni alloy by the grain refinement, Cu-Al-Ni SMA ribbons were fabricated by melt spinning apparatus. The variations of microstructure, mechanical properties and transformation characteristics with the condition of rapid solidification and annealing time-temperature were investigated in Cu-Al-Ni SMA ribbons. The ribbons fabricated by melt spinning obtained around 1.5nm in width and 50-60${\mu}{\textrm}{m}$ in thickness. With increasing wheel speed in order of 10m/s, 15m/s, 20m/s, 30m/s and 3m/s, the grain size was decreased in order of 10${\mu}{\textrm}{m}$, 6.25${\mu}{\textrm}{m}$, 5.5${\mu}{\textrm}{m}$, 3${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$. $M_{s}$ and $A_{s}$ temperature were decreased with decreasing grain size. By X-ray diffraction test, ordered $\beta$$_1$ phase was observed in all the SMA ribbons and the volume friction of it was increased with increasing wheel speed. With increasing wheel speed, strain was increased from 4.2% to 5.8% and fracture mode has changed from mixture of intergranular and dimple fracture to mixture of fiber structure and dimple fracture. The grain size of ribbon heat-treated at $600^{\circ}C$ was increased with increasing time. In the heat-treated ribbons at 55$0^{\circ}C$, ${\gamma}$$_2$ phases were observed.d.d.

• Journal of the Korean Magnetics Society
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• v.11 no.1
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• pp.1-7
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• 2001

We investigated to DC magnetic characteristics, the dependence of annealing temperature on the crystal grain and the crystalline orientation for grain-oriented silicon ribbon with 100 $\mu\textrm{m}$ final thickness manufactured by three times cold rolling method using the hot-rolled silicon steel plate as a raw material. The growth of (110)[001] Goss texture were almost observed in the whole area of the sample. The values of the saturation magnetic flux density B$\sub$s/ and the average ${\alpha}$ angle have 1.9 T and 4.6 degrees respectively. From this result we could be confirmed that the three times cold rolling method has a possibility of manufacture for oriented ultra-thin silicon ribbons much more simple and cheeper than the existing oriented silicon steel manufacturing method by means of more simplified producing process.

• Current Photovoltaic Research
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• v.7 no.3
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• pp.65-70
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• 2019

As a demand of higher power photovoltaic modules, shingled, multi-busbar, half-cell, and bifacial techniques are developed. Multi-busbar module has advantage for large amount of light havesting. And, half-cell is high power module for reducing resistive losses and higher shade tolerance. Recently, researches on multi-busbar is focused on reliability according to adhesion and intermetallic compound between Sn-Pb solder and Ag electrode. And half-cell module is researched to comparing with full-sized cell module for structure difference. In this study, we investigated the factors affecting to efficiency and adhesion of multi-wires half-cell module according to wire thickness, solder thickness, and flux. The results of solar simulator and peel test was that peel strength and efficiency of soldered cell is not related. But samples with flux including high solid material showed high efficiency. The results of FE-SEM and EDX line scan on cross-section between wire and Ag electrode for different flux showed thickness of solder joint between wire and Ag electrode is increasing through solid material increasing. Flux including high solid material would affect to solder behavior on Ag electrode. Higher solid material occurred lower growth of IMC layer because solder permeate to sider of wire ribbon than Ag electrode. And it increased fill factor for high efficiency. In soldering process, amount of solid material in flux and solder thickness are the factor related with characteristic of soldered photovoltaic cell.

• The Journal of the Korean dental association
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• v.12 no.9
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• pp.691-694
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• 1974

The trends of restoration on abrased teethis mostly based on gnathology or on practical experience. This study was performed on plaster models from 60 young men whose teeth and occlusion are clinically normal. A pair, upper and lower models, were mounted on HANAU articulator. Iron ball bearing 0.2mm 0.5mm 0.7mm and 1.0mm in diameter was attached on mesiobuccal cusp of upper first molar. [table I] Long ribbon shape of cold cure resin was inserted and jaw was closed gently so as not to move disturb original position of iron ball. The resin bite registration was measured minimun thickness from each lingual cusps of upper jaw and buccal cusps of lower jaw by means of Bowley gauge. The results were as follows (graph). 1) The distance from upper lingual cusps and lower buccal cusps: backward cusps showed smaller than standard cusp (upper mesio-buccal cusp) and forward cusps showed longer than standard. 2) The measurements from upper lingual cusps are not coincide with lower buccal cusps.

• Journal of Korea Foundry Society
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• v.23 no.1
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• pp.47-51
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• 2003

This experimental study was carried out to investigate the solidification characteristics of polystyrene added styronaphthalene pattern materials using various castability test methods. The styronaphthalene showed an excellent filling capacity and shaping behavior having about 0.2 mm meniscus radius. The shell thickness of styronaphthalene showing smooth wall at the solid/liquid interface increased with the increasing of polystyrene addition. The solidification microstructure of styronaphthalene showed a typical thin ribbon reinforced composite structure, which has fibrous amorphous skeleton of polystyrene and crystalline naphthalene. From the results of this study, it was found that the polystyrene added styronaphthalene showed a precision shaping behavior as disposable pattern material under the atmospheric condition.