• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.580-586
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• 2002

We investigated the effect of ionic component on crystalline morphology development during isothermal annealing in a sodium neutralized sulfonated poly(ethylene terephthalate) ionomer (Ion-PET) by time-resolved small-angle x-ray scattering (TR-SAX S) using synchrotron radiation. At early stage in Ion-PET, SAXS intensity at a low annealing temperature (Ta = 120 $^{\circ}C)$ decreased monotonously with scattering angle for a while. Then SAXS profile showed a peak and the peak position progressively moved to wider angles with isothermal annealing time. Finally, the peak intensity decreased, shifting the peak angle to wider angle. It is revealed that ionic aggregates (multiplets structure) of several nm, calculated by Debye-Bueche plot, are formed at early stage. They seem to accelerate the crystallization rate and make fine crystallites without spherulite formation (supported by optical microscopy observation). From decrease of peak intensity in SAXS,it is suggested that new lamellae are inserted between the preformed lamellae so that the concentration of ionic multiplets in amorphous region decreases to lower the electron density difference between lamellar crystal and amorphous region. In addition, analysis on the annealing at a high temperature (Ta = 210 $^{\circ}C)$ by optical microscopy, light scattering and transmission electron microscopy shows a formation of spherulite, no ionic aggregates, the retarded crystallization rate and a high level of lamellar orientation.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.6
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• pp.271-276
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• 2020

The relationship between the hardness and interlamellar spacing of discontinuous precipitates (DPs) formed by continuous cooling was studied for Mg-9%Al-1%Zn alloy. After solution treatment at 683 K for 24 h, the specimens were cooled to room temperature with different cooling rates ranging from 0.2 to 2 K·min^-1, in order to obtain DPs with various interlamellar spacings. It was found that cooling rate of 2 K·min^-1 yielded only small amount of nodular DPs at the grain boundaries, while cooling rates below 2 K·min^-1 yielded both DPs and continuous precipitates (CPs). The volume fraction of DPs increased with increasing cooling rate up to 0.5 K·min^-1, over which it abruptly decreased. The hardness of DPs was increased with an increase in the cooling rate, whereas the interlamellar spacing of the DPs was decreased with respect to cooling rate. The hardness of the DPs formed by continuous cooling was correlated with the interlamellar spacing and can follow a Hall-Petch type relation as in the case of pearlite with lamellar morphology.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1381-1382
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• 2008

Cholesteric Blue phase (ChBP) is constructed by the regular arrangement of the double helix, whereas the Smectic Blue phase (SmBP) has the inter-connected multi-lamellar structure. Orientation fluctuations of polymer stabilized ChBP and spontaneously super-cooled SmBP are discussed. Spatial topology of the defects play key role on the dynamic properties.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.91-91
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• 2013

• Journal of Korea Foundry Society
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• v.31 no.6
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• pp.362-365
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• 2011

In the present work, the corrosion properties of Mg-xSn (x = 1, 3, 5, 7 and 9 wt.%) alloys have been investigated. Potentiodynamic polarization and immersion tests were carried out in 3.5% NaCl solution of pH 7.2 at room temperature to measure the corrosion properties of Mg-xSn (x = 1, 3, 5, 7 and 9 wt.%) alloys. With increase of the Sn contents, the volume fraction of the $Mg_2Sn$ phase was increased. The corrosion rate of Mg-xSn alloys was increased up to 7 wt.%Sn and decreased above 9 wt.%Sn. Initiation of galvanic site during immersion mainly occurred at Mg/$Mg_2Sn$ interface and propagation went into ${\alpha}$-Mg. For this reason, corrosion properties of Mg-xSn (added from 1 wt.%Sn to 7 wt.%Sn alloys) alloys are decreased because the galvanic site was increased with increasing Sn addition. In Mg-9wt.%Sn alloy, however, the corrosion site were changed from Mg/$Mg_2Sn$ interface to ${\alpha}$-Mg/$M_2Sng$ interface in lamellar structure. Preferentially corrosion of ${\alpha}$-Mg/$M_2Sn$ interface in lamellar structure impeded corrosion propagation went into ${\alpha}$-Mg.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.9-15
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• 2008

Microstructure and contact resistance of the Au-Sn solder joints were characterized after flip-chip bonding of the Au/Sn bumps processed by successive electrodeposition of Au and Sn. Microstructure of the Au-Sn solder joints, formed by flip-chip bonding at $285^{\circ}C$ for 30 sec, was composed of the $Au_5Sn$+AuSn lamellar structure. The interlamellar spacing of the $Au_5Sn$+AuSn structure increased by reflowing at $310^{\circ}C$ for 3 min after flip-chip bonding. While the Au-Sn solder joints formed by flip-chip bonding at $285^{\circ}C$ for 30 sec exhibited an average contact resistance of 15.6 $m{\Omega}$/bump, the Au-Sn solder joints reflowed at $310^{\circ}C$ for 3 min after flip-chip bonding possessed an average contact resistance of 15.0 $m{\Omega}$/bump.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.330-342
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• 2003

The formation of emulsions and micelles in water/ceramide PC104/CholE $O_{20}$/C$_{16}$E $O_{20}$ and water/ceramide PC104/CholE $O_{20}$ mixtures was investigated through the phase behavior studies. The phase diagrams showed the existence of micelle and emulsion regions in both systems. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) showed the wider micellar and emulsion regions than the single surfactant system (CholE $O_{20}$). From FT-IR measurements, it was found that the polyoxyethylene (POE) groups of surfactants formed the hydrogen bonds with amido carbonyl group in ceramide PC104. This result indicated that the hydrophilic part (EO) of surfactants could stabilize the lamellar structure and emulsion of ceramide PC104. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) resulted in the smaller emulsion droplet size due to the effect of curvature at the interface, thus further increasing emulsion stability. With the penetration of $C_{16}$E $O_{20}$into the interfacial layer of surfactants in emulsion, the curvature of the interface might be altered for the formation of smaller emulsion droplets. The mixed surfactant system could incorporate up to 4 wt. % of ceramide PC104 into emulsion more than single surfactant system.ystem.m.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.3
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• pp.121-127
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• 2023

When high carbon steel is heated in an appropriate austenizing temperature range and subjected to austempering, the size and shape of lamellar structure can be controlled. The high carbon steel sheet having the pearlite structure has excellent elastic characteristics because it has strong restoring force when properly rolled, and is applied in a process known as patenting-process using lead bath. In the case of isothermal treatment using lead-medium, it is possible to quickly reach a uniform temperature due to high heat transfer characteristics, but it is difficult to replace it with process technology that requires treatment to remove harmfulness lead. In this study, we intend to develop fluidization technology using garnet powder to replace the lead medium. After heating the high-carbon steel, the cooling rate was changed by compressed air to the vicinity of the nose of the continuous cooling curve, and then maintained for 90 s and then exposed to room temperature. The microstructure of the treated specimens were analyzed and compared with the existing products treated with lead bath. The higher the flow rate of compressed air, the faster the cooling rate to the pearlite transformation temperature, so lamellar spacing decreases and the hardness tends to increase.

• Journal of the Korean institute of surface engineering
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• v.34 no.6
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• pp.531-536
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• 2001

Co-22 %Cr alloy films are promising for high-density perpendicular magnetic recording media with their perpendicular anisotropy and large coercivity of 3000 Oe. We observed that a self organized nano structure (SONS) of fine ferromagnetic Co-enriched phase and paramagnetic Cr-enriched phase appears inside the grain of Co-Cr magnetic alloy thin films at the elevated substrate temperature after do-sputtering. The periodic fine Co-enriched phase and Cr-enriched phase is the plate shape of 80 (equation omitted)-wide and 1000 (equation omitted)-long. Cr-enriched phases are located at the center of grains. We prepared 5000 (equation omitted) -thick Co-22 %Cr films on polyimide substrate with varying substrate temperature of $ 30^{\circ}C$, $ 150^{\circ}C$ ,200 $^{\circ}C$, $300^{\circ}C$, and $400^{\circ}C$, respectively. A transmission electron microscope equipped with energy dispersive X-ray analyzer is employed to observe the microstructure of each samples after Co-enri-ched phase are etched selectively. The self organized nano structure of Co-enriched and Cr-enriched lamellar is observed above the substrate temperture of $150^{\circ}C$. No compositional change is observed with substrate temperature. The compositional phase separation in self organized structure becomes clear as the substrate temperature increases. Our results implies that the self organized nano structure in Co-22 %Cr film is ideal for ultra high density recording media by recording selectively on Co-enri-ohed phase.

• Fibers and Polymers
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• v.4 no.1
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• pp.15-19
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• 2003

The self-assembly of asymmetric ABC triblock copolymers in the ordered structure is investigated using an isothermal-isobaric molecular dynamics simulation. Unlike symmetric A BC triblock copolymers, more fascinating mophologies are observed in asymmetric ones because of a larger difference of incompatibility between the components. Various modes of self-assembly in assymmetric ABC triblock copolymers are also observed depending on the block composition. When the composition of block A Is changed from 0.125: to 0.25 at the same $f_B$ : 0.25, the morphological transition from the “cylinder in cylinder” to “cylinders at cylinder” structure is observed in the simulation. In the case of ABC triblocks with $f_B$=0.5, a lamellar-type structure is changed to a cylinder-type structure with increasing the length of block A. When the midblock length increases further to $f_B$=0.625, the “spheres on cylinder” structure is observed in both the $A_{10}$$B_{50}$$C_{20}$ and $A_{20}$$B_{50}$$C_{10}$ triblocks. From these results, the phase diagram of ABC triblock copolymers can be constructed.