• Journal of Welding and Joining
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• v.13 no.3
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• pp.106-115
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• 1995

To know the bonding phenomena of Ti/Cu brazed joint, a characteristic of microstructures in bonding interlayer of vacuum brazed pure Ti to Cu has been studied in the temperature range from 1088 to 1133K for various bonding times using Ag-28wt%Cu filler metal. Also intermediate phases formed in bonded interlayer and behavior of layer growth have been investigated. The obtained results in this study are as follows: 1) Liquid insert metal width at the each brazing temperature was proportional to the square root of brazing time, and it was considered that the liquid insert metal width was controlled by the diffusion rate process of primary .alpha.-Cu formed at the Ti side. 2) Intermediate phases formed near the Ti interface were .betha.-Ti and intermetallic compounds TiCu, Ti$_{2}$Cu, Ti$_{3}$Cu, and TiCu. 3) .betha.-Ti formed in Ti base metal durig brazing transformed to lamellar structure, .alpha.-Ti + Ti$_{2}$Cu. The structure came from the eutectoil decomposition reaction in cooling. And the width of .betha.-Ti layer was proportional to the square root of brazing time, and it was considered that the growth of .betha.-Ti layer was controlled by interdiffusion rate process in .betha.-Ti. 4) The layer growth of TiCu, Ti$_{3}$Cu$_{4}$ and TiCu, phases formed near the Ti interface was linerface was linearly proportional to the brazing time, and it was considered that the layer growth of these phases was controlled by the chemical reaction rate at the interface.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.141-146
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• 2021

With increasing interest in fluorinated compounds, nucleophilic fluorination reaction has been generally used for synthesizing fluorine-containing chemicals. However, alkali metal fluorides (MFs) generally have low solubility and reactivity in organic solvent. To overcome these problems, various phase transfer catalysts (PTCs) have been investigated. Calix-arene is known as to capture the metal cation(M⁺), and therefore in this review, we would like to introduce several kinds of calix-arene based PTCs, such as bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA), oligo-ethylene glycol linked bis-triethyleneglycol crown-5-calix[4]arene (BTC5A), and ionic liquid functionalized calix-arene based catalyst, as well as ion-pair receptor crown-6-calix[4]arene-capped calix[4]pyrrole.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.2
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• pp.61-74
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• 1998

Some photopolymer, poly(vinyl cinnamoyl acetate)(PVCiA) was synthesized by esterification of polymer(vinyl alcohol)(PVA) with monochloroacetic acid, followed by reaction poly(vinyl monochloroacetate)(PVAhA) and potassium cinnamate. When esterification of PVA with monochloroacetic acid was reacted in the dimethyl sulfoxide(DMSO), in the synthesis of PVChA, it is very good yield and the successive cinnamoyl acetoxyl esterification of PVCiA can be successfully synthesized. But PVCiA is low photosensitive polymer if net added photosensitizing dyes. Here, we synthesized photosensitizing dyes.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.983-984
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• 2014

• Journal of Welding and Joining
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• v.21 no.2
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• pp.89-96
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• 2003

The change of microstructures in the base metal during transient liquid phase bonding process of directionally Ni base superalloy, GTD-111 was investigated. Bonds were fabricated using a series of holding times(0-7.2ks) at three different temperatures(1403, 1418 and 1453K) under a vacuum of 13.3mPa. In raw material, ${\gamma}$- ${\gamma}$' eutectic phases, platelet η phases, MC carbide and PFZ were seen in interdendritic regions or near grain boundary and size of primary ${\gamma}$' precipitates near interdendritic regions were bigger than core region. The primary ${\gamma}$' precipitates in dendrite core were dissolved early in bonding process, but ${\gamma}$' precipitates near interdendritic regions were dissolved partially and shape changed. The dissolution rate increased with increasing temperature. Phases in interdendritic regions or near pain boundary continually changed with time at the bonding temperature. In the bonding temperature of 1403K, eutectic phases had not significantly changed, but η phases had transformed from platelet shape to needle morphology and PFZ region had widened with time. The interdendritic region and near pain boundary were liquated partially at 1423k and fully at 1453k by reaction of η phases and PFZ. In the bonding temperature of 1453K, interdendritic region and near pain boundary were liquated and then new phases which mixed with η phases, PFZ and MC carbide crystallized during cooling. Crystallized η phases transformed from rod shape to platelet shape with increasing holding time.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1995.11a
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• pp.25-25
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• 1995

Liquid phase sintering of 90W-6Ni-4Mn alloy has been investigated as functions of sintering atmosphere, heating rate, and reduction temperature. The present work accounts for the thermodynamic oxidatiodreduction reactions of constituent powders of W, Ni and Mn. By discounting these reactions, the previous investigations would obtain only the alloy with large pores and the lowered relative sintered density, by the liquid phase sintering under a dry hydrogen atmosphere. the sintering cycle consisted of a rapid heating to reduction temperatures under high purity nitrogen atmosphere, and holding for 4 hours and sintering at $1260^{\circ}C$ for 1 hour under a dry hydrogen gas. The relative density of the sintered alloy increased with increasing heating rate. As the reduction temperature increased, the relative density increased to the lm theotical density at the duction temture above $1150^{\circ}C$. The mimsturcatre of sintered alloys has been analysed by a scanning election microscope. The sintered density was compared with those obtained from the other investigators. It was found that the reduction $1150^{\circ}C$ results in the lowered densification of 90W-6Ni-4Mn alloy. This is caused by the fact that reducing reactions of W and Ni oxides contained in W an Ni powders concomitantly leads to oxidizing reaction of Mn powder the oxidized Mn is hardly reduced at sintering temperature and thereby remains large pores in the alloy. It is concluded that the W-Ni-Mn alloy with full density can be obtained by the precise control of atmosphere, heating rate, and sintering temperature.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1651-1655
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• 2007

Rod-like polymerizable LC molecules having two different reactive groups, i.e. acryl and diacetylene groups were prepared. 4-Hydroxyphenyldiacetylenes were synthesized by the coupling reaction of 1-bromoalkynes with 4-ethynylphenol and then reacted with 4-(6-acryloyloxyalkyloxy)benzoic acid to give polymerizable LC molecules 4a-d. The mesomorphic properties of compounds 4a-d were investigated by differential scanning calorimetry, polarized optical microscopy and X-ray diffractometry. Compounds 4a-c exhibited smectic and nematic phases, but compound 4d having a longest alkyl tail among the series formed only a smectic phase. Photopolymerizability of acryl and diacetylene groups was investigated by IR spectroscopy. An anisotropic polymer film could be prepared by selective polymerization of acryl groups with 365 nm UV light in the presence of a photoinitiator (2,2-dimethoxy-2-phenylacetophenone). The subsequent reaction of diacetylene groups with 254 nm UV light disrupted the anisotropic structure, suggesting that these LC molecules could be used for imaging on the film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.243-247
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• 2005

In this study, in order to develop low temperature sintering ceramics for ultrasonic vibrator application, PNW-PMN-PZT system ceramics were manufactured according to the amount of CaCO$_3$ addition, and their piezoelectric, dielectric and microstructural characteristics were investigated. The ceramic specimens could be sintered at sintering temperature below 1000 $^{\circ}C$ due to the effect of Li$_2$CO$_3$-CaCO$_3$ liquid phase produced by the reaction of Li$_2$CO$_3$ and CaCO$_3$. At 0.2 wt% Li$_2$CO$_3$ and 0.25 wt％ CaCO$_3$ added specimen sintered at 920 $^{\circ}C$, the density, electromechanical coupling factor(k$_{p}$), mechanical quality factor(Q$_{m}$) and dielectric constant showed the optimal value of 7.78 g/㎤, 0.49, 1396, and 1300, respectively, for ultrasonic vibrator application.ion.

• Carbon letters
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• v.25
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• pp.50-54
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• 2018

Large-size graphene samples are successfully prepared by combining ultrosonic assisted liquid phase exfoliation process with oxidation-deoxidation method. Different from previous works, we used an ultrasound-treated expanded graphite as the raw material and prepared the graphene via a facile oxidation-reduction reaction. Results of X-ray diffraction and Raman spectroscopy confirm the crystal structure of the as-prepared graphene. Scanning electron microscopy images show that this kind of graphene has a large size (with a diameter over $100{\mu}m$), larger than the graphene from graphite powder and flake graphite prepared through single oxidation-deoxidation method. Transmission electron microscopy results also reveal the thin layers of the prepared graphene (number of layers ${\leq}3$). Furthermore, the importance of preprocessing the raw materials is also proven. Therefore, this method is an attractive way for preparing graphene with large size.

• Mass Spectrometry Letters
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• v.9 no.4
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• pp.95-99
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• 2018

An innovative, simple, and rapid assay method based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed and validated for the simultaneous determination of eight statin drugs in human urine. A simple sample clean-up procedure using the "dilute and shoot" (DAS) approach enabled a fast and reliable analysis. The influence of the dilution factor was investigated to ensure detectability and reduce the matrix effect. Chromatographic separation was performed on a Phenomenex Kinetex C18 column ($50{\times}3.0mm$ i.d., $2.6{\mu}m$) using an elution gradient of mobile phase A composed of 0.1% acetic acid, and mobile phase B composed of acetonitrile, at a flow rate of 0.35 mL/min. Quantitation was performed on a triple quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode using electrospray ionization in positive ion mode. The total chromatographic run time was 15 min. The method was validated for selectivity, sensitivity, recovery, linearity, accuracy, precision, and stability. The present method was successfully applied to the analysis of Rosuvastatin in urine samples after oral administration to healthy human subjects.