• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.15-20
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• 1986

Formation of powders and electromechanical coupling factor of $Pb(Mn_{1/3} Sb_{2/3})_{0.08} Ti_{0.495}Zr_{0.425}O_3$ by hydro-thermal synthesis are described. The hydrothermal reactions each were accomplished at 12$0^{\circ}C$~25$0^{\circ}C$ for 5hours and sintering was accomplished at 1, .20$0^{\circ}C$ for 1hours. The PZT powders by hydrothermal synthesis were formed above 16$0^{\circ}C$ and the forms were cubic types. The ratio of grain size of sintered sample to powder was slowly decreased with the rising of hydrothermal reactino temperature but decreased rapidly above 22$0^{\circ}C$ Sintering density was decreased with the rising of hydrothermal reaction temperature above 16$0^{\circ}C$ but dielectric constant was increased. Electromechanical coupling factor $K_P$ was almost constant at 16$0^{\circ}C$~24$0^{\circ}C$ range and the value of $K_P$ was about 0.43-0.45.

• Elastomers and Composites
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• v.51 no.2
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• pp.81-92
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• 2016

1,3-Diphenylguanidine (DPG) is commonly used as a secondary accelerator which not only acts as booster of cure but also activating silanization reaction. The aim of this study is to increase the interaction between silica and rubber by using DPG. In this study, mixing was proceeded in two steps. The T-1 compound is mixed DPG with silica and silane coupling agent in the kneader at high temperature which is named as $1^{st}$ mixing step. T-3 compound is mixed DPG with curatives in the two-roll mill at low temperature which is named as $2^{nd}$ mixing step. The T-2 compound is mixed a half of DPG in $1^{st}$ mixing step and the remainder is mixed in $2^{nd}$ mixing step. Total DPG content was equal for all compounds. When DPG is mixed with silica, silane coupling agent during the $1^{st}$ mixing step, a decrease in cure rate and an increase in scorch time can be seen. This indicates that DPG is adsorbed on the surface of silica. during rubber processing. However, bound rubber content is increased and dynamic properties are improved. These results are due to the highly accelerated silanization reaction. However, there are no significant difference in 100%, 300% modulus.

• Journal of the Korean Chemical Society
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• v.21 no.6
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• pp.404-412
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• 1977

Electrochemical reduction of nitrobenzene (${\phi}NO_2$) and its derivatives on Pb electrode was studied by means of galvanostatic measurements and coulometric electrolysis in ethanol-water solvent. In acidic solutions phenylhydroxyl amine and aniline ethanol-water solvent. In acidic solutions phenylhydroxyl amine and aniline were produced while nitrosobenzene and coupled products such as azo-and hydrazobenzene were produced in basic solutions. Nitrosobenzene (${\phi}NO$) was not found to be an intermediate in the reduction reactions of ${\phi}NO_2$ in acidic solutions. No direct coupling between ${\phi}NO\;and\;{\phi}NHOH$ was observed to occur in the electrolyte solutions used. Mechanisms of the production of phenylhydroxylamine and nitrosobenzene are deduced from Tafel slope, pH dependence and reaction order with respect to nitrobenzene. Mechanism for the reduction of substituted nitrobenzenes seems to be identical to that of nitrobenzene.

• Journal of the Korean Chemical Society
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• v.24 no.6
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• pp.457-462
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• 1980

Phosphates and phosphoric amides were synthesized by the reaction of phosphoryl chloride with allyl alcohol, 2,3-dibromopropanol, 2-pyrrolidone and ethylenimine. All of these compounds were thermally very unstable. Allyl phosphorodichoridate and diallyl phosphorochloridate gave significant amount of polymeric products when they were distilled. IR spectra showed characteristic P=O stretching bands between 1300 and $1200 cm^{-1}$ and NMR spectra were very complicated due to the long range coupling effect of phosphorus atom. And mass spectrum of 2,3-dibromopropyl phosphorodichloridate gave no indication of molecular ion peak.

• Journal of applied mathematics & informatics
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• v.34 no.5_6
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• pp.359-367
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• 2016

This paper deals with the Cauchy problem for heat equations with coupling moving reactions of mixed type. After obtaining the infinite Fujita blow-up exponent, we classify optimally the simultaneous and non-simultaneous blow-up for two components of the solutions. Moreover, blow-up rates and set are determined. By using the analogous procedures, one can fill in the gaps for the other two systems, which are studied in the paper 'Australian and New Zealand Industrial and Applied Mathematics Journal' 48(2006)37-56.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.165-165
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• 2006

We prepared nonlinear optical (NLO) polymers possessing thermal and temporal stability, which were based on the polyimides appended with NLO chromophores. NLO chromophores with a terminal hydroxyl group have been synthesized by coupling between aminobenzene or julolidine donor and phenylene bridge, and then subsequent coupling between the resulting product and tricyanofuran acceptor. The chromophores were chemically bonded to the polyimides backbone through Mitsunobu reaction. The NLO polymers showed $160-170^{\circ}C$ of Tgs and were thermally stable up to $200^{\circ}C$. We obtained optical quality films by spincoating and evaluated their electro-optical properties and temporal stability.

• Elastomers and Composites
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• v.50 no.1
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• pp.62-67
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• 2015

The surface modification of microfibriled cellulose (MFC) was carried out through the hydrolysis-condensation reaction using (3-aminopropyl)triethoxysilane (APS) and 3-glycidyloxypropyltriethoxysilane (GPS) and then the modified cellulose was compounded with bio-degradable poly(lactic acid) (PLA). Also, pristine MFC was compounded with PLA as a control groups. The confirmation of surface modification for the pristine MFC was characterized by FT-IR and SEM/EDX. The thermal and mechanical properties of the PLA/MFC composites depended on the content of MFC and the type of silane coupling agents. From the thermal, morphological and mechanical behaviors of the PLA/MFC composites, it was found that GPS-MFC was more successful to improve the interface adhesion between PLA matrix and the surface of MFC than that of APS-MFC.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.352-355
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• 1998

Dense $ Pb(Zr, Ti)O_3(PZT)/Al_2O_3$ nanocomposites were prepared by the 28 GHz microwave heating method and conventional electric furnace sintering. Electrical and mechanical properties of the composites were investigated. The fracture strength of the PZT composites with 0.1vol% $Al_2O_3$ was significantly improved in both sintering methods. Smaller grain size and effective reinforcement of the PZT matrix by the second phase were considered to be responsible for the excellent fracture strength. Planar electromechanical coupling factor Kp of the composites sintered by 28GHz microwave heating was higher than that of the materical prepared by the conventional route. It seemed that the control of the reaction between PZT and $Al_2O_3$ by the microwave rapid sintering resulted in the high piezoelectric properties.

• Journal of the Korean Vacuum Society
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• v.4 no.3
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• pp.334-341
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• 1995

IB-AI-VIB2 및 IB-AI-VIB2 :Co2+ 결정을 고순도 원소를 출발 물질로 하고 iodine을 수송 매체로 사용하여 chemical transport reaction method로 성장시켰다. 성장된 결정의 결정구조는 chalcopyrite 구조였으며, energy gap은 direct band gap으로 3.514~1.814 eV 정도로 주어졌으며, cobalt를 불순물로 첨가할 때 energy gap은 감소하였다. IB-AI-VIB2 :Co2+ 결정에서 첨가된 cobalt가 모체결정의 Td symmetry site에 Co2+ ion으로 위치하여, Co2+ ion의 energy 준위 사이의 전자전이에 기인하는 불순물 광흡수 peaks가 나타났다. 이 불순물 광흡수 peaks에 결정장 이론을 적용하여 구산 1st-order spin-orbit coupling parameter(λ)는 -183~ -189cm-1정도였고, 2nd-order spin-orbit coupling parameter(P)는 225~239 cm-1정도였으며, crystal field parameter(Dq)는 328~395cm-1, Racah parameter(B)는 531~552cm-1정도였다.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.732-739
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• 1993

Good yields were usually obtained in Pd(O)-catalyzed Suzuki aryl-aryl coupling reaction, even when both coupling partners had an ortho tertiary benzamide functional group. The direct ortho functionalization of oligomeric tertiary benzamides at Snieckus condition is dependent on the chain length. Tertiary benzamide 1 can be o,o-dilithiated only by metal-halogen exchange of the 2,6-dihalo-compound. Bis-tertiary benzamide 9 can be o,o'-dilithiated with excess(4.1 equivalents) s-butyllithium/TMEDA as the lithiating agent. Tris-tertiary benzamide 21 is hard to o,o"-difunctionalize due to steric interactions among the tertiary benzamide functional groups, and due to steric interactions between these functional groups and others (if present) on the termini of the terphenyl unit.