• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.266-274
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• 1995

The extractions of aqueous Eu3+ and Tb3+ ions into ethylacetate or dichloromethane were conducted by using 12-crown-4, 15-crown-5 and 18-crown-6 ethers as ligand. Benzoate ion was selected as counter anion for the complexes formed between the lanthanide ions and crown ethers. Fluorescence spectra of the lanthanide ions induced by the energy transfer from benzoate anion to the cations were also measured. The quantitative analysis of the lanthanide ions extracted into organic phase were made on the basis of the results of fluorescence. The measured extractivity is interpreted in terms of the ion-dipole interaction.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.137-140
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• 2007

The ordering of nanopores in AAO has been improved by using laser interference lithography. After growing Fe and Cu on this substrate in vacuum and removing AAO, Fe nanodots are fabricated. The nanopores in AAO and nanodots are ordered in one dimension following the prepatterning. It has been confirmed from the magnetic hysteresis loop that the Fe nanodots have vortex structure and the dipolar interaction is dominant among them.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.29-36
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• 2001

The permeation properties of $O_2\;and\;N_2$ were measured for bromobisphenol A polysulfone(BPSf), bisphenol A trimethylsilylated polysulfone(TMSPSf) and their blend membrane to investigate the structure-properties relationships. BPSf shows relatively high permselectivity. It can be explained that the strong polarity of bromine in BPSf increases chain packing ability. In this case the distance of polymer chains is reduced by increasing of interchain interaction by induced dipole. TMSPSf shows relatively high permeability. The higher value of permeability coefficients for TMSPSf is due to the substitution of very bulky trimethylsilyl groups. The replacement of phenyl hydrogens of bisphenol A polysulfone(PSf) with trimethylsilyl groups results in higher fractional free volume(FFV). In this work, taking into account the complimentary features of BPSf and TMSPSf, BPSf/TMSPSf blend was prepared and the compatibility in mixing are examined. The BPSf/TMSPSf blend shows higher permeability than commercial PSf, with minimum loss of selectivity. The miscibility of the BPSf/TMSPSf blend is confirmed by the single glass transition temperature.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.193-197
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• 2011

The thickness dependence of the magnetic switching volumes in electrodeposited CoPt films was investigated from the magnetization reversal and the magnetic interaction behavior. As the sample thickness is increased, the field difference between the wall pinning field ($H_{DW}$) and the nucleation field ($H_N$) as well as the absolute value of ${\Delta}$area are increased. Therefore, the decrement tendency of the switching diameter with increasing sample thickness can be well explained by the domain wall motion controlled by the domain wall pinning and the strength of dipolar interaction.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.319-325
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• 2015

Submicron-sized $CeO_2:Er^{3+}/Yb^{3+}$ upconversion phosphor particles were synthesized by spray pyrolysis, and their luminescent properties were characterized by changing the concentration of $Er^{3+}$ and $Yb^{3+}$. $CeO_2:Er^{3+}/Yb^{3+}$ showed an intense green and red emission due to the $^4S_{3/2}$ or $^2H_{11/2}{\rightarrow}^4I_{15/2}$ and $^4F_{9/2}{\rightarrow}^4I_{15/2}$ transition of $Er^{3+}$ ions, respectively. In terms of the emission intensity, the optimal concentrations of Er and Yb were 1.0 % and 2.0%, respectively, and the concentration quenching was found to occur via the dipole-dipole interaction. Upconversion mechanism was discussed by using the dependency of emission intensities on pumping powers and considering the dominant depletion processes of intermediate energy levels for the red and green emission with changing the $Er^{3+}$ concentration. An energy transfer from $Yb^{3+}$ to $Er^{3+}$ in $CeO_2$ host was mainly involved in ground-state absorption (GSA), and non-radiative relaxation from $^4I_{11/2}$ to $^4I_{13/2}$ of $Er^{3+}$ was accelerated by the $Yb^{3+}$ co-doping. As a result, the $Yb^{3+}$ co-doping led to greatly enhance the upconversion intensity with increasing ratios of the red to green emission. Finally, it is revealed that the upconversion emission is achieved by two photon processes in which the linear decay dominates the depletion of intermediate energy levels for green and red emissions for $CeO_2:Er^{3+}/Yb^{3+}$ phosphor.

• Ceramist
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• v.8 no.1
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• pp.50-56
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• 2005

압전재료의 다양한 에너지 변환특성 중 기계-전기 에너지간 변환 특성만을 이용하고자 하는 경우로 한정하고, 압전재료의 물성 및 진동모드, 재료물성 평가 사례들을 요약하여 소개하였다. 그러나 이상에서 설명한 압전특성은 매우 개략적인 개념으로서 우수한 압전 응용부품을 개발하기 위해서는 몇 가지 유의할 사항들이 있다. 압전재료는 보다 기본적으로 열에너지, 기계에너지, 전기에너지, 나아가서 Maxwell 방정식에 의해서 전기장과 연결되는 자기에너지까지도 연결시켜서 상호간에 에너지 변환작용을 일으킬 수 있는 특성을 가진다. 기계적 변형(S) = 탄성변형효과 + 역압전효과 + 열팽창효과 전기적 변위(D) = 압전효과 + 유전효과 + 초전효과 즉, 압전 응용부품이 온도변화 및 자기장이 인가되는 환경에서 순수하게 압전현상만을 이용하고자 한다면, 응용분야 및 주위환경에 따라 압전세라믹 소자가 외부 환경변화에 반응을 하지 않도록 적절한 차단 대책을 수립하여야만 한다. 그러나 압전재료의 외부 자기장의 변화에 대한 반응도는 전기장에 대한 반응도에 비해서 매우 작으므로 통상 무시해도 무방하다고 본다. 그리고 압전재료에서 전기장-기계장의 선형성이 보장되는 크기에는 뚜렷한 한계가 있고, 선형성 영역을 벗어나면 이력특성에 의해 비선형 특성 및 포화상태를 보이게 된다는 점 또한 주의하여야 할 점이다. 또한 압전특성은 Curie 온도이하에서만 존재하고, 그 이상의 온도에서는 쌍극자들의 지나친 운동성에 의해 결정 대칭성이 변하여 압전특성이 소멸되므로 사용 온도 구간에 엄격한 제한을 두어야 함도 응용에 유의하여야 한다.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.45-51
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• 1985

Rate constants and activation parameters for the methanolysis of t-butyl halide (t-BuCl, t-BuBr, t-BuI) in various MeOH-DMSO mixtures were measured by conductometric method. Taft's solvatochromic parameters, such as polarity-polarizability(SPP's), ${\pi}^{\ast}$, hydrogen bond donor (HBD) acidity, ${\alpha}$, and hydrogen bond acceptor (HBA) basicity, ${\beta}$ of the solvents, were determined by the so called solvatochromic method using five indicators. The variation of methanolysis rate with the solvent composition was discussed on the basis of the activation parameters and the correlation of the rates with the solvatochromic parameters. It is concluded that the polarity-polarizability, HBD acidity and HBA basicity of the mixtures had an effect on the ionization of t-butyl halide cooperatively, also that the specific interaction between the leaving groups and the solvents, such as ion-dipole and hydrogen bond acceptor-donor interaction, is the most important factor of solvent effects on the stabilization of transition states.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.456-460
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• 1999

The YHB radial distribution functions of a linear gas molecule CO were calculated by a computer within the Stockmayer molecular potential molel, which assumed thc CO molecule as a simple dipolar molecule. To examine the validity of the obtained YHB radial distribution of CO gas molecule, the density dependent pressures of CO at several temperatures were also calculated. The calculated pressures showed a good agreement with literially known experimental CO pressure data. The temperatures examined were 273, 298, and 373 K and the densities were up to $0.013/{\AA}^3$ (maximum pressure = 1000 atm). Since the calculated pressures showed a good agreement with the experimental values, the obtained YHB radial distribution functions of CO molecule seemed good enough to obtain and predict various equilibrium physical and chemical quantities of CO molecule sensitive to density such as pressure. It was also found that in CO gas system the dipole-dipole interaction is effective up to approximately 2.5 molecular diameter.

• Journal of the Korean Electrochemical Society
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• v.22 no.2
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• pp.53-59
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• 2019

To examine the solution structure of electrolytes, it is very important to understand ion-ion and ion-solvent interactions. In this review, we introduce the basic principle of dielectric relaxation spectroscopy (DRS) and studies of electrolyte structure. DRS is a type of impedance method, which measures the dielectric properties of electrolytes over a high frequency domain at levels of tens of GHz. Therefore, DRS provides information on the different polar chemical species present in the electrolyte, including the type and concentration of free solvents and ion pairs with dipole moments. The information of DRS is complementary to the information of conventional analytical techniques (Infrared/Raman spectroscopy, nuclear magnetic resonance (NMR), etc.) and thus enables a broad understanding of electrolyte structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.129-129
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• 2010

플라즈마 처리를 통하여 수직 합성된 다중벽 탄소나노튜브가 원뿔형 다발이 될 수 있으며 원뿔형 탄소나노튜브 다발은 기존의 구조적, 기계적 성질의 향상과 더불어 향상된 전계방출 능력을 가질 것으로 기대되어 이를 X-선원, 전계방출디스플레이(FED), 유기발광다이오드(OLED) 백라이트 등의 전자빔 원으로 적용하기 위한 연구가 진행되고 있다. 원뿔형 탄소나노튜브 다발의 형상 제어를 통하여 전계방출특성을 향상시킬 수 있으며 이를 위해 원뿔형 탄소나노튜브 다발이 생성되는 메커니즘과 조사되는 플라즈마의 역할에 대해서 이해하는 것이 중요하다. 본 연구에서는 플라즈마 생성부와 조사부를 분리한 유도결합형 플라즈마 원을 사용하여 입사되는 이온의 에너지, 조사량, 입자 종을 독립적으로 제어하였고 이를 통하여 원뿔형 탄소나노튜브 다발이 형성되는 메커니즘과 플라즈마의 역할을 밝혀내었다. 알곤 및 수소 플라즈마 처리에서는 원뿔형 탄소나노튜브 다발이 형성되지 않았으나 질소 및 산소 플라즈마 처리에서는 원뿔형 탄소나노튜브 다발이 형성되었다. 특히 산소 플라즈마 처리가 원뿔형 탄소나노튜브 다발 형성에 효과적이었다. 원뿔형 탄소나노튜브 다발의 형성 메커니즘은 탄소나노튜브의 분극과 쉬스 전기장의 상호작용을 이용한 모델을 사용하여 설명하였다. 질소 및 산소 플라즈마 처리에서는 탄소나노튜브 끝단에 생성되는 C-N, C-O 결합에 의해 향상된 유도 쌍극자와 쉬스 전기장에 의해 탄소나노튜브 끝단이 모여 원뿔형 탄소나노튜브 다발이 생성됨을 밝혀내었다. 산소 플라즈마 처리에서 입사되는 이온의 에너지 조절에 의한 쉬스 전기장 조절과 조사량 조절을 독립적으로 수행하여 원뿔형 탄소나노튜브 다발의 직경 및 높이가 쉬스 전기장 및 조사량에 따라 조절 가능함을 보였다. 이로부터 입사되는 이온의 입자 종, 쉬스 전기장 및 조사량 조절 등의 플라즈마 인자 조절을 통하여 원뿔형 탄소나노튜브 다발의 형상 제어가 가능함을 보였다. 탄소나노튜브의 형상 제어와 더불어 세슘 입자 삽입을 통한 탄소나노튜브의 일함수 감소를 통하여 향상된 전계 방출 특성을 갖는 탄소나노튜브 팁의 제조 가능성을 확인하였다.