• 한국전기전자재료학회논문지
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• 제19권12호
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• pp.1092-1098
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• 2006

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the $Pb(Zr_xTi_{1-x})O_3$ (PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by3 sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The composition of powder and precursor solution were PZT(70/30) and PZT(30/70), respectively. The PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The XRD patterns of all PZT thick films shelved typical perovskite polycrystalline structure. The porosity of the thick films was decreased with increasing the number of coatings and 6-time coated films with 1.5 M showed the dense microstructure and thickness of about $60{\mu}m$. The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 1.5 M, 6-time coated showed the 698. The remanent polarization the 1.5 M and 6-time coated PZT thick films was $38.3{\mu}C/cm^2$.

• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1795-1802
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• 2005

Potential energy curves and internuclear (M-X) distance variations for dissociation reactions of $[MX_4]^{2-}$ into ($[MX_3]^-$ + $X^-$) have been calculated using ab initio Hartree-Fock (HF), second order M$\ddot{o}$ller-Plesset perturbation (MP2), and Density Functional Theory (DFT) methods with a triple zeta plus polarization (TZP) basis set. The equilibrium geometrical structures of $[MX_4]^{2-}$ are optimized to tetrahedral geometry for $[NiX_4]^{2-}$ and square planar geometry for ($[PdX_4]^{2-}$ and $[PtX_4]^{2-}$). The bond (M-X) distances of $[NiCl_4]^{2-}$, $[NiBr_4]^{2-}$, $[PdCl_4]^{2-}$, $[PdBr_4]^{2-}$, $[PtCl_4]^{2-}$, and $[PtBr_4]^{2-}$ at the DFT level are 2.258, 2.332, 2.351, 2.476, 2.367, and 2.493 $\AA$, respectively. The dissociation energies for the bond dissociation of ($[MX_3]^-$${\cdot}{\cdot}{\cdot}$$X^-$) at the DFT level are found to be 4.73 eV for $[NiCl_4]^{2-}$, 4.89 eV for $[NiBr_4]^{2-}$, 4.93 eV for $[PdCl_4]^{2-}$, 5.57 eV for $[PdBr_4]^{2-}$, 5.44 eV for $[PtCl_4]^{2-}$, and 5.87 eV for $[PtBr_4]^{2-}$. As the (M${\cdot}{\cdot}{\cdot}$X) distance of ($[MX_3]^-$${\cdot}{\cdot}{\cdot}$$X^-$) increases, the distance variation (Rt) of trans (M-X) bond at the trans-position is shorter than those (Rc) of two cis (M-X) bonds at the cisposition. Simultaneously the atomic charge variation of trans-X atom is more positive than those of equilibrium $[MX_4]^{2-}$ structures, while the variation of leaving X group is more positive.

• 대한기계학회논문집B
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• 제39권6호
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• pp.513-518
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• 2015

농도차발전은 전 세계적으로 높은 잠재적 에너지량으로 인하여 최근 많은 주목을 받고 있다. 본 연구에서는 양이온과 음이온의 선택적 분리를 통하여 전기를 생성하는 역전기투석을 이용하여 다양한 농도 공급원의 조합으로부터 성능을 평가하였다. 역전기투석 장치의 분극곡선은 전류가 증가할 때 전압이 선형적으로 감소하였고, 최대출력밀도는 내부저항과 외부저항이 일치하는 부분에서 얻어졌다. 내부 유로두께가 감소하고 공급유량이 증가할 때 역전기투석 장치에서 생성되는 출력이 증가하는 것을 발견하였고, 공급유체의 펌핑에 의해 발생되는 출력 손실을 고려한 정미출력은 공급유량이 22.5mL/min 에서 최대값을 가졌다. 최종적으로 담수화 브라인, 해수, 강물, 폐수, 기수를 조합하여 역전기투석 장치의 성능을 평가하였고 정삼투 과정에서 발생하는 브라인과 강물을 이용할 때 $1.75W/m^2$ 으로 최대값을 얻었다.

• 한국수소및신에너지학회논문집
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• 제23권1호
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• pp.43-48
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• 2012

This paper presents the characterization of micro-tubular SOFCs using three different anode current collecting methods of inlet current collection (IC), both current collection (BC) and total current collection (TC). The maximum power densities of SOFCs at $750^{\circ}C$ using IC, BC and TC were 56 mW/$cm^2$ (0.43 V, 0.13 A/$cm^2$), 236 mW/$cm^2$ (0.43 V, 0.55 A/$cm^2$) and 261 mW/$cm^2$ (0.43 V, 0.61 A/$cm^2$) respectively. It was confirmed by impedance spectroscopy that both the polarization resistance and the ohmic resistance were dramatically increased at SOFC with IC.

• Current Applied Physics
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• 제18권11호
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• pp.1338-1344
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• 2018

Band parameters and superconductivity of yttrium hypocarbide ($Y_2C$) have been investigated. The computations are performed using first-principles pseudopotential method within a generalized gradient approximation. The equilibrium lattice parameters have been determined and compared with experiment. Moreover, the material of interest is found to be stiffer for strains along the a-axis than those along the c-axis. A band-structure analysis of $Y_2C$ implied that the latter has a metallic character. The examination of Eliashberg Spectral Function indicates that Y-related phonon modes as well as C-related phonon modes are considerably involved in the progress of scattering of electrons. By integrating this function, the value of the average electron-phonon coupling parameter (${\lambda}$) is found to be 0.362 suggesting thus that $Y_2C$ is a weak coupling Bardeen-Copper-Schrieffer superconductor. The use of a reasonable value for the effective Coulomb repulsion parameter (${\mu}^*=0.10$) yielded a superconducting critical temperature $T_c$ of 0.59 K which is comparable with a previous theoretical value of 0.33 K. Upon compression (at pressure of 10 GPa) ${\lambda}$ and $T_c$ are increased to be 0.366 and 0.89 K, respectively, showing thus the pressure effect on the superconductivity in $Y_2C$. The spin-polarization calculations showed that the difference in the total energy between the magnetic and non-magnetic $Y_2C$ is weak.

• Corrosion Science and Technology
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• 제18권6호
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• pp.312-317
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• 2019

The objective of this study was to investigate the corrosion behavior of aluminum (AA1100) in a mixed solution of 0 ~ 0.1 g/L Na₂S + 0.3 ~ 3 g/L NaCl + 0 ~ 10 mL/L H₂O₂. Potentiodynamic polarization tests were performed. Effects of solution compositions on corrosion potential, corrosion rate, and pitting potential of aluminum were statistically analyzed with a regression model. Results suggested that localized corrosion susceptibility of aluminum was increased in the solution with increasing concentration of NaCl because the pitting potential was lowered linearly with increasing NaCl concentration. On the contrary, H₂O₂ mitigated the galvanic corrosion of aluminum by increasing the corrosion potential. It also mitigated localized corrosion by increasing the pitting potential of aluminum. Na₂S did not exert a noticeable effect on the corrosion of aluminum. These effects of different chemical species at various concentrations were independent of each other. Synergy or offset effect was not observed.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2669-2674
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• 2012

Crown ether is one of well-known host molecules and able to selectively sequester metal cation. We employed M06-2X density functional theory with IEFPCM and SMD continuum solvation models to study selectivity of dibenzo-18-crown-6-ether (DB18C6) for alkaline earth dications, $Ba^{2+}$, $Sr^{2+}$, $Ca^{2+}$, and $Mg^{2+}$ in the gas phase and in aqueous solution. $Mg^{2+}$ showed predominantly strong binding affinity in the gas phase because of strong polarization of CO bonds by cation. In aqueous solution, binding free energy differences became smaller among these dications. However, $Mg^{2+}$ had the best binding, being incompatible with experimental observations in aqueous solution. The enthalpies of the dication exchange reaction between DB18C6 and water cluster molecules were computed as another estimation of selectivity in aqueous solution. These results also demonstrated that $Mg^{2+}$ bound to DB18C6 better than $Ba^{2+}$. We speculated that the species determining selectivity in water could be 2:1 complexes of two DB18C6s and one dication.

• 전기화학회지
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• 제8권2호
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• pp.88-93
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• 2005

고체산화물 연료전지의 작동온도를 낮추고 셀의 출력 밀도를 향상시키기 위해 연료극 지지체식 셀을 제조하고 공기극의 구조를 개선시켜 그 특성을 조사 분석하였다. 셀 제조는 습식법에 의해 이루어졌으며, 제조된 연료극 지지체상에 전해질을 코팅하고 최종적으로 공기극을 코팅하였다. 제조된 셀은 $8mol\%\;V_2O_3$로 안정화된 $ZrO_2(YSZ)$ 전해질 층 및 Ni/YSZ 연료극 지지체로 이루어졌으며, 공기극은 $(La_{0.85}Sr_{0.15})_{0.9}MnO_{3-x}(LSM),\;LSM/YSZ(LY)$ 복합체, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3{LSCF)$를 두층 또는 3층으로 두께를 변화시키면서 코팅하였다 임피던스로 전기화학적 특성을 조사하였으며, $3\%$수분을 함유한 수소와 공기로 $800^{\circ}C$ 이하에서 단전지의 성능을 평가하였다 작동온도 $800^{\circ}C$에서, $LY\;9{\mu}m/LSM\;9{\mu}m/LSCF\;17{\mu}m$의 다층이 코팅된 전지가 $590mW/cm^2$로 가장 좋은 성능을 나타냈으며, $0.244{\Omega}cm^2$로 가장 작은 분극저항을 가졌다. 측정된 임피던스 결과, 공기극의 분극저항이 3층 코팅된 셀의 경우 가장 작게 나타났음을 확인하였으며, 이것은 LY복합전극에 의한 전극 계면 저항 감소뿐 만 아니라 LSCF에 의한 공기극의 산소환원 반응의 전하이동 저항이 감소하였기 때문인 것으로 해석된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.545-549
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• 2001

We have produced electrolyte solution out of 1.15M LiPF$\sub$6/ EC/EMC/DEC/PC(30/55/10/5 by vol%) as a reference, and at the same time, performed basic physical property test using a single solvent of 1.15M LiPF$\sub$6/DEC, DMC, EMC and a 2 component electrolyte solution of 1.15M LiPF$\sub$6/ EC/DEC(1/2 by vo%%) and PC/DEC(1/2 by vol%). Cyclic Voltammetry Analysis showed that, compared to existing carbonate organic solvent, the addition of DEC, DMC and EMC brought the de-decomposition peak of salt anion of PF$\sub$6/$\^$-/ and the solvent at lower oxidization potential of 2.3V, 0.7V and 2.1V(vs. Li/Li$\^$+/\`). In addition, a kinetics current peak, in which intercalation of Li$\^$+/ is proceeded at 750mv, 450mv(vs. Li/Li$\^$+/), was confirmed. These findings suggest that the DEC solvent decomposition occurred at an electric potential lower than that of oxidization of existing carbonate organic solvent. Through the impedance analysis, we checked electric charge transfer resistance(R$\sub$ct/) according to the electric potential of Li$\^$+/ intercalation at 750mv(vs. Li/Li$\^$+/), which was the same as the resistance (R$\sub$f/) and cyclic voltammetry of SEI film that was formed at Reference. By doing so, we found that the significant decrease of polarization resistance(R$\sub$p/) when Reference was played a part in the formation of compact SEI layer at the initial decomposition reaction.

• 한국결정성장학회지
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• 제14권4호
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• pp.151-154
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• 2004

Issues of ferroelectric high-density memories (>64 Mb) indispensable for upcoming ubiquitous era have been on the cell integration less than $0.1\;\mu\textrm{m}^2$ and reliabilities. Thus nanoscale control of microstructures of ferroelectric films with large switching polarization has been one of the issues to obtain the uniform electrical properties for realization of high-density memories. In this study the grain orientations and distributions of BT-based films by spin-on coatings were examined by FEG-SEM/EBSD. Ferroelectric domain characteristics by PFM were also performed to study the dependence of reliabilities on the grain orientations and distributions. It is believed that understandings of the nucleation and growth mechanisms of the a- or b-axis oriented films during the thermal processes such as RTA and furnace annealing affecting on grain orientation and uniformity could be possible based on our experimental results.