• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.61-62
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• 2006

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric actuator, PMN-PNN-PZT ceramics using ${Fe_2}{O_3}$ and $WO_3$ as sintering aids were manufactured with the amount of $WO_3$ addition, and the specimens were sintered at 900, 930, $960^{\circ}C$, respectively. Thereafter, their dielectric and piezoelectric properties were investigated. The sintering aids were proved to lower the sintering temperature of piezoelectric ceramics due to the effects of ${Fe_2}{O_3}$ and $WO_3$ liquid phase. At 0.3wt% $WO_3$ added specimen sintered at $930^{\circ}C$, kp, Qm, dielectric constant and $d_{33}$ showed the optimum values of 0.60, 1402, 1440 and 360[pC/N], respectively, for multilayer piezoelectric actuator application.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.281.2-281.2
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• 2016

Two-dimensional van der Waals (2D vdWs) materials have been extensively studied for future electronics and materials sciences due to their unique properties. Among them, black phosphorous (BP) has shown infinite potential for various device applications because of its high mobility and direct narrow band gap (~0.3 eV). In this work, we demonstrate a few-nm thick BP-based nonvolatile memory devices with an well-known poly(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)] ferroelectric polymer gate insulator. Our BP ferroelectric memory devices show the highest linear mobility value of $1159cm^2/Vs$ with a $10^3$ on/off current ratio in our knowledge. Moreover, we successfully fabricate the ferroelectric complementary metal-oxide-semiconductor (CMOS) memory inverter circuits, combined with an n-type $MoS_2$ nanosheet transistor. Our memory CMOS inverter circuits show clear memory properties with a high output voltage memory efficiency of 95%. We thus conclude that the results of our ferroelectric memory devices exhibit promising perspectives for the future of 2D nanoelectronics and material science. More and advanced details will be discussed in the meeting.

• Macromolecular Research
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• v.14 no.2
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• pp.209-213
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• 2006

The ring-opening polymerization of D,L-lactide initiated by tin(II) 2-ethylhexanoate $(Sn(Oct)_2)$ on the surface-initiated magnetite $(Fe_{3}O_4)$ nanoparticles was performed at $130^{\circ}C$. The effects of the polymer molar mass and concentration on the amount of surface polymer were investigated. The number average molecular weights, $M_n$, obtained by both NMR and GPC methods fit well within the accuracy of the applied methods and ranged from 1,100 to $4,040g\;mol^{-1}$. A surface functionalization density of up to 625 initiation sites per particle was obtained. The composition of various core-shell particles was determined by TGA, with results indicating magnetite $(Fe_{3}O_4)$ contents, ${\mu}m$, between 17 and 59 wt%. Under the influence of a magnetic field, the heating generated by superparamagnetic core-shell particles suspended in toluene presented guidelines for an optimization of magnetic particle systems with respect to an application for hyperthermia.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.43-46
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• 2009

The magnetic and structural properties of the (8, 0) BN nanotubes with transition metals (TM) of Fe, Co, or Ni substitution for B or N were investigated using a first-principles calculation. It was found that TM substitution makes the cross section being distorted and the bond length TM-B or TM-N being longer than that of the original B-N one. The magnetic moment is larger for the TM substitution for B than one for N, and it is mainly due to the 3d electrons of TM atoms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.338-339
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• 2005

본 연구에서는 $Fe_2O_3$를 첨가한 $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr_xTi_{1-x})O_3$ 세라믹스에서 Zr/Ti 비 변화에 따른 소결 및 압전, 유전특성을 조사하였다. $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3$+0.25Wt% $Fe_2O_3$ 계에서 Zr/(Ti+Zr)비(x)를 0.39에서 0.42까지 변화시킨 조성을 1100 - $1250^{\circ}C$ 온도에서 2시간 소결하여 이의 결정구조 및 미세조직을 분석하였고, 압전, 유전 특성 및 RAINBOW 액츄에이터로의 응용을 조사하였다. $1150^{\circ}C$에서 소결한 0.405 조성(x)에서 유전상수(${\varepsilon}r$) = 4669, 전기기계결합계수(kp) = 0.75, 압전상수($d_{33}$) = 810 pC/N의 우수한 특성 값을 나타내었으며, 닥터블레이드법에 의해 RAINBOW 액츄에이터를 제작하여 변위특성을 조사하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.603-603
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• 2013

3D 배열구조의 Vertical nanowire Integrated Nanogenerator (VING)은 낮은 출력, 유연 기판 상에 부적합, 나노선의 부서지기 쉬움, 장기 안정성, 균일한 나노선의 성장을 필요로 하는 문제점을 가지고 있다. 본 연구에서는 이러한 VING방식의 단점을 보완하여 2D 배열 구조의 Lateral nanowire Integrated Nanogenerator (LING)로 고출력 전압, 유연기판의 상에 적합 등을 개선하는 방향으로 연구를 하였다. 본 연구의 실험 방법으로는 RF magnetron sputter를 이용하여 AZO Seedlayer를 제작하였으며 제작된 AZO Seedlayer를 photolithography 공정으로 제작하였다. 패터닝된 샘플을 Hydro thermal synthesis method로 성장시켰다. 구조적 분석으로는 XRD, FE-SEM 등을 이용하여 측정하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.33.2-33.2
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• 2009

Dielectric and piezoelectric properties of Lead-free $(1-x)(Bi_{0.5}K_{0.5})TiO_3-xBiFeO_3$ceramics prepared by a conventional solid state reaction method were investigated in the range of x = 0~10 mol%. Piezoelectric coefficient was increased from 31 pC/N at x = 0 mol% to 64 pC/N at x = 6 mol% then decreased with increasing x. Electromechanical coupling factor ($K_p$) was increased up to 0.18 at x = 10 mol%. On the other hand, mechanical quality factor ($Q_m$) was decreased. Grain size was not much changed with various x and a single perovskite with tetragonal symmetry was maintained at all compositions forming a solid solution between $(Bi_{0.5}K_{0.5})TiO_3$ and $BiFeO_3$. Depolarization temperature ($T_d$) was gradually decreased with increasing x from $302^{\circ}C$ at x = 0 to $245^{\circ}C$ at x = 10 mol%.

• Journal of Magnetics
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• v.18 no.1
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• pp.30-33
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• 2013

The magnetocaloric effect and magnetization behavior have been analyzed in the double-perovskite $La_{0.7}Ba_{0.3}Mn_{1-X}Fe_XO_3$ compound with the sintering temperature at 1273 K. Samples were fabricated by the conventional solid-state reaction method. X-ray diffraction measurement revealed that all the samples had a single phase in orthorhombic. Detailed investigations of the magnetic entropy behavior of the samples were discussed with the variation of $T_C$. The magnetic entropy changes, ${\Delta}S_M$ of approximately 0.36-1.14 J/kg K were obtained in the temperature range of 145-350 K for the $La_{0.7}Ba_{0.3}Mn_{1-X}Fe_XO_3$ compound. The enhancement of the magnetic entropy change is believed to be due to changes in the microstructure, which changes the magnetic part of the entropy of a solid around the magnetic ordering temperature.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.318-323
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• 1990

The bis(malonato)diaquochromate(III) ion, $Cr(C_3H_2O_4)_2^-$ in acidic solution hydrolyzes to give $Cr(C_3H_2O_4)^{+}.$ This reaction is catalyzed by ferric ion and the rate law for this cation catalyzed-aquation in a $HClO_4/NaClO_4$ medium, $I = 1.00 M, is-d[Cr(C_3H_2O_4)_2^-]/dt = ({\kappa}_1[Fe^{3+}] + {\kappa}_2[H^+])[Cr(C_3H_2O_4)_2^-]$ where ${\kappa}_1(25^{\circ}C) = 4.72×10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 22.5 Kcal/mol, {\Delta}S^{\neq} = - 2.58 eu) and {\kappa}_2(25^{\circ}C) = 4.75{\times}10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 21.2 Kcal/mol, {\Delta}S^{\neq} = - 7.13 eu).$ Rapid preequilibrium association of basic Cr-bound oxygen with $Fe^{3+},$ followed by rate-determining ring opening, is proposed to account for the ${\kappa}_1,$ hydrolysis pathway.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.207-214
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• 2012

High temperature deformation behavior of a $Ni_{30}Fe_{53}Co_{17}$ alloy, with its extraordinary low coefficient of thermal expansion less than $10{\times}10^{-6}K^{-1}$ at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be in the ~1373K, $10^{-2}s^{-1}$ region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size.