• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2529-2534
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• 2012

Poly(3,4-ethylenedioxythiophene) coated Manganese Dioxide (PEDOT/$MnO_2$) composite electrode was fabricated by simply immersing the $MnO_2$ electrode in an acidic aqueous solution containing 3,4-ethylenedioxythiophene (EDOT) monomers. Analysis of open-circuit potential of the $MnO_2$ electrode in the solution indicates the reduction of outer surface of $MnO_2$ to dissolved $Mn^{2+}$ ions and simultaneously oxidation of EDOT monomer to PEDOT on the $MnO_2$ surface to form a PEDOT shell via a galvanic displacement reaction. Analysis of cyclic voltammograms and specific capacitance of the PEDOT/$MnO_2$, conductive carbon added $MnO_2$ and conductive carbon added PEDOT/$MnO_2$ electrodes suggests that the conductive carbon acted mainly to provide a continuous conducting path in the electrode to improve the rate capability and the PEDOT layer on $MnO_2$ acts to increase the active reaction site of $MnO_2$.

• Korean Chemical Engineering Research
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• 제56권3호
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• pp.349-355
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• 2018

$BaMnAl_{11}O_{19}$는 요소를 이용한 균일용액침전법으로 제조되었으며, X선 회절분석과 장방출 주사현미경으로 분석되었다. 침전제의 농도가 증가하면서 Al 종은 $Al(OH)_3$에서 AlOOH로 변화되었으며, 소성과정에서 $BaMnAl_{11}O_{19}$ 상으로 쉽게 변화하였다. 합성시간이 증가하면서 $BaMnAl_{11}O_{19}$ 상의 비율은 크게 증가하지 않는 반면 $BaAl_2O_4$ 상의 비율은 급격하게 증가하였다. 금속염 전구체의 반응속도는 Al, Ba, Mn 순으로 빨라, 침전제의 농도와 합성시간에 따라 $BaMnAl_{11}O_{19}$ 상의 비율이 달라진다. $BaAl_2O_4$와 $BaMnAl_{11}O_{19}$는 촉매 연소 성능을 향상시키고, $BaMnAl_{11}O_{19}$ 만이 CO 배출을 억제시키는 것을 확인하였다.

• 한국세라믹학회지
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• 제42권7호
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• pp.503-508
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• 2005

A simple and effective method for the synthesis of LiMn$_{2}$O$_{4}$ powder as a cathode material for lithium secondary battery is reported. Micrometer size LiMn$_{2}$O$_{4}$ was prepared by combustion synthesis technique employing initial mixture of l.l LiNO$_{3}$ -1.3Mn-0.7MnO$_{2}$-1NaCl composition. Parametric study of the combustion process including molar ratio of Mn/MnO$_{2}$ and NaCl concentration were carried out under air atmosphere. The combustion products obtained were additionally heat treated at the temperature 900$^{\circ}C$ and the washed by distilled water. The results of charging-discharging characteristics revealed that LiMn$_{2}$O$_{4}$ cell synthesized in the presence of NaCl had a high capacity and much better reversibility than one formed without NaCl An approximate chemical mechanism for LiMn$_{2}$O$_{4}$ formation is proposed.

• 한국전기전자재료학회논문지
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• 제23권4호
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• pp.303-310
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• 2010

We fabricated $La_{0.6}Sr_{0.4}MnO_3$ thin films using radio frequency (RF) magnetron sputtering. They were grown on sapphire substrates with various deposition conditions. After the growth of the $La_{0.6}Sr_{0.4}MnO_3$ thin films, they were annealed at various temperatures to be crystallized. We successfully fabricated single phase $La_{0.6}Sr_{0.4}MnO_3$ thin films with high electrical conductivity. The room temperature resistivity was $1.5{\times}10^{-2}{\Omega}{\cdot}cm$. It can be considered that $La_{0.6}Sr_{0.4}MnO_3$ thin films are one of the feasible candidates for electrodes for integrated device applications.

• 한국자기학회지
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• 제9권3호
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• pp.131-135
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• 1999

층상 페로브스카이트형 구조를 가진 망간 산화물의 전자구조를 이해하기 위하여 단일 층상을 가진 LaSrMnO4의 전자구조를 제1원리의 국소 밀도 범함수 이론을 근거로 사용하는 Full Potential Linearized Augmented Plane Wave(FLAPW)방법으로 구하였다. 또한 홀 농도 변환에 따른 자기구조의 변화의 이해를 위해 Mn4+의 Sr2MnO4의 전자구조 계산을 행하여 전자구조를 비교하였다. 총에너지 계산 결과, LaSrMnO4는 면내의 반강자성 구조가 강자성 구조보다 더 낮은 에너지를 가지고 있었다. 또한, Mn-O 팔면체의 c축으로의 야안-텔러 왜곡(Jahn-Teller distortion)에 의해 에너지 갭이 나타나며, 이에 따른 3z2-r2 궤도 정렬에 의해 2차원 면내의 반강자성 상태가 안정됨을 볼 수 있었다.

• Journal of Magnetics
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• 제18권1호
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• pp.26-29
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• 2013

$Mn_xFe_{3-x}O_4$ powders have been fabricated by using sol-gel methods; their crystallographic and magnetic properties were investigated by using X-ray diffraction, scanning electron microscopy, M$\ddot{o}$ssbauer spectroscopy, and vibrating sample magnetometer. The $Mn_xFe_{3-x}O_4$ ferrite powders annealed at $500^{\circ}C$ had a single spinel structure regardless of the $Mn^{2+}$-doping amount and their lattice constants became larger as the $Mn^{2+}$ concentration was increased. Their Mossbauer spectra measured at room temperature were fitted with 2 Zeeman sextets due to the tetrahedral and octahedral sites of Fe ions, which made them ferrimagnetic. The magnetic behavior of $Mn_xFe_{3-x}O_4$ powders showed that the $Mn^{2+}$-doping amount made their saturation magnetization increase, but there were no severe effects on their coercivities. The saturation magnetization of the $Mn_xFe_{3-x}O_4$ powder varied from 38 emu/g to 70.0 emu/g and their minimum coercivity was 111.1 Oe.

• 한국결정성장학회지
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• 제31권4호
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• pp.190-195
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• 2021

상온에서 PET 기판 위에 Mn-SnO₂/Ag/Mn-SnO₂ 3중 다층막을 RF/DC 마그네트론 스파터링 방식으로 제조하였다. EMP 시뮬레이션 결과에 따라 Mn-SnO₂의 막 두께는 40 nm, Ag 막 두께는 13 nm로 고정하였다. 550 nm 파장대역에서 측정한 3중막의 투과율은 82.9에서 88.1 % 범위였으며 면저항은 5.9에서 6.9 Ω/☐로 변화하였다. 가장 높은 성능지수(ϕ_TC)는 48.1 × 10^-3 Ω^-1로 나타났다. 곡률반경 4, 5 mm 조건에서 inner 밴딩과 out 밴딩의 굽힘시험을 10,000회 실시한 결과 Mn-SnO₂/Ag/Mn-SnO₂ 3중막의 저항변화율은 약 1.5 %로 탁월한 기계적 유연성을 보였다.

• 한국재료학회지
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• 제22권12호
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• pp.675-681
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• 2012

We aimed to examine the co-doping effects of 1/6 mol% $Mn_3O_4$ and 1/4 mol% $Cr_2O_3$ (Mn:Cr = 1:1) on the reaction, microstructure, and electrical properties, such as the bulk defects and grain boundary properties, of ZnO-$Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi = 0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Cr-doped ZBS, ZBS(MnCr) varistors were controlled using the Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$), ${\alpha}$-spinel ($Zn_7Sb_2O_{12}$), and ${\delta}-Bi_2O_3$ (also ${\beta}-Bi_2O_3$ at Sb/Bi ${\leq}$ 1.0) were detected for all of the systems. Mn and Cr are involved in the development of each phase. Pyrochlore was decomposed and promoted densification at lower temperature on heating in Sb/Bi = 1.0 system by Mn rather than Cr doping. A more homogeneous microstructure was obtained in all systems affected by ${\alpha}$-spinel. In ZBS(MnCr), the varistor characteristics were improved dramatically (non-linear coefficient, ${\alpha}$ = 40~78), and seemed to form ${V_o}^{\cdot}$(0.33 eV) as a dominant defect. From impedance and modulus spectroscopy, the grain boundaries can be seen to have divided into two types, i.e. one is tentatively assigned to ZnO/$Bi_2O_3$ (Mn,Cr)/ZnO (0.64~1.1 eV) and the other is assigned to the ZnO/ZnO (1.0~1.3 eV) homojunction.

• 한국세라믹학회지
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• 제22권4호
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• pp.61-65
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• 1985

$BaTiO_3$ powders doped with $BaTiO_3$ and $Nb_2O_5$ at 9$0^{\circ}C$ for 1hr. were synthesized by Direct Wet Process. These powders were very homogeneous and fine particle size. To obtain the highe PTCR effect AST($1/3Al_2O_3$.$3/4SiO_2$.$1/4TiO_2$) and $MnO_2$ were added in the semiconduc-ting $BaTiO_3$. In this case $Bi_2O_3$ and $MnO_2$ were used in the form of $Bi(NO)_3$ and $MnCl_2$.$4H_2O$ solution for Direct Wet Process. $BaTiO_3$ doped Nb2O5 and $MnO_2$ demostrated greater PTCR effect than $BaTiO_3$ doped $Nn_2O_5$ only.

• 한국전기전자재료학회논문지
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• 제25권5호
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• pp.398-402
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• 2012

Synthesis of $Li_2MnSiO_4$ was attempted by the conventional solid-state reaction method, and the phase formation behavior according to the change of the calcination condition was investigated. When the mixture of the three source materials, $Li_2O$, MnO and $SiO_2$ powders, were used for calcination in air, it was difficult to develop the $Li_2MnSiO_4$ phase because the oxidation number of $Mn^{2+}$ could not be maintained. Therefore, two-step calcination was applied: $Li_2SiO_3$ was made from $Li_2O$ and $SiO_2$ at the first step, and $Li_2MnSiO_4$ was synthesized from $Li_2SiO_3$ and MnO at the second step. It was easy to make $Li_2MnSiO_3$ from $Li_2O$ and $SiO_2$. $Li_2MnSiO_4$ single phase was developed by the calcination at $900^{\circ}C$ for 24 hr in Ar atmosphere as the oxidation of $Mn^{2+}$ was prevented. However, the $Li_2MnSiO_4$ was ${\gamma}-Li_2MnSiO_4$, one of the polymorph of $Li_2MnSiO_4$, which could not be used as the cathode materials in Li-ion batteries. By applying the additional low temperature annealing at $400^{\circ}C$, the single phase ${\beta}-Li_2MnSiO_4$ powder was synthesized successfully through the phase transition from ${\gamma}$ to ${\beta}$ phase.