• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.8
• /
• pp.737-743
• /
• 2006

[ $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ ] powder was prepared using a simple combustion method. specially, ratio of 2:1, 3:2, 1:1, 2:3, 1:2 was adopted as acetate source/nitrate source. The diffraction pattern of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ powder showed that this compound could be classified as hexagonal $a-NaFeO_2$ structure (space group : $R\bar{3}m$). The size of powder was less than $1{\mu}m$. Small particle size of cathode powder would give a good ionic and electronic conductivity to cathode electrode, which made of cathode powder. As the increase of nitrate source-ratio, discharge capacity of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ at high charge-discharge rate was increased. When the ratio of acetate source/nitrate source was 1:2, discharge capacity at 10 C rate (2000 mA/g) was 180 mAh/g. It was $10{\sim}15%$ larger than that of powder, which have 2:1 as acetate source/nitrate ratio.

• Journal of Magnetics
• /
• v.9 no.1
• /
• pp.5-8
• /
• 2004

For the ferromagnetic combined samples, results of x-ray diffraction patterns showed no evidence of reaction between the $La_{0.67}Ca_{0.33}MnO_3, La_{0.67}Sr_{0.33}MnO_3$ and $CoFe_2O_4$. For the amount of $CoFe_2O_4$ increased, the Curie temperature of combined samples showed no appreciable change, whereas a metal-semiconductor transition temperature rapidly decreased. For the $La_{0.67}Sr_{0.33}MnO_3$ and 20 wt % $CoFe_2O_4$ combined sample, the metal-semiconductor transition temperature was decreased to 160 K compared with the $La_{0.67}Sr_{0.33}MnO_3$ with 192 K.

• Nuclear Engineering and Technology
• /
• v.20 no.2
• /
• pp.105-111
• /
• 1988

The chemical effects resulting from the capture of the thermal neutron by manganese in various crystalline permanganates, that is, potassium permanganate ammonium permangante and barium permanganate, have been investigated. The effect of pH of solvent on the distribution of radioactive manganese chemical species, that is, cationic $^{56}$ Mn, $^{56}$ MnO$_2$ and $^{56}$ MnO$_4$$^{[-10]}$ produced in the permanganates by $^{55}$ Mn(n, ｒ) $^{56}$ Mn reaction was studied by using various adsorbents and ion-exchanger, that is, zeolite A-3, kaolinite, alumina, manganese dioxide and Dowex-50 The distribution of radioactive MnO$_4$$^{[-10]}$ in kaolinite and alumina has higher than that in other adsorbents and ion-exchanger at a representative pH value of 4, 7 and 9, respectively. The yield of radioactive MnO$_4$$^{[-10]}$ is higher at pH 4 End pH 9 than at pH 7. The thermal annealing behavior of recoil manganese atoms produced in the permanganates by $^{55}$ Mn(n, ｒ) $^{56}$ Mn reaction was also studied. The retention of MnO$_4$$^{[-10]}$ in the thermal annealing is increased as annealing temperature increases when it was treated at 10$0^{\circ}C$ and 13$0^{\circ}C$. The recoil effect of permanganates was explained by the hot zone model.

• Journal of the Korean Magnetics Society
• /
• v.9 no.6
• /
• pp.296-300
• /
• 1999

Cross-shape structures of spin tunneling junctions were fabricated using DC magnetron sputtering and metal masks. The film structures were $substrate/Ta/NiFe/FeMn/NiFe/CoFe/Al_2O_3/CoFe/NiFe$ and $substrate/Ta/NiFe/CoFe/ Al_2O_3/CoFe/NiFe/FeMn/NiFe$. Fabrication conditions of insulating layer ($Al_2O_3$) and thickness and sputtering power of each film layer were varied, and maximum magnetoresistance ratio of 24.3 % was obtained. Magnetic characteristic variations in the above mentioned two structures and two types of substrates (Corning glass 7059 and Si(111)) were compared. Annealing of the junctions was performed to find out magnetic characteristic variations expected from the device fabrication. Magneoresistance Ratio were observed to maintain as-deposited value up to 150 $^{\circ}C$ annealing and then to drop rapidly after 180 $^{\circ}C$ annealing.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.4
• /
• pp.1067-1072
• /
• 2014

In this study, we report a new approach for $Mn_3O_4$-graphene nanocomposite by ex situ method. This nanocomposite shows two-dimensional aggregation of nanoparticle, and doping effect by decorated manganese oxide ($Mn_3O_4$), as well. The graphene film was made through micromechanical cleavage of graphite on the $SiO_2/Si$ wafer. Manganese oxide ($Mn_3O_4$) nanoparticle with uniform cubic shape and size (about $5.47{\pm}0.61$ nm sized) was synthesized through the thermal decomposition of manganese(II) acetate, in the presence of oleic acid and oleylamine. The nanocomposite was obtained by self-assembly of nanoparticles on graphene film, using hydrophobic interaction. After heat treatment, the decorated nanoparticles have island structure, with one-layer thickness by two-dimensional aggregations of particles, to minimize the surface potential of each particle. The doping effect of $Mn_3O_4$ nanoparticle was investigated with Raman spectra. Given the upshift in positions of G and 2D in raman peaks, we suggest that $Mn_3O_4$ nanoparticles induce p-doping of graphene film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.313-316
• /
• 2002

비철금속 습식 제련용 고효율 장수명의 양극을 개발하기 위해서 산소 과전압이 낮은 $MnO_{2}$를 촉매로 사용하여 반도체 산화물계의 산소선택성 전극을 제조하고 산화물 coating층의 미세구조와 전기화학적 특성을 분석하였다. PVDF : $MnO_{2}$의 함량비플 1 : 1 에서 1 : 40까지 정량적으로 변화시켰고， 용제의 점도에 지배적인 영향을 미치는 DMF의 함량을 각각의 고정된 PVDF : $MnO_{2}$의 함량비에서 변화시켜 용제를 제조하였으며 4% $HNO_{3}$ 용액에 세척된 Pb전극을 1.5 mm/sec 의 속도로 5회 dipping 하였다. PVDF : $MnO_{2}$ = 1 : 6인 경우 PVDF의 양이 증가하고 DMF의 양이 감소할수록 피막층이 두꺼워지고 PVDF : DMF = 4 : 96인 경우 pb 전극의 피막층이 얇기 때문에 박리현상이 일어났으며 이는 산화물 용제의 낮은 점도 때문인 것으로 판단된다. 또한 PVDF : DMF = 10 : 90의 경우는 5회 dipping 하여 약 $150{\mu}m$의 피막층을 형성하였다. PVDF : Mn02의 함량비가 1:1에서 1:6 까지는 DMF의 함량에 무관하게 전극 특성이 나타나지 않았지만 $MnO_{2}$의 양이 상대적으로 증가하면 cycle 이 증가하더라도 거의 일정한 전류 값을 갖고$MnO_2$와 PVDF의 비가 20:1 이상의 조성에서는 균일한 CV 특성을 나타냈다 이는 $MnO_{2}$가 효과적으로 촉매 작용을 한 것으로 판단되며 anodic polarization에 의한 산소 발생 과전압도 약 1.4V 정도로 감소되었다.

• Journal of the Korean Ceramic Society
• /
• v.25 no.2
• /
• pp.173-183
• /
• 1988

Effects of oxide additives such as MoO3, MnO2 ZrO2 and Fe2O3 on the phase separation and the chemical durability of sodium borosilicate glasses which are the host of waste glasses have been investigated as the basic study on the nuclear-waste immobilization through vitrification. MoO3 and MnO2 were found to be phase separation promotors which increased the temperature as well as catalyzed nucleation and growth for the phase separation of the 10Na2-O-3OB2O3-6OSiO2 (wt%) parent glass within the immiscibility region. The glasses had the interconnected phase-separated structure as the amount of addition increased. On the other hand, ZrO2 and Fe2O3 were inhibitors which showed the reverse effects to the above promotors. It was also found that addition of MoO3 could cause the phase separaton of the 20Na2O-10B2O3-70SiO2(wt%) glass even within the miscibility region. Addition of ZrO2 and Fe2O3 increased the chemical durability of the parent glass within the immiscibility region. Within the miscibility region, however, the addition of 1.96 wt % of MoO3 increased the chemical durability considerably, while MnO2 had little effects.

• Journal of the Korean Ceramic Society
• /
• v.13 no.3
• /
• pp.13-20
• /
• 1976

The magnetic properties, especially the magnetostriction, of ferroxplana $Zn_{1-x}$$M_X$Y(x=0.0, 0.2, 0.4, 0.6) were investigated at room temperature. In general, the Curie temperature and the permeability of ferroxplana $Zn_{1-X}$$Mn_X$Y increased while the amount of the other phase decrease with increased concentration of dopant $Mn^{2+} for $Zn^{2+}. The magnetostriction constnats K1, K2, K3 and K4 for ZnY were ＋0.3, -5.0, -4.3 and $-4.8{\times}$$10^{-6} while that for 4Zn^0.8$ $Mn^0.2$Y were ＋2.5, -5.4, -6.0 and $-3.4{\times}10^{-6}$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.1
• /
• pp.64-70
• /
• 2006

In this study, the $LiCoO_2/LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ mixed cathode electrodes were prepared and their electrochemical performances were measured in a high cut-off voltage. As the content of $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ increased in a mixed cathode, the reversible specific capacity and cycleability of the electrode enhanced, but the rate capability was deteriorated. On the contrary the rate capability of the cathode enhanced, but the reversible specific capacity and cycleability were deteriorated, increasing the content of $LiCoO_2$ in the mixed cathode. The cell of $LiCoO_2/LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ ($50:50 wt\%$) mixed cathode delivered a discharge capacity of ca. 168 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of ca. 152 mAh/g was obtained at a 2.0 C rate. However, the cell showed very stable cycleability: the discharge capacity of the cell after 20th charge/discharge cycling maintains ca. 163 mAh/g.

• Journal of the Korean Ceramic Society
• /
• v.38 no.10
• /
• pp.894-900
• /
• 2001

The spinel $Li{Mn_2}{O_4}$ catalysts for $CO_2$ decomposition were synthesized by a sol-gel method using manganese acetate and lithium hydroxide as starting materials through drying at $150^{\circ}C$ for 12 hrs under oxygen atmosphere followed by heat treatment at $480^{\circ}C$ for 12 hrs. The synthesized $Li{Mn_2}{O_4}$ were reduced by hydrogen for 3 hrs at various temperatures and the decomposition rate of carbon dioxide was investigated at 300, 325, 350, 375 and $400^{\circ}C$ using the $Li{Mn_2}{O_4}$ reduced by hydrogen gases. As a result of experiment, the optimum temperature of hydrogen reduction and $CO_2$ decomposition was shown $350^{\circ}C$. The physicochemical properties of the spinel $Li{Mn_2}{O_4}$ the reduced $Li{Mn_2}{O_4}$ and the $Li{Mn_2}{O_4}$ after $CO_2$ decomposition were examined with XRD, SEM and TGA.