• Korean Journal of Materials Research
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• v.14 no.8
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• pp.595-599
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• 2004

We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.143-146
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• 2007

Birnessite-type manganese dioxide($MnO_2$) was coated uniformly onto carbon nanotubes (CNTs) through a spontaneous direct redox reaction between CNTs and permanganate ions($MnO_4\;^-$). The initial specific capacitance of the $MnO_2/CNT$ nanocomposite in an organic electrolyte at a large current density of 1 A/g was 250 F/g, which is equivalent to 139 mAh/g based on the total weight of the electrode material including the electroactive material, conducting agent and binder. The specific capacitance of the $MnO_2$ in the $MnO_2/CNT$ nanocomposite was as high as 580 F/g (320 mAh/g), indicating excellent electrochemical utilization of the $MnO_2$. The addition of CNTs as a conducting agent can improve the high rate capability of $MnO_2/CNT$ nanocomposite considerably. An analysis of the in-situ X-ray absorption near-edge structure (XANES) showed an improvement in the structural and electrochemical reversibility of the $MnO_2/CNT$ nanocomposite by heat-treatment.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.428-441
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• 1992

We synthesized a series of binuclear pentadentate Schiff base complexes such as $Co(Ⅱ)_2$ (BSPP)($H_2O)_2$, $Co(Ⅱ)_2$ (BSPD)($H_2O)_2$, $Mn(Ⅱ)_2$ (BSPP)($H_2O)_2$ and $Mn(Ⅱ)_2$ (BSPD)($H_2O)_2$, mononuclear pentadentate Schiff base complexes such as Co(Ⅱ)(BSP)($H_2O)$ and Mn(Ⅱ)(BSP)($H_2O)$. The composition of these complexes identified by IR, UV-visible spectrum, T.G.A., DSC, and elemental analysis. The electrochemical redox processes have been examined by cyclic voltammetry and differential pulse polarography with glassy carbon electrode in 0.1M TEAP-Py(-DMSO and -DMF) as a supporting electrolyte solution. As a result of electrochemical measurements, the reduction processes for pentadentate binuclear Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to four steps in $M(Ⅲ)_2$ / $Mn(Ⅱ)_2$ and $Mn(Ⅱ)_2$ / $M(Ⅰ)_2$ (M; Co, Mn) two processes through each two reduction steps with one electron, by contrast, the mononuclear pentadentate Schiff base cobalt(Ⅱ) and manganese(Ⅱ) complexes occurred to two steps in M(Ⅲ) / M(Ⅱ) and M(Ⅱ) / M(Ⅰ) (M; Co, Mn) two processes with one electron reduction steps.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.193-199
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• 2006

The catalytic oxidation of toluene over $-Al_2O_3$ supported copper-manganese oxide catalysts in the temperature range of $160-280^{\circ}C$ was investigated by employing a fixed bed flow reactor. The catalysts were characterized by BET, scanning electron microscopy (SEM), temperature-programmed reduction(TPR), temperature-programmed oxidation(TPO), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD) techniques. Catalytic oxidation of toluene was achieved at the below $280^{\circ}C$, and the optimal content of copper and manganese in the catalyst was found to be 15.0 wt％Cu-10.0 wt％Mn. From the TPR/TPO and XPS results, the redox peak of 15 Cu-10 Mn catalyst shifted to the lower temperature, and the binding energy was shifted to the higher binding energy. Furthermore, It is considered that $Cu_{1.5}Mn_{1.5}O_4$ is superior to Mn oxides and CuO in the role as active factor of catalysts from the XRD results and also catalytic activities are dependent on the redox ability and high oxidation state of catalysts.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.6
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• pp.246-251
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• 2001

The $[(Pb_{1-x}$La_{2x/3})TiO_3$, X=0.2] powder was synthesized by the hydrothermal method, and their sintering and dielectric properties according to Mn additive were examined. The relative density of sintered PLT specimen at $1150^{\circ}C$ for 5 hrs with Mn 0.02 mol% additive was 96.7%. The dielectric properties of sintered PLT specimen were changed by content of Mn and increacement of sintering temperature. Dissipation factor was improved by increasing of measuring temperature. Curie temperature of sintered PLT specimens was decreased with increasing of Mn additive.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.348-351
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• 2012

The effect of the addition of Cu on the catalytic activity of the $Mn/CeO_2-ZrO_2$ catalyst for the low-temperature SCR reaction of NO was investigated. Three different amounts of Cu, 5, 10, and 15 wt%, were impregnated on the $Mn/CeO_2-ZrO_2$ catalyst. The characteristics of the synthesized catalysts were examined by BET, XRD, XPS, and $H_2-TPR$ analyses. The de-NOx efficiency of the Cu-added catalysts increased with the amount of Cu. When 15 wt% Cu was impregnated, the deNOx efficiency was the highest, reaching as high as 99%. The increased deNOx efficiency is attributed to the enhanced reducing power stemming from the interaction between Mn and Cu on the catalyst surface.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.60-64
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• 1992

In the ceramics of PFN-PFW system modified with MnO2 dielectric properties and the relation of its microstructure have been investigated. The amount of MnO2 variations was 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 mol%, respectively. In the result of the microstructure and electrical properties, the solid solution range of MnO2 was 0.15 mol%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1056-1060
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• 2004

In this study, 0.96B $i_{0.5}$($Na_{0.84}$ $K_{0.16}$)$_{0.5}$Ti $O_3$ + 0.04SrTi $O_3$ + 0.3 wt% N $b_2$ $O_{5}$+0.2 wt% L $a_2$ $O_3$ + xwt % Mn $O_2$ were investigated as a function of the amount of Mn $O_2$ addition in order to improve dielectric and piezoelectric properties of Lead-free piezoelectric ceramics. With increasing the amount of Mn $O_2$ addition, the density, electromechanical coupling factor( $k_{p}$), piezoelectric constant( $d_{33}$, $g_{33}$) and curie temperature (Tc) showed the maximum value of 5.7 g/㎤, 38 %, 219 pC/N, 26 mVㆍm/N and 32$0^{\circ}C$ at 0.1 wt% Mn $O_2$ addition, respectively, and mechanical quality factor( $Q_{m}$ ) showed the maximum value of 158 at 0.3 wt% Mn $O_2$ addition.ddition.ion.n.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.612-616
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• 2000

The effect of Co dopant on the (La, Sr)MnO3 cathode was investigated. La2Zr2O7 and SrZrO3 were formed as the reaction products between YSZ and LSMC. The reactivity of LSMC with YSZ increased with increasing Co content. However, the cathodic polarization resistance decreased with increasing Co doping. Therefore, doping Co at Mn site in the (La, Sr)MnO3 cathode was effective on controlling the polarization resistance of the cathode. The polarization property of LSMC-YSZ composite(60 wt%: 40 wt%) cathode was better than that of LSMC single cathode.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.92-97
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• 2008

Selective catalytic reduction (SCR) of NO with ammonia was carried out over the physical mixture of $MnO_2$ and K or Cu-loaded activated carbons (AC) at low temperature. Introduction of oxygen affected positively the reduction of NO. Metal-impregnated AC showed significantly enhanced catalytic activity. Without water, the mixed catalyst of $MnO_2$ and K-loaded AC exhibited the best activity in the reduction of NO at $120^{\circ}C$. On the contrary, the activities of all the catalysts were significantly diminished in the presence of water. The mixed catalyst of $MnO_2$ and Cu-loaded AC treated with nitric acid and heat (1 : 1, w/w) exhibited the better activity for the reduction of NO than each single catalyst in presence of water.