• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.236-239
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• 2003

In this study, to develop the low temperature sintering ceramics for piezoelectric transformer, PSN-PNN-PZT system ceramics were manufactured as a function of $MnO_2$ addition. Its dielectric and piezoelectric characteristics were investigated. With increasing the amount of $MnO_2$ addition, electromechanical coupling factor(kp) were increased until 0.3wt% $MnO_2$ and that after decreased. mechanical quality factor(Qm) showed the maxinum value at 0.5wt% $MnO_2$. For piezoelectric transformer application, the 0.5wt% $MnO_2$ added specimen sintered at $1,000^{\circ}C$ showed the proper value of ${\varepsilon}r$= 1,646, kp=0.55 and Qm=439.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.511-516
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• 2004

A Li$[Co_{0.17}Li_{0.28}Mn_{0.55}]O_2$ cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as ${\alpha} -NaFeO_2$ structure type with the lattice constants of a = 2.8405(9) ${\AA}$ and c = 14.228(4) ${\AA}$. According to XANES analysis, the oxidation state of Mn and Co ions in the compound were 4+ and 3+, respectively. During the first charge process, the irreversible voltage plateau at around 4.65 V was observed. The similar voltage-plateau was observed in the initial charge profile of other solid solution series between $Li_2MnO_3\;and\;LiMnO_2$ (M=Ni, Cr...). The first discharge capacity was 187 mAh/g and the second discharge capacity increased to 204 mAh/g. As the increase of cycling number, one smooth discharge profile was converted to two distinct sub-plateaus and the discharge capacity was slowly decreased. From the Co and Mn K-edge XANES spectra measured at different cyclic process, it can be concluded that irreversible transformation of phase is occurred during continuous cycling process.

• Nuclear Engineering and Technology
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• v.21 no.1
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• pp.12-17
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• 1989

The correction factor of neutron fraction absorbed by $^{55}$ Mn in the MnSO$_4$ bath was determined for the absolute measurement of neutron emission rate by using the solution circulation-type manganese sulfate bath system. For the determination of this correction factor, I/f, the atomic number desnsity and the effective neutron capture cross section data of Mn, S and impurity elements in the MnSO$_4$ solution were determined. For the atomic number density determination, the MnSO$_4$ solution concentration was determined by using the volumetric EDTA titration and gravimetric method. The impurity contents were analyzed by using the ICP method. For the calculation of effective neutron capture cross sections, a FORTRAN computer program EASCAL was developed in this study. in which Westcott's parameters and Axton's empirical relations are used.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.55-61
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• 1994

Mn-Zn ferrite powder was obtained by wet method that was to be coprecipitated the metal ions of Fe2+, Mn2+ and Zn2+ with alkali solution. The target composition of the ferrite powder was 52 mol% Fe2O3, 24 mol% MnO, and 24 mol% ZnO, that was based on the region of high permeability. And the other ferrite powder was prepared by the dry method that was to be mixed the metal oxides as the above chemical composition. The wet method was compared with dry method for the powder properties and the electromagnetic characteristics of sintered cores. The synthesized powder by wet method was smaller particle size, narrower particle distribution, and higher purity than that of dry method. The initial permeability of sintered sample prepared by the wet method was 14000~28000, on the other side, 9000~15500 in case of the dry method.

• Journal of Magnetics
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• v.16 no.4
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• pp.457-460
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• 2011

In this paper, magnetic property and magnetocaloric effect (MCE) in perovskite manganites of the type $La_{(0.75-X)}Ce_XCa_{0.25}MnO_3$ (x = 0.0, 0.2, 0.3 and 0.5) synthesized by using the standard solid state reaction method have been reported. From the magnetic measurements as a function of temperature and applied magnetic field, we have observed that the Curie temperature ($T_C$) of the prepared samples strongly dependent on Ce content and was found to be 255, 213 and 150 K for x = 0.0, 0.2 and 0.3, respectively. A large magnetocaloric effect in vicinity of $T_C$ has been observed with a maximum magnetic entropy change (${\mid}{\Delta}S_M{\mid}_{max}$) of 3.31 and 6.40 J/kgK at 1.5 and 4 T, respectively, for $La_{0.55}Ce_{0.2}Ca_{0.25}MnO_3$. In addition, relative cooling power (RCP) of the sample under the magnetic field variation of 1.5 T reaches 59 J/kg. These results suggest that $La_{0.55}Ce_{0.2}Ca_{0.25}MnO_3$ compound could be a suitable candidate as working substance in magnetic refrigeration at 213 K.

• Investigative Magnetic Resonance Imaging
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• v.6 no.1
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• pp.35-40
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• 2002

Purpose : To evaluate the NMR relaxation properties and imaging characteristics of tissue-specificity for a newly developed macromolecular MR agent. Materials and methods : Phthalocyanine (PC) was chelated with paramagnetic ion, Mn.2.01g (5.2 mmol) of Phthalocyanine was mixed with 0.37g (1.4 mmol) of Mn chloride at $310^{\circ}C$ for 36 hours and then purified by chromatography (CHC13/CH3OH 98/2 v/v, Rf, 0.76) to obtain 1.04g (46%) of MnPC (molecular weight= 2000d). The $T1}T2$ relaxivity of MnPC was measured in 1.5T(64 MHz) MR using 0.1 mM MnPC. The MR image characteristics of MnPC was evaluated using spin-echo (TR/TE=500/14 msec) and gradient-echo (FLASH) (TR/TE=80/4 msec, flip angle=60) techniques in 1.57 MR scanner. The images of rabbit liver were obtained every 10 minutes up to 4 hours. To study the effect of concentration on image, 20 mM, 50 mM, 100 mM of MnPC were tested. Results : The relaxivities of MnPC at 1.5T(64MHz) were Rl=7.28 $mM^{-1}S^{-1},{\;}R2=55.56mM^{-1}S^{-1}$. Compared to the values of Gd-DTPA (Rl[=4.8 $mM^{-1}S^{-1})$], R2[=5.2 $mM^{-1}S^{-1}])$]), both T1/T2 relaxivities of MnPC were higher than those of Gd-DTPA. For both of SE and FLASH techniques, the contrast enhancement reached maximum at 10 minutes after bolus injection and the enhancement continued for more than 2 hours. When compared with small molecular weight liver agents such as Gd-EOB-DTPA, Gd-BOPTA and MnDPDP, MnPC was characterized by more prolonged enhancement time. The time course of MR images also revealed biliary excretion of MnPC. Conclusion : We developed a new macromolecular MR agent, MnPC. The relaxivities of MnPC were higher than those of small molecular weight Gd-chelate. Hepatic uptake and biliary excretion of MnPC suggests that this agent is a new liver-specific MR agent.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.55-55
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• 2011

• YAKHAK HOEJI
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• v.38 no.6
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• pp.725-732
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• 1994

To provide a basis for setting up an environmental pollution policy of Pusan, an investigation of metal contents in the soil of Pusan was carried out from May, 1993 to April, 1994. Soil was sampled from 10 sites of industrial area,8 sites of commercial area, 8 sites of residential area, 8 sites of green area and 8 sites of agricultural area. The industrial area was the most heavily polluted and the average contents of Cd, Cu, Zn, Mn, Pb and As were 0.580, 19.377, 67.348, 59.638, 58.555 and 1.006 ppm, respectively. In the soil of commercial area, the average contents of Cd, Cu, Zn, Mn, Pb and As were 0.453, 19.110, 63.384, 56.006, 37.466 and 0.578 ppm, respectively, and the average contents of Cd, Cu, Zn, Mn, Pb and As were 0.289, 10.312, 55.246, 55.536, 17.695 and 0.610 ppm, respectively, in the soil of residential area. The green area was the least polluted and the average contents of Cd, Cu, Zn, Mn, Pb and As were 0.215, 5.949, 19.366, 37.244, 6.856 and 0.295 ppm, respectively. In the soil of agricultural area, the average contents of Cd, Cu, Zn, Mn, Pb and As were 0.160, 7.077, 25.365, 51.485, 10.607 and 0.499 ppm, respectively The fact that the Cd content of agricultural area was lower than that of green area is remarkable.

• Journal of the Korean Electrochemical Society
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• v.20 no.3
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• pp.55-59
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• 2017

In this study, thermoelectric characteristics of perovskite $La_{0.5}Ca_{0.5}MnO_3$ (LCMO) nanomaterials were investigated by theoretical simulation and experimental analysis. Thermoelectric power factors calculated by DFT simulation were gradually enhanced as increase in annealing temperature. Maximum power factor was obtained with high magnitude of $S^2{\sigma}=566{\mu}W/m{\cdot}K^2$ at 1100 K through a dominant improvement of Seebeck coefficient compared with electrical conductivity. Experimentally, the LCMO nanomaterials were hydrothermally synthesized and then treated by post thermal annealing with temperature variation. X-ray diffraction and SEM analysis illustrated that LCMO exhibited orthorhombic perovskite structures with small grain size of 16~19 nm over 873 K. The results directly confirmed that improvement of crystallinity and decrease of mean grain size given by post thermal annealing lead to enhancements of electrical conductivity and Seebeck coefficient, respectively.

• Journal of the Korean Chemical Society
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• v.58 no.4
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• pp.351-358
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• 2014

Anionic (sodium lauryl sulphate, NaLS) cationic (cetyl ammonium bromide, CTAB) and non-ionic (Tween-80) surfactants have been found to inhibit the rate of oxiadation L-proline and L-methionine by alkaline $KMnO_4$. A first order dependence of rate of oxidation was observed with respect to $MnO_4{^-}$. The order of reaction in substrate and alkali was found to be fractional nearby 0.65 and 0.55 in Aminoacid and $OH^-$, respectively. An aggregation/association between $MnO_4{^-}$ and surfactant has been confirmed spectrophotometrically. A mechanism, involving kinetically inactive [$MnO_4{^-}$ surfactant] aggregate and consistent with kinetic data, has been proposed. The effect of surfactants has been discussed in terms of hydrophobic and electrostatic interactions.