• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.242-246
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• 2017

The application of composite cathode materials including $LiFePO_4$ (lithium iron phosphate) of olivine crystal structure, which has high thermal stability, were investigated as alternatives for hybrid battery-capacitors with a $LiMn_2O_4$ (spinel crystal structure) cathode, which exhibits decreased performance at high temperatures due to Mn-dissolution. However, these composite cathode materials have been shown to have a reduction in capacity by conducting life cycle experiments in which a $LiFePO_4$/activated carbon cell was charged and discharged between 1.0 V and 2.3 V at two temperatures, $25^{\circ}C$ and $60^{\circ}C$, which caused a degradation of the anode due to the lowered voltage in the anode. To avoid the degradation of the anode, composite cathodes of $LiFePO_4/LiMn_2O_4$ (50:50 wt%), $LiFePO_4$/activated carbon (50:50 wt%) and $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (50:50 wt%) were prepared and the life cycle experiments were conducted on these cells. The composite cathode including $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ of layered crystal structure showed stable voltage behavior. The discharge capacity retention ratio of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ was about twice as high as that of a $LiFePO_4/LiMn_2O_4$ cell at thermal stability experiment for a duration of 1,000 hours charged at 2.3 V and a temperature of $80^{\circ}C$.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.50-55
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• 2011

Energy resistance welding (ERW) is a pipe-producing process that has high productivity and low manufacturing cost. However, the high heat input of ERW degrades the mechanical property of the pipe. This study investigates the effect of heat input and alloying elements on microstructure and mechanical properties of ERW pipes. As the heat input increased, the ferrite amount increased. The ferrite amount in the weld centerline was larger than t at in the weld boundary. Medium carbon steels (S45C and K55) having 0.3~0.4wt.% carbon yielded a significant difference of ferrite amount in the weld centerline and weld boundary. High alloyed steels (DP780 and K55) having 1.5~1.6wt.% Mn showed a ferrite rich zone in the weld centerline. These phenomena are probably due to decarburization and demanganisation in the weld centerline. As the ferrite fraction increased, the hardness decreased a little for the S45C steels. In addition, DP780 steels and K55 steels showed that the hardness drops when those steels have a ferrite rich zone. But we demonstrated the good tensile property of the DP780 steels and K55 steels in which Mn is included.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.378-384
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• 1995

Effects of $La_2O_3$, $MnO_2$ on the dielectric and piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ system were investigated. The addition of La2O3 to the system enhanced electromechanical coupling factor (kp), piezoelectric constant (d33), but hardly changed mechanical quality factor (Qm). On the other hand, the addition of $MnO_2$ increased Qm significantly, but did not degrade kp and d33 so much. The piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ containing 0.1wt% $La_2O_3$, 0.4wt% $MnO_2$ were very good and kp, d33, Qm were 55%, 350$\times$10-12C/N, 780, respectively. The size of the grains was proportional to the change of c/a (tetragonality) ratio caused by the addition of $La_2O_3$ and $MnO_2$, and dielectric, piezoelectric properties were sensitive to the amountof pyrochrole phase.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.84-89
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• 2012

Attempts were made to develop a stable gray pigment at reducing atmosphere, substituting Ti in $ZrTiO_4$ with Mn, Fe, Co and Cu The pigment synthesized at $1300~1500^{\circ}C$ by solid state method with the composition of $ZrTi_{1-x-y}A_xB_yO_4$ (x = y = 0.005, 0.015, 0.035, 0.055, 0.075, 0.095, 0.115, 0.135, 0.155, 0.175 and 0.195 mole, A = Mn(III), Fe(III), Co(II, III) and Cu(II) (chromophores), B = Sb (counterion). The pigments were fired at $1400^{\circ}C$ for 3 h with substitute amount changes of Mn, Fe, Co and Cu to $ZrTiO_4$ crystals, and analyzed by Raman spectroscopy to figure out substitute limits. Results indicated 0.035 mole for Mn, 0.115 mole for Fe, 0.015 mole for Co and 0.015 mole for Cu as substitute limits, respectively. Figs. 1, 2, 3, and 4 represent each substitute pigments of Mn, Fe, Co and Cu. Synthesized pigment was applied to a lime and a lime-magnesia glaze at 7 wt% each, and fired at reducing atmosphere of $1240^{\circ}C$, soaking time 1h. Gray color was obtained with CIE-$L^*a^*b^*$ values at 44.55, -0.65, 1.19(Mn), 40.36, -0.90, 0.30(Fe), 42.63, -0.03, -1.49(Cu) and -40.79, -0.28, -0.91(Co), respectively.

• Journal of environmental and Sanitary engineering
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• v.16 no.4
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• pp.55-61
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• 2001

There are many reservoirs used as the source of water supply and they show various specific characteristics in water quality depend seasonal. Especially, there were not a little variations of water quality in summer, as a natural consequence it follows that stratification occured phenomenon and changed anaerobic condition in the bottom of reservoir, and then accumulated Fe and Mn substance in soil and sediment were resolved into water, it attributes to coloration. G purification plant located in Y gun is very small plant in which coloration occurs by Fe and Mn in every summer. Using this plant as a model, the removal methods of Fe and Mn were studied. After prechlorination plus LAS coagulation, Fe, Mn, $NH_3-N$ were decreased from 7.290 mg/l to 0.080 mg/l, from 0.480 mg/l to 0.075 mg/l, from 0.55 mg/l to 0.04 mg/l. But $THM_{s}$ was increased from 0.050 mg/l to 0.044 mg/l. It shows that the prechlorination plus LAS coagulation treatment process in purification plant is effective to remove Fe and Mn ion.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.81-87
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• 2009

An indium-tin oxide (ITO) coated spinel manganese oxide (${LiMn_2}{O_4}$, LMO) is prepared and its high-temperature ($55^{\circ}C$) cycle performance and rate capability are examined. A severe electrolyte decomposition and film deposition is observed on the un-coated ${LiMn_2}{O_4}$ cathode, which leads to a significant electrode polarization and capacity fading. Such an electrode polarization is, however, greatly reduced for the ITO-coated (> 2 mol%) LMO cathode, which leads to an improved cycle performance. This can be rationalized by a suppression of electrolyte decomposition, which is in turn indebted to a decrease in the direct contact area between LMO and electrolyte. The suppression of film deposition on the ITO-coated LMO cathode is confirmed by infra-red spectroscopy. The rate capability is also improved by the surface coating, which may be resulted from a suppression of resistive film deposition and high electric conductivity of ITO itself.

• Journal of Sensor Science and Technology
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• v.16 no.2
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• pp.120-125
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• 2007

The effect of $MnO_{2}$ as a sintering additive on the microstructures and the piezoelectric properties, especially mechanical quality factor, of 0.05 Pb$(Sb_{0.5}Nb_{0.5})O_{3}$-0.95 Pb$(Zr_{0.52}Ti_{0.48})O_{3}$ (PSN-PZT) piezoelectric ceramics was investigated. The samples were sintered at $1250^{\circ}C$ for 2 h. The crystal structure and surface morphology of the sample were examined using XRD and FE-SEM, respectively. A study on the influence of $MnO_{2}$ additives on the dielectric and piezoelectric properties showed that the $MnO_{2}$-added PSN-PZT system exhibited a high mechanical quality factor and well-situated piezoelectric properties. The optimized results of $d_{33}$ (319 pC/N), $k_{p}$ (55 %), and $Q_{m}$ (751.24) were obtained at 0.2 wt% $MnO_{2}$ added PSN-PZT piezoelectrics.

• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.803-813
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• 2015

The growth of Irpex lacteus F17 and manganese peroxidase (MnP) production in a selfdesigned tray bioreactor, operating in solid-state conditions at a laboratory scale, were studied. The bioreactor was divided into three layers by three perforated trays. Agroindustrial residues were used both as the carrier of bound mycelia and as a nutrient medium for the growth of I. lacteus F17. The maximum biomass production in the bioreactor was detected at 60 h of fermentation, which was consistent with the CO₂ releasing rate by the fungus. During the stationary phase of fungal growth, the maximum MnP activity was observed, reaching 950 U/l at 84 h. Scanning electron microscopy images clearly showed the growth situation of mycelia on the support matrix. Furthermore, the MnP produced by I. lacteus F17 in the bioreactor was isolated and purified, and the internal peptide sequences were also identified with mass spectrometry. The optimal activity of the enzyme was detected at pH 7 and 25℃, with a long half-life time of 9 days. In addition, the MnP exhibited significant stability within a broad pH range of 4-7 and at temperature up to 55℃. Besides this, the MnP showed the ability to decolorize the polymeric model dye Poly R-478 in vitro.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.55-65
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• 1991

Soil-to-plant transfer coefficients of Mn-54, Co-60, Zn-65, and Cs-137 were estimated for the edible parts of the rice, soybean, lettuce, carrot, and squash grown in different soils by radiotracer uptake experiments using pot cultures. The transfer coefficients of radionuclides were in the order of Zn-65 > Mn-54 > Cs-137 > Co-60 in most of the cases studied. The coefficients for soybean were roughly an order of magnitude higher than those for rice. Among vegetables, lettuce mostly showed the highest value and squash, the lowest. In the strongly acidic soils, transfer coefficients were much higher than in the moderately acidic soils. From the data obtained. crop-specific transfer coefficients of the four nuclides were proposed for the use in Korean food-chain radiation dose assessment.

• Journal of Microbiology and Biotechnology
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• v.21 no.1
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• pp.20-27
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• 2011

The purification and characterization of a $Mn^{2+}$-dependent alkaline serine protease produced by Bacillus pumilus TMS55 were investigated. The enzyme was purified in three steps: concentrating the crude enzyme using ammonium sulfate precipitation, followed by gel filtration and cation-exchange chromatography. The purified protease had a molecular mass of approximately 35 kDa, was highly active over a broad pH range of 7.0 to 12.0, and remained stable over a pH range of 7.5 to 11.5. The optimum temperature for the enzyme activity was found to be $60^{\circ}C$. PMSF and AEBSF (1 mM) significantly inhibited the protease activity, indicating that the protease is a serine protease. $Mn^{2+}$ ions enhanced the activity and stability of the enzyme. In addition, the purified protease remained stable with oxidants ($H_2O_2$, 2%) and organic solvents (25%), such as benzene, hexane, and toluene. Therefore, these characteristics of the protease and its dehairing ability indicate its potential for a wide range of commercial applications.