• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.228-231
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• 2004

We have studied local magnetization reversal and magnetic properties induced by Laser annealing method in the strip-patterned Ta/NiFe/FeMn/Ta and Ta/NiFe/FeMn/NiFe/Ta multilayers fabricated by ion-beam deposition. The films were exposed to the emission of the DPSS (Diode Pumped Solid State, Nd:YAG) laser under 600 G. The laser beam intensity increased up to 440 mW. When the laser illuminated the patterned film with the power of above 200 m W, the intensity of MR peak located in +87 Oe shrunk. A new MR peak was generated at -63 Oe. When the laser power is 400 mW, the location of positive MR peak(H$\sub$ex/) was changed slightly from +87 Oe to +76 Oe, and the MR ratio was decreased from 0.9% to 0.1 %. On the other hand, the new (negative) MR peak shifted from -63 Oe to -80 Oe, with the MR ratio increased up to 0.3%. As the illuminated area expanded, the intensity of opposite MR peak increased and it of negative MR peak decreased. This proved that the local reversal of exchange biasing should be realized by laser annealing.

• Journal of Electrochemical Science and Technology
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• v.3 no.2
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• pp.72-79
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• 2012

$Li_2MnSiO_4$ was synthesized using the solid-state method under an Ar atmosphere at three different calcination temperatures (900, 950, and $1000^{\circ}C$). The optimization of the carbon coating was also carried out using various molar concentrations of adipic acid as the carbon source. The XRD pattern confirmed that the resulting $Li_2MnSiO_4$ particles exhibited an orthorhombic structure with a $Pmn2_1$ space group. Cyclic voltammetry was utilized to investigate the capacitive behavior of $Li_2MnSiO_4$ along with activated carbon (AC) in a hybrid supercapacitor with a two-electrode cell configuration. The $Li_2MnSiO_4$/AC cell exhibited a high discharge capacitance and energy density of $43.2Fg^{-1}$ and $54Whkg^{-1}$, respectively, at $1.0mAcm^{-2}$. The $Li_2MnSiO_4$/AC hybrid supercapacitor exhibited an excellent cycling stability over 1000 measured cycles with coulombic efficiency over > 99 %. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3005-3012
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• 2013

The effect of Mn-promotion on high surface area Al-pillared montmorillonite (AlMMT) supported Co nanoparticles prepared by hydrothermal method have been investigated. A series of different weight% Mn-promoted Co nanoparticles were prepared and characterized by XRD, TPR, TGA, BET and SEM techniques. An increase in the surface area of MMT is observed with Al-pillaring. Fischer-Tropsch catalytic activity of the as prepared catalysts was studied in a fixed bed micro reactor at $225^{\circ}C$, $H_2/CO$ = 2 and at 1 atm pressure. The data showed that by the addition of Mn the selectivity of $C_1$ dropped drastically while that of $C_2-C_{12}$ hydrocarbons increased significantly over all the Mn-promoted Co/AlMMT catalysts. The $C_{13}-C_{20}$ hydrocarbons remained almost same for all the catalysts while the selectivity of $C_{21+}$ long chain hydrocarbons decreased considerably with the addition of Mn. The catalyst with 3.5%Mn showed lowest $C_{21+}$ and highest $C_2-C_{12}$ hydrocarbons selectivity due to cracking of long chain hydrocarbons over acidic sites of MMT.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.411-414
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• 2005

It is reported that $\varepsilon$ (HCP) and $\gamma$ (FCC) phases of a Fe-17Mn alloy transform to $\alpha'$ phase, which has BCC structure, under a deformation condition. In this study, we investigated the effect of strain-induced-transformed $\alpha'$ phase on sliding wear of the Fe-17Mn alloy that originally had e and y phases. Wear tests of the materials were carried out using a pin-on-disk wear tester at various loads of 0.5N-50N under a constant sliding speed condition of 0.38m/s against glass $(83\%\;SiO_2)$ beads. The sliding distance and radius were loom and 9 mm, respectively. Wear rate of the Fe-17Mn alloy was calculated by dividing the weight loss, measured to the accuracy of $10^{-5}g$ by the measured specific gravity and sliding distance. Worn surface and wear debris of the specimens were examined using an SEM and XRD. During the wear, $\alpha'$ phase of BCC structure was formed by strain-induced transformation when the applied wear load exceeded critical values. The $\alpha'$ phase formed by the strain induced transformation increased the wear rate of the Fe-17Mn alloy.

• Fire Science and Engineering
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• v.9 no.2
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• pp.29-36
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• 1995

In this study, the effect of Mn $O_2$ additive on the electrical characteristics of PZN-PSS-PZT Pyroelectric materials for the fire detactor was studies. PZT ceramics used this experimental is 4 composite system $[$Pb(Z $n_{1}$3/ N $b_{2}$3/) $O_3$＋Pb(S $n_{1}$3/ S $b_{2}$3/) $O_3$＋PbTi $O_3$＋PbZr $O_3$$]$The dielectric constants and dissipation factors decreases as to Mn $O_2$ concentration increases. At the Mn $O_2$ 0.5($\omega$t%), Pyroelectric coefficient shows 8(10$^{-8C}$$\textrm{cm}^2$$^{\circ}C$) which have the highst value among other additive contents. It is found that output voltage shows maximum peck at Mn $O_2$0.7($\omega$t％) is associated with the higher pyroelectric coefficient and Lowered dielectric constant.t.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.570-574
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• 1995

Magnetoresistance of NiFeCo/Cu/NiFeCo/FeMn uncoupled exchange biased sandwiches has been studied. The magnetoresistance change ratio, ${\Delta}R/R_{s}$ showed 4.1 % at a saturation field as low as 11 Oe in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(23\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. In this system, the magnetoresistance was affected by interlayer material and thickness. When Ti and Cu were used as the interlayer material in this structure, maximum magnetoresistance change ratio were 0.32 % and 4.1 %, respectively. 6.1 % MR ratio was obtained in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(15\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. The magnetoresistance change ratio decreased monotonically as the interlayer thickness increased. It was found that the exchange bias field exerted by FeMn layer to the adjacent NiFeCo layer was ~25 Oe, far smaller than that reported in NiFe/Cu/NiFe/FeMn spin valve structure(Dieny et. al., ~400 Oe). The relationship between the film texture and exchange anisotropy ha been examined for spin valve structures with Ti, Cu, or non-buffer layer.

• KSBB Journal
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• v.14 no.1
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• pp.119-123
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• 1999

A jet-loop reactor was used for the biological treatment of ethylene glycol(EG) which is a main component of polyester weight-loss wastewater, and is difficult to be removed by physicochemical treatments. Volumetric oxygen coefficient(kLa) of jet-loop reactor was significantly larfgeer that of air-lift reactor. When organic loading rates of synthetic polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$.day and 3.07 $kgCOD_{Cr}/m^3$.day, the effluent concentrations were measured as 154 $mgCOD_{Mn}/L$ and 156$mgCOD_{Cr}/L$, and removal efficiencies were found as 93%and 93.6%, respectively. The specific removal rate was proportionally increased from 0.25 to 1.60 $kgCOD_{Mn}$-removed/kgMLVSS.day as specific loading rate was increased from 0.25 to 1.72 $kgCOD_{Mn}$/kgMLVSS.day. Also, kinetics constants such as $K_s$, k, $K_d$, and Y were estimated as 89 mg/L, $0.05 hr^{-1}$, 0.1$day^{-1}$ and 0.78 respectively. When the organic loading rates of real polyester weight-loss wastewater were 2.64 $kgOD_{Mn}/m^3$. and 5.24 $kgCOD_{Cr}/m^3$. day, the effluent concentrations were measured as 150 $mgCOD_{Mn}$/L, and 306 $mgCOD_{Cr}$/L, and removal efficiencies were found as 93.2% and 93%, respectively. This study demonstrated that EG in the wastewater could be efficiently removed biologically using a jet-loop reactor.

• Journal of the Korean Chemical Society
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• v.43 no.6
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• pp.636-643
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• 1999

Green-emission intensity of a $Zn_{2-x}Mn_xSiO_4$ phosphor, which is a potential candidate as a green component in PDP device, significantly increases provided that the compound is additionally heat treated at 900$^{\circ}C$ after solid state reaction at 1300$^{\circ}C$. In order to verify origin of such an intensity enhancement after the additional heat treatment in association with the electronic and local structural change at around Mn ions, the Mn K-edge X-ray absorption spectra were recorded. From the analyses of the preedge peak corresponding to $1s{\rightarrow}3d$ bound state transition and XANES spectrum, it is known that most Mn ions are in +2 oxidation state and substitute Zn ion site regardless of the thermal treatment. In addition, EXAFS analyses revealed that Mn ions formed $MnO_4$ tetrahedra with the Mn-O bond length shortened by 0.01${\AA}$ and with reduced Debye-Waller factor in the thermally treated sample.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.4
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• pp.23-40
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• 1990

This study has been carried out to investigate into some effects of Mn content with varying amounts and austenite grain size on hardenability in boron-added Fe-C-Cr-Mo alloy systems. (1) Austenite grains have been found to hardly grow in the temperature range of $900^{\circ}C$ to $950^{\circ}C$, whereas they grow rapidly in the temperature range of $975^{\circ}C$ to $1100^{\circ}C$. (2) Austenite grain growth is considerably small with increasing holding time at a given austenitizing temperature and is, in particular, hardly found to occur at a temperature of $900^{\circ}C$. (3) The hardenability improves ramarkably as Mn content is increased at three different austenitizing temperatures $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. (4) The maximum hardenability is obtained from steels A, B and C austenitized at the $900^{\circ}C$, although Mn content is varied in each specimen.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.150-152
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• 2005

$La_{0.2}Ca_{0.8}MnO_3$ colossal magnetoresistance (CMR) powders and pellets were synthesized by sol-gel process involving a stable metal chelate complex with acetylacetone. The structural changes of reaction mixture were monitored by FT-IR spectroscopy and X-ray diffractometry. The microstructure of sintered samples and the cation composition of gel powder were studied by FE-SEM/EDS and ICP-AES. The magnetic property was investigated as a function of temperature.