• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.552-555
• /
• 1995

The magnetic properties of Mg-Mn ferrites were investigated in the composition range of $Mg_{a}Mn_{b}Fe_{c}O_{4\pm\delta}$ (a+b+c=3) with the addition of $Al_{2}O_{3}$. In $MgO-MnO-Fe_{2}O_{3}$ ternary system, the spinel single phase existed within the composition range of MgO-50 mol%, MnO-70 mol% and $Fe_{2}O_{3}-60\;mol%$. The saturation magnetic flux density increased with the increase of $Fe_{2}O_{3}$ content and showed the maximum at the stoichiometric composition of $(Mg,Mn)Fe_{2}O_{4}$. In $Mg_{x}Mn_{1-x}Fe_{2}O_{4}(x=0.2~0.8)$ system, the saturation magnetic flux density showed the maximum at $Mg_{0.2}Mn_{0.8}Fe_{2}O_{4}$. The addition of $Al_{2}O_{3}$ resulted in the decrease of saturation magnetic flux density but increased the electrical resistivity.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.7
• /
• pp.1091-1096
• /
• 2007

Water dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with four kinds of aminoacids ligands: arginine, cystein, histidine, and methionine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, and FT-IR spectroscopy. The optical properties of the aminoacids capped ZnS:Mn colloidal nanocrystals were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 575 nm (orange light emissions) with PL efficiencies in the range of 4.4 to 7.1%. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were in the range of 5.3 to 11.7 nm.

• Journal of Power System Engineering
• /
• v.9 no.1
• /
• pp.76-81
• /
• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.442-445
• /
• 2001

In this study, microstructural and dielectric properties of $Pb_{0.83}(La_{0.2}Ce_{0.8})_{0.08}TiO_3$(PCT) ceramics as a function of $MnO_2$ addition were investigated for 30MHz ceramic resonator application. Grain size was gradually increased according to the increase of $MnO_2$ addition amount and showed the highest value of $1.502{\mu}m$ at the 0.9wt% $MnO_2$. Moreover, density showed the highest value of $7.582 g/cm^3$ at the 0.7wt% $MnO_2$.All the composition ceramics,curie temperature was nearly constant around $330^{\circ}C$

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1537-1539
• /
• 1997

In this study, the dielectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ Ceramics have been investigated as a addition of the amount of $MnO_2(0{\leq}x{\leq}0.9wt%)$. The Temperature-dependant dielectric characteristics of 0.9PMN-0.1PT relaxor ferroelectric system were improved by enhencing the extent of the diffuse phase transition(DPT). The maximum dielectric permittivity decreased by substitution $MnO_2$ and the dielectric loss decreased with increasing $MnO_2$ substitution amount. It is expected decreasing in inner heat energy for temperature with increasing $MnO_2$ substitution.

• Journal of the Korean Magnetics Society
• /
• v.15 no.2
• /
• pp.113-117
• /
• 2005

Multiferroic $HoMnO_3$ single crystal was prepared using 4-point focused floating zone furnace, and polycrystalline $HoMn_{1-x}\;^57Fe_xO_3$ (x=0.00, 0.01, 0.02, 0.05) powders have been prepared by solid state reaction. Their magnetic and crystallographic properties are studied using MPMS, PPMS, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structure found to be a hexagonal and a magnetic easy-axis is (110) direction. As the external applied magnetic field increases, temperature of the dielectric constant anomaly is decreased. $HoMn_{0.95}\;^{57}Fe_{0.05}O_3$ shows huge quadrupole splitting value from the $M\ddot{o}ssbauer$ spectra.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.12
• /
• pp.1058-1064
• /
• 1994

Mn/In$_2O_3$ systems with a variety of Mn mol${\%}$ were prepared to investigate the effect of Mn-addition on the catalytic activity of Mn/In$_2O_3$ in the oxidative coupling of methane. The oxidative coupling of methane was examined on pure In$_2O_3$ and Mn/In$_2O_3$ catalysts by cofeeding gaseous methane and oxygen under atmospheric pressure between 650 and 830 $^{\circ}C$. Although pure In$_2O_3$ showed no C$_2$ selectivity, both the C$_2$ yield and the C$_2$ selectivity were increased by Mn-doping. The 5.1 mol${\%}$ Mn-doped In$_2O_3$ catalyst showed the best C$_2$ yield of 2.6${\%}$ with a selectivity of 19.1${\%}$. The electrical conductivities of pure and Mn-doped In$_2O_3$ systems were measured in the temperature range of 25 to 100 $^{\circ}C$ at PO$_2$'S of 1 ${\times}$ 10$^{-7}$ to 1 ${\times}$ 10 $^{-1}$ atm. The electrical conductivities were decreased with increasing Mn mol${\%}$ and PO$_2$, indicating the specimens to be n-type semiconductors. Electrons serve as the carriers and manganese can act as an electron acceptor in the specimens. Manganese ions doped in In$_2O_3$ inhibit the ionization of neutral interstitial indium or the transfer of lattice indium to interstitial sites and increase the formation of oxygen vacancy, giving rise to the increase of the concentration of active oxygen ion on the surface. It is suggested that the active oxygen species adsorbed on oxygen vacancies are responsible for the activation of methane.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2008.11a
• /
• pp.9-10
• /
• 2008

Triple layers structure of $SiO_2$/ZnS:Mn/ZnS was synthesized by using ion substitution and chemical precipitation method. Each layer thickness was controlled by adjusting the concentration of manganese (II) acetate ($Mn(CH_3COO)_2$) and tetraethyl orthosilicate (TEOS). The structure and morphology of prepared phosphors were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microscopic analyzer (EPMA). Photoluminescence (PL) properties of ZnS with different layer thickness and amount of Mn activator were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of Mn activator.

• Progress in Superconductivity and Cryogenics
• /
• v.14 no.1
• /
• pp.1-3
• /
• 2012

LMO($LaMnO_3$) buffer layer of superconducting coated conductor was deposited on IBAD-MgO template in the plasma atmosphere at $650^{\circ}C$ which is relatively low compared with conventional deposition temperature of more than $800^{\circ}C$. Deposition method of LMO was DC sputtering, and target and deposition chamber were connected to the cathode and anode respectively. When DC voltage was applied between target and chamber, plasma was formed on the surface of target. The tape substrate was located with the distance of 10 cm between target and tape substrate. When anode bias was connected to the tape substrate, electrons were attracted from plasma in target surface to the tape substrate, and only tape substrate was heated by electron bombardment without heating any other zone. The effect of electron bombardment on the surface of substrate was investigated by increasing bias voltage to the substrate. We found out that the sample of electron bombardment had the effect of surface heating and had good texturing at low controlling temperature.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.4
• /
• pp.235-240
• /
• 2000

Screen-printing and doctor blade method were investigated and proposed as an electrode coating process for high power capacitor. CV measured from the amorphous $MnO_2$ electrode prepared by screen-printing shows closer to ideal capacitor characteristics. Specific capacitances calculated from CVs with potential scan rate of 50mV/s were 5.8, 81.8, and 172.0 F/g for electrode thickness of $140{\mu}m,\;24{\mu}m,\; 3{\mu}m$, respectively. Assumed that utilization of active $MnO_2$ in electrode of screen-printing is $100\%$, those were $3.4\%$ in one of paste method and $47.6\%$ in one of doctor blade method. The screen-printing can be good technique to coat thin film on current collector for high power application.