• Journal of Environmental Science International
• /
• v.13 no.6
• /
• pp.537-542
• /
• 2004

$V_{2}O_{5}/TiO_{2}$ catalysts promoted with Mn were prepared and tested for selective catalytic reduction of NOx in $NH_3.$ The effects of promoter content, degree of catalyst loading were investigated for NOx activity while changing temperatures, mole ratio, space velocity and $O_2$ concentration. Among the various $V-{2}O_{5}$ catalysts having different metal loadings, $V-{2}O_{5}$(1 wt.%) catalyst showed the highest activity(98%) under wide temperature range of $200-250^{\circ}C.$ When the $V-{2}O_{5}$ catalyst was further modified with 5 wt.% Mn as a promoter, the highest activity(90-47%) was obtained over the low temperature windows of $100-200^{\circ}C.$ From Mn-$V_{2}O_{5}/TiO_{2}$, it was found that by addition of 5 wt.% Mn on $V_{2}O_{5}/TiO_{2}$ catalyst, reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and NOx reduction. According to the results, NOx removal decreased for 10%, but the reaction temperature down to $100^{\circ}C.$

• Journal of the Korean Ceramic Society
• /
• v.37 no.4
• /
• pp.295-301
• /
• 2000

The effect of V2O5 addition on the low temperature sintering of Pb(Mn1/3Sb2/3)O3-PZT ceramics, which is known as a prominent material for piezoelectric transformer application was studied, and the densification behavior and piezoelectric characteristics of the samples as a function of heating rate were also examined. V2O5 led the system to liquid phase sintering by forming liquid phase during sintering, which accelerated densification through the particle rearrangement in the early stage of sintering. The liquid phase mostly existed at grain boundaries retarded the evaporation of PbO, while the densification temperature and the weight loss of V2O5-free samples were higher than those of samples with V2O5. Faster heating improved the densification of the samples regardless of V2O5 addition. The low temperature sintering at 100$0^{\circ}C$ was achieved in PMS-PZT ceramics with high density and reasonable dielectric and piezoelectric characteristics. This result revealed optimistic way to the development of multi-layered piezoelectric transformers.

• Metals and materials international
• /
• v.24 no.6
• /
• pp.1394-1402
• /
• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• Proceedings of the Korean Magnestics Society Conference
• /
• 1992.03a
• /
• pp.54-55
• /
• 1992

• Proceedings of the Korean Magnestics Society Conference
• /
• 1999.10a
• /
• pp.34-35
• /
• 1999

• Journal of the Korean Ceramic Society
• /
• v.28 no.4
• /
• pp.297-304
• /
• 1991

Dielectric hysteresis characteristics of Pb(Zr0.52Ti0.48)O3 ceramics have been investigated as a function of the amount of MnO2 addition ranged from 0.0 wt% in Pb(Zr0.52Ti0.48)O3 ceramics enhanced the dielectric strength, aging effect and remanent polarization, while reduced the coercive field. These results could be explained by the effect of Mn-Vo association due to the substitution of Mn for the (Zr, Ti) site in PZT.

• Journal of the Korean Ceramic Society
• /
• v.33 no.8
• /
• pp.883-888
• /
• 1996

• Economic and Environmental Geology
• /
• v.53 no.6
• /
• pp.687-694
• /
• 2020

Two oxidizing agents (KMnO4, H2O2), and one neutralizing agent (NaOH) were applied to evaluate Mn removal in mine drainage. A Mn2+ solution and artificial mine drainage were prepared to identify the Fe2+ influence on Mn2+ removal. The initial concentrations of Mn2+ and Fe2+ were 0.1 mM and 1.0 mM, respectively. The injection amount of oxidizing and neutralizing agents were set to ratios of 0.1, 0.67, 1.0, and 2.0 with respect to the Mn2+ mole concentration. KMnO4 exhibited a higher removal efficiency of Mn2+ than did H2O2 and NaOH, where approximately 90% of Mn2+ was removed by KMnO4. A black MnO2 was precipitated that indicated the oxidation of Mn2+ to Mn4+ after an oxidizing agent was added. In addition, MnO2 (pyrolusite) is a stable precipitate under pH-Eh conditions in the solution. However, relatively low removal ratios (6%) of Mn2+ were observed in the artificial mine drainage that included 1.0 mM of Fe2+. The rapid oxidation tendency of Fe2+ as compared to that of Mn2+ was determined to be the main reason for the low removal ratios of Mn2+. The oxidation of Fe2+ showed a decrease of Fe concentration in solution after injection of the oxidizing and neutralizing agents. In addition, Mn7+ of KMnO4 was reduced to Mn2+ by Fe2+ oxidation. Thus, the concentrations of Mn increased in artificial mine drainage. These results revealed that the oxidation method is more effective than the neutralization method for Mn removal in solution. It should also be mentioned that to achieve the Mn removal in mine drainage, Fe2+ removal must be conducted prior to Mn2+ oxidation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.292-293
• /
• 2007

In the study, in order to develop low temperature sintering ceramics for multilayer piezoelectric transformer, $(Pb,Ca,Sr)Ti(Mn,Sb)O_3$ ceramics were fabricated using $Na_2CO_3$, $Li_2CO_3$, $MnO_2$ and $Bi_2O_3$ as sintering aids and their dielectric and piezoelectric properties were investigated according to the amount of $Bi_2O_3$ addition. At the sintering temperature of $900^{\circ}C$, density, thickness vibration mode electromechanical coupling factor ($k_t$), thickness vibration mode mechanical quality factor ($Q_{mt}$) and dielecteic constant (${\varepsilon}_r$) showed the optimum value of $6.94[g/cm^3]$, 0.497, 3,162 and 209, respectively, for multilayer piezoelectric transformer application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.6
• /
• pp.472-477
• /
• 2000

Oxides of the form Mn$_{4}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO present properties that make them useful as power NTC thermistor for current limited. Electrical properties of Mn$_{3}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO power NTC thermistor such as I-V characteristics tim constant activation energy and heat dissipation coefficient measured as a function of temperature and composition. In Mn$_{4}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO system with the 5wt% addition of Co$_{3}$/O$_{4}$ it can be seen that resistivity and B-constant were increased as the ratio of ZnO/Mn$_{3}$/O$_{4}$ was increased. Heat dissipation constant, I-V characteristics and time constant showed similar behaviour compared with those of conventional thermistors. In particular resistance change ratio ($\Delta$R) the important factor for reliability varied within $\pm$5% indicating the compositions of these products could be available for power thermistor.