• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.26 no.3
• /
• pp.115-120
• /
• 2016

$CeO_2$ is used as a co-catalyst with $TiO_2$ to improve the catalytic activity of $MnO_x$ and characterization of nano-sized powder is identified with de-NOx efficiency. A comparison between $MnO_x-CeO_2/TiO_2$ and single $CeO_2$ was conducted in terms of microstructural analysis to observe the behavior of $CeO_2$ in the ternary catalyst. The $MnO_x-CeO_2/TiO_2$ catalyst was synthesized by sol-gel method and the average particle size of the single $CeO_2$ is about $285{\mu}m$ due to the low thermal stability, whereas the particle size $MnO_x-CeO_2/TiO_2$ is about 130 nm. The strong interaction between Ce and Ti was identified through the EDS mapping by transmission electron microscopy (TEM). The improvement about 20 % of $de-NO_x$ efficiency is observed in the low-temperature ($150^{\circ}C{\sim}250^{\circ}C$) and vigorous oxygen exchange by well-dispersed $CeO_2$ is the reason of catalytic activity improvement.

• Resources Recycling
• /
• v.22 no.3
• /
• pp.57-64
• /
• 2013

Sulfurization reaction characteristics of $Eu_2O_3$, uranium oxides($UO_2$, $U_3O_8$), mixture of $Eu_2O_3$ and uranium oxides, Eu-doped uranium oxides($(U,Eu)O_2$, $(U,Eu)_3O_8$), and phase-separated products prepared by HOX (High temperature OXidation) of $(U,Eu)O_2$ were investigated in the temperature range from 400 to $800^{\circ}C$. Only $Eu_2O_3$ in the mixture of $Eu_2O_3$ and uranium oxides was converted into $Eu_3S_4$ by sulfurization reaction at $450^{\circ}C$ without reaction between them. Sulfurization reaction behavior of $(U,Eu)_3O_8$ and $(U,Eu)O_2$ up to $600^{\circ}C$ was similar to $U_3O_8$ and $UO_2$, respectively, while they were sulfurized into Eu-rich $(U,Eu)S_x$ and ${\alpha}-US_2$ at $800^{\circ}C$. In the sulfurization of RE-rich $(U,Eu)_4O_9$ and $U_3O_8$ prepared by high temperature oxidation, it was confirmed that RE-rich $(U,Eu)S_x$ and UOS phases were formed at $600^{\circ}C$. For Eu-rich $(U,Eu)O_2$ and $UO_2$ prepared by reduction of HOX products, it was identified that Eu-rich (U,Eu)OS was formed at $450^{\circ}C$ by sulfurization of Eu-rich $(U,Eu)O_2$, while $UO_2$ remained unreacted.

• Analytical Science and Technology
• /
• v.22 no.5
• /
• pp.432-438
• /
• 2009

In order to develop the analytical method for the pharmaceutical tablets containing ranitidine HCl by square wave voltammetry (SWV), $5.00{\times}10^{-5}M$ ranitidine HCl solutions prepared with phosphate buffers of various pH values were investigated by SWV. The well defined main peak due to the electrochemical reduction of $-NO_2$ in the structure of ranitidine moved towards the cathodic direction by -70 mV/pH as the pH values were increased indicating the involvement of hydrogen in its reduction. The calibration curve, the plot of peak currents (Ip) vs. concentrations of ranitidine HCl in the range between $1.00{\times}10^{-7}M$ and $1.00{\times}10^{-5}M$ showed linearity with slopes of $232,530{\mu}A/M$ (pH 6.14), $289,015{\mu}A/M$ (pH 7.07) and $232,843{\mu}A/M$ (pH 8.01). When one pharmaceutical tablet was simply dissolved in the phosphate buffer with a pH value of 6.14 and determined by standard addition method using SWV, the within-day precision study (n=4) resulted in the contents of ranitidine HCl as $171{\pm}2.1mg$ ($102{\pm}1.3%$ of the specified contents, RSD of 1.2%) in a tablet of Curan$^{(R)}$. The inter-day precision for 5 days was 1.1% of RSD. For Zantac$^{(R)}$ the within-day precision study (n=4) showed the contents of ranitidine HCl as $167{\pm}0.8mg$ ($99{\pm}0.5%$ of the specified contents, RSD of 0.5%) in a tablet and the inter-day precision for 5 days was 0.3% of RSD.