• Journal of Korean Society for Atmospheric Environment
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• v.23 no.1
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• pp.64-73
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• 2007

The catalytic activity of transition metals (Cu, Co, Mn, Fe and Ni) supported on ${\gamma}-Al_2O_3$ for the oxidation of toluene was investigated in the microreactor of fixed-bed type. The catalytic activity of transition metals for the oxidation of toluene turned out to be increasing in the order of Ni$Cu/{\gamma}-Al_2O_3$ catalysts for the oxidation of toluene increased with the increasing loadings of copper, reached the maximum activity at 5% loadings of copper, and decreased with higher loadings of copper in the catalysts. The activity of $Cu/{\gamma}-Al_2O_3$ catalysts for the oxidation of toluene decreased with the increasing calcination temperatures. This might result from the decreasing surface area of catalysts due to the sintering of copper oxide as well as ${\gamma}-Al_2O_3$ supports. The 5wt% $Cu/{\gamma}-Al_2O_3$ catalysts calcined at $400^{\circ}C$ for 4 hrs in the air showed the highest activity for the oxidation of toluene. Mutual inhibition was observed for the binary mixture of toluene and xylene. The activity of the easy-to-oxidize toluene was greatly decreased while the difficult-to-oxidize xylene was slightly decreased in the binary mixture of toluene and xylene. It might suggest that the inhibition of toluene and xylene in the binary mixture resulted from the competitive adsorption for the adsorbed oxygen on the catalytic surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.138-141
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• 2004

[ $MnO_2$ ]가 첨가된 $0.9Pb(Zr_{0.5}Ti_{0.5})O_3-0.2Pb[(Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3}]O_3$(0.8PZT-0.2PZNN) 세라믹스는 그 압전특성과 유전특성이 뛰어나지만 $1000^{\circ}C$ 이하의 낮은 소결 온도에서는 소결되지 않는다. $1000^{\circ}C$이하의 낮은 소결온도에서 소결하기 위해 CuO를 첨가한 결과, 소결온도 $920^{\circ}C$에서 소결성은 우수하였으나 그 압전 특성의 저하가 두드러졌다. 이는 XRD에서 확인한 결과에 따르면 CuO의 첨가가 우수한 MPB 조성으로 판명된 $MnO_2$ 가 첨가된 0.8PZT-0.2PZNN 세라믹스의 결정구조를 Rhombohedral 구조로 바꾸기 때문인 것으로 보였으며 이러한 문제는 PZNN의 비율을 조절하여 0.875PZT-0.125PZNN 세라믹스를 선택함으로 인해 해결할 수 있었다. 그러나 여전히 낮은 $Q_m$값을 높이기 위해서 $Al_2O_3$를 첨가하였고 그 결과 시편의 tetragonality 감소와 $Q_m$값의 증가를 확인할 수 있었으나 그 첨가량이 0.2wt% 이상일 경우에는 밀도의 감소로 인한 압전특성의 저하가 나타났다. 밀도의 향상을 위해 Zn and Ni excess 조성을 선택하였고 그 결과 0.5wt% $MnO_2$와 0.2wt% CuO 그리고 0.3wt% $Al_2O_3$를 첨가한 0.875PZT-0.125PZNN 세라믹스(Zn and Ni excess 조성)를 $920^{\circ}C$에서 소결한 경우 $k_p=0.581,\;Q_m=809,\;d_{33}=345\;pC/N\;and\;{\varepsilon}_{33}/{\varepsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.511-521
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• 2000

Investigation was carried out lean burn de-NOx properties of Pt-$TiO_2$ bifunctional catalyst by propylene in order to get the high de-NOx activity and the wide temperature window under coexistence of $SO_2$ and $H_2O$. Only noncatalyst and carrier catalyst themselves had NOx conversion activity at high temperature over $400^{\circ}C$. NOx conversion activity of catalysts exchanged copper ion resulted in Cu-$TiO_2$>Cu-ZSM-5>Cu-$Al_2O_3$>CU-YZ>Cu-AZ. Catalysts impregnated with platinum based on titania gave the results of high NOx conversion activity at low temperature. $250^{\circ}C$. Bifunctional catalysts based on Pt-$TiO_2$ showed high NOx conversion activity both at a low zone of $300^{\circ}C$ and a high zone of $500^{\circ}C$. Pt-$TiO_2$/$Al_2O_3$ catalyst gave the highest NOx conversion activity at a low temperature zone. and Pt-$TiO_2$/$Mn_2O_3$(21) catalyst gave the highest NOx conversion activity at a high temperature zone. Under the coexistence of $SO_2$ and $H_2O$. NOx conversion activities of 0.55wt%Pt-$TiO_2$/5wt%Cu-ZSM-5 catalyst was high both at a low and high temperature zone, and increased depending on oxygen concentration. 0.55wt%Pt-$TiO_2$/5wt%Cu-ZSM-5 catalyst showed the best correlation between de-NOx activities and the propyl ere conversion rates to CO on the log function.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.185-188
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• 1999

Biepitaxial Y$_1Ba_2Cu_3O_{7-x}$ (YBCO) and La$_{0.2}Sr_{0.8}MnO_3$ (LSMO) thin films have been prepared on SrTiO$_3$ buffer layer and MgO seed layer grown on Al$_2O_3$(11${\bar{2}}$0)substrates by dc-sputtering with hollow cylindrical targets, respectively. We charaterized Josephson properties and significantly large magnetoresistance in YBCO and LSMO films with 45$^{\circ}$ grain boundary junction, respectively. The observed working voltage (I$_cR_n$) at 77 K in grain boundary junction was below 10${\mu}$V, which is typical I$_cR_n$ value of single biepitaxial Josephson junction. The field magnetoresistance ratio (MR) of LSMO grain boundary juncoon at 77K was enhanced to 13%, which it was significant MR value with high magnetic field sensitivity at a low field of 250 Oe. These results indicate that inserting the insulating layer instead of the grain boundary layer with metallic phase can be possible to apply a new SIS Josephson junction and a novel magnetic device using spin-polarized tunneling junction.

• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.485-489
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• 2017

Polyethylene terephthalate (PET) has been widely applied in polymers and packaging industries to produce synthetic fibers, films, drink bottles or food containers. Therefore, it has become one of the major plastic wastes. In this article, glycolysis known as one of the main methods in PET chemical recycling was investigated using a glycol to break down the polymer into a monomer. Glycolysis of PET and ethylene glycol was performed in a micro-tubing reactor under various conditions. The effect of glycolysis conditions on the product distribution was investigated at experimental conditions of the EG/PET ratio of 1~4, the reaction time of 15~90 min and the reaction temperature of $250{\sim}325^{\circ}C$ with Mn and Cu catalysts. The highest yield of bis (2-hydroxyethyl) terephthalate monomer (BHET) was obtained as 89.46 wt% under the condition of the reaction temperature of $300^{\circ}C$ and the time of 30 min using 10 wt% $Cu/{\gamma}-Al_2O_3$ catalyst, with the PET and ethylene glycol ratio of 1 : 2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.459-462
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• 2001

Interface effects on properties of NTC thermistors having Mn-Co-O spinel crystal structure system are analyzed by a mixing rule in case of mixed types and layered types between CuO and Al$_2$O$_3$ added compounds. With adding CuO and Al$_2$O$_3$, The compounds form completely solid solution and their resistance and B constant are changed due to the variation of conduction electrons by their ionic substitutions. The properties of mixed NTC thermistors are depended on the logarithmic mixing rule by a dispersed phase and they show slightly lower values due to the lattice mixing affect in compared with calculated values. The resistance of layered NTC thermistors is depended upon the series mixing rule containing the value of an interface layer and effected by the variation of its thickness, and it is changed rapidly to the logarithmic mixing rule by the connection between two layers with increasing the interface layer

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.569-574
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• 2000

To improve the ductility of $Al_3Hf$ and $Al_3Ta$ intermetallic compounds, which are the potential temperature structural materials, the mechanical alloying behaviour and the effect of ternary additions on the $Ll_2$ phase formation were investigated. During the mechanical alloying by the SPEX mill, the $Ll_2$ $Al_3Hf$ intermetallic compound was formed after 6 hours of milling in AL-25%Hf system. In AL-25%Ta system, however, only the $D0_{22}$ $Al_3Ta$ intermetallic compound was formed until 30 hours of milling and the $Ll_2$ phase was not observed. In AL-12.5%M-25%Ta(M=Cu, Zn, Mn, Fe, Ni) systems, the additions of Cu and Zn had no effect on the $D0_{22}$ structure of the binary $Al_3Hf$ and the additions of Mn, Fe and Ni produced the amorphous phase. Therefore it was considered that these ternary additions could not overcome the energy difference between $Ll_2$ and $D0_{22}$ structures in the $Al_3Hf$ intermetallic compound. In AL-12.5%M-25%Hf(M=Cu, Zn, Mn, Fe, Ni)systems, the additions of Cu and Zn did not affect the $Ll_2$ structure of the binary $Al_3Hf$ but the additions of oMn, Fe and Ni produced the amorphous phase as they did in AL-12.5%M-25%Ta systems. Therefore, it was considered that the Ni, Mn and Fe additions promote the formation of amorphous phase in $Al_3X$ intermetallic compounds.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.327-336
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• 1994

The synergistic effects in mechanical mixture catalysts of Mo-V-O and metal oxide were investigated for the selective oxidation of acrolein. The metal oxides used are $SnO_2$, ${\alpha}-Sb_2O_4$, $WO_3$, ${\alpha}-Al_2O_3$, CuO, $MnO_2$, $Cu_2O$, MgO, CoO, and ZnO. Mechanical mixtures of Mo-V-O plus $SnO_2$ or ${\alpha}-Sb_2O_4$ had resulted in higher conversion of acrolein and higher yield of acrylic acid than Mo-V-O. The origin of the synergy is attributed to the cooperation of Mo-V-O and $SnO_2$ or ${\alpha}-Sb_2O_4$, in which $SnO_2$ or ${\alpha}-Sb_2O_4$ forms dissociated oxygens at their oxygen vacancies and transports them to Mo-V-O. $Cu_2O$, MgO, CuO, and $MnO_2$, increased conversion of acrolein but decreased yield of acrylic acid. CoO and ZnO inhibited the catalytic performance of Mo-V-O. The different role of these metal oxides is explained in terms of their oxidation-reduction properties.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.247-260
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• 1999

Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

• Journal of Environmental Science International
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• v.26 no.3
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• pp.303-309
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• 2017

Aeration with low energy micro-bubble generation and $UV/H_2O_2$ processes was introduced to verify the possibility of oxidation treatment for acid mine drainage. During 10 hours of aeration with micro-bubbles, Fe and As concentrations were decreased to 18.1 and 61.8%, respectively, while Cu, Cd, Al were kept at influent concentrations. Other heavy metals such as Mn, Cr, Pb, Zn, and Ni concentrations fluctuated due to the repetition of oxidation and release. Twenty days of aeration indicated the oxidation possibility for Cu, Cd, and Al. With the employment of $UV/H_2O_2$ processes, more than 77% of Cu and Fe removed, whereas slightly more than 30% of Cd and Al removed.