• 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.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.560-565
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• 2005

Catalytic performances of zeolite catalysts such as H-mordenite(HM), H-Beta$(H{\beta})$, H-USY(HUSY) for the transmethylation between 1-methylnaphthalene(1-MN) and 2-methylnaphthalene(2-MN) were investigated in a fixed-bed flow reactor. $H{\beta}$ showed higher and more stable conversion than others to exhibit a high and stable 2-MN/1-MN ratio of 2.3 and 2,6-DMN/2,7-DMN ratio of 1.3 at the $1^{st}$ hour of time on stream under the reaction conditions as follows: reaction temperature of $350^{\circ}C$, reaction pressure of 1.5 MPa, WHSV of $2.7g_{feed}/g_{cat}{\cdot}h$ and the molar ratio of 1-MN and 2-MN of 1:1. The catalytic behavior has been discussed in relation with the catalyst pore structure and acidity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.80-83
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• 2003

Generally, forging process has been known to enhance most of the mechanical properties by developing the continuous metal flow across the forged stocks. However, we have found out that forging of Al 6061 did not always give the enhancement of the mechanical properties but the degradation of the original characteristics, especailly for a extruded Al 6061. There are several candidates for the culprit of this unfavorable phenomenon. We have been trying to clear out the cause of the mechanical degradation of the forged a extruded Al 6061. One of the most plausible causes seems to be that the particles containing Mn and/or Cr is coarsened and redistributed preferencially onto grain boundaries due to a repetitive exposure in an elevated temperature condition. On the other hand, a continuously cast Al 6061 did not show any strength degradation after a hot forging under the same process condition with the extruded Al 6061.

• Journal of Korea Foundry Society
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• v.35 no.6
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• pp.147-154
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• 2015

The effects of Sc and Sr elements on the modification of the eutectic $Mg_2Si$ phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic $Mg_2Si$ phase with additions of the Sr and Sc elements. Here, a fine eutectic $Mg_2Si$ phase and a decrease in the growth temperature of the eutectic $Mg_2Si$ phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic $Mg_2Si$ phase decreased and the effect on the modification of the eutectic $Mg_2Si$ phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic $Mg_2Si$ phase, and the resulting microstructure of the eutectic $Mg_2Si$ phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine ${\alpha}$-Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro-shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.

• Journal of Welding and Joining
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• v.8 no.4
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• pp.35-45
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• 1990

Casting are widely used nodays as complicated and diversified forming materials due to its superior castability. However the welding of cast iron has not been accompaniced satisfactory resulting in an microstructure change happened in the heat affected zone (HAZ), especially the graphite are formed and shaped consecutively in the area and it has great impact on the crack occuring and growth together with martensite forming in this area. It case of gray cast iron welding, it is required for pre-heat treatment or specific welding consumables to restrain forming the martensite in the HAZ. In this study, by applying the plasma surface overlaid welding. Fe-Mn-Al steel powder has been used for improvement of anti-crackability in the HAZ and much attention has been paid to establish the overlaid welding method for gray cast iron so that optimum welding conditions may prevent the cracking. With our experiments, we have found that to prevent defects which may occur in the HAZ, the overlaid welding technique for gray cast iron has been developed.

• Economic and Environmental Geology
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• v.21 no.1
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• pp.29-44
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• 1988

Equilibrium relations between garnet and orthopyroxene have been investigated by reversal experiments in the range of 20-45Kb and $975-1400^{\circ}C$ in the $FeO-MgO-Al_2O_3-SiO_2$(FMAS) system. A mixture of PbO with about 55 mol per cent $PbF_2$ was used as a flux and proved very effective. The Fe-Mg exchange reaction seems to have little or no compositional dependence at these conditions. Combination of the experimental results with the garnet mixing model of Ganguly and Saxena(1984) yields the following geothermometric expression for the common natural assemblages that can be represented essentially within the system $FeO-MgO-CaO-MnO-Al_2O_3-SiO_2$. $$T^{\circ}C=(1971+11.91P(Kb)+1510(X_{Ca}+X_{Mn})^{Gt}/(lnK_D+0.96)-273$$.

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

Interface effects on properties of NTC thermistors having Mn-Co-O spinel crytal 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 thennistors 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.

• Journal of Plant Biology
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• v.16 no.3_4
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• pp.40-44
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• 1973

Hawkeye(Fe-chlorosis resistant) and PI 54619-5-1(Fe-chlorosis sensitive) soybeans were grown with and without DPTA(diethylene triamine pentaacetic acid) in Yolo loam soil. The major purpose of the study was to compare leaf-stem distribution of microelements for different treatments which increase concentrations of microelements in plants to evaluate the role of the chelating agent in increasing translocation of the microelements. Plant responses and yields were recorded and Fe, Mn, Zn, Cu, Al, Co, N, Sn, Pb and Mo contents of leaves and stems were determined by emission spectrography. Sulfur(soil pH4) increased leaf concentrations of Mn, Zn, Cu, CO, Ni, Sn and Pb. DTPA, particularly at 50ppm in soil, increased leaf concentrations of Fe, Mn, Zn, Cu, Co, Ni and Mo. It increased Ti in leaves for the PI 54619-5-1 soybeans only. DTPA increased the ratios of the concentration in leaves to that in stems for Fe, Zn, Cu, Al, Ti, CO, Ni and Mo. Sulfur which increased the microelement concentration in both leaves and stems did not have this effect. DTPA increased the ratio at soil pH 6 and 8.5 in leaves to that in stems of the bush bean plants for Fe, Zn, Cu, Ni, but to a lesser extent in bush beans than in soybeans. PI 54619-5-1 soybeans tended to contain less of most of the metals than did Hawkeye soybeans.

• 한국해양학회지
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• v.29 no.4
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• pp.338-356
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• 1994

Sediment samples from the continental shelf of the South Sea of Korea are analysed to determine the concentration of Al, Fe, Mn, cu, Ni, Zn, Co, Cr and Pb. among these samples, fine-grained sediments were also analysed by a sequential extraction technique to know geochemical forms of the metals in this environments. The total concentration of Al, Fe, Cr, Ni, Cu and Zn in bulk sediments decreased gradually with the increase of distance from the coastal zone. This distribution patterns are well coincide with grain size distribution. However, the patterns of Mn, co and Pb do not follow such and overall distribution. The concentration of Pb, particularly, did not show any features in areal distribution, which may be result from different pathways to the sediments, compared to the other metals. the speculation data show that a considerable amount of Cd, Mn and Co are bounded in the carbonate fraction, accounting for 42.8%, 40.3% and 30.6%, respectively. Cu, Zn, Mn and Fe are largely associated to oxide fraction with proportions of 34.4%, 23.1%, 15.5% and 13.7%, respectively. However, the metals in residual fraction account for more than 50% of the total metal concentration, except for Mn. These observations emphasize that residual fraction in the dominant component controlling the elemental concentration.quartz and glauconite grains.Accordingly,these sediments are interpreted as an extension part of transgressive sand deposit that are widely distributed on the continental shalf floor of southern Yellow Sea.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.41-41
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• 2007

For use in spintronic materials, dilute magnetic semiconductors (DMS) are under consideration as spin injectors for spintronic devices[l]. $TiO_2$-based DMS doped by a cobalt, iron, and manganese et al. was recently reported to show ferromagnetic properties, even at temperatures above 300K and the magnetic ordering was explained in terms of carrier-induced ferromagnetism, as observed for a III-V based DMS. An anomalous Hall effect (AHE) and co-occurance of superparamagnetism in reduced Co-doped rutile $TiO_{2-\delta}$ films have also been reported[2]. Metal segregation in the reduced metal-doped rutile $TiO_2-\delta$ films still remains as problems to solve the intrinsic DMS properties. Superlattice films have been proposed to get dilute magnetic semiconductor (DMS) with intrinsicroom-temperature ferromagnetism. For a $TiO_2$-based DMS superlattice structure, each layer was alternately doped by two different transition metals (Fe and Mn) and deposited to a thickness of approximately $2.7\;{\AA}$ on r-$Al_2O_3$(1102) substrates by pulsed laser deposition. The r-$Al_2O_3$(1102) substrates with atomic steps and terrace surface were obtained by thermal annealing. Samples of $Ti_{0.94}Fe_{0.06}O_2$(TiFeO), $Ti_{0.94}Mn_{0.06}O_2$(TiMnO), and $Ti_{0.94}(Fe_{0.03}Mn_{0.03})O_2$ show a low remanent magnetization and coercive field, as well as superparamagnetic features at room temperature. On the other hand, superlattice films (TiFeO/TiMnO) show a high remanent magnetization and coercive field. An anomalous Hall effect in superlattice films exhibits hysisteresis loops with coercivities corresponding to those in the ferromagnetic Hysteresis loops. The superlattice films composed of alternating layers of $Ti_{0.94}Fe_{0.06}O_2$ and $Ti_{0.94}Mn_{0.06}O_2$ exhibit intrinsic ferromagnetic properties for dilute magnetic semiconductor applications.