• Journal of Environmental Science International
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• v.15 no.3
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• pp.221-227
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• 2006

Oxidative TCE decomposition over $TiO_2$-supported single and complex metal oxide catalysts has been conducted using a continuous flow type fixed-bed reactor system. Different types of commercial $TiO_2$ were used for obtaining the supported catalysts via an incipient wetness technique. Among a variety of titanias and metal oxides used, a DT51D $TiO_2\;and\;CrO_x$ would be the respective promising support and active ingredient for the oxidative TCE decomposition. The $TiO_2-based\;CrO_x$ catalyst gave a significant dependence of the catalytic activity in TCE oxidation reaction on the metal loadings. The use of high $CrO_x$ contents for preparing $CrO_x/TiO_2$ catalysts might produce $Cr_2O_3$ crystallites on the surface of $TiO_2$, thereby decreasing catalytic performance in the oxidative decomposition at low reaction temperatures. Supported $CrO_x$-based bimetallic oxide systems offered a very useful approach to lower the $CrO_x$ amounts without any loss in their catalytic activity for the catalytic TCE oxidation and to minimize the formation of Cl-containing organic products in the course of the catalytic reaction.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.1-10
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• 2010

This is an overview paper reporting our most recent work on processing and microstructure of nano-structured oxides and their photoluminescence and photo-catalysis properties. Zinc oxide and related transition metal oxides such as vanadium pentoxide and titanium dioxide were produced by a combination of magnetron sputtering, hydrothermal growth and atmosphere controlled heat treatment. Special morphology and microstructure were created including nanorods arrays, core-brushes, nano-lollipops and multilayers with very large surface area. These structures showed special properties such as much enhanced photoluminescence and chemical reactivity. The photo-catalytic properties have also been promoted significantly. It is believed that two factors contributed to the high reactivity: the large surface area and the interaction between different oxides. The transition metal oxides with different band gaps have much enhanced photoluminescence under laser stimulation. Use of these complex oxide structures as electrodes can also improve the energy conversion efficiency of solar cells. The mixed oxide complex may provide a promising way to high-efficiency photo emitting materials and photo-catalysts.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.43-48
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• 2010

Polyamide derived from azo compound of o-amino phenol coupled with acetyl acetone, maleic anhydride acid and p-phenylene diamine were prepared. The prepared polyamide (PA) was refluxed with metal salts of transition metal ions include, $Co^{+2},\;Cr^{+2},\;Ni^{+2},\;Cu^{+2},\;Zn^{+2},\;Cd^{+2}$ and $Fe^{+3}$ in dimethyl formamide (DMF) in different molar ratios. These complexes were characterized and identified by elemental and thermal analysis, IR, 1H NMR spectra. The data showed that PA ligand coordinates with metal ions in abidentate manner through donating N=N and O-H groups. The metal ions are surrounded by coordinated water molecules and anions to establish the geometrical structure of the complexes. The thermal analysis degradation at different temperatures explained the weight loss of hydrated water and the decompositions of complexes until a constant weight loss of metal oxides is obtained.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.252-254
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• 2002

Metal oxides with high dielectric constants have the potential to expend scaling of transistor gate capacitance beyond that of ultrathin silicon dioxide. However, during deposition of most metal oxides on silicon, an interfacial region of SiOx is formed and limits the specific capacitance of the gate structure. We deposisted aluminum oxide and examined the composition of the interfacial layer by employing high-resolution X-ray photoelectron spectroscopy and X-ray reflectivity. We find that the interfacial region is not pure SiO$_2$, but is composed of a complex depth-dependent ternary oxide of $AlSi_xO_y$ and the pure SiO$_2$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.368-375
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• 2006

Single and complex metal oxide catalysts supported onto a commercial DT51D $TiO_2$ have been investigated for gas-phase TCE oxidation in a continuous flow type fixed-bed reaction system to develop a better design approach to catalysts for this reaction. Among the $TiO_2$-supported single metal oxides used, i.e., $CrO_x,\;FeO_x,\;MnO_x,\;LaO_x,\;CoO_x,\;NiO_x,\;CeO_x\;and\;CuO_x$, with the respective metal contents of 5 wt.%, the $CrO_x/TiO_2$ catalyst was shown to be most active for the oxidative TCE decomposition, depending significantly on amounts of $CrO_x\;on\;TiO_2$. The use of high $CrO_x$ loadings greater than 10 wt.% caused lower activity in the catalytic TCE oxidation, which is probably due to production of $Cr_2O_3$ crystallites on the surface of $TiO_2$. $CrO_x/TiO_2$-supported $CrO_x$-based bimetallic oxide catalysts were of particular interest in removal efficiency for this TCE oxidation reaction at reaction temperatures above $200^{\circ}C$, compared to that obtained with $CrO_x$-free complex metal oxides and a 10 wt.% $CrO_x/TiO_2$ catalyst. Catalytic activity of 5 wt.% $CrO_x-5$ wt.% $LaO_x$ in the removal reaction was similar to or slightly higher than that acquired for the $CrO_x$-only catalyst. Similar observation was revealed for 5 wt.% $CrO_x$-based bimetallic oxides consisting of either 5 wt.% $MnO_x,\;CoO_x,\;NiO_x\;or\;FeO_x$. These results represent that such $CrO_x$-based bimetallic systems for the catalytic TCE oxidation on significantly minimize the usage of $CrO_x$ that is well known to be one of very toxic heavy metals, and offer a very useful technique to design new type catalysts for reducing chlorinated volatile organic substances.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.217-217
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• 2011

Recently, demand for thermally stable metal nanoparticles suitable for chemical reactions at high temperatures has increased to the point to require a solution to nanoparticle coalescence. Thermal stability of metal nanoparticles can be achieved by adopting core-shell models and encapsulating supported metal nanoparticles with mesoporous oxides [1,2]. However, to understand the role of metal-support interactions on catalytic activity and for surface analysis of complex structures, we developed a novel catalyst design by coating an ultra-thin layer of titania on Pt supported silica ($SiO_2/Pt@TiO_2$). This structure provides higher metal dispersion (~52% Pt/silica), high thermal stability (~600$^{\circ}C$) and maximization of the interaction between Pt and titania. The high thermal stability of $SiO_2/Pt@TiO_2$ enabled the investigation of CO oxidation studies at high temperatures, including ignition behavior, which is otherwise not possible on bare Pt nanoparticles due to sintering [3]. It was found that this hybrid catalyst exhibited a lower activation energy for CO oxidation because of the metal-support interaction. The concept of an ultra-thin active metal oxide coating on supported nanoparticles opens-up new avenues for synthesis of various hybrid nanocatalysts with combinations of different metals and oxides to investigate important model reactions at high-temperatures and in industrial reactions.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.363-370
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• 2019

The recent development of information and communication technologies brings new changes to automobile traffic systems. The most typical example is the advancement of dedicated short range communication(DSRC). DSRC mainly consists of an intelligent transportation system(ITS), an electronic toll collection system(ETCS) and an advanced traveler information system(ATIS). These wireless communications often cause unnecessary electromagnetic waves, and these electromagnetic waves, in turn, cause frequent system malfunction. To solve this problem, an absorber of electromagnetic waves is suggested. In this research, various materials, such as powdered metal and iron oxides, are used to test the possibility for an effective absorption of the unnecessary electromagnetic waves. The various metal powders are made into a thin sheet form by compositing through processing. The electromagnetic characteristics(complex permittivity, complex permeability) of the fabricated sheet are measured. As a result, we achieve -6.5 dB at 940 MHz(77.6 % absorption rate) with a 1.0 mm-thickness electromagnet wave absorber, and -9.5 dB at 940 MHz(88.8 % absorption rate) with a 2.0 mm-thickness absorber.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.3
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• pp.25-31
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• 2016

Mechanical properties of Y2O3-containing tetragonal ZrO2 polycrystals(Y-TZP) were investigated. Several additives were used to modify the hardness and fracture toughness of Y-TZP. The effects of these individual additives were discussed and their interactions were also analysed. Each additive, such as CoO, Fe2O3, MnO2 was found to deteriorate the mechanical properties of Y-TZP when it was used singly. But the fracture toughness of Y-TZP was significantly improved when these additives and Al2O3 were added in combination at a certain ratio. The addition of CoO, Fe2O3 and MnO2 into Y-TZP resulted in the more complex behavior of fracture toughness and hardness. The specimen with 1.5 wt%-Fe2O3, 3.0 wt% -Al2O3 and 1.5 wt%-CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of $10.8MPa{\cdot}m1/2$ with Vickers hardness of 1201 kgf/mm2. However, the toughness decreased as the ratio increased and macrocracks developed beyond the ratio of 25%. Sample No. 16 is improved high Physical and Mechanical Properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.311-314
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• 1998

The effects of the additions of transition metal oxides on ZrO$_2$ - Y$_2$O$_3$ (Y$_2$O$_3$ - containing tetragonal zirconia polycrystals : Y-TZP) system has been studied by investigating fracture toughness and phase stability of the sintered specimens. In the specimens sintered at 1450$^{\circ}C$ for 2hrs in air the phase transformation from tetragonal to monoclinic was observed. The ratios of monoclinic phase to tetragonal phase were changed with the additions of CoO, Fe$_2$O$_3$ and MnO$_2$, respectively, from 0.00 to 8.00wt%. The fracture toughness was increased with increasing the monoclinic to tetragonal phase ratio and was maximum at the ratio of about 18%. However, the hardness was decreased with increasing the ratio. The additions of CoO, Fe$_2$O$_3$ and MnO$_2$ together into Y-TZP resulted in more complex behaviors of fracture toughness and hardness. The specimen with the additions of 1.5wt% Fe$_2$O$_3$, 3.0wt% Al$_2$O$_3$ and 1.5wt% CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$\^$$\frac{1}{2}$/ and Vickers hardness of 1201kgf/mm$^2$.

• Journal of the Korean institute of surface engineering
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• v.26 no.2
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• pp.87-107
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• 1993

The grain size of the final products of WC-Co and WC-Ni composite powders is dependent on the size of the starting material and the conditions employed for the reduction and carburization. APT-Co and -Ni com-plex salts were prepared by the substitution reaction between ammonium ions in APT and the metal ions in Co(NO3)2 and Ni(NO3)2 solutions of different concentrations(0.1 to 0.7M) at $50^{\circ}C$ and the grain sizes of the com-plex salts was $0.54~0.76\mu\textrm{m}$. The complex which calcined the complex salts at $700^{\circ}$~80$0^{\circ}C$ for 60min. were 0.2~0.5$\mu\textrm{m}$. W-Co($5.92^{\circ}C$) and -Ni(6.95%) powders which reduced the complex oxides with H2d atmo-sphere(flow rate;600cc/min.) at $700^{\circ}$~$800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$. The mean grain sizes of WC-Co and WC-Ni composite powders which carburized both complex metals of W-Co and W-Ni at $800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$, and take place the coarsening of the grain above $800^{\circ}C$ and the optmium ratio of C3H8 and H2 was 0.2 for the control of the free carbon. The effect of Co contents on the particle sizes decreased from 0.4 to $0.25\mu\textrm{m}$ with increasing the content from 2.0 to 7.6w%. The activation energies on the reductions of oxides and the formations of carbides were as follows ; W-Co : Q = 8.7 kcal/mole, W-Ni : Q = 8.1 kcal/mole, WC-Co pow-der : Q = 17.8 kcal/mole, WC-Ni powder : Q = 16.6 kcal/mole.