• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.264-264
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• 2013

Strong metal-support interaction effect is an important issue in determining the catalytic ac-tivity for heterogeneous catalysis. In this study, we investigated the support effect and the role of organic capping layers of two-dimensional Pt nanocatalysts on reducible metal oxide supports under the CO oxidation. Several reducible metal oxide supports including CeO2, Nb2O5, and TiO2 thin films were prepared via sol-gel techniques. The structure, chemical state and optical property were characterized using XRD, XPS, TEM, SEM, and UV-VIS spectrometer. We found that the reducible metal oxide supports have a homogeneous thin thickness and crystalline structure after annealing at high temperature showing the different optical band gap energy. Langmuir-Blodgett technique and arc plasma deposition process were employed to ob-tain Pt nanoparticle arrays with capping and without capping layers, respectively on the oxide support to assess the role of the supports and capping layers on the catalytic activity of Pt catalysts under the CO oxidation. The catalytic performance of CO oxidation over Pt supported on metal oxide thin films under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) was tested. The results show that the catalytic activity significantly depends on the metal oxide support and organic capping layers of Pt nanoparticles, revealing the strong metal-support interaction on these nanocatalysts systems.

• The Journal of Advanced Prosthodontics
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• v.3 no.3
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• pp.113-118
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• 2011

PURPOSE. The objective of the present study was to evaluate the effect of five different metal framework designs on the fracture resistance of the metal-ceramic restorations. MATERIALS AND METHODS. For the purpose of this study, the central incisor tooth was prepared, and the metal analogue of it and a master die were fabricated. The counter die with the 0.5 mm clearance was used for fabricating the wax patterns for the metal copings. The metal copings with five different metal framework designs were designed from Group 1 to 5. Group 1 with the metal collar, Group 2, 3, 4 and 5 with 0 mm, 0.5 mm, 1 mm and 1.5 mm cervical metal reduction respectively were fabricated. Total of fifty metal ceramic crown samples were fabricated. The fracture resistance was evaluated with the Universal Testing Machine (Instron model No 1011, UK). The basic data was subjected to statistical analysis by ANOVA and Student's t-test. RESULTS. Results revealed that the fracture resistance ranged from 651.2 to 993.6 N/$m^2$. Group 1 showed the maximum and Group 5 showed the least value. CONCLUSION. The maximum load required to fracture the test specimens even in the groups without the metal collar was found to be exceeding the occlusal forces. Therefore, the metal frameworks with 0.5 mm and 1 mm short of the finish line are recommended for anterior metal ceramic restoration having adequate fracture resistance.

• Journal of Welding and Joining
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• v.14 no.1
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• pp.47-56
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• 1996

The purpose of this study is to develope an insert metal which can be brazed at lower temperature than the conventionally used insert metal and provide higher strength joint than base metal. In the review of binary phase diagram concerning Ti, Cu and Ni resulted in the discovery of Si having eutectic composition with them. The microstructure and the distribution of elements in reaction zone between CP Ti and insert metal were investigated by Optical Microscopy, SEM/EDX, EPMA, X-RAY. The newly developed insert metal is Ti-15wt%Cu-18wt%Ni-2wt%Si, which can yield the lower brazing temperature(1183K) compared with the conventional Ti-Cu-Ni system insert metal. The joints with this insert metal had tensile strength of 385MPa in the bonding temperature range of 1183K to 1243K.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.92-97
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• 1996

The fatigue crack propagation behavior in SA106 Gr.C main steam pipe weld joint was investigated in air environment. Crack growth rate tests were conducted on base metal and weld metal at load ratio of 0.1 and 0.3 and at frequency of 10Hz. The fatigue crack growth rates of the base metal and the weld metal were above the ASME reference line and the fatigue crack propagation rate of the weld metal was higher than those of the base metal. Fatigue crack growth rate increased with increasing the load ratio and the effect of the load ratio was more significant in the weld metal. The post weld heat treatment increased the fatigue crack growth rates of the base metal by reducing compressive residual stress and decreased those of the weld metal by reducing weld defects.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.534-539
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• 2001

The formation mechanism of microconstituents in brazed joints of duplex stainless steel and Cr-Cu alloy which is an essential process of rocket engine manufacturing was investigated using Cu base insert metal. $SUS329J_3L$ and C18200 were used for base metal and AMS 4764 was used for insert metal. The brazing was carried out under various conditions. There were various phases in the joints, because of reaction between liquid insert metal and base metals. Since liquid insert metal reacts with duplex stainless steel, liquid Cu from insert metal infiltrated into the $\alpha/\beta$ interface of duplex stainless steel. Through the process of Cu infiltration, isolated stainless steel pieces come into the liquid insert metal. Since liquid insert metal reacts with Cr-Cu alloy. Cr precipitates from C18200 come into the liquid insert metal. With increment of bonding temperature and holding time, amounts and sizes of phases increased. but Cr-Mn compounds decreased at 1303k for 1.2ks and Mn-rich phases disappeared Fe-Cr compounds formed.

• Journal of the Korean Ceramic Society
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• v.11 no.1
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• pp.3-9
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• 1974

The role of added metal oxide in the adherence mechanism of low melting glass to several metal plates such as oxygen free high conducting copper, low carbon steel, chrominum galvanized on copper, and stainless steel was investigated. The metal oxide which added to glass were cupric oxide, ferric oxide, chromic oxide, and stainless steel oxide. The glass to that various metla oxide were added, sealed with several metal plates in the electric furnace at $650^{\circ}C$ for 5 minutes. The results as follows; 1) The interfacial reaction was promoted and strong chemical bonding with glass and metals by which the surface energy was decreased showed excellent sealing by addition of metal oxide. 2) When the interfacial reaction of glass and metals was promoted by addition of metal oxide found out that various adhernece mechanism were related to the sealing. 3) When the amount of metal oxide addition was 3-5% the excellent sealing was achieved.

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.257-262
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• 2005

In order to improve the quality of the sheared surface in cutting of inner structure bonded sheet metal the cut-off operation is mainly investigated, which is the typical shearing process in sheet metal forming technology. The sandwich sheet metals considered have inner structure which is constructed in the form of crimped expanded metal and woven metal. The inner structure is bonded between solid sheet by resistance welding or adhesive bonding. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface is measured and quantitatively compared with the help of the optical microscope after cut-off operation. From test results we found that the influence of sheared position can be observed and explained clearly and this result can be utilized to get the better sheared surface.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.110-114
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• 2008

Determination of weld-induced residual stress has been an important issue in nuclear power industry because several failures were reported in dissimilar metal weld parts due to primary water stress corrosion cracking. In this context, a couple of remarkable round robin analyses were conducted to quantify the welding simulation variables and to establish optimized numerical analysis process. The purpose of the present research is to introduce welding simulation results for a safety and relief nozzle, which has a dissimilar metal weld part as well as a similar metal weld part. First, finite element analyses are carried out to calculate residual stresses at the inside of nozzle considering only dissimilar metal welding. Subsequently, residual stresses taking into account both the dissimilar and similar metal welding are computed. The similar metal weld effect is evaluated by compa

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.86-87
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• 2005

Aluminum(Al) sputtering is best known method to form Al film for the Si wafer in the process of 180nm and above. In the Al metal line process, one of the frequently founded and well-known defect was metal depression. In this paper, several experiments were performed such as temperature, Ar gas flow rate, thickness change in other to reduce the metal depression and find the origination of metal depression. Through experiments, it is found that metal depression was significantly related to the temperature. And the Ar gas flow rate did not influence to the creation of depression. The off status ESC also showed stable metal film without depression by same mechanism of temperature decrease. Also, thickness is strongly influence to the metal depression.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.33-38
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• 2004

In order to improve the quality of the sheared surface in cutting of inner structure bonded sheet metal the cut-off operation is mainly investigated, which is the typical shearing process in sheet metal forming technology. The sandwich sheet metals considered have inner structure which is constructed in the form of crimped expanded metal and woven metal. The inner structure is bonded between solid sheet by resistance welding or adhesive bonding. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface is measured and quantitatively compared with the help of the optical microscope after cut-off operation. From test results we found that the influence of sheared position can be observed and explained clearly and this result can be utilized to get the better sheared surface.