• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1161-1168
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• 1999

The redox property of oxide materials of the 3rd period transition metals(Cr~Zn), V, Mo, and W was studied with temperature-programmed reduction/temperature-programmed oxidation(TPR/TPO) experiment. The peak temperatures of TPO spectra were equal to or lower than those of TPR spectra. And the peak shapes of TPO spectra were broader than those of TPR ones. The activation energies of TPR/TPO for the oxides of the 3rd period transition metals showed in the range of 33~149 kJ/mol, while for the oxides of V, Mo, and W, they showed relatively higher values. The change of activation energies of TPR/TPO with various metal oxides showed a similar trend to the change of their metal-oxygen bond strengths. The change of activation energies of o-xylene oxidation for various metal oxides was proportional to the difference (${\Delta}E_a$) between the activation energy of TPR and that of TPO. From these results, we concluded that the oxidation of o-xylene over various metal oxide catalysts follows the Mars-van Krevelen mechanism including the surface reduction-oxidation of the metal oxide itself.

• Journal of Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.130-134
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• 2016

The anodization of ADC12 aluminum alloy was investigated in the metal anionic acid media. Anodic oxide films containing foreign elements were formed on ADC12 Al alloy by anodization in the anion complex solution. Furthermore, the rough surface and cracks were considerably smoothened by the deposit of metal anions. When the size of metal anion was small, relatively large amount of metal anions was loaded in anodic films. Existence of $MoO_3$, $TiO_2$ and MgO was confirmed by XPS. According to the results of Tafel analysis, Mo oxide represented the most noble anti-corrosion potential due to $MoS_2$ formation. Corrosion current densities were generally higher than that of pristine anodic oxide without anion complexes.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.970-977
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• 1999

Effect of Mo interlayer on the relaxation of residual stress in AlN/Cu pint bonded by active-metal brazing method was investigated. The stress analyses by finite-element-method, the measurement of pint strength and the observation of fracture surface were carried out and their results were compared with each other. From the results of stress analysis it is confirmed that a Mo interlayer led to a shift of maximum stress concentration site from AlN/insert-metal interface$\rightarro$ insert-metal/Mo$\rightarro$Mo interlayer. Additionally, with increase of the Mo interlayer thickness the stress concentration with tensile component was separately built both at the interface of Cu/Mo and AlN/Mo. whereby the residual stress in the free surface of AlN close to the bonded interface was drastically reduced. The AlN/Mo/Cu pints with Mo interlayer thickness of above 400$\mu\textrm{m}$ showed the strengths higher than 200 MPa. upto max. 275 MPa, while the AlN/Cu pint only max. 52 MPa.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.298.1-298.1
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• 2016

Two-dimensional materials have been received significant interest after the discovery of graphene due to their fascinating electronic and optical properties for the application of novel devices. However, graphene lack of certain bandgap which is essential requirement to achieve high performance field-effect transistors. Analogous to graphene materials, molybdenum disulfide ($MoS_2$) as one of transition-metal dichalcogenides family presents considerable bandgap and exhibits promising physical, chemical, optical and mechanical properties. Here we studied nonvolatile memory based on $MoS_2$ which is grown by chemical vapor deposition (CVD) method. $MoS_2$ growth was taken on $1.5{\times}1.5cm^2$ $SiO_2$/Si-substrate. The samples were analyzed by Raman spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Current-voltage (I-V) characteristic was carried out HP4156A. The CVD-$MoS_2$ was analyzed as few layers and 2H-$MoS_2$ structure. From I-V measurement for two metal contacts on CVD-$MoS_2$ sample, we found typical resistive switching memory effect. The device structures and the origin of nonvolatile memory effect will be discussed.

• Tribology and Lubricants
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• v.10 no.4
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• pp.43-50
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• 1994

In order to elucidate the effects of co-existing additives (S$_{8}$, TBP: Tri butyl phosphate, ZnDTP: Zinc-dialkyl dithiophosphate) and the role of reacted surface film on the friction behavior of MoDTP (molybdenum dialkyl dithiophosphate), a friction experiment using a dual circular pipe edge surface type friction tester and XPS (X-ray photoelectronic spectrum) surface analysis were conducted. Friction reduction with MoDTP lubricant was proved to be greatly influenced by co-existing additive species. It was dependent on the properties of the film formed through the reaction between the additive and the surface. Phosphate film reduced the friction coefficient of MoDTP through suppression of diffusion of Mo compounds towards the metal substrate. On the other hand, sulfate film, which is inherently rich in lattice defects, did not lead to any appreciable friction reduction with MoDTP since the diffusion of the Mo compound towards the metal substrate was not effectively suppressed. With ZnDTP additive, the sulfide film formed through decomposition greatly influenced the lubricating performance of MoDTP. As such, properties of surface films formed from additives were proved to yield significant influence on the lubrication performance of MoDTP.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.41-51
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• 1998

The research was conducted to measure the heavy metal pollution of soils and vegetations adjacent to the closed Daeseong coal mine in Keumsan, Chungnam. The studied area was divided into two sites ; the coal-bearing polluted and the non-polluted without coal. The samples of the weathered soils and vegetations(Miscnthus sinenis(MS) and Pinus rigida(PR)) were collected from both area. Cr, Mo, Ni, and Fe concentrations were high in the polluted soils, whereas Co, Sc, and Zn concentrations were high in the non-polluted soils. In the vegetations, Co, Cr, Sc, and Fe concentrations in the roots of MS and PR growing on the polluted sites were higher than the above-ground. However, on the non-polluted sites, Mo and Ni concentrations had an opposite trend. In the above-ground parts, high heavy metal concentrations (except Cr) were shown in MS of the non-polluted sites, whereas in the roots, heavy metal concentrations (except Zn) were high in the polluted sites. In the average heavy metal concentrations of two plants, most elements (except Zn) were lower in the plants than the soils. Comparing with vegetations and adjacent forest soils, heavy metal concentrations of the MS were similar to those of soil concentrations relative to the PR, suggesting that absorptions of the elements were higher in the MS than the PR.

• Applied Science and Convergence Technology
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• v.26 no.1
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• pp.16-19
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• 2017

A thin metal layer of molybdenum is placed between the conventional barrier layer and the stainless steel substrate for investigating the diffusion property of iron (Fe) atoms. In this study, the protection probability was confirmed by measuring the concentration of out-diffused Fe using a SIMS depth profile. The Fe concentration of chromium (Cr) barrier layer with 10 nm molybdenum (Mo) layer is 5 times lower than that of Cr barrier without the thin Mo layer. The insertion of a thin Mo metal layer between the barrier layer and the stainless steel substrate effectively protects the out-diffusion of Fe atoms.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1378-1379
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• 2006

Carbon nanotubes (CNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of acetylene in $H_2$ over well-dispersed metal particles supported on MgO. The yield, quality and diameters of CNTs were obtained by control of catalyst metal compositions to be used. The optimization condition of carbon nanotubes with high yield is when Co and Mo are in a 1:1 ratio and Fe metal contents to Co is increased on magnesium oxide support. It is also found that the diameter of the as-prepared CNTs can be controlled mainly by adjusting the molar ratio of Fe-Mo, Co-Fe, and Co-Mo versus the MgO support. Our results indicated that desired diameter distribution of CNTs is obtained by choosing or combining the catalyst to be employed.

• Proceedings of the Korean Vacuum Society Conference
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• 2006.02a
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• pp.88-88
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• 2006