• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.260-264
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• 2016

In this study, fractured surface morphology and mechanical properties of Ni-Cr-Mo alloys with various contents of Mo for dental material use have been evaluated by mechanical test. The alloys used were Ni-13Cr-xMo alloys with Mo contents of 4, 6, 8, and 10 wt.%, prepared by using a vacuum arc-melting furnace. Ni-13Cr-xMo alloys were used for mechanical test without heat treatment. The phase and microstructure of alloys using an X-ray diffraction (XRD) and optical microscopy (OM) were evaluated. To examine the mechanical properties of alloys according to microstructure changes, the tensile test and the hardness test were carried out using tensile tester. To understand the mechanism of Mo addition to Ni-Cr alloy on mechanical property, the morphology and fractured surfaces of alloys were investigated by field-emission scanning electron microscope (FE-SEM). As a result, 79Ni-13Cr-8Mo alloy was verified that the tensile strength and the hardness were better than others. Varying Mo content, the changes of microstructures of alloys were identified by OM and SEM and that of 79Ni-13Cr-8Mo alloy was proved fabricated well. Microstructures of alloys were changed depending on Mo content ratio. It has been observed that 8% alloy had the most suitable mechanical property for dental alloy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.3
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• pp.332-340
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• 2014

The purpose of this study was to establish the optimal growth temperature and to select genetic resources for production of cowpea sprouts. Seowon was treated between $15^{\circ}C$ and $30^{\circ}C$ at intervals of $3^{\circ}C$ to investigate growth temperature. Twelve resources, including Seowon, IT154149, IT154153, Tvu7426, and Tvu7778, were used for cultivating sprouts at a temperature of $27^{\circ}C$. The yield ratio of cowpea sprouts was highest at $27^{\circ}C$ (657%), and was reduced when growth temperature was decreased. The hard seed rate was lower when the growth temperature was increased. Vitamin C content was highest at $24^{\circ}C$ (2.85 mg/g), ranged between 2.15 and 2.29 mg/g at other growth temperatures, and increased with the length of the growth period. The inorganic component content of cowpea sprouts did not vary based on growth temperature, while the amino acid content increased with increasing growth temperature between $15^{\circ}C$ and $24^{\circ}C$, and then subsequently decreased as growth temperature rose from $24^{\circ}C$ to $30^{\circ}C$. IT154153 had the highest yield ratio of cowpea sprouts per genetic resource (647%), followed by Seowon (615%), and Tvu7426 (608%). Genetic resources with a higher yield ratio had smaller seeds, a thinner seed coat, and superior germinability. The inorganic components found at highest concentrations in the cowpea sprouts were potassium, magnesium, calcium, sodium, iron, molybdenum, and zinc (in that order). In comparison to raw seeds, the protein, calcium, zinc, molybdenum, and iron content in the cowpea sprouts was higher, while the content of aluminum and boron was lower.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.2
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• pp.67-74
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• 2009

440A martensitic stainless steels which were modified with reduced carbon content (${\sim}$0.5%) and addition of small amount of nickel, vanadium, tungsten and molybdenum were manufactured. Effects of alloying elements and heat treatment on the pitting corrosion in 3.5% NaCl were investigated through the electrochemical polarization tests. The lowest pitting potential, $E_p$, was obtained when austenitizing temperature was $1250^{\circ}C$ and this is because of the grain coarsening. When austenitized at $1050^{\circ}C$ and tempered at $350{\sim}750^{\circ}C$, the highest $E_p$ was obtained at $350^{\circ}C$, while the lowest at $450^{\circ}C$ and $550^{\circ}C$ regardless of alloying elements added. But $E_p$ was increased a little at the tempering temperature of $450^{\circ}C$ and $550^{\circ}C$ when 0.4 wt.% of tungsten was added. More pitting was observed at $450{\sim}550^{\circ}C$, and pitting was formed at regions where Cr concentration is low or grain boundaries are intersecting and showed irregular shape.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.42-48
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• 2011

440A martensitic stainless steels which were modified with reduced carbon content(~0.5%) and addition of small amount of nickel, vanadium, tungsten and molybdenum were manufactured. Effects of alloying elements and tempering temperatures on the uniform corrosion in the solution of lN H2S04 were investigated through the electrochemical polarization test. When tempering temperature is constant, corrosion current density in active-passive transition point, Icorr, decreased a little with an increase of austenitizing temperature. In addition to this, when austenitizing temperature is constant, longer holding time showed a little lower Icorr and Ipass, passive current density. And when austenitized at $1050^{\circ}C$ and tempered in a range of $350{\sim}750^{\circ}C$, best anti-corrosion properties were obtained at $350^{\circ}C$ tempering temperature while worst at $450^{\circ}C$ or $550^{\circ}C$. The specimens tempered at below $450^{\circ}C$ and above $550^{\circ}C$, similar and good anti-corrosion characteristics were obtained regardless of alloying elements added, showing anti-corrosion characteristics are influenced more by tempering temperature than by alloying elements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.735-738
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• 2000

The characteristics of wire electrical discharge machining (WEDM) are governed by many factors such as the power supply type, operating condition and electrode material. This work deals with the effect of wire electrode materials on the machining characteristics such as, metal removal rate, surface characteristics and surface roughness during WEDM A wire's thermal physical properties are melting point, electrical conductivity and vapor pressure. One of the desired qualities of wire is a low melting point and high vapor pressure to help expel the contaminants from the gap. They are determined by the mix of alloying elements (in the case of plain brass and coated wire) or the base core material(i.e. molybdenum). Experiments have been conducted regarding the choice of suitable wire electrode materials and influence of the properties of these materials on the machinability and surface characteristics in WEDM, the experimental results are presented and discussed from their metallurgical aspect. And the coating effect of various alloying elements(Au, Ag, Cu, Zn, Cr, Mn, etc.) to the Cu or 65-35 brass core on them was reviewed also. The removal rate of some coated wires are higher than that of 65-35 brass electrode wire because the wire is difficult to break due to the wire cooling effect of Zn evaporation latent heat and the Zn oxide on the surface is effective in preventing short circuit. The removal rate increases with increasing Zn content from 35, 40 and Zn coated wire

• Journal of Korea Foundry Society
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• v.16 no.2
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• pp.141-148
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• 1996

In high chromium cast iron, the control of matrix microstructure as well as carbide structure is important to the performance as a wear resistant material. In this study, 3.0% C-24.0% Cr white cast irons with various molybdenum contents(residual, 1.0%, 3.0% and 5.0%) were solidified conventionally and unidirectionally for studying their effects on the microstructure and hardness. In the conventional casting, two sets of castings were poured from each melt. One set of the castings consisted of cylindrical bars of 10 and 20mm by 155mm long. The second set of the castings was a cylindrical bar of 30mm by 200mm long. On the other hand, a pep-set mold set on the Cu plate was employed to make the solidification unidirectionally. X-ray diffraction method was used to observe retained austenite and carbides in the high chromium cast iron. The morphology of eutectic $M_7C_3$ carbides changed from needle-like type to nodular type with the increase of Mo content. And, the presence of $M_2C$ carbides was identified in the sample where Mo was added over 3.0 %. Primary and eutectic carbides appeared as rod type and corngrain type, respectively in the unidirectionally solidified samples which were cut to parallel to the solidification direction. In the EDX analysis, Cr concentration was higher in the primary and eutectic $M_7C_3$ carbides, Mo in the $M_2C$ carbides, and Fe in the matrix.

• The Korean Journal of Ecology
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• v.19 no.3
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• pp.209-216
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• 1996

In order to identify the habitat characteristics of water shield (Brasenia schreberi), water quality and sediment characters were investigated. Water shield had peculial habitats such as old reservoir, developed basin-like reservior, a water depth within 1.5 m, constant water level, and thick sediment layer at the bottom. The species had very dense populations under the favorable growing conditions and occasionally grew together with Utricularia japonica. When water shield decreased, Nelumbo nucifera, Nuphar japonicum and Zizania latifolia increased. Natural populations of water shield need protection because it is endangered by the human activities and their harvest. The optimal conditions for the growth of water shield was near neutral pH. low conductivity and low turbidity. Therefore the input of pollutants should be controlled for its growth. The inorganic ion contents such as K, Mg, and Na were higher in the water shield growing area. Especially iron content of the sediments in the reservoirs with water shield was nearly five times as high as that in the reservoirs without water shield. thus iron might be one of the major limiting factors for the growth. It was considered that molybdenum can be another major factor because water shield is a nitrogen fixing plant.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.2
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• pp.139-147
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• 1996

Eight Philoppine forages were studied to obtain the following: 1) nutrient concentrations and digestibility, 2) distribution of the various minerals in fiber fractions through mineral analyses of neutral detergent fiber(NDF) and acid detergent fiber(ADF) residues, and 3) correlation coefficients among the factors affecting forage quality and mineral concentrations. These Philippine forages were paragrass [Brachiaria mutica (Forsk.) Stapf], stargrass (Cynodon plectostachyum Pilger), napiergrass (Pennisetum purpureum Schumach.) calopo (Calopogonium muconoides Desv.), centrocema (Centrocema pubescens Benth.), gliricidia [Gliricidia sepium (Jacq.) Walp.] leucaena [Leucaena leucocephala (Lam.) de Wit.] and sesbania [Sesbania grandiflora (L.) Poir]. Species differences(p<0.01) were observed on various nutrient fractions including mineral composition and digestibility. The cell wall(NDF) fraction, prepared by boiling in neutral detergent solution, contained the following proportions of the total mineral originally present (%): calcium (Ca), 0.7; phosphorus(P), 14.3; magnesium(Mg), 1.9; potassium(K), 3.7; copper(Cu), 16.4; zinc(Zn), 2.9; molybdenum(Mo), 9.3; cobalt(Co), 16.2; manganese(Mn), 5.6, and iron(Fe), 81.3. The ligno-cellulose(ADF) fraction, prepared by boiling in acid detergent solution, contained the following proportions of the total mineral originally present(%): Ca, 0.2; P, 4.4; Mg, 0.7; K, 2.8; Cu, 32.3; Zn, 1.1; Mo, 8.9; Co, 4.7; Mn, 5.4; and Fe, 36.8. Correlation coefficients among the factors affection forage quality and mineral concentrations were also observed. Evidently, 75 and 45% of the minerals in grasses and legumes was positively correlated to CP and IVDMD, respectively. Moreover, 55, 80 and 75% of the forage minerals was negatively correlated to NDF, ADF and ADL fraction, respetively, implying that most of the minerals reside in the non-structural cell components.

• Composites Research
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• v.16 no.3
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• pp.41-48
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• 2003

In this work, the effect of molybdenum disilicide(MoSi$_2$) content on the impact properties of carbon-carbon composites(C/C composites) was investigated in the presence of MoSi$_2$. The content of MoSi$_2$ was varied in 0, 4, 12 and 20 wt% on the basis of resin matrix for anti-oxidation properties of the composites under high temperature. As a result, the composites made with MoSi$_2$ resulted in an increase of interfacial adhesion between fibers and matrix, which could improve the impact properties of the composites. Especially, 12 wt% Mosi$_2$ composites showed the highest impact properties in the present system. This was probably due to the existence of brittle-to-ductile transition(BDT) properties of MoSi$_2$ in the vicinity of 90$0^{\circ}C$, resulting from increasing the interfacial adhesion force among fibers, filler, and matrix in the composites.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1090-1096
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• 2010

This pitting corrosion study of welded joints of austenitic stainless steels (AISI 304L and 316L) has addressed the differentiating solidification mode using three newly introduced filler wires with a flux-cored arc welding process (FCAW). The delta ferrite (${\delta}$-ferrite) content in the welded metals increased with an increasing equivalent weight ratio of chromium/nickel ($Cr_{eq}/Ni_{eq}$). Ductility dip cracking (DDC) was observed in the welded metal containing ferrite with none of AISI 304L and 0.1% of AISI 316L. The potentiodynamic anodic polarization results revealed that the $Cr_{eq}/Ni_{eq}$ ratio in a 3.5% NaCl solution didn't much affect the pitting potential ($E_{pit}$). The AISI 316L welded metals with ${\ddot{a}}$-ferrite content of over 10% had a superior $E_{pit}$ value. Though the AISI 316L welded metal with 0.1% ferrite had larger molybdenum contents than AISI 304L specimens, it showed a similar $E_{pit}$ value because the concentration of chloride ions and the corrosion product induced severe damage near the DDC.