• 한국재료학회지
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• 제24권9호
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• pp.488-494
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• 2014

The effect of tungsten (W) addition on the hardenability of low-carbon boron steels was investigated using dilatometry, microstructural observations and secondary ion mass spectroscopy. The hardenability was discussed with respect to transformation behaviour aspects depending on the segregation and precipitation of boron at austenite grain boundaries. A critical cooling rate producing a hardness corresponding to 90 % martensite structure was measured from a hardness distribution plot, and was used as a criterion to estimate hardenability at faster cooling rates. In the low-carbon boron steel, the addition of 0.50 wt.% W was comparable to that of 0.20 wt.% molybdenum in terms of critical cooling rate, indicating hardenability at faster cooling rates. However, the addition of 0.50 wt.% W was not more effective than the addition of .0.20 wt.% molybdenum at slower cooling rates. The addition of 0.20 wt.% molybdenum completely suppressed the formation of eutectoid ferrite even at the slow cooling rate of $0.2^{\circ}C/s$, while the addition of 0.50 wt.% W did not, even at the cooling rate of $1.0^{\circ}C/s$. Therefore, it was found that the effect of alloying elements on the hardenability of low-carbon boron steels can be differently evaluated according to cooling rate.

• 한국주조공학회지
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• 제33권1호
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• pp.1-7
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• 2013

The effect of the Mo addition on the high temperature creep properties of the 9Cr-3W steel was also evaluated. Two experimental steels, (9Cr-3W and 9Cr-3W-0.5Mo), were prepared using a vacuum induction melting process, followed by hot rolling and heat treatment processes. Three types of precipitates, ($M_{23}C_6$, Nb-rich MX and V-rich MX) were observed in a typical tempered martensitic matrix. Significant effects of the Mo addition on the tensile properties were not observed. However, the creep properties at $650^{\circ}C$ under applied stresses of 140 and 150 MPa were considerably enhanced by the Mo addition. The microstructural observation after the creep test indicated that the addition of Mo could function to retain the recovery of the martensitic matrix, thus resulting in the enhanced creep properties of the 9Cr-3W-0.5Mo steel. Furthermore coarsening of the $M_{23}C_6$ carbides and formation of Laves phases were observed in both samples after the creep tests.

• 반도체디스플레이기술학회지
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• 제6권2호
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• pp.25-28
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• 2007

Electroless Ni-P coating is widely used for chemical, electronic, and semiconductor equipment parts because of its corrosion resistance. The incorporation of chemically-inert PTFE particles into the Ni-P films improves properties such as, non-stick, anti-adhesive and better corrosion resistance. However, soft PTFE particles degrade the hardness, wear and abrasion resistance. In this study, effects of PTFE and W addition to the Ni-P-coatings were compared by the XRD, SEM, sheet resistance, contact angle, and microhardness measurements. The change in sheet resistance was negligible, but contact angle was doubled by the addition of PTFE and W. The microhardness was lower for Ni-P-PTFE, but higher for Ni-P-PTFE-W coatings, compared to that of Ni-P coatings.

• 한국표면공학회지
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• 제16권2호
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• pp.41-47
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• 1983

An investigation has been performed on the effects of temperature and Ni addition on the wetting behaviour of Cu on W substrate in hydrogen atmosphere. An sessile drop method was used to measure a wetting angle. The concentration profiles of W, Cu and Ni elements in W/Cu - 5 Ni specimen were made by EPMA. With increasing temperature, the wetting angle of Cu droplet on W plate decreases and the time to reach an equilibrium wetting angle is shortened in hydrogen atmosphere. The addition of Ni improves appreciably the wettability of Cu on W. With increasing Ni content in Cu liquid droplet(0, 1, 3, 5%), the wetting angle is decreased from 21$^{\circ}$to 0$^{\circ}$.

• Corrosion Science and Technology
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• 제5권5호
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• pp.153-159
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• 2006

Austenitic stainless steels with addition of various amounts of Mo and W were evaluated in terms of corrosion and contact resistance to determine optimum alloy composition of metallic bipolar plate for PEMFC. The corrosion property was evaluated by both acid fume exposure test at $130^{\circ}C$ and by electrochemical polarization tests in $H_3PO_4$ solution at $80^{\circ}C$. Austenitic stainless steel with proper amount of Mo and W demonstrated not only good corrosion resistance but also low contact resistance. Analyses on the passive film show that partial substitution of Mo by W enhances passive film stability and repassivation property. Test results suggest that austenitic stainless steel with 2 wt%Mo and 4 wt%W has optimum composition for metallic bipolar plate used in PEMFC.

• 한국세라믹학회지
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• 제26권5호
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• pp.705-711
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• 1989

The glass-ceramics was prepared with the scoria(CaO-MgO-Al2O3-SiO2 system) of the locally occurring volcanic ejecta containing 10-13w/o of (FeO＋Fe2O3) by melting at 140$0^{\circ}C$ for 4 hours and thermally treated for nucleation and crystallization. The sucrose was added to the scoria to adjust the Fe2+/Fe3+ ratio during the melting process. The addition of 1-2w/o of sucrose showed the glass-ceramics body with the finest particle developed and dispersed over the entire range. It is concluded that the impurity content of iron oxide and titanium oxide play the most-influencial effect on the crystallization. When 1-2w/o of sucrose was added to the scoria, the value of Fe2+/Fe3+ ratio was 0.93-1.32 and showed the best result of crystallization. The nucleation temperature and time were calculated by the measurements of exothermic peak temperatures of DTA for quenched and thermally treated glasses. The nucleation temperature of scoria glass without the addition of sucrose was estimated as 75$0^{\circ}C$, but the addition of sucrose by 2w/o showed the nucleation temperature 6$25^{\circ}C$. The nucleation time was calculated with the same DTA curves. The nucleation times estimated were about 150min. for both of glasses without and with sucrose added. Finally, the activation energies for crystallization were calculated with the DTA data. The calculated activation energies were 143 Kcal/mole for the glass without addition of sucrose and 90Kcal/mole, 87Kcal/mole, 85Kcal/mole and 71Kcal/mole for the glasses of 1w/o, 2w/o, 3w/o and 4w/o addition respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
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• pp.11-14
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• 2003

Sintered Cu-W has been used for the electrode of GIS for interrupting the abnormal current. In this study the effect of Ni addition in Cu-W electrode was investigated. Cu-W electrodes used contains 0.1~0.2wt% Ni and were conducted the experiments which was attacked by DC arc test (70V-70A) for 300 times periodically. As the contents of Ni in Cu-W electrode increase, the hardness and electrical conductivity were decreased. The weight change ($\Delta$mg) of electrode after DC arc test increased with increasing Ni contents and test times. The hardness and electrical conductivity of electrode after DC arc test were decreased compared with non-arc affected electrode, which was owing to the defects near surface of electrode and degradation by arc heat. It was considered that Cu in the Cu-W electrode was scattered to all directions by arc heat, therefore, the electrodes were damaged and deformed in the surface and cross-section of electrode. It is difficult to estimate directly the characteristics of Cu-W electrode for GIS related with high voltage and current from the results of DC arc test conducted in this study. However, the results of the effect of Ni addition in Cu-W electrode could be applied for the research of electrode for GIS.

• Food Science and Biotechnology
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• 제16권4호
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• pp.576-579
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• 2007

The effects of temperature and Korean bramble (Rubus coreanum Miquel) tissue concentrate on heterocyclic aromatic amine (HAA) formation in fried ground beef patties were investigated. Various amounts of Korean bramble tissue (4.0, 7.0, and 11.0%, w/w) were added to ground beef patties were fried at 2 different temperatures (190 and $225^{\circ}C$) for 10 min/side. It was observed in the fried ground beef patties fried at $190^{\circ}C$ with the addition of 11.0%(w/w) Korean bramble that the mutagenicity decreased by 64%, and formation of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-I-methyl-6-phenylimidazo[4,5-b]-pyridine(PhIP) reduced by 55 and 86%, respectively. Although no difference in total mutagenicity was shown in patties fried at $225^{\circ}C$ with the addition of 4.0, 7.0, and 11.0%(w/w), different levels of reduction of PhIP formation in patties fried at $225^{\circ}C$ with the addition of 4.0, 7.0, and 11.0%(w/w) were shown 49, 63, and 75%, respectively.

• Fisheries and Aquatic Sciences
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• 제16권3호
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• pp.143-147
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• 2013

The influence of carrageenan addition on the gelatinization of salt-based surimi gels was investigated by measuring compressive properties and Hunter color scale values. Hydrocolloid kappa (${\kappa}$)-carrageenan at 0%, 0.2%, and 1.0% and NaCl (2% w/w), KCl (1.5% w/w), and a mixture of NaCl (2% w/w) and KCl (1.5% w/w), were added to Alaska pollock surimi. Gel compressive properties were assessed by measuring the breaking force and gel strength. The gelling property of ${\kappa}$-carrageenan-induced surimi gel was significantly increased by the incorporation of KCl rather than NaCl. The addition of ${\kappa}$-carrageenan increased the breaking force and gel strength of surimi gels. Gels with 1% ${\kappa}$-carrageenan and KCl had the highest breaking force and gel strength. The addition of ${\kappa}$-carrageenan caused an increase in the whiteness values of the surimi gels.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권2호
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• pp.68-72
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• 2004

The performance of copper-tungsten for electrodes used in an ultra high voltage interruption system was evaluated by means of an interruption test, which requires a large-scale apparatus and high cost. In this study, prior to the interruption test, the characteristics of a Cu-W electrode were estimated through the DC arc test, which is a simple, low cost procedure. The DC arc characteristics of a 20wt%Cu-80wt%W electrode were investigated with the change of tungsten powder size distribution and the addition of nickel. In specimens containing a high volume fraction of large sized tungsten particles, the relative density and hardness of sintered Cu-W electrodes increased while the electrical conductivity and the DC arc resistance decreased. Furthermore, the relative density became enhanced with the increase of the amount of nickel while the hardness and electrical conductivity diminished and the DC arc resistance worsened.