• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.127-138
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• 2014

As increasing concerns about potential risks and hazards in children's products, the laws and regulations for heavy metals and phthalate retardants contained in the children's products have been reinforced in many countries. Especially, in Korea, environment and health laws and regulations for children's products was declared in 2009. This study was researched in terms of contents and migration of phthalates and heavy metals in 124 children's products sold in the Korean market. The results for contents of heavy metals showed that 123 products contained different 14 heavy metals depending on kinds of products. As the results of migration by sucking, the heavy metals in the products such as black, plastic dolls, wood toys, and bottom mat for swimming were transferred into extraction solution. Ba, Cu, Zn, and Sn were transferred from most of these products into the extraction solution and Co, Ni and Pb were additionally transferred into several products. As the results of migration through a skin, while Ba, Cu, and Zn were transferred from most products containing the heavy metals, as for accessories, Cr, Ba, Ni, Zn, and Cu were migrated. The results of contents of phthalates presented that 21 products contained DBP, DEHP and DINP. Only 2 products showed the migration of DEHP by sucking. DEHP in most products were transferred and DBP for 2 products and DINP for 7 products were migrated.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.23-29
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• 2017

Mechanical properties and hardness distributions in arc brazed joints of Dual phase steel using Cu-Al insert metal were investigated. The maximum tensile shear load was 10.4kN at the highest brazing current. It was about 54% compared to tensile load of base metal. This joint efficiency is higher than that of joint of DP steel using Cu-based filler metals which are Cu-Si, Cu-Sn. Fracture positions can be divided into two types. Crack initiation commonly occurred at three point junction among upper sheet, lower sheet and the fusion zone. However crack propagations were different with increasing the brazing current. In case of the lower current, it instantaneously propagated along with the interface between fusion zone and upper base material. On the other hand, in case of higher current, a crack propagation occurred through fusion zone. When the brazing current is low (60, 70A), the interface shape is flat type. However the interface shape is rough type, when the brazing current is high (80A). It is thought that the interface shapes were the reason why the crack propagations were different with brazing current. The interface was the intermetallic compounds which consisted of $(Fe,Al)_{0.85}Cu_{0.15}$ IMC formed by crystallization at $1200^{\circ}C$during cooling. Therefore the maximum tensile shear load and the fracture behavior were determined by a interface shape and effective sheet thickness of the fracture position.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.44-52
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• 1996

Influence of frictional and mechanical properties was studied with the content(8-18 wt.%) and shapes(flake of irregular) of graphite that was used as lubricant components of copper-based sintered materials. The density, hardness and bending strength of friction materials with the shape of flake graphite were lower and decreased rapidly than that of irregular, as the content of graphite increases up to 18 wt.%. In friction test, wear rate was about 2.0-$2.5{\times}10^{-7}\textrm{cm}^3$/kgf.m and coefficient of friction was 0.30-0.37, independent on graphite content and shape. As the temperature of friction materials increased, wear rate decreased rapidly because oxides such as $Cu_2O$ and $SnO_2$ in the surface of friction material were formed.

• Tribology and Lubricants
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• v.12 no.3
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• pp.48-54
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• 1996

Examined in this paper, is the effect of B$_{4}$C addition on the frictional characteristics of Cu-Sn based sintered friction materials. For the specimens 1wt%, 2wt% and 4wt% of B$_{4}$C were added into the reference material. A pin-on-disk type friction tester was used to,measure the friction torque with respect to the surface temperature and sliding distance. Wear mechanism of each specimen is analyzed in the view point of the oxide film formation. The specimen containing 4wt% of B$_{4}$C showed stable friction and low wear since the oxide film was sustained up to higher surface temperature ranges.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.1-9
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• 2002

The metallurgical reaction properties between the pad consisted of 0.5 $\mu\textrm{m}$Au/5 $\mu\textrm{m}$Ni/Cu layers on a conventional ball grid array (BGA) substrate and In-15 (wt.%)Pb-5Ag solder ball were characterized during the reflow process and solid aging. During the reflow process of 1 to 5 minutes, it was observed that thin $AuIn_2$ or Ni-In intermetallic layer was formed at the interface of solder/pad. The dissolution rate of the Au layer into the molten solder was about $2\times 10^{-3}$ $\mu\textrm{m}$/sec which is remarkably low in comparison with a eutectic Sn-37Pb solder. After solid aging treatment for 500 hrs at $130^{\circ}C$, the thickness of $Ni_{28}In_{72}$ intermetallic layer was increased to about 3 $\mu\textrm{m}$ in all the conditions nevertheless the initial reflow time was different. These result show that In atoms in the solder alloy were diffused through the $AuIn_2$ phase to react with underlaying Ni layer during solid aging treatment. From the microstructural observation and shear tests, the reaction properties between In-15Pb-5Ag alloy and Au/Ni surface finish were analyzed not to trigger Au-embrittlement in the solder joints unlike Sn-37Pb composition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.346-353
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• 2012

The Laser-Induced Breakdown Spectroscopy (LIBS) has great advantages as an analytical technique, namely real-time analysis without sample preparation, ideal for mobile chemical sensor for space exploration. The LIBS plasma characteristics are strongly dependent on the surrounding pressure. In this study, seven types of target (C, Ti, Ni, Cu, Sn, Al, Zn) were investigated for their elemental lifetime. The target was located in vacuum chamber which has the pressure range of 760 to $10^{-5}$ torr. As the pressure is decreased, the elemental lifetimes of carbon and titanium declined, while all other targets showed increased lifetimes until reaching 1 torr and declined with continued pressure decrease. The boiling point and electronegativity amongst the physicochemical properties of the samples are used to explain this peculiarity.

• Journal of Conservation Science
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• v.34 no.1
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• pp.59-67
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• 2018

This study investigated manufacturing technique and provenance of the Gilt-bronze Seated Bhaisajyaguru (Medicine Buddha) Statue of Janggoksa Temple. The statue had the following : Cu(68.8%)-Sn(10.4%)-Pb(17.1%), it is similar to other medium or large Buddha statue. As results of comparison lead isotope ratio of sample with the provenance data were plotted in zone 3 of the South Korean galena map. According to this result of Bronze Buddha could be made into galena of the located in same area the temple. The results of this study were compared with the Bronze Bodhisattva statue of Goseongsa Temple. The manufacturing techniques were different based on the characteristics of Buddha statues and thus could be made into galena of the located in same area the temple.

• Analytical Science and Technology
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• v.22 no.5
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• pp.422-431
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• 2009

The analytical results of wear metals such as Na, Mg, Al, Si, P, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Mo, Ag, Cd, Sn, Ba, Pb in oil samples are compared by portable and bench-top XRF methods as a basic study for the development of portable X-ray fluorescence spectrometer. The instrumental parameters such as measurement time of portable and bench-top XRF were optimized using certified reference materials of hydrocarbon oil with 20 wear metals in concentration range from 10 to 900 mg/kg. The analytical results of 20 wear metals in certified reference materials and new/used engine oil samples were compared by empirical and fundamental parameter methods.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.169-175
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• 2012

Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.123-128
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• 2018

Effect of activators in flux on the printability and wettability of a solder paste was evaluated in this study. The activators in this study were dicarboxylic acids, which were oxalic acid (n = 0), malonic acid (n = 1), succinic acid (n = 2), glutaric acid (n = 3), adipic acid (n = 4), and pimelic acid (n = 5). When the solder pastes were observed with a SMT scope, solder with glutaric acid showed clean and shiny surface when it was melted. Slump ratio of the solder pastes was low when the carbon numbers of the dicarboxylic acid were 1-3. Spreadability was high when the carbon number was over 2. Zero cross time of wetting balance test was under 1 sec when the carbon number was over 3. When activator was oxalic acid or malonic acid, zero cross time was over 1 sec and maximum wetting force was low. Fluxes with the oxalic acid and malonic acid showed decomposition at the temperature close to melting point. Among the dicarboxylic acids, glutaric acid provided excellent slump, spreadability, and wettability.