• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.275-282
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• 2010

The laboratory column experiments were used to transport of metal elements by infiltration-related dispersion and/or diffusion in mine tailing of the Guryong gold mine. The mine tailing shows the neutral pH (for a pore water) and contains quartz, chlorite, pyrite and calcite. Both a non-reactive solute ($Cl^-$ of 100 mg $L^{-1}$) and a reactive solute (1N HCl), were injected continuously through columns. The breakthrough curve in the non-reactive experiment reached at a maximum under 1.5 pore volumes (PV). The longitudinal dispersion (0.607 cm) and hydrodynamic dispersion coefficient ($1.96{\times}10^{-7}cm^{2}sec^{-1}$) were calculated by the slope. In the reactive experiment, the plateau curve was appeared in the pH values of 5.3, 4.5 and 1.7. The releases of metal elements such as Fe, Mn, Al, Cu, Zn, Pb, and Cd were observed to be related to the pH buffering. High concentrations of Mn, Cd and Zn were observed at the first pH plateau (4 PV and pH 5.3), whereas Fe, Cu, Al and Pb were released as the pH decreased to 4.0 or less. The resulting order of metals mobility, based on the effluent water, is Mn=Cd>Zn>Cu>Fe>Al>Pb.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.256-256
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• 2010

투명전극부터 디스플레이 산업에 이르기까지 광범위하게 응용되어지고 있고 개발되어지고 있는 투명전도산화물(TCO)은 ZnO, In2O3, SnO2 등을 기본으로 하는 n-type 재료가 대부분이다. 그러나 투명전도 산화물을 이용한 light emitting diode(LED), 투명한 태양전지, p-형 TFT와 같은 투명전자소자의 개발을 위해서는 p-type 소재가 필수적이다. p-type TCO 소재는 비교적 연구 개발 실적이 매우 부진한 실정이었다. 1997년 넓은 밴드갭을 가지는 ABO2(delafossite) 산화물이 p-type으로서 안정적이라는 것을 보고함에 따라 이에 대한 연구가 활발히 진행되고 있다. 현재 ABO2 형태를 가진 Delafossite구조 산화물이 가장 유망한 p-type 투명전도체 소재로 거론되고 있다. Delafossite 구조가 p-type 투명전도체에 적합한 결정구조인 이유는 밴드갭이 넓고 공유결합에 유리하기 때문이다. Delafossite구조는 상온에서 2종류의 polytype(상온에서 Rhombohedaral구조와 hexagonal 구조)이 존재하며 이들은 각각 3R 및 2H의 결정 구조를 가지고 있다. ABO2의 delafossite구조에서 Cu+의 배열은 c-축을 따라 Cu-O-Cr-O-Cu의 연속적인 층 구조로서 2차원연결로 보여 진다. 보고된 Cu- base delafossite구조를 가지는 재료들은 CuAlO2, CuGaO2, CuInO2 등 여러가지가 있다. 본 연구에서는 PLD를 이용하여 c-plane 사파이어 기판위에 성장된 delafossite구조인 CuCrO2박막의 특성을 알아보았다. p-type 특성을 위하여 CuCrO2에 Zn를 첨가하였으며 그에 따른 구조적 전기적 특성을 조사하였다. 성장온도와 산소분압을 $500{\sim}700^{\circ}C$, 0~10mTorr로 변화시켜 특성을 연구하였다. 성장온도 $700^{\circ}C$, 산소분압 10mTorr에서 c-plane 사파이어 기판위에 c-축 배향의 에피성장된 CuCrO2:Zn 박막을 얻을 수 있었다. Mg를 도핑함에 따른 p-type 특성보다 현저히 떨어지는 것을 확인하였다. 또한 동일한 조건임에도 특정한 이차상의 존재를 통해 도핑된 Zn의 위치를 추측할 수 있었다. 온도와 분압에 따른 결정성과 표면상태를 SEM을 통해서 확인하였다.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.56-72
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• 1999

Airborne concentrations of welding fumes in which 13 different metals such as Al, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Si, Sn, Ti, and Zn were analyzed were measured at 18 factories including automobile assembly and manufactures, steel heavy industries and shipyards. Air samples were collected by personal sampler at each worker's worksite(n=339). Blood levels of Cd, Cu, Fe, Mn, Pb and Zn were also measured from samples taken from 447 welders by atomic absorption spectrometry and compared with control values obtained from 127 non-exposed workers. The results were as follows ; 1. Among various welding types, $CO_2$ welding 70.2 % were widely used, shielded metal arc welding(SMAW) 22.1 % came next, and rest of them were metal inert gas(MIG) welding, submerged arc welding(SAW), spot welding(SPOT) and tungsten inert gas(TIG) welding. 2. Welding fume concentration was $0.92mg/m^3$($0.02{\sim}15.33mg/m^3$) at automobile assembly and manufactures, $4.10mg/m^3$($0.02{\sim}70.75mg/m^3$) at steel heavy industries and $5.59mg/m^3$($0.30{\sim}91.16mg/m^3$) at shipyards, respectively, showing significant difference among industry types. Workers exposed to high concentration of welding fumes above Korean Permissible Exposure Limit(KPEL) amounted to 7.9 % and 12.5 %, in $CO_2$ welding and in SMAW at automobile assembly and manufactures and 62.7 % in $CO_2$ welding, and 12.5 % in SMAW at shipyards, and 66.2 % in $CO_2$ welding and 70.6 % in SMAW at steel heavy industries. 3. Geometric mean of airborne concentration of each metal released from welding fumes was below one 10th of KPEL in all welding types. Percentage of workers, however, exposed to airborne concentration of metals above KPEL amounted to 16.8 % in Mn and 7.6 % in Fe in $CO_2$ welding; 37.5 % in Cu in SAW, 30 % in Cu in TIG; and 25 % in Pb in SPOT welding. As a whole, 76 Workers(22.4%) were exposed to high concentration of any of the metals above KPEL. 4. There were differences in airborne concentration of metals such as Al, Cd, Cr, Cu. Fe. Mn, Mo, Ni, Pb, Si, Sn, Ti and Zn by industry types. These concentrations were higher in shipyards and steel heavy industries than in automobile assembly and manufactures. Workers exposed to higher concentration of Pb above KPEI amounted to 7.4 % of workers(7/94) in automobile assembly and manufactures. In shipyards, 19.2 % of workers(19/99) were over-exposed to Mn and 7.1 % (7/99) to Fe above KPEL. In steel heavy industries, 14.4 %(21/146), 7.5 %(11/146) and 13 %(19/146) were over-exposed to Mn, Fe and Cu, respectively. As a whole, 76 out of 339 workers(22.4%) were exposed to any of the metals above KPEL. 5. Blood levels of Cd, Cu, Fe, Mn, Pb, and Zn in welders were $0.11{\mu}g/100m{\ell}$, $0.84{\mu}g/m{\ell}$, $424.4{\mu}g/m{\ell}$, $1.26{\mu}g/100m{\ell}$, $5.01{\mu}g/100m{\ell}$ and $5.68{\mu}g/m{\ell}$, respectively, in contrast to $0.09{\mu}g/100m{\ell}$, $0.70{\mu}g/m{\ell}$, $477.2{\mu}g/m{\ell}$, $0.73{\mu}g/100m{\ell}$, $3.14{\mu}g/100m{\ell}$ and $6.15{\mu}g/m{\ell}$ in non-exposed control groups, showing significantly higher values in welders but Fe and Zn.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.65-72
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• 2004

The tendency and degree of hot cracking of high strength 5083, 6N01 and 7N01 Al alloy welds by using DCSP-GTAW through modified Varestraint test and autogenous butt welding were investigated. In hot cracking test, 6N01 alloy showed the highest susceptibility to hot cracking in the weld metal and HAZ. Cracking susceptibilities generally increased with increase of solidification temperature range of the base metal and bead penetration-to-width ratio of the weld metal. The cracks in welds of the alloys vertically formed to solid-liquid interface and propagated along with columnar grain boundaries. The fracture facets of cracks showed the typical morphology of solidification crack observed as dendritic structures. Especially, in 6N01 alloy, liquation cracks which were due to elements of Si, Fe and Mg also observed in HAZ near fusion boundary. In butt welding of different Al alloys, the bead crack was mainly occurred in the welds of 6N01, 7N01 and other Al alloys together with 6N01 or 7N01. In the butt welds of 7N01, it was found that the component of Cu had an effect on the higher susceptibility to the hot cracking.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.179-180
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• 2012

Aluminum alloys are widely known as non-ferrous metal with light weight and high strength. Consequently, these materials take center stage in the aircraft and automobile industry. The Al7075 aluminum alloy is based on the Al-Zn-Mg-Cu and one of the strongest wrought aluminum alloys. Aluminum nitride has ten times higher thermal conductivity($319W/m{\cdot}K$) than Al2O3 and also has outstanding electric insulation($1{\times}1014{\Omega}{\cdot}cm$). Furthermore, it has high mechanical property (430 MPa) even though its co-efficient of thermal expansion is less than alumina For these reasons, it has great possibilities to be used for not only the field which needs high strength lightweight but also electronic material field because of its suitability to be applied to the insulator film of PCB or wafer of ceramic with high heat conduction. This paper investigates the mechanical properties and corrosion behavior of aluminum alloy Al7075 deposited with aluminum nitride thin films To improve the surface properties of Al7075 with respect to hardness, and resistance to corrosion, aluminum nitride thin films have been deposited by pulsed DC reactive magnetron sputtering. The pulsed DC power provides arc-free deposition of insulating films.

• Korean Journal of Environmental Agriculture
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• v.24 no.3
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• pp.222-231
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• 2005

Most of the tailings have been left without any management in abandoned metalliferous mines and have become the main source of heavy metal contamination of agricultural soils and crops in the these areas. To compare of environmental assessment of heavy metals in tailings derived from various 25-metalliferous mines in Korea, 3 different analysis methods such as water soluble, 0.1 M-HCl extractable, and total acid digestion method (aqua regia) were used. The chemical composition of water soluble in mine tailing were in the order ${SO_4}^{2-}>Ca^{2+}>Mn^{2+},\;Na^+,\;Al^{3+}>Mg^{2+},\;Fe^{3+}>Cl^-$. Specially, pH, EC, ${SO_4}^{2-},\;and\;Ca^{2+}$ concentrations in tailing varied considerably among the different mines. The average total concentrations of Cd, Cu, Pb, Zn, and As in tailing were 31.8, 708, 4,961, 2,275 and 3,235 mg/kg, respectively. Specially, the contents of Cd, Zn and As were higher than those of countermeasure values for soil contamination (Cd : 4, Zn : 700 and As : 15 mg/kg in soil) by Soil Environmental Conservation Act in Korea. The rates of water soluble heavy metals to total contents in tailings were in the order Cd > Zn > Cu > Pb > As. The rates of 0.1M-HCl extractable Cd, Cu, Pb, Zn, and As (1M-HCl) to total content were 17.4, 10.2, 6.5, 6.8 and 11.4% respectively. The enrichment factor of heavy metals in tailings were in the order As > Pb > Cd > Cu > Zn. The pollution index in tailing Au-Ag mine tailing were higher than those of other mine tailing. As a results of enrichment factor and pollution index for heavy metal contaminations in mine tailing of metalliferous mines, the main contaminants are mine waste materials including tailings.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.98-103
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• 2012

Recently, development of Al-based alloys for high mechanical performance has been an important issue in automotive industry. The present study focused on the design of a high strength Al-based alloy for rheo-diecasting. The research was based on thermodynamic calculation and experimentals to optimize the alloy compositions. Two important considerations were carried out: i) to obtain uniform slurry with fine and globular microstructures for rheo-diecasting, ii) to be strengthend by T6 heat treatment. In order to evaluate the effect of Si content on the slurry microstructure and castability, thermodynamic calculation and fluidity test were carried out. The effects of various alloying components, such as Mg, Cu and Zn, on age hardenability were also investigated. The mechanical properties of the rheo-diecasting products using the newly developed alloy are 324MPa in tensile strength, 289MPa in yield strength, and 11.2% in elongation after T6 heat treatment.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.93-104
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• 1996

This study evaluated relative hot cracking susceptibility of commercial aluminum alloy welds, and then suggested possible mechanisms operated in the weld fusion zone and in the heat affected zone based on the observed cracking morphologies, fractography and microstructural features. The fusion zone solidification cracking was found to be mainly due to a microsegregation of Cu, Si, and Mg in grain boundaries, while liquation cracking in the HAZ was by the incipient melting of the segregated grain boundaries and the consitutional liquation of large aging precipitates and intermetallic compounds in the partially melted zone adjacent to the fusion line which experienced a rapid thermal excursion during welding.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.1-4
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• 2006

The $MgB_2$ tapes with several metal powder addition were fabricated by PIT method with or without heat treatment. The $J_c$ value of $5.600A/cm^2$ and $16.000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol % of Cu added $MgB_2$ tape without heat treatment respectively. The $J_c$ value of $8.000A/cm^2$ and $35,000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol. % of Al added $MgB_2$ tape with heat treatment, respectively. The $J_c-B$ curve shows enhancement in $J_c$ under magnetic field. which suggests enhancement in workability and grain connectivity with several metal powder addition.

• Korean Journal of Heritage: History & Science
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• v.41 no.1
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• pp.5-19
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• 2008

Thirty six samples of Western asia glass vessel shards which were excavated from South Mound of Hwangnamdaechong were each measured for thickness, pore size and specific gravity and analyzed for ten major compositions and thirteen trace elements. The glass samples with colorless, greenish blue and dark purple blue were well classified by principal component analysis(PCA). All glass shards of Hwangnamdaechong belonged to Soda glass system ($Na_2O-CaO-SiO_2$) which have the range of 14~17% $Na_2O$ and 5~6% CaO. The corelation coefficients of (MgO, $K_2O$) and (MnO, CuO) showed above 0.90. The concentrations of thirteen trace elements apparently differentiated from colorless, greenish blue and dark blue glasses. We found that thirteen trace elements were very important indices for studying raw material of glass and the origin of glass making. Colorless glass : The specific gravity is $1.50{\pm}0.04$. Circle or oval circle pores are observed with regular direction in internal zone and the longest one is about 0.35 mm. The raw material of sodium must be the plant ash because sodium glasses contain HCLA(High CaO, Low $Al_2O_3$) and HMK(high MgO, high $K_2O$) and suggested to Sasanian glass. The total amount of coloring agent of colorless glass is below 1 % which is too small to attribute to the color. Greenish blue glass : The specific gravity is $1.58{\pm}0.04$. The fine pores which are 0.1~0.2mm are dispersed in internal zone. Sodium glasses are distributed to HCLA and HMK. Therefore the greenish blue glass also have used plant ash for raw material of sodium with the same as colorless glass. It was also suggested to the glass of Sasanian. The total amount of coloring agent of greenish blue glass is about 4% under the influence of working MnO, $Fe_2O_3$ and CuO. Dark purple blue glass : The specific gravity is $1.48{\pm}0.19$. There are rarely pores in internal zone. They are distributed to HCLA and LMK(Low MgO, Low $K_2O$) and suggested to Roman glass. The raw material of sodium is estimated to natron. The total amount of coloring agents of greenish blue is about 3% by $Fe_2O_3$ and CuO. These studies for western asia glass shards from South Mound of Hwangnamdaechong could be used in the future as the standard data which could be compared with those of other several graves in Korea and dispersed in foreign areas.