• Journal of Welding and Joining
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• v.23 no.6
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• pp.93-98
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• 2005

The purpose of this study is to investigate the characteristics of pb-free $Zn-(3\~6)\%Al-(1\~6)\%Cu$ solder alloys for ultra high temperature(>573K) which applied to air craft, space satellite, automotive, oil, gas well exploration and data logging of geo-thermal wells. Melting range, solderability, electric resistivity, microstructure and mechanical properties were examined with solder alloys casted in Ar gas atmosphere. $Zn-4\%Al-(1\~3)\%Cu,\;Zn-5\%Al-(2\~4)\%Cu\;and\;Zn-6\%Al-(3\~5)\%Cu$ alloys satisfied the optimum melting range of 643 to 673k for ultra high temperature solder. A melting temperature increased with increasing Cu content, but decreased with increasing Al content. The spreadability was improved with increasing hi content. But the content of Cu had no effect on the spreadability. The electric resistivity was lowered with increasing Al and decreasing Cu content. In all Zn-Al-Cu solder alloys, primary dendritic $\varepsilon$ phase(Zn-Cu), dendritic $\eta$ phase(Zn-Cu-Al), $\alpha(Al-Zn)-\eta$ eutectic and eutectoid phase were observed. The addition of Al increased the volume fraction of eutectic and eutectoid phase and it decreased f phases. Also, the addition of Cu increased slightly the volume fraction of e, the eutectic and eutectoid phases. With increasing total content of Al and Cu, a hardness and a tensile strength were linearly increased, but anelongation was linearly decreased.

• Journal of Ecology and Environment
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• v.34 no.3
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• pp.315-322
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• 2011

We investigated the effect of Pb uptake by Pinus densiflora and the Pb fraction in forest soil. We also investigated the change in soil physicochemical characteristics, microbial activity, and root exudates of Pinus densiflora in Pb-contaminated soils. Three-year-old pine seedlings were exposed to 500 mg/kg Pb for 12 months. The metal fractions were measured using sequential extraction procedures. Additionally, factors that affect solubility (three soil enzyme activities and amino acids of root exudate compounds) were also determined. The results showed that Pb contamination significantly decreased enzyme activities due to soil characteristics. In addition, organic matter, nitrate content, and Pb concentration were time dependent. The results indicate that changes in the Pb fraction affected Pb uptake by pine trees due to an increase in the exchangeable Pb fraction. The concentrations of organic acids were higher in Pb-spiked soil than those in control soil. Higher rhizosphere concentrations of oxalic acid resulted in increased Pb uptake from the soil. These results suggest that pine trees can change soil properties using root exudates due to differences in the metal fraction.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.246-249
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• 2002

• 한국전기화학회:학술대회논문집
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• 1999.04a
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• pp.49-49
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• 1999

• 한국문화재보존과학회:학술대회논문집
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• 2004.10a
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• pp.137-153
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• 2004

We have analyzed the ingredients of 17 pieces of Bronze Age bronze ware, and an additional 22 pieces of Koryo and Chosun dynasty bronze ware. We have also conducted analysis of the extraction sites where these bronze ware items were found. For analyzing the main ingredient the bronze ware items have been divided into 3 groups - Cu-Sn(70?75:20), Cu-Pb-Sn(70:10:10), Cu-Pb-Sn(60:10:20) type respectively. In tile cases of the Cu-Pb-Sn groups the division comes down to differences in the Cu content as the main component, and elements such as Ni, Fe, Co contribute as a micro ingredient. The geographical and periodic characteristics of ancient bronze ware items show that theircompositional element changes from Cu:Sn to Cu:Pb:Sn and the Cu content decreases with the period,while the Pb content increases with the period. Bronze ware items from Suchon Ri, Gongju (that were used in 3 B.C.) form very different categories from 3rd ${\~}$ 2nd B.C.. They additionally formed very different categories from those bronze ware items analyzed in this research. These bronze ware itemsare shown to be geographically close and periodically overlapped, but made of a new elemental composition. This shows an inflow of a production technical culture present in the new bronze wares. The main component content of Cu is lower, and the Co and Fe contents (as microelements) are much higher than that of other bronze ware items. Such facts showthat those bronze ware items used completely different materials from bronze ware items in other cultural areas, or that there were differences in smelting techniques In the places where ancient bronze ware items have been extracted, it is presumed that the materials originated from the southern parts of Korea andnorthern parts and southern parts of China. .As more bronze ware scientific research is compiled one can conclude that that there will be enough scientific evidence to study the Bronze Age culture of Koreasystematically.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.848-850
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• 1999

In this study, PZT etching was performed using planar inductively coupled Ar(20)/$Cl_2/BCl_3$ plasma, The etch rate of PZT film was 2450 $\AA/min$ at Ar(20)/$BCl_3$(80) gas mixing ratio and substrate temperature of $80^{\circ}C$. X-ray photoelectron spectroscopy (XPS) analysis for film composition was utilized. The chemical bond of PbO is broken by ion bombardment, and the peak of metal Pb in a Pb 4f peak begins to appear upon etching, decreasing Pb content faster than Zr and Ti. As increase content of additive $BCl_3$, the relative content of oxygen decreases rapidly. We thought that abundant Band BCl radicals made volatile oxy-compound such as $B_{x}O_{y}$ and/or $BClO_x$ bond. To understand etching mechanism, Langmuir probe and optical emission spectroscopy (OES) analysis were utilized for plasma diagnostic.

• YAKHAK HOEJI
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• v.5 no.1
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• pp.24-26
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• 1960

Micro-determination of Lead by Dithizone Method was studied as follows: 1) Max. absorption wave length of Dithizone-pb complex in CC $l_{4}$ soln. is 510m.mu., 2) at the range of 5.gamma.-120.gamma. pb content, Bourguer-Beer's law hold good, 3) co-existence of F $e^{++}$ Z $n^{++}$, and C $u^{++}$ interfere.rfere.

• Journal of the Korean Ceramic Society
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• v.42 no.10 s.281
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• pp.698-702
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• 2005

Dielectric and Piezoelectric properties of complex perovskite 0.92Pb($Zr_{1/2}Ti_{1/2})O_{3}-(0.08-x)Pb(Cu_{1/3}Nb_{2/3})O_{3}-xPb(Mn_{1/3}Nb_{2/3})O_{3}(0{\leq}x{\leq}0.080$) (PZT-PCN-PMN) system were investigated as a function of PMN content. With the increase of PMN content of the sintered specimens, tetragonal phase was coexisted with rhombohedral phase, the dielectric constant was decreased, mechanical quality factor ($Q_{m}$) was inceased, and optimal sintering temperature was increased up to 1050$^{\circ}C$. For the composition of x = 0.064 sintered at 1050$^{\circ}C$ for 2 h, 1939 of maximum mechanical quality factor ($Q_{m}$), 57$\%$ of electromechanical coupling factor ($k_{p}$), and 1100$^{\circ}C$ of dielectric constant, 0.37$\% $ of dielectric loss (tan $\delta$) were obtained.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.83-90
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• 1990

The semiconducting $(Pb_1\;_xSn_x)_1$ $_yTe_y$, one of the low - temperature thermoelectric materials, has been prepared and its chemical composition and nonstoichiometry has been analyzed. The content of Pb in the specimens was determined by the complexometric back - titration method with EDTA and Pb(II) standard solutions. Te - content was analyzed with the redox titration method. The electrical conductivity and the thermoelectric power have also been measured by the DC 4 - probe and the heat-pulse technique, respectively. All of the specimens showed a nonstoichiometric behavior in their chemical compositions (Te excess), thus gave rise to a p - type semiconducting property, and the nonstoichoimetry became bigger as the Sn - content increased. The thermoelectric power vs. temperature results have been analyzed upon the basis of the Fermi level vs. temperature profiles in the saturation regime. The specimen of x=0.1 evolved a transition from p - to n - type property at about 670K, which has been explained by the fact that the mobility of electrons is bigger than that of holes in the temperature range of the intrinsic regime.

• Economic and Environmental Geology
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• v.28 no.3
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• pp.221-229
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• 1995

The heavy metal contents and their dispersion patterns in stream water, stream sediments, land plants and aquatic larvae collected from the hydrologic system flowing via the wasted ore dump of the Moak Au-Ag mine were investigated systematically in order to evaluate the environmental impacts of the abandoned metal mine. The heavy metal content increases abruptly in the vicinity of the wasted ore dump, then attenuated with increasing distance from the mine area. Attenuating rates were stream water > stream sediments > land plants > aquatic larvae. On the other hand, the cumulative content of heavy metals was stream sediments >aquatic larvae > land plants > stream water. Each element tends to be enriched selectively according to media; Zn > Cu > Cd > Pb in stream water, Zn > Pb > Cu > Cd in stream sediments and land plants, and Zn > Cu > Pb > Cd in aquatic larvae. These results show that the degree of enrichment and dispersion of pollutant extruded from the wasted ore dump are different according to elements and media, and that the circulation system of materials of each medium is different. The heavy metals, especially Cu, Pb and Zn, of polluted downstream sediments occur in high proportions of Fe-Mn oxides and organic bounded forms, which show high potential of a secondary pollution source. The content of heavy metals and their dispersion patterns in stream sediments are different from those of ten years ago; pollution levels of heavy metals were degraded in various ranges. The Zn and Cu-polluted areas were widened whereas Fe and Pb-polluted areas were reduced. In crops collected from the farm lands in downstream area, the pepper was more concentrated in all heavy metal than rice. The pepper showed some contaminated level in Cu(9.7ppm) and Zn(149ppm), and the rice in Zn(90ppm). However, both crops showed no significant level in Cd(<0.2ppm) and Pb(<0.5ppm).