• Mass Spectrometry Letters
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• v.3 no.2
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• pp.58-61
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• 2012

A method based on flow injection-isotope dilution-cold vapor-inductively coupled plasma mass spectrometry (FI-IDCV-ICP/MS) has been applied to determine trace level of mercury in fly ash. $^{200}Hg$ isotopic spike was added to 0.25 g of BCR176R fly ash and then decomposed by microwave digestion procedure with acid mixture A (8 mL $HNO_3$ + 2 mL HCl + 2 mL HF) and acid mixture B (8 mL $HNO_3$ + 2 mL $HClO_4$ + 2 mL HF) for applying IDMS. Mercury cold vapor was generated by using reductant solution of 0.2% (w/w) $NaBH_4$ and 0.05% (w/w) NaOH. The measurements of n($^{200}Hg$)/n($^{202}Hg$) isotope ratio was made using a quadrupole ICP/MS system. The accuracy in this method was verified by the analysis of certified reference material (CRM) of fly ash (BCR 176R). The indicative value of Hg in BCR 176R fly ash was $1.60{\pm}0.23$ mg/kg (k = 2). The determined values of Hg in BCR 176R fly ash by the method of FI-CV-ID-ICP/MS described in this paper were $1.60{\pm}0.24$ mg/kg (k = 3.18) and the analysis results were in well agreement with the indicative value within the range of uncertainty.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.695-708
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• 2008

In order to evaluate the geochemical behaviors of elements with waste rocks in the abandoned Jangpoong Cu mine area, total concentration analysis and leaching experiments were performed. The content of elements within waste rocks compared with background values decreased in order of As>>Cu>Pb>Cd>Co. Leaching experiments were carried out at various extraction environments, considering the acid rain ($0.00001{\sim}0.001N\;HNO_3$) and the acid mine drainage ($0.001{\sim}0.1N$ HNO3). After 24 hours of reaction with different acidic solution, the leaching characteristics of waste rocks were classified into three types according to final pH of leaching solution. Type I refers to the case that the final pH of leaching solution was lower than that of the reaction solution due to the dissolution of acidic minerals from rocks, while type 2 and 3 refer to the case that the final pH maintained higher than that of the reaction solution. Theses types include in acid buffering minerals such as clay minerals and carbonate minerals. The leaching characteristics of the elements after the reaction could be categorized into As-Co-Fe, Cu-Mn-Cd-Zn, and Pb. As-Co-Fe started to get leached under 2.5 of pH regardless of changes in the final pH, and Cu-Mn-Cd-Zn showed different initial leaching pH according to the types of final pH changes. Based on the pH value where leaching started regardless of leaching concentration, the relative mobility of each element was in the order of Mn Zn>Cd>Cu>>Fe Co>As>Pb. Thus, more higher mobility elements(Zn, Mn and Cu) were leached by reacting with acid rain water. Acid mine drainage may result in distributions of elements having relatively less mobility(As, Fe, Co and Pb).

• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.198-205
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• 2012

The corrosion properties of anodized films on aluminium 6070 alloy in a sulfuric acid have been studied. Comparison to evaluate the anodized A6070 and pure 6070 specimen, corrosion tests in $HNO_3$ vapor environment of the 20 wt.% were performed up to 72 hours. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM, and EDS. The oxide film anodized in the sulfuric acid solution contained 5 to 10 wt.% of sulfur. In the initial stages of corrosion, anodized specimens exhibited corrosion resistance than the pure specimen. However, the corrosion conditions in 24 hours, corrosion was far more anodized specimen than pure specimen. Therefore, anodized films contained sulfur, nitric acid vapor in the environment is thought to stimulate corrosion.

• Analytical Science and Technology
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• v.9 no.4
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• pp.336-344
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• 1996

The extraction of trace cobalt, copper, nickel, cadmium, lead and zinc in urine samples of organic and alkali metal matrix into chloroform by the complex with a dithizone was studied for graphite furnace AAS determination. Various experimental conditions such as the pretreatment of urine, the pH of sample solution, and dithizone concentration in a solvent were optimized for the effective extraction, and some essential conditions were also studied for the back-extraction and digestion as well. All organic materials in 100 mL urine were destructed by the digestion with conc. $HNO_3$ 30 mL and 30% $H_2O_2$ 50 mL. Here, $H_2O_2$ was added dropwise with each 5.0 mL, serially. Analytes were extracted into 15.0 mL chloroform of 0.1% dithizone from the digested urine at pH 8.0 by shaking for 90 minutes. The pH was adjusted with a commercial buffer solution. Among analytes, cadmium, lead and zinc were back-extracted to 10.00 mL of 0.2 M $HNO_3$ from the solvent for the determination, and after the organic solvent was evaporated, others were dissolved with $HNO_3-H_2O_2$ and diluted to 10.00 mL with a deionized water. Synthetic digested urines were used to obtain optimum conditions and to plot calibration-eurves. Average recoveries of 77 to 109% for each element were obtained in sample solutions in which given amounts of analytes were added, and detection limits were Cd 0.09, Pb 0.59, Zn 0.18, Co 0.24, Cu 1.3 and Ni 1.7 ng/mL, respectively. It was concluded that this method could be applied for the determination of heavy elements in urine samples without any interferences of organic materials and major alkaline elements.

• Journal of the East Asian Society of Dietary Life
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• v.7 no.4
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• pp.512-518
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• 1997

This study was performed to determine the amount of aluminum, which is one of the factors of Alzheimer's disease, In some fishes caught from some areas of the west coast in Korea. The 46 aquatic products were composed of fishes, molluscs, and salt-fermented products (jeot-gal). The 24 fishes were Hickory shad, Gobies, Pomfref, Atkafish, Flounder, Jambeng-ie Monk fish, Yellow hair tail, Mackerel, Bartailed flathead, Alaska pollack, Brown croaker, Eel, Fine-spotted flounder, Black spotted grouper, Sea-eel, Pacific saury, Areliscus honaleus, Small boil-dried anchovy, Croaker, Hair tail, Sea bream genuine, Motleystrip rainbowfish, and Bastard halibut. The 15 Molluscs were Whip-arm octopus, Sea arrow, Common squid, Han chi, Cuttle fish, Turban shell, Pond snail, Orient calm, Surf calm, Butter calm, Crib shell, Oyster, Egg cockle, Little neck calm, and Arkshell. The 7 salt-fermented products were salt-fermented Shrimp, Little neck, Oyster, Shad, Gonjeng-ie, Hqangsegi, and Squid. All of them were ashed with 5$m\ell$ HNO$_3$ and then with 10$m\ell$ ternary solution (HNO$_3$ : H$_2$SO$_4$ : HClO$_4$= 10 : 1 : 4). After ashing of the samples, the aluminum amount were measured by ICP. The aluminum amount of molluscs was significantly higher than that of fishes and salt-fermented products(p＜0.01). The aluminum amount of Orient calm and Healak in molluscs were 827.70, 812.55ppm, respectively, which were the most amounts compared nth that of the other samples. But the aluminum amounts of Bartailed flathead and Sea bream, genuine In fishes were 0.98, 0.97ppm, respectively, which were the least amounts compared with that of other samples. This study was limited within 46 aquatic samples, therefore I hope there will be wider efforts to determine about auminum amount in broade range of aquatic foods for the prevention of Alzheimer's disease.

• Analytical Science and Technology
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• v.13 no.3
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• pp.323-331
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• 2000

Two chelating resins, XAD-16-TAC and XAD-16-TAO were synthesized by Amberlite XAD-16 macroreticular resin with 2-(2-thiazolylazo)-p-cresol (TAC) and 4-(2-thiazolylazo)-orcinol (TAO) as functional groups. The sorption behaviour of Zr(IV), Th(IV) and U(VI) with two chelating resins were examined with respect to the effect of pH and masking agent by batch methods. It was obtained that the optimum pH was in the range of 5-6, and two chelating resins showed good separation efficiency of Zr(IV) or Th(IV) by using $NH_4F$ as a masking agent. Characteristics of desorption were investigated with 0.1-2 M $HNO_3$ as desorption agent. It was found that 2 M $HNO_3$ showed high desorption efficiency to most of metal ions except Zr(IV). XAD-16-TAC resin is applied to separation and preconcentration of trace Zr(IV) from mixed metal ions. Also, Th(IV) ion can be successfully separated from U(VI) and Zr(IV) ion by using XAD-16- TAO resin.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.38-43
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• 1999

An experimental study was carried out, in order to set up the procedure for evaluation of hot fire test, to investigate the effect of mixture on combustion performance and combustion stability , and to determine the optimum design condition for designing the liquid rocket engine. $HNO_3$/Kerosene uni-element liquid rocket engine(thrust 24 $\iota{b}_f$, chamber pressure 200 psia) using impinging streams doublet injector was designed, and ground hot-fire test was carried out. To prevent or reduce the hard start during ignition period, two step ignition method was used. This was accomplished by maintaining about 25% of the designed operating pressure doting transient period, then chamber pressure was built up to the designed operating pressure. Maximum combustion efficiency was at O/F ratio 3.6, and combustion efficiency is decreased with increasing momentum ratio.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.34-39
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• 2009

In this study, a needle coke was oxidized in a mixture of dilute nitric acid and sodium chlorate ($NaClO_3$) solutions and followed by heat treatment. The samples were analyzed with using XRD, FESEM, elemental analyzer, BET, and Raman spectroscopy. Double layer capacitance was measured with the charge and discharge measurements. The consisting layers of the needle coke were expanded to single phase showing only (001) diffraction peak by the acid treatment for 24 hours. The oxidized coke returned to a graphite structure appearing (002) peak after heat treatment above $200^{\circ}C$. The structure returned could be more easily accessible to the ions by the first charge, and improve the double layer capacitance at the second charge. The two-electorde cell from acid treated coke and $300^{\circ}C$ heat treatment exhibited the maximum capacitances of 32.1 F/g and 29.5 F/ml at the potential of $0{\sim}2.5\;V$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.121-125
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• 2011

Ribbon silicon solar cells have been investigated because they can be produced with a lower material cost. However, it is very difficult to get good texturing with a conventional acid solution. To achieve high efficiency should be minimized for the reflectance properties. In this paper, acid vapor texturing and anti-reflection coating of $SiN_x$ was applied for EFG Ribbon Si Wafer. P-type ribbon silicon wafer had a thickness of 200 ${\mu}m$ and a resistivity of 3 $\Omega-cm$. Ribbon silicon wafers were exposed in an acid vapor. Acid vapor texturing was made by reaction between the silicon and the mixed solution of HF : $HNO_3$. After acid vapor texturing process, nanostructure of less than size of 1 ${\mu}m$ was formed and surface reflectance of 6.44% was achieved. Reflectance was decreased to 2.37% with anti-reflection coating of $SiN_x$.

• Journal of the Semiconductor & Display Technology
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• v.13 no.2
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• pp.29-35
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• 2014

In this study general solar cell production process was complemented, with research on improvement of solar cell efficiency through surface structure and thermal annealing process. Firstly, to form the pyramid structure, the saw damage removal (SDR) processed surface was undergone texturing process with reactive ion etching (RIE). Then, for the formation of smooth pyramid structure to facilitate uniform doping and electrode formation, the surface was etched with HND(HF : HNO3 : D.I. water=5 : 100 : 100) solution. Notably, due to uniform doping the leakage current decreased greatly. Also, for the enhancement and maintenance of minority carrier lifetime, antireflection coating thermal annealing was done. To maintain this increased lifetime, front electrode was formed through Au plating process without high temperature firing process. Through these changes in two processes, the leakage current effect could be decreased and furthermore, the conversion efficiency could be increased. Therefore, compared to the general solar cell with a conversion efficiency of 15.89%, production of high efficiency solar cell with a conversion efficiency of 17.24% was made possible.