• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.699-703
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• 1992

An oriental drug, named NP-S, traditionally used as a therapeutic agent for hepatitis B was characterized by separating into volatile and non-volatile fractions. The volatile fraction contained ammonia as determined by ammonia kit and eight peaks when it was analyzed by gas chromatography that are not identified yet. The elemental analysis showed that the non-volatile fraction contained 15.5% carbon, 4.8% hydrogen, 11% nitrogen, and 10% sulfur along with a few trace elements such as Cl, Si, Mg and Zn. NP-S contained 6.7% peptide, 0.3% free amino acids such as Lys, Pro, Arg, lie, Tyr, Phe, His, Thr and Ser and 0.1% inorganic phosphate. The drug showed antimicrobial activity against Salmonella typhimurium, StaPhylococcus aureus and Candida albieans and also had antioxidant activity when thiobarbituric acid reacting substances(TBARS) method was applied.

• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.147-154
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• 2014

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was studied in aqueous solutions containing various concentrations of hydroxide ion ($OH^-$) and silicate ion ($SiO_3{^{2-}}$) by voltage-time curves, and corrosion resistance of the PEO film-covered specimen was investigated by immersion test in 0.5 M NaCl solution. From the analyses of the voltage-time curves, it is suggested that two different types of anions are essentially needed for the formation of PEO films on AZ31 Mg alloy: film formation agent and local film breakdown agent. $SiO_3{^{2-}}$ ion acts only as a film formation agent but $OH^-$ ion acts not only as a film formation agent but also film breakdown agent. The PEO films prepared on AZ31 Mg alloy in alkaline silicate solution showed very good corrosion resistance without any pitting or filiform corrosions up to 480 h of immersion in 0.5 M NaCl.

• Analytical Science and Technology
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• v.13 no.2
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• pp.215-221
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• 2000

Analysis of fly ashes from the MSW incinerators was carried out using XRF, ICP-MS and ICP-AES. It was found that the major elements of fly ash were Ca, K, Na, Si, Al, S, Cl and O by the XRF analysis. The XRD spectra showed that the fly ashes were mainly consisted with the chlorides, hydroxides, carbonates and also oxides of former elements. For the determination of minor elements such as Zn, Pb, Cu, Cr, and Cd, we used ICP-AES and ICP-MS after microwave digestion and the results were compared with the result of XRF.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.124-128
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature Process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as functional water cleaning are being studied. The electrolyzed water was generated by an electrolysis system which consists of anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH$_4$Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO$_2$ concentration changes dissolved from air. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about 9$\ell$chemicals, while EW did only 400$m\ell$ HCI electrolyte or 600$m\ell$ NH$_4$Cl electrolyte. It was hence concluded that EW cleaning technology would be very effective for eliminating environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.347-360
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• 1989

Spinel, mullite, forsterite and cordierite composition powders were synthesized from Mg(NO3)2.6H2O, Al(NO3)3.9H2O and SiCl4-ethanol solution by spray pyrolysis method and the sinterability of these powders were investigated. The bulk density of spinel and mullite specimens sintered at 1,$700^{\circ}C$ for 1hr was 3.56g/㎤(99.5% relative density) and 3.16g/㎤(99.7% relative density), respectively. (Green compacts were made from powders prepared at 1,00$0^{\circ}C$). The bulk density of forsterite and cordierite specimens sintered at 1,480 and 1,40$0^{\circ}C$ for 2hrs were 3.217 and 2.155g/㎤, respectively. (Green compacts were made from powders prepared at 1,00$0^{\circ}C$). The constituent compositions of spinel and mullite specimens sintered at 1,$700^{\circ}C$ for 1hr were 27.5wt% MgO and 70.5wt% Al2O3, respectively. Vickers microhardness and fracture toughness of spinel sintered at the above condition were 13.7GPa and 2.6MN.m3/2, respectively, and room temperature bending strength, 425MPa, was nearly maintained even at the elevated temperature. In the case ofmullite specimens, those values were 13.5GPa, 2.2MN/m3/2 and 430MPa, respectively.

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.247-259
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• 1998

Groundwater quality of the natural mineral water was investigated in hydrochemical aspects in order to ensure that mineral water meets stringent health standards. There exist 20 mineral water plants in the Daebo granite and 4 mineral water plants in the Bulguksa granite, respectively. Both granite areas show some differences in water chemistry. The pH, EC, hardness, total ionic contents in groundwater of the Daebo granite area are higher relative to those of the Bulguksa granite area. The content of major cations is in the order of Ca>Na>Mg>K, while that of major anions shows the order of $HCO_3>SO_4$>Cl>F. The fact that the $Ca-Na-HCO_3$ type is most predominant among water types may reflect that the dissolution of plagioclase that is most abundant in granitic rocks plays a most important role in groundwater chemistry. Representative correlation coefficients between chemical species are variable depending on geology. In the Daebo granite area, $Ca-HCO_3(0.84),{\;}Mg-HCO_3(0.81),{\;}SiO_2-Cl(0.74),{\;}Na-HCO_3(0.70)$ show relatively good correlationships. In the Bulguksa granite area, fairly good correlationships are found among some components such as K-Mg(0.93), $K-HCO_3(0.92)$, Mg-Cl(0.92), $Cl-HCO_3(0.91)$, and K-F(0.90). According to saturation index, most chemical species are undersaturated with respect to major minerals, except for some silica phases. Groundwater is slightly undersaturated with respect to calcite, whereas it is still greatly undersaturated with respect to dolomite, gypsum and fluorite. Based on the phase equilibrium it is clear that groundwater is mostly in equilibrium with kaolinite and becomes undersaturated with respect to feldspars, evolved from the stability area of gibbsite during water-rock interaction. While the activity of silica increases, there is no remarkable increase in the acivities of alkali ions and pH, which indicates that some amounts of silicic acid dissolved from silica phases as well as feldspars were provided to groundwater. It is concluded that chemical evolution of groundwater in granite aquifers may continue to proceed with increasing pH.

• Clean Technology
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• v.7 no.3
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• pp.215-223
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as electrolyzed water(EW) are being studied. In this work, intentionally contaminated Si wafers were cleaned using the electrolyzed water. The electrolyzed water was generated by an electrolysis system which consists of three anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH4Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. Contact angles of UPW, AW, and CW on DHF treated Si wafer surfaces were measured to be $65.9^{\circ}$, $66.5^{\circ}$ and $56.8^{\circ}$, respectively, which characterizes clearly the eletrolyzed water. To analyze the amount of metallic impurities on Si wafer surface, ICP-MS was introduced. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. To analyze the number of particles on Si wafer surfaces, Tencor 6220 were introduced. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about $9{\ell}$ chemicals, while EW did only $400m{\ell}$ HCl electrolyte or $600m{\ell}$ NH4Cl electrolyte. It was hence concluded that EW cleaning technology would be very effective for promoting environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.613-617
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• 2010

Ferro-Nickel slag is one of the by-products in Ferro-Nickel manufacturing process. The slag is composed of $SiO_2$, MgO, $Fe_2O_3$ and others. But the slag has been buried at landfill despite having valuable elements. This study tried to extract Mg ion and fabricate Mg compound from ferro-nickel slag using hydrochloric acid solution. Mg ion was extracted with Si, Fe and other ions in HCl solution. So reprocess was needed for gaining high purity Mg ion. It was thought that Si ion or $SiO_2$ precipitated in HCl solution and removed from solution in filtering process. Fe ion converted into $Fe(OH)_3$ after reacted with $NH_4OH$ and precipitated in HCl solution. After these process, the filtrate was composed of high purity Mg ion. $MgCl_2{\cdot}NH_4Cl{\cdot}6H_2O$ was obtained through drying of filtrate and this product was changed into MgO by burning process ($600^{\circ}C$-30 min). That is, 1st material or solution for manufacturing 2nd product was fabricated using acid dissolution method and other treatments.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.105-110
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• 2012

In this paper, a yellow phosphor $Sr_3SiO_5:Eu^{2+}$ that emits efficiently at the 450 nm excitation for warm white LED is studied. In addition, the effects of various flux $BaF_2$, $NH_4Cl$ on the emission spectra were investigated. The samples were synthesized through conventional solid state reaction under reducing atmosphere of 95% $N_2$-5% $H_2$ mixture at the high temperature. All phosphors showed a excitation band from 450 nm and broad band emission peaking at region of 580 nm. The optimal concentration of $BaF_2$ flux is 3 wt% for $Sr_3SiO_5$ with doping 0.05mol Eu phosphors fired in a reductive atmosphere. The phosphor showed highest emission peaking at 582 nm.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.354-361
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• 2014

In order to utilize silicon carbide (SiC) as an inner part of fluidized bed reactor (FBR) for manufacturing poly-silicon, we have carried out the thermodynamic calculation on the overall reactions including poly-silicon synthesis and compatibility of SiC with FBR process. The resources of silicon included $SiH_4(MS)$, $SiHCl_3(TCS)$ and $SiCl_4(STC)$ and the thermodynamic yield of the FBR with MS, TCS and STC were compared each other with variable range of temperature, pressure and hydrogen to silicon ratio. The silicon yield of MS, TCS and STC were 100%, 28% and 4%, respectively, throughout the conventional FBR conditions. Silicon carbide having high hardness and strength showed strong resistance to granule collisions during the FBR process using a lab-scale reactor. And it also showed quite good compatibility with the typical FBR processes of MS and TCS resources.