• Bulletin of the Korean Chemical Society
• /
• v.24 no.11
• /
• pp.1613-1617
• /
• 2003

In the phosphoric acid based etchant, the dissolution rates of Mo films were measured by microgravimetry and the corrosion potentials of Mo and Al were estimated by Tafel plot method with various concentrations of nitric acid. Dissolution rate of Mo increased with the nitric acid concentration and reached a limiting value at high concentration of nitric acid in ambient condition. Corrosion potentials of Mo and Al shifted to positive direction and the difference between potentials of both metals was about 1,100 mV and 1,200 mV with 1% and above 4% of $HNO_3$, respectively. For a Mo/Al bilayers, the dissolution rate inversion is the main reason for good taper angle in shower etching process. Taper angles are observed by scanning electron microscope (SEM) after wet etching process for Mo/Al layered films with different concentrations of $HNO_3$. In the etch side profile, it was found that Al corroded faster than Mo below 4% of $HNO_3$ in dip etching process, however, Mo corroded faster above 4%. Trend for variation of taper angle of etched side of Mo/Al layered film can be explained by considering the effect corrosion rates of both metals with various concentrations of $HNO_3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.123-123
• /
• 2008

본 논문에서는 Cu의 ECMP 적용을 위해 $HNO_3$ 전해액의 active, passive, transient, trans-passive 영역을 I-V 특성 곡선을 통해 알아보았고, LSV (Linear sweep voltammetry)와 CV (Cyclic voltammetry)법을 통하여 전기화학적 특성을 비교 분석하였다.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.10 no.2
• /
• pp.117-124
• /
• 2002

This study was carried out to investigate variation of heavy metal contents for feed materials during composting and to evaluate the effect of pre-treatment methods on heavy metal analysis. Dry ashing, $HNO_3-HClO_4$, aqua-regia, HCl reflux, $HNO_3-HClO_4-HF$, autoclaving methods of $HNO_3$, HCl, and $HNO_3(2+1)$ were used as pre-treatment for heavy metal analysis. In analyzing standard material SRM 2781, recovery efficiencies of pre-treatment methods were 50-60% for Cr and Zn, >100% for Ni, and 80-90% for Cd and Cu. Recovery efficiency of dry ashing for SRM 2781 was the lowest. In composting raw material, Cd concentration by autoclaving methods was 3 to 4 times higher than the other methods and recovery efficiency of dry ashing was also the lowest. During composting, Cd content was the highest in autoclaving. Cr and Cu concentrations were the lowest in dry ashing and aqua-regia, respectively. Variation coefficients of Pb and Zn between pre-treatment methods were generally low.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2002.11a
• /
• pp.389-390
• /
• 2002

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.2
• /
• pp.113-120
• /
• 1999

Winter and summer samples were collected from January 3 to February 7, 1997 and July 26 to September 11, 1997, respectively, in Seoul. This study was to characterize the concentrations of the annular denuder system (ADS) were $HNO_3$, $HNO_2$, $SO_2$ and $NH_3$ in the gas phase, and $PM_{2.5}$ ($d_p$〈2.5$mu extrm{m}$), $SO_4^{2-}$, NO3-, and $NH_4^+$ in the particulate phase. All chemical species monitored from this study showed statistical seasonal variations except for $SO_4^{2-}$ . Nitric acid (HNO3) and ammonia ($NH_3$) exhibited substantially higher concentrations during the summer, while nitrous acid ($HNO_2$) and sulfur dioxide ($SO_2$) concentrations were higher during the winter. $PM_{2.5}$, $NO_3^-$, and $NH_4^+$ were higher leves in the winter. High correlations were found among $PM_{2.5}$, $NO_3^-$ $SO_4^{2-}$ and $NH_4^+$ during two seasons.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.5 no.2
• /
• pp.123-132
• /
• 2007

This study was performed to evaluate the co- and mutual separation for Am, Cm and RE elements from the simulated multi-component solution equivalent to real HLW level by a Zr-DEHPA(di-(2-ethylhexyl) phosphoric acid containing Zirconium)/$NDD(n-dodecane)-HNO_3$ extraction system. Zr-DEHPA was self-synthesized and the optimal condition of (15g/L Zr-1M DEHPA)/NDD-1M $HNO_3$ was selected taking into consideration of prevention of the third phase, and effects of concentration of DEHPA, nitric acid and impregnant amount of Zr on the co-extraction of Am, Cm and RE. In that condition, the extraction yields were 81% (Am), 85% (Cm), more than 80% (RE elements), 98% (Mo), 85% (Fe), 98% (U), 73% (Np), and less than 5% (other elements) so that the system developed for the co-extraction of Am-Cm/RE was proved to be available. For that, however, U, Np, Mo and Fe was elucidated to have to be removed in advance, and Zr inducing the third phase formation was found to be practically excluded. The co-extracted Am-Cm/RE were sequentially separated in an order of Am-Cm (stripping agent : 0.05 M DTPA-1M Lactic acid of pH 3.6)${\rightarrow}RE$ (stripping agent : 5M $HNO_3$), and then their separation factors were evaluated. At above conditions, Am of 65.4%, Cm of 63.9%, RE (except for Y) of more than 85% were stripped.

• Clean Technology
• /
• v.19 no.3
• /
• pp.347-350
• /
• 2013

Desorption characteristics for ions adsorbed onto sericite was performed by means of $HNO_3$ solution which was selected as the best desorbing agent in the previous work. Elution of nickel ions adsorbed onto sericite using $HNO_3$ solution was confirmed by means of scanning electron microscopy (SEM) & energy dispersive X-ray spectroscopy (EDX) analysis. Desorption efficiency for nickel ions was 100% at the 20 mM of concentration. Also, nickel ions was completely desorbed within 1.0 of S/L (mg/mL) ratio which is defined as the ratio of adding amount of adsorbent and volume of desorbing agent and desorption process was quickly carried out within 60min. Finally, removal efficiency of reused sericite for nickel ions was constantly maintained until the 4th cycle.

• The Journal of Korean Academy of Prosthodontics
• /
• v.23 no.1
• /
• pp.83-95
• /
• 1985

The purpose of this study was to evaluate microstructures on the etched surface of 11 base metal alloys for dental restorations and to observe the relationship between the etching pattern and beryllium. For this purpose, the following experiments were done; 11 base metal alloys were etched in (1) 10% $H_2SO_4$, (2) 10% $H_2SO_4$, 9 parts+methanol 1 part (3) Conc. $HNO_3$ 25%+glacial acetic acid 25%+$H_2O$ 50% (4) Conc. $HNO_3$ 5% (5) 2% glacial acetic acid added to Conc. $HNO_3$ 1% solution, with their etching conditions varied. Etched surface of alloys were examined under the scanning electron microscope. Results were as follows; 1. Almost all of Ni-Cr-Be alloys showed gooed etchd surface in $H_2SO_4$, solution, while some of those alloys which contains no beryllium showed good etched surface in $HNO_3$ solution. 2. Main components of etching solution can vary etching pattern of alloys. 3. Gamma prime phase relief, which can be found in all Ni-Cr-Be alloys, can't be found in any alloy that contains no beryllium.

• Korean Journal of Environmental Agriculture
• /
• v.19 no.4
• /
• pp.319-323
• /
• 2000

This study was conducted to compare fractionations and availability of heavy metal in paddy soils near five abandoned mining areas. The sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from water $soluble(H_2O)$, $exchangeable(0.5M\;KNO_3)$, organically bound(0.5M NaOH), $oxide/carbonate(0.05M\;Na_2-EDTA)$, and $sulfide/residual(4M\;HNO_3)$. EDTA and $HNO_3$ extractable of Cd, Pb, and Zn, and NaOH and $HNO_3$, extractable of Cu were predominant chemical forms. The ratio of $H_2O+KNO_3$ extractable of Cd, Zn, Cu, and Pb were 25.1, 8.7, 4.0, and 0.4%, respectively. The ratio of $H_2O+KNO_3$ extractable heavy metal were negatively correlated with soil pH, while $EDTA+HNO_3$ extractable heavy metal were positively correlated. The most consistent distribution patterns were found when the soil samples were grouped according to their total contents. Specially, the ratio of $H_2O+KNO_3$ extractable heavy metal were higher as total contents of heavy metal were increased. The ratio of $H_2O+KNO_3$ extractable heavy metal(Cd 1.06, Cu 0.15, Pb 0.01, and Zn 0.05%) were lower at the high soil pH than those(Cd 31.31, Cu 4.06, Pb 1.75, and Zn 10.16%) at the low level. Compared to other chemical forms, the degree of contribution for $KNO_3$ extractable form to the Cd uptake to brown rice was high, whereas that for EDTA and $HNO_3$ extractable forms were high to the Zn.

• Korean Journal of Materials Research
• /
• v.16 no.4
• /
• pp.235-240
• /
• 2006

We investigated the effect of ZnO filler on the microstructure of $BaO-B_2O_3-ZnO-P_2O_5$ glass system to find an etching mechanism of barrier ribs. The sintering behavior of composites heated in the temperature range $560-600^{\circ}C$ was studied by volumetric shrinkage rate and microstructure. The etching test was carried out in $HNO_3$ solution at $50^{\circ}C$ for 10 min. The volumetric shrinkage of sintered sample decreased with the increased firing temperature because of the formation of two crystals. Glass and ZnO filler react forming the $BaZn_2(PO_4)_2$ crystal phases during the sintering process. Etching phenomenon of sintered samples by $HNO_3$ showed that the $BaZn_2(PO_4)_2$ crystal phase was strongly leached compared to glass matrix, crystal phases and fillers. Therefore, the control of interface by condition of sintering is so important to achieve etching effect in barrier ribs.