• Journal of Environmental Science International
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• v.30 no.6
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• pp.487-500
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• 2021

To evaluate the geochemical characteristics and assess the pollution in surface sediments of the Nakdong River estuary, two sites adjacent to the estuary bank (Hh1 and Hh2) and one site at the upper part of the estuary bank (Hh3) were investigated. The surface sediments were analyzed for their contents of metals (Cu, Pb, Ni, Cr, Zn, and Al), organic matter (IL, COD, TOC, and TN), and grain size from 2018 to 2020. As a result of the pollution assessment, there was little anthropogenic contamination by most of the metals. The surface sediments in Hh2 had comparatively abundant silt and clay, whereas the other sites were mainly composed of sand. The organic index and contents of organic matter were highest at Hh2. Multivariate statistical analyses (cluster analysis and Pearson correlation analysis) showed that the contents of organic matter and pollution were associated with fine sediment. These results suggest that the geochemical characteristics were changed by the estuary bank built in the research area and that the increase in fine sediment attributable to the low-energy environment resulted in an increase in organic matter pollution.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.659-667
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• 2012

Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at $850^{\circ}C-950^{\circ}C$ in a helium environment containing the impurity gases $H_2$, CO, and $CH_4$, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high-temperature corrosion behavior of Alloy 617 for the VHTR application.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.321-327
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• 2008

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

• Design & Manufacturing
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• v.17 no.2
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• pp.55-61
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• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• Journal of Ecology and Environment
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• v.47 no.3
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• pp.157-167
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• 2023

Background: The most hazardous wastewater sources in the northern part of the Middle Nile Delta, Egypt; receiving a massive amount of agricultural, industrial, and sewage drainage are Kitchener drain which is one of the tallest drainage systems, and Burullus Lake which represents the 2nd largest Egyptian coastal lake. Results: The current work is to determine the abundance and frequency of cyanophytes, chlorophytes, and bacillariophytes and the correlation between them and environmental abiotic components. Among sixty nine microalgal species, 19 species are belong Cyanophyta, 26 belong Chlorophyta and 24 belong Bacillariophyta. Genus Scenedesmus (Chlorophyta) was the most abundant in the study area (13 species), followed by Genus Oscillatoria (9 species) and Genus Navicula (7 species). Nostoc muscorum and Chlorella vulgaris were the most common and recorded in all sites (100% of the locations) under study. The application of the two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis revealed agglomerating of 4 groups (communities) at 4th level of classification and reasonable segregation between these groups. Zinc, cadmium and lead were showed the highest levels (0.26±0.03, 0.26±0.06, and 0.17±0.01 ppm, respectively). Conclusions: The correlation analysis between water and community variables indicated a high negative correlation of total algae richness with nickel (r = -0.936, p < 0.01). Cyanophyta and Bacillariophyta were correlated negatively (r = -0.842, p < 0.01). However, Chlorophyta showed a negative richness with each of Ni and Pb (r = -0.965, -0.873, respectively) on one hand and a high positive correlation was revealed (r = 0.964) with all environmental variables on the other hand.

• International Journal of Computer Science & Network Security
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• v.24 no.6
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• pp.200-206
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• 2024

Laser induced breakdown spectroscopy (LIBS) technique has been used for the elemental composition of the soils. In this technique, a high energy laser pulse is focused on a sample to produce plasma. From the spectroscopic analysis of such plasma plume, we have determined the different elements present in the soil. This technique is effective and rapid for the qualitative and quantitative analysis of all type of samples. In this work a Q-switched Nd: YAG laser operating with its fundamental mode (1064 nm laser wavelength), 5 nanosecond pulse width, and 10 Hz repetition rate was focused on soil samples using 10 cm quartz lens. The emission spectra of soil consist of Iron (Fe), Calcium (Ca), Titanium (Ti), Silicon (Si), Aluminum (Al), Magnesium (Mg), Manganese (Mn), Potassium (K), Nickel (Ni), Chromium (Cr), Copper (Cu), Mercury (Hg), Barium (Ba), Vanadium (V), Lead (Pb), Nitrogen (N), Scandium (Sc), Hydrogen (H), Strontium (Sr), and Lithium (Li) with different finger-prints of the transition lines. The maximum intensity of the transition lines was observed close to the surface of the sample and it was decreased along the axial direction of the plasma expansion due to the thermalization and the recombination process. We have also determined the plasma parameters such as electron temperature and the electron number density of the plasma using Boltzmann's plot method as well as the Stark broadening of the transition lines respectively. The electron temperature is estimated at 14611 °K, whereas the electron number density i.e. 4.1 × 10¹⁶ cm^-3 lies close to the surface.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1830-1835
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• 2024

The current study aims to study the impacts of the substitution of magnesium with nickel concentrations on physical and γ-ray shielding capacity of magnesium alloys. The density of the magnesium alloys under study is varied from 3.677 g/cm³ to 5.652 g/cm³, with raising the nickel content from 26.7 wt% to 54.8 wt% and reducing the magnesium concentration from 72.6 wt% to 44.2 wt%, respectively. Additionally, the examination of the γ-ray shielding capacity using the Monte Carlo simulation code shows that the substitution of magnesium by nickel content in the magnesium alloys was associated with an enhancement in the γ-ray shielding capacity, where the linear attenuation coefficient for the studied alloys was enhanced by 53.22 %, 52.45 %, and 52.52 % at γ-ray energies of 0.662 MeV, 1.252 MeV, and 1.408 MeV, respectively, with raising the nickel concentration from 26.7 wt% to 54.8 wt%. Simultaneously, the half-value thickness for magnesium alloys was reduced from 2.47 cm to 1.62 cm (at gamma ray energy of 0.662 MeV), from 3.39 cm to 2.22 cm (at gamma ray energy of 1.252 MeV), and from 3.60 cm to 2.36 cm (at gamma ray energy of 1.408 MeV), raising the nickel concentration from 26.7 wt % to 54.8 wt%, respectively. The study shows that the substitution of magnesium for nickel greatly enhanced the radiation shielding capacity of the magnesium alloys.

• Economic and Environmental Geology
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• v.27 no.2
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• pp.171-180
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• 1994

Several ultramafic bodies and ultramafic origin talc deposits are distributed in Chungnam province near the contact zone with Ogchun fold belt They occur as discontinued belt form with northeast trending, and most of them are more or less sepentinized. Major, trace, and rare earth elements analyses were made of the ultramafics from the study area to constrain their origin and genetic relationships. Compared to the primitive mantle estimates of privious workers, the correlations defined by the studied rock samples indicate similar Ni but very lower $Al_{2}O_{3}$, CaO and $TiO_{2}$ contents. It is inferred that source material of the studied rocks might be residual mantle which had undergone a large degree of partial melting event. The REE patterns show relatively flat to enriched in LREE (chondrite normalized La/Yb and Sm/Yb ratios are 1.1-5.2 and 1.2-1.6). Several alternative explaination are possible for LREE enrichment patterns in the studied ultramafic rocks such as 1) enrichment due to late stage alteration, 2) enriched pre-melting composition, and 3) mixing of two components. Based on the result, the LREE enrichment characteristic of the studied rocks might be result from the mixture of two geochemically distinct components; one is depleted residual mantle and the other component which determine the abundances of incompatible elements and responsible for the LREE enrichment.

• Journal of the Korean earth science society
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• v.25 no.6
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• pp.428-442
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• 2004

Dustfall samples were collected by the modified American dust jar (bulk type) at 5 sampling sites in the Nakdong river area from lune 2002 to May 2003. Nineteen chemical species (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Si, V, Zn, $Cl^-$, $NO_3^-$, $SO_4^{2-}$, and $NH_4^+$) were analyzed via the combination of ICP/AES, AAS, IC and UV. The purposes of this study were to qualitatively evaluate the chemical composition of dustfalls by examining their regional and seasonal distribution patterns. Computation of the enrichment factor showed that well-defined anthropogenic sources, particularly in Pb were found in the order Gamjeondong (industrial area), Wondong, Silla University, Samrangiin and Mulgum. The seasonal mean of soil contribution showed its highest value (16.3%) during the winter with an annual mean of 11.2%. The concentration ratio of [$SO_4^{2-}/NO_3^-$] was found to be highest (5.12) during the winter, while the lowest ratio value (3.30) was seen during the all. fall, Also regional equivalent ratios of [$SO_4^{2-}/NO_3^-$] were found in the order: Silla University (6.78), Gamjeondong (4.98), Mulgum (3.95), Wondong (3.85), and Samrangjin (2.87). Seasonal distribution of water soluble components for total dustfall were found in the order: spring (71.6%), summer (61.2%), fall (49.2%) and winter (48.6%) with a mean ratio of 57.6%. Regional contribution of sea salts of water soluble ions were found in the order: Silla university (34.5%), Gamjeondong (28.3%), Wondong (17.3%), Samrangiin (17.2%) and Mulgum (13.8%), the total mean contribution rate was 22.1%. As for the chemical composition of dustftll on the lower Nakdong river, there is a decreased influence of sea salt and artificial anthropogenic sources and increased influence of soil particle inland. Also, the total amount of deposition on the lower Nakdong river has decreased, with the river's surface serving as a confounding factor in resuspending dusts.