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Lee J.-H.,Korea Testing and Research Institute KTR | Kim S.-J.,Mokpo Maritime University
Science of Advanced Materials | Year: 2016

The black ceramic coating layer was successfully prepared by plasma electrolytic oxidation (PEO) with electrolytes containing sodium tungstate (Na2WO4). Different gradients of black color were obtained with sodium tungstate concentrations in the electrolyte. Black colorization of PEO coating was not realized without sodium silicate (Na2SiO3) in the electrolyte. The corrosion current density of black ceramic coating layer was increased as compared to that of PEO coating produced without Na2WO4, suggesting that the corrosion resistance of the black PEO coating could be deteriorated by addition of the coloring agent in the electrolyte. © 2016 by American Scientific Publishers All rights reserved.

Han M.-S.,Mokpo Maritime University | Park I.-C.,Mokpo Maritime University | Kim M.-J.,Kunsan National University | Jeong J.-Y.,Mokpo Maritime University | And 3 more authors.
Science of Advanced Materials | Year: 2016

A new surface treatment method that enables materials to service under harsher environment is requested along with industrial development. Among the surface modification techniques, the thermal spray coating technology is applied where corrosion or high temperature oxidation occurs. It provides some advantages including easy application to objects with complex geometry and being able to control thickness of the coating. The drawbacks of the process are non-homogeneity of coating layer and creation of voids due to the characteristics of the deposition process of molten particles. In this research, copper alloy showing good corrosion resistance in seawater was coated by using atmospheric pressure plasma (APP) coating technology, and the cavitation resistance for the resultant coating was investigated. It was revealed that the CoNiCrAlY APP coating layer presented better resistance than that of the substrate. © 2016 by American Scientific Publishers All rights reserved.

Lee J.-H.,Korea Testing and Research Institute KTR | Kim S.-J.,Mokpo Maritime University
Journal of Nanoscience and Nanotechnology | Year: 2016

In this paper, a ceramic oxide thin film was produced on commercial Al-Mg alloy by plasma electrolytic oxidation (PEO). The influence of PEO treatment time on the wettability of the coating was evaluated by measuring the contact angle of the coatings. It was revealed that the PEO treated surface was hydrophilic due to the porous nature of PEO coating. The rare-earth element sealing treatment was applied to the PEO treated Al-Mg alloy using cerium-based sealing solution. The result of the electrochemical study exhibited that the Ce-sealed PEO coating showed two orders of magnitude lower corrosion current density than the substrate, indicating a significant improvement in corrosion resistance. It is supposed that effective sealing by improved wettability through nanoscale porosity in the ceramic oxide may exert synergistic effects with the corrosion protection effect of Ce element. Copyright © 2016 American Scientific Publishers All rights reserved.

Lee J.-H.,Korea Testing and Research Institute KTR | Kim S.-J.,Mokpo Maritime University
Nanoscience and Nanotechnology Letters | Year: 2016

Plasma electrolytic oxidation (PEO) is a novel coating technique for lightweight metals such as Al, Mg and Ti. The process involves complex interactions between process parameters including substrate composition, current modes and electrolyte composition. In this research, ceramic oxide coating was formed in silicate based alkaline solution on 5083-O Al alloy by pulsed PEO technique with different duty ratios (2080%) and frequencies (1002000 Hz). The PEO coatings were characterized using FE-SEM, XRD and 3D microscope. The voltage-time response during PEO process was found to be highly dependent upon both duty ratio and frequency. It was also revealed that changing pulse parameters in PEO process exerted a significant influence on both surface and cross-sectional morphology of the coating. Copyright © 2016 American Scientific Publishers.

Hong J.,Yonsei University | Hong J.,Korea Testing and Research Institute KTR | Ku S.H.,Korea Institute of Science and Technology | Lee M.S.,Sungkyunkwan University | And 5 more authors.
Biomaterials | Year: 2014

Inflammatory response in myocardial ischemia-reperfusion injury plays a critical role in ventricular remodeling. To avoid deleterious effects of overwhelming inflammation, we blocked the expression of receptor for advanced glycation end-products (RAGE), a key mediator of the local and systemic inflammatory responses, via RNAi mechanism. Herein, a facial amphipathic deoxycholic acid-modified low molecular weight polyethylenimine (DA-PEI) was used as a siRNA delivery carrier to myocardium. The DA-PEI conjugate formed a stable complex with siRNA via electrostatic and hydrophobic interactions. The siRAGE/DA-PEI formulation having negligible toxicity could enhance intracellular delivery efficiency and successfully suppress RAGE expression both invitro and invivo. Furthermore, the cardiac administration of siRAGE/DA-PEI reduced apoptosis and inflammatory cytokine release, subsequently led to attenuation of left ventricular remodeling in rat myocardial infarction model. The potential therapeutic effects of RAGE gene silencing on myocardial ischemia-reperfusion injury may suggest that the siRAGE/DA-PEI delivery system can be considered as a promising strategy for treating myocardial infarction. © 2014 Elsevier Ltd.

Chung B.Y.,Korea Atomic Energy Research Institute | Song C.H.,Korea Testing and Research Institute KTR | Park B.J.,Chungbuk National University | Cho J.Y.,Chonbuk National University
Pedosphere | Year: 2011

A pot experiment was conducted in a plastic film house to evaluate the translocation and uptake of heavy metals (Pb, Cd, Cu, and Zn) into brown rice (Oryza sativa L.) and the heavy metals residues in soils which had previously been irrigated with domestic wastewater for a long time (3 years). The range of Pb, Cd, Cu, and Zn was 5.10 ± 0.01, 0.105 ± 0.017, 5.76 ± 0.42, and 23.56 ± 1.40 mg kg -1, respectively in the domestic wastewater-irrigated soil, and 0.370 ± 0.006, 0.011 ± 0.001, 0.340 ± 0.04, and 2.05 ± 0.18 mg kg -1, respectively, in the domestic wastewater-irrigated brown rice. The results indicated that application of domestic wastewater to arable land slightly increased the levels of Pb, Cd, Cu, and Zn in soil and brown rice (P < 0.01). The concentrations of heavy metals in brown rice were lower than the recommended tolerable levels proposed by the Joint FAO/WHO Expert Committee on Food Additives. However, the continuous monitoring and pollution control of hazardous materials from domestic wastewater are needed in order to prevent excessive build-up of heavy metals in the food chain. © 2011 Soil Science Society of China.

Shim K.H.,Gachon University | Jeong K.-H.,Gachon University | Bae S.O.,Gachon University | Kang M.O.,Gachon University | And 7 more authors.
International Journal of Nanomedicine | Year: 2014

As increasing variants of nanoparticles (NPs) are being used in various products, it has become apparent that size alone can no longer adequately explain the variety of generated toxic profiles. Recent studies with NPs have suggested that various sizes of NPs could determine in vitro toxicity. In an attempt to address concerns regarding neurotoxicity of zinc oxide (ZnO) and silica (SiO2) NPs, these were examined after exposing them via oral, dermal, and intravenous administrations of NPs and their toxicological effects on the brain over a prescribed period of time were assessed. After 28 days of repeated oral administrations of ZnO or SiO2 independently, possibly due to damages to the blood brain barrier (BBB), neurotoxicity, were investigated by Evans blue technique. Next, in order to assess whether ZnO NPs could compromise the BBB, ZnO NPs were intravenously injected on day 0, 7, 14, 21 and 28 no further treatment was administered for 62 days. Deposition of SiO2 in brain from repeated dermal and oral administrations for 90 days were evaluated by transmission electron microscopy coupled with scanning energy-dispersive X-ray spectroscopy. Physiochemical profiles were principally determined on particle size at the beginning of the current toxicity investigations on ZnO and SiO2 NPs. The BBB was found to be intact after independent repeated oral administrations of ZnO or SiO2 NPs for 28 days, suggesting no significant damage. Neuronal death was also not observed after the intravenous administrations of ZnO NPs. After 90 days of repeated dermal and oral administration of SiO2 NPs, no deposition of NPs was observed in hippocampus, striatum, and cerebellum regions using transmission electron microscope analyses. These observations suggest that the BBB was not compromised and was able to block penetration of ZnO and SiO2 NPs, resulting in significant neurotoxic effects. Moreover, absence of SiO2 in three regions of brain after dermal and oral administrations for 90 days suggested that brain was protected from SiO2. No behavior change was observed in all studies, suggesting that 90 days may not be long enough to assess full neurotoxicity of NPs in vivo. © 2014 Shim et al.

Lee J.,Korea Testing and Research Institute KTR | Han S.,Korea Testing and Research Institute KTR | Kim H.,Korea Testing and Research Institute KTR | Lee U.,Korea Testing and Research Institute KTR
Engineering Failure Analysis | Year: 2012

In this paper, the cause of failure of the 420 stainless steel jaws in a joint was investigated. It was found that the martensitic stainless steel ASTM type 420 jaws used in connection joints of a water supply pipeline were cracked after 6. months in service. The failed parts were investigated by means of stereoscopic microscope, optical microscope, scanning electron microscope equipped with energy dispersive X-ray spectroscopy micro-analysis, inductively coupled plasma atomic emission spectroscopy, carbon-sulfur analyzer and Rockwell hardness tester, in order to identify the causes of failure and suggest preventive solutions. The study shows that failure was mainly due to intergranular corrosion cracking caused by the precipitation of chromium-rich carbides (or oxides) formed during heat treatment along grain boundaries. © 2012 Elsevier Ltd.

Yu B.K.,Korea Testing and Research Institute KTR | Lyu M.S.,Korea Testing and Research Institute KTR | Sun Y.S.,Korea Testing and Research Institute KTR | Cho K.S.,Korea Testing and Research Institute KTR
Journal of the Korean Society of Food Science and Nutrition | Year: 2012

As(III) and As(III) were analyzed in bamboo salts by hydride generation ICP-AES. In order to quantify the total amount of As in bamboo salts, AsH3 was producted by reacting with 6 mol/L hydrochloric acid and NaBH4, which was then analyzed by hydride generation ICP-AES. As(III) was quantified simultaneously after selectively quantifying As(III). As(III) was quantified by determining the total amount of As and then correcting for the amount of As(III). To improve the reliability of the analysis we repeated the experiment several times to check the detection limit, quantification limit, and measurements of our testing methods. According to the result of our quantification analysis of As existing in bamboo salt, the range of total As content was 0.05 mg/kg~0.2 mg/kg and As(III) was over 90% of the total As.

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