• Corrosion Science and Technology
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• v.19 no.3
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• pp.122-130
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• 2020

In this study, a corrosion failure analysis of a heat transport pipe was conducted, as the result of a pinhole leak. Interestingly, the corrosion damage occurred externally in the pipeline, resulting in severe thickness reduction near the seam line. Also, while a stable magnetite protective film formed on the inner surface, the manganese oxide formation occurred only on the outer surface. The interior and exterior of the pipe were composed of ferrite and pearlite. The large manganese sulfide and alumina inclusions were found near the seam line. In addition, the manganese sulfide inclusions resulted in grooving corrosion, which progressed in the seam line leading to the reduction in the thickness, followed by the exposure of the alumina in the matrix to the outer surface. To note, the corrosion was accelerated by pits generated from the boundaries separating the inclusions from the matrix, which resulted in pinhole leaks and water loss.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.557-566
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• 2011

A cold spray coating (CSC) of copper was studied for its application to a high-level radioactive waste (HLW) disposal canister. Several copper coatings of 10 mm thick were fabricated using two kinds of copper powders with different oxygen contents, and SS 304 and nodular cast iron were used as their base metal substrates. The fabricated CSC coppers showed a high tensile strength but were brittle in comparison with conventional non-coating copper, hereinafter defined to as "commercial copper". The corrosion behavior of CSC coppers was evaluated by comparison with commercial coppers, such as extruded and forged coppers. The polarization test results showed that the corrosion potential of the CSC coppers was closely related to its purity; low-purity (i.e., high oxygen content) copper exhibited a lower corrosion potential, and high-purity copper exhibited a relatively high corrosion potential. The corrosion rate converted from the measured corrosion current was not, however, dependent on its purity: CSC copper showed a little higher rate than that of commercial copper. Immersion tests in aqueous HCl solution showed that CSC coppers were more susceptible to corrosion, i.e., they had a higher corrosion rate. However, the difference was not significant between commercial copper and high-purity CSC copper. The decrease of corrosion was observed in a humid air test presumably due to the formation of a protective passive film. In conclusion, the results of this study indicate that CSC application of copper could be a useful option for fabricating a copper HLW disposal canister.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.480-480
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• 2010

In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1,500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photo-electron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Sheet resistance of 4 Ohms cm was achieved after the deposition and 30 min annealing in the hydrogen at $350^{\circ}C$. Elevation of the substrate temperature during the deposition process up to $350^{\circ}C$ leads to decreasing of the film's resistance due to rearrangement of the crystalline structure.

• Journal of Radiation Protection and Research
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• v.44 no.3
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• pp.110-117
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• 2019

Background: This study aimed to estimate occupational doses and patient peak skin doses (PSDs) during interventional radiology procedures. Materials and Methods: We examined data from brain embolization (n = 30), hepatic chemoembolization (n = 50), and uterine embolization (n = 12). The PSDs were measured using radiochromic film around the patient's head (group 1) or abdominal/pelvic region (group 2). Acquisition technical data and kerma-area products (KAP) were also recorded. Occupational doses were measured using $Instadose^{TM}$ dosimeters near the left eye region (LER), chest, and left ankle. Results and Discussion: The third quartile (median) KAP values were $408.1(235.3)Gy{\cdot}cm^2$ for group 1 and $584.4(449.4)Gy{\cdot}cm^2$ for group 2. The average PSDs were greatest during vascular procedures, reaching 1,004.4 (786.4) mGy, and the highest PSD was 2,352.6 mGy (during hepatic chemoembolization). The third quartile (median) occupational doses were 0.35 (0.21) mSv at the LER, 0.25 (0.15) mSv at the chest, and 1.47 (0.64) mSv at the left ankle. Occupational doses at the LER were higher than at the chest, which highlights the importance of protective glasses and suspended shields. The occupational doses at the ankle region were also high, which highlights the importance of using a lead-lined curtain attached to the table. Conclusion: The results indicate that physicians can reach, for eye region, the weekly occupational dose limit after around 15 procedures, even when using proper protection. The average PSD values were below the threshold for tissue reactions, although the complexity of these procedures emphasises the importance of considering related risks.

• Korean Journal of Materials Research
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• v.29 no.1
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• pp.11-15
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• 2019

Severe wall thinning is found on the tube of a low-pressure evaporator(LPEVA) module that is used for a heat recovery steam generator(HRSG) of a district heating system. Since wall thinning can lead to sudden failure or accidents that lead to shutdown of the operation, it is very important to investigate the main mechanism of the wall thinning. In this study, corrosion analysis associated with a typical flow-accelerated corrosion(FAC) is performed using the corroded tube connected to an upper header of the LPEVA. To investigate factors triggering the FAC, the morphology, composition, and phase of the corroded product of the tube are examined using optical microscopy, scanning electron microscopy combined with energy dispersive spectroscopy, and x-ray diffraction. The results show that the thinnest part of the tube is in the region where gas directly contacts, revealing the typical orange peel type of morphology frequently found in the FAC. The discovery of oxide scales containing phosphate indicates that phosphate corrosion is the main mechanism that weakens the stability of the protective magnetite film and the FAC accelerates the corrosion by generating the orange peel type of morphology.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.237-253
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• 2022

The methyl 2-(1,3-dithietan -2- ylidene)-3-oxobutanoate (MDYO) and 2-(1,3-dithietan-2-ylidene) cyclohexane -1,3-dione (DYCD) were synthesized and tested at various concentrations as corrosion inhibitors for 316L stainless steel in 1 M HCl using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), surface analysis techniques (SEM / EDX and Raman spectroscopy) and Functional Density Theory (DFT) was also used to calculate quantum parameters. The obtained results indicated that the inhibition efficiency of MDYO and DYCD increases with their concentration, and the highest value of corrosion inhibition efficiency was determined in the range of concentrations investigated (0.01 × 10^-3 - 10^-3 M). Polarization curves (Tafel extrapolation) showed that both compounds act as mixed-type inhibitors in 1M HCl solutions. Electrochemical impedance spectra (Nyquist plots) are characterized by a capacitive loop observed at high frequencies, and another small inductive loop near low frequencies. The thermodynamic data of adsorption of the two compounds on the stainless steel surface and the activation energies were determined and then discussed. Analysis of experimental results shows that MDYO and DYCD inhibitors adsorb to the metal surface according to the Langmuir model and the mechanism of adsorption of both inhibitors involves physisorption. SEM-EDX results confirm the existence of an inhibitor protective film on the stainless steel surface. The results derived from theoretical calculations supported the experimental observation.

• Computers and Concrete
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• v.32 no.2
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• pp.119-138
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• 2023

Concrete carbonation is a prevalent phenomenon that leads to steel reinforcement corrosion in reinforced concrete (RC) structures, thereby decreasing their service life as well as durability. The process of carbonation results in a lower pH level of concrete, resulting in an acidic environment with a pH value below 12. This acidic environment initiates and accelerates the corrosion of steel reinforcement in concrete, rendering it more susceptible to damage and ultimately weakening the overall structural integrity of the RC system. Lower pH values might cause damage to the protective coating of steel, also known as the passive film, thus speeding up the process of corrosion. It is essential to estimate the carbonation factor to reduce the deterioration in concrete structures. A lot of work has gone into developing a carbonation model that is precise and efficient that takes both internal and external factors into account. This study presents an ML-based adaptive-neuro fuzzy inference system (ANFIS) approach to predict the carbonation depth of fly ash (FA)-based concrete structures. Cement content, FA, water-cement ratio, relative humidity, duration, and CO2 level have been used as input parameters to develop the ANFIS model. Six performance indices have been used for finding the accuracy of the developed model and two analytical models. The outcome of the ANFIS model has also been compared with the other models used in this study. The prediction results show that the ANFIS model outperforms analytical models with R-value, MAE, RMSE, and Nash-Sutcliffe efficiency index values of 0.9951, 0.7255 mm, 1.2346 mm, and 0.9957, respectively. Surface plots and sensitivity analysis have also been performed to identify the repercussion of individual features on the carbonation depth of FA-based concrete structures. The developed ANFIS-based model is simple, easy to use, and cost-effective with good accuracy as compared to existing models.

• Journal of dental hygiene science
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• v.5 no.2
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• pp.83-88
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• 2005

In spite of relatively low level of radiation dose used at dental clinics, long term exposure may be harmful, so radiation workers at dental clinics must be well aware of its danger. This study was radiation safety management by dental hygienists in order to take preventive measures for dental hygienists and suggest ideas to develop radiation safety training programs. For this, we contacted dental hygienists working at the local dental clinics for 4 months from December of 2003 to march of 2004 and obtained the following findings. 1. Regarding the intraoral radiographic method, the average daily photographing frequency of standard films stood at one to five pieces (47.5%), and the average weekly photographing frequency of digital radiation medicine stood at less than one piece (69.8%), and the average weekly photographing frequency of bitewing films stood at less than one piece (67.7%), and and the average weekly photographing frequency of occlusal films stood at less than one piece (95.5%), and the dentistries whose average weekly photographing frequency of pediatric films stood at one to five pieces accounted for 47.1 percent. 2. Regarding the extraoral radiographic method, the average weekly photographing frequency of panorama film stood at one to five pieces (63.7%), and less than one piece (20.9%), the average weekly photographing frequency of cephalometric film stood at less than one piece (72.3%), and one to five pieces (20.1%). 3. Concerning the radiation safety management training program, only 18.7% of total 278 surveyed attended the training progra., Attendance tendency of the training program by general characteristics showed statistically significant difference according to age (p<0.01), working experience (p<0.001), and marital status (p<0.01). 4. When asked about the protective equipments against radiation exposure, 40.6% of them said "modest", and 71.1% appeared equipped with led apron as a protective tool.

• Journal of Life Science
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• v.24 no.6
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• pp.595-602
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• 2014

Styela Clava tunic (SCT) has found some applications in many areas of medical treatment including as an anti-inflammatory compound, a wound healing film, in guided bone regeneration, and as a food additive. The protective effect of SCT aqueous extract (AE-SCT) on cell death induced by $H_2O_2$ treatment was investigated by measuring the changes in cell viability in HepG2 cells after AE-SCT treatment. High concentrations of antioxidant compounds including flavonoids (3.3 mg/g) and phenolics (32.3 mg/g) were detected in AE-SCT but no significant cytotoxicity was observed in HepG2 cells treated with AE-SCT. The viability of HepG2 cells was also not changed by treatment with different concentrations of AE-SCT after $H_2O_2$ treatment. However, cell viability was significantly increased in cells treated with three different concentrations of AE-SCT before $H_2O_2$ treatment. The greatest increase in cell viability was observed in the group treated with $50{\mu}g/ml$ AE-SCT, when compared with vehicle-treated group. FACS and DAPI staining analysis indicated that the decrease in number of dead cells was dependent on the concentration of AE-SCT. Alterations in the Bax/Bcl-2 ratio after $H_2O_2$ treatment were significantly restored by treatment with different concentrations of AE-SCT. These results indicate that AE-SCT, which contains high levels of antioxidants, may protect cells against death induced by $H_2O_2$ treatment.