• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.740-747
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• 2009

The purpose of this study is to identify the effect of electrolyte compositions on electrodeposited copper foil. First of all, the polyimide substrate was pretreated with plasma. Finally, copper foil was deposited on a Cu/Ni/Polyimide substrate using the electroplating technique. As the quantity of Cu increased, preferred orientations changed into (111). Increasing sulfuric acid, on the other hand, brought down the preferred orientation of (111). The lowest sheet resistance, surface roughness, and fine adhesion were detected when the ratio of $Cu^{2+}$ and $H_2SO_4$ is 50:50(g/l).

• Corrosion Science and Technology
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• v.9 no.1
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• pp.20-28
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• 2010

According to the bipolar model, ion selectivity of some species in the passive film is important factor to control the passivation. An increase of cation selectivity of outer layer of the passive film can stabilize the film and improves the corrosion resistance. Therefore, the formation and roles of ionic species in the passive film should be elucidated. In this work, two types of solution (hydrochloric or sulfuric acid) were used to test high N and Mo-bearing stainless steels. The objective of this work was to investigate the formation of oxyanions in the passive film and the roles of oxyanions in passivation of stainless steel. Nitrogen exists as atomic nitrogen, nitric oxide, nitro-oxyanions (${NO_x}^-$), and N-H species, not nitride in the passive film. Because of its high mobility, the enriched atomic nitrogen can act as a reservoir. The formation of N-H species buffers the film pH and facilitates the formation of oxyanions in the film. ${NO_x}^-$ species improve the cation selectivity of the film, increasing the oxide content and film density. ${NO_x}^-$ acts similar to a strong inhibitor both in the passive film and at active sites. This facilitates the formation of chromium oxide. Also, ${NO_x}^-$ can make more molybdate and nitric oxide by reacting with Mo. The role of Mo addition on the passivation characteristics of stainless steel may differ with the test environment. Mo exists as metallic molybdenum, molybdenum oxide, and molybdate and the latter facilitates the oxide formation. When nitrogen and molybdenum coexist in stainless steel, corrosion resistance in chloride solutions is drastically increased. This synergistic effect of N and Mo in a chloride solution is mainly due to the formation of nitro-oxyanions and molybdate ion. Oxyanions can be formed by a 'solid state reaction' in the passive film, resulting in the formation of more molybdate and nitric oxide. These oxyanions improve the cation selectivity of the outer layer and form more oxide and increase the amount of chromium oxide and the ratio of $Cr_2O_3/Cr(OH)_3$ and make the film stable and dense.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.495-502
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• 2008

To analyze the growth of SOB(Thiobacillus novellus) and biochemical corrosion of concrete, simulation test method and device were developed, and basic conditions for SOB growth were established. Two types of simulation tests were conducted according to a transplant method and a concentration of $H_2SO_4$. As a result, the SOB growth in distinct manners and antibiosis of specimen were observed. In the case of the specimens indirectly transplanted with SOB through culture solution submersion at a hydrogen sulfide level of 120 ppm, the rapid activation of SOB and the resulting sulfuric acid production were observed. However, SOB were shown to grow rapidly and then die out in a relative short period of time. Meanwhile, in the case of the specimens directly transplanted with SOB at a hydrogen sulfide level of 50 ppm, the long-term growth of SOB was possible, but the production of sulfuric acid by SOB did not progress. In the case of the antibiotic metal-mixed specimens, SOB with destroyed cell membranes and internal organizations were observed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.101-101
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• 2018

Quantitative measurement of chloride ion concentration has an important role in various fields of electrochemistry, medical science, biology, metallurgy, architecture, etc. Among them, its importance of architecture is ever-growing due to unexpected degradations of building structure. These situations are caused by corrosion of reinforced concrete (RC) structure of buildings. And chloride ions are the most powerful factors of RC structure corrosion. Therefore, precise inspection of chloride ion concentration must be required to increase the accuracy of durability monitoring. Multi-walled Carbon nanotubes (MWCNTs) have high chemical resistivity, large surface area and superior electrical property. Thus, it is suitable for the channels of electrical signals made by the sensor. Silver nanoparticles were added to giving the sensing property. CuBTC, one of the metal organic frameworks (MOFs), was employed as a material to improve the sensing property because of its hydrophilicity and high surface area to volume ratio. In this study, sensing element was synthesized by various chemical reaction procedures. At first, MWCNTs were functionalized with a mixture of sulfuric acid and nitric acid because of enhancement of solubility in solution and surface activation. And functionalized MWCNTs, silver nanoparticles, and CuBTC were synthesized on PTFE membrane, one by one. Electroless deposition process was performed to deposit the silver nanoparticles. CuBTC was produced by room temperature synthesis. Surface morphology and composition analysis were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), respectively. X-ray photoelectron spectroscopy (XPS) was also performed to confirm the existence of sensing materials. The electrical properties of sensor were measured by semiconductor analyzer. The chloride ion sensing characteristics were confirmed with the variation of the resistance at 1 V.

• Advances in nano research
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• v.14 no.5
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• pp.435-442
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• 2023

Sports activities, including playing tennis, are popular with many people. As this industry has become more professionalized, investors and those involved in sports are sure to pay attention to any tool that improves athletes' performance Tennis requires perfect coordination between hands, eyes, and the whole body. Consequently, to perform long-term sports, athletes must have enough muscle strength, flexibility, and endurance. Tennis rackets with new frames were manufactured because tennis players' performance depends on their rackets. These rackets are distinguished by their lighter weight. Composite rackets are available in many types, most of which are made from the latest composite materials. During physical exercise with a tennis racket, nanocomposite materials have a significant effect on reducing injuries. Materials as strong as graphite and thermoplastic can be used to produce these composites that include both fiber and filament. Polyamide is a thermoplastic typically used in composites as a matrix. In today's manufacturing process, materials are made more flexible, structurally more vital, and lighter. This paper discusses the production, testing, and structural analysis of a new polyamide/Multi-walled carbon nanotube nanocomposite. This polyamide can be a suitable substitute for other composite materials in the tennis racket frame. By compression polymerization, polyamide was synthesized. The functionalization of Multi-walled carbon nanotube (MWCNT) was achieved using sulfuric acid and nitric acid, followed by ultrasonic preparation of nanocomposite materials with weight percentages of 5, 10, and 15. Fourier transform infrared (FTIR) and Nuclear magnetic resonance (NMR) confirmed a synthesized nanocomposite structure. Nanocomposites were tested for thermal resistance using the simultaneous thermal analysis (DTA-TG) method. scanning electron microscopy (SEM) analysis was used to determine pores' size, structure, and surface area. An X-ray diffraction analysis (XRD) analysis was used to determine their amorphous nature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.618-625
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• 2018

With the passing of time, exposed concrete structures are affected by a range of environmental, chemical, and physical factors. These factors seep into the concrete and have a deleterious influence compared to the initial performance. The importance of identifying and preventing further performance degradation due to the occurrence of deterioration has been greatly emphasized. In recent years, evaluations of the target life have attracted increasing interest. During the freezing-melting effect, a part of the concrete undergoes swelling and shrinking repeatedly. At these times, chloride ions present in seawater penetrate into the concrete, and accelerate the deterioration due to the corrosion of reinforced bars in the concrete structures. For that reason, concrete structures located onshore with a freezing-melting effect are more prone to this type of deterioration than inland structures. The aim of this study was to develop a high performance mortar mixed with a mineral admixture for the durability properties of concrete structures near sea water. In addition, experimental studies were carried out on the strength and durability of mortar. The mixing ratio of the silica fume and meta kaolin was 3, 7 and 10 %, respectively. Furthermore, the ultra-fine fly ash was mixed at 5, 10, 15, and 20%. The mortar specimens prepared by mixing the admixtures were subjected to a static strength test on the 1st and 28th days of age and degradation acceleration tests, such as the chloride ion penetration resistance test, sulfuric acid resistance test, and salt resistant test, were carried out at 28 days of age. The chloride diffusion coefficient was calculated from a series of rapid chloride penetration tests, and used to estimate the life time against corrosion due to chloride ion penetration according to the KCI, ACI, and FIB codes. The life time of mortar with 10% meta kaolin was the longest with a service life of approximately 470 years according to the KCI code.

• Journal of Conservation Science
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• v.26 no.4
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• pp.437-443
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• 2010

The influence of noxious corrosive gas, which is the product of fossil fuel, and the acidic descent material, which becomes the reason for such reaction, on wax which protects the cultural assets, and the habitat factor were researched. It could be viewed that corrosion occurred rapidly due to the acidic descent material, which have the long staying on the material, rather than harmful corrosive gas. Also, it could be figured out that such corrosion began from whitening phenomenon of coated wax. As the acidity increased, more whitening phenomenon occurred, and eventually, it could be found out that whitening effect began due to the acidic descent material, corrosive gas and various 0.1 M acid solution, which lead to the exposure of internal metal, and corrosion occurred. The wax with the greatest resistance to the acidity due to its least changing aspect seemed to be Renaissance wax, except sulfuric acid.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.247-252
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• 2013

Sulfonated poly(ether ether ketone) (SPEEK) with a certain degree of sulfonation were synthesized by reacting PEEK and sulfuric acid at different reaction time. Then ion-selective composite carbon electrodes (ISCCE) were fabricated by coating the prepared SPEEK on the surface of carbon electrodes. The specific capacitance and resistance of the ISCCE were analyzed by electrical impedance spectroscopy. The ion exchange capacities (IEC) of the SPEEKs were measured in the range of 1.60~2.57 meq/g depending on the sulfonation time. The SPEEK more than 2.5 meq/g of IEC was considered unsuitable for fabricating the ISCCE because it was dissolved in water. The specific capacitance of the prepared ISCCE increased with increasing the IEC of coated SPEEKs and the capacitance was improved up to about 20% compared to that of uncoated carbon electrode. In addition, the electrical resistance of coating layer decreased significantly with increasing the IEC of coated SPEEKs. It is expected that the desalination efficiency of conventional capacitive deionization process can be improved by using the prepared ISCCE coated with SPEEK.

• Membrane Journal
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• v.32 no.3
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• pp.191-197
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• 2022

Ammonia nitrogen can be effectively recovered from livestock manure waste, etc. by using the gas permeable membrane technology. In this case, ammonia gas in the waste passes through the pores in one-side of membrane, impregnated in waste, and then reach the opposite side of the membrane. The permeated ammonia gas molecules are captured and recovered by acid (such as sulfuric acid) in the solution existing on the opposite side of the membrane. In order to improve ammonia nitrogen removals in the inlet part, high pH should be maintained in the feed waste including ammonia nitrogen to recover, which requires the cost of the chemical. To resolve this issue, previous studies tested various methods, for example, utilization of cheap calcium hydroxide or aeration together with inhibition of unwanted nitrification. The gas permeable membranes used for the recovery of ammonia nitrogen may be characterized, not only by proper heat and chemical resistance, but also by hydrophobicity, allowing selective ammonia gas permeation through the hydrophobic membrane pores. Future research should consider the relevant pilot or upscale processes using on-site wastes with various properties, and identify the optimal design/operation conditions as well as economic feasibility improvement plans.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.2
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• pp.161-167
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• 1988

Studies were carried out to examine the effects of simulated acid rain on the various crops of rice, peper, tomato, pumpkin, egg plant, potato, soybean, radish, cucumber, common pea, sweet potato, corn, lettuce, chinse cabbage, spinach, under the condition of the rains of pH 3.0. The rain was adjusted to pH 4.0, 3.0, 2.0 with sulfuric acid, and soybeans were exposed with the various pH levels, eighteen times every other days. The symptoms of damage, ratios of destroyed leaf and sulphur content by leaves were investigated. The results obtained were as follows. 1. The exposure to the rain resulted in the reddish brown or white pigment spots in the leaves surface and the colour was developed red and darker along the edge of spots. 2. Most crops were affected with acid rain of pH 3.0 at which the amount of chlorophyl was decreased. 3. The spinach, chinese cabbage, lettuce were sensitive to the acid rain, however, the peper, tomato pumpkin were resistance to it. 4. The content of chlorophyl was decreased with increasing leave injury. 5. The sulphur content in leave was increased with increasing acidity of the rain, however the yield was decreased.