• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.234-245
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• 2003

Most of the concrete bridge structures are exposed to damage due to the excessive traffic loading and the aging of the structure. The damage of concrete causes the further deterioration of the function in the concrete structure due to corrosion of the reinforced bars and decohesion between the concrete and the reinforced bar. The quick rehabilitation of the damaged concrete structures has become of great importance in the concrete structural system in order to avoid the further deterioration of the structures. Recently fiber sheets are used for strengthening the damaged concrete structures due to its many advantages such as its durability, non-corrosive nature, low weight, ease of application, cost saving, control of crack propagation, strength to thickness ratio, high tensile strength, serviceability and aesthetic. However, the lack of analytical procedures for assessing the nominal moment capacity by the fiber sheet reinforcement leads to difficulties in the effective process of decisions of the factors in the strengthening procedure. In this work, flexural strengthening effects by fiber sheets bonded on bottom face of the member are studied for the reinforced concrete T beam. In addition, auxiliary flexural strengthening effects by U-type fiber sheets bonded on bottom and side faces of the member to prevent delamination of the bottom fiber sheet are theoretically investigated. The analytical solutions are compared with experimental results of several references to verify the proposed approach. It is shown that the good agreements between the predicted results and experimental data are obtained.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.613-621
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• 2012

Steel corrosion is one of the most critical deteriorations in concrete structures due to the problems associated with both durability and structural safety issues. For protection of steel against corrosion problems, researches to improve concrete durability and steel corrosion protection such as rebar coating by hot-dip galvanizing steel have been carried out. This study was performed to quantitatively evaluate anti-corrosion and structural performance of concrete structures reinforced with hot-dip galvanizing steel rebar. Preliminary tests for several metal coatings such as zinc, aluminum, and their alloy (Zn 45% + AL 55%) were performed. After evaluation of corrosive characteristics, Zn was selected for the coating material and the corrosion behaviors in Zn-coated steel were evaluated in various conditions. Furthermore, tensile and adhesive strengths were evaluated for the normal and the hot-dip galvanized steel. The crack patterns and structural behaviors of RC specimens with the normal and coated steel were investigated. Also, corrosion characteristics including corrosion in various coating metal and potential change in metal with notch were evaluated. Structural performances of tensile and adhesive strengths as well as RC beam behavior under flexural/shear loading were evaluated. The test and evaluation results showed that the applicability of hot-dip galvanized steel rebar can be used as corrosion resistant reinforcements for RC structures.

• Journal of Environmental Health Sciences
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• v.20 no.1
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• pp.62-67
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• 1994

Introduction : Recently, water and environmental pollution becomes serious social problem and high technology makes this pollution accelerate. Hydrogen sulfide, the main subject of our research, is one of the most dangerous air pollutant like SO$_x$ and NO$_x$. The major contaminant in coal gasification is H$_2$S, which is very toxic, hazardous and extremely corrosive. Therefore, control of hydrogen sulfide to a safe level is essential. Although commercial desulfurization process called liquid scrubbing is effective for removal of H$_2$S, it has drawbacks, the loss of sensible heat of the gas and costly wastewater treatment. Many investigations are carried out about high-temperature removal ol H$_2$S in hot coal-derived gas using metal oxide or mixed metal qxide sorbents. It was reported that ZnO was very effective sorbent for H2S removal, but it has big flaw to vaporize elemental zinc above 600\ulcorner \ulcorner As alternative, metal oxides such as CaO, $Fe_2O_3$, TiO$_2$ and CuO were added to ZnO. Especially, different results are reported for $Fe_2O_3$ additive. Tamhankar et al. reported SiO$_2$ with 45 wt% $Fe_2O_3$ sorbent is favorable for removal of H$_2$S and regeneration.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.779-785
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• 2015

Cathodic protection is recognized as the most cost-effective and technically appropriate corrosion prevention method for the submerged zone of offshore structures, ships, and deep-sea facilities. When cathodic protection is applied, the cathodic currents cause dissolved oxygen reduction, generating hydroxyl ions near the polarized surface that increase the interfacial pH and result in enhanced carbonate ion concentration and precipitation of an inorganic layer whose principal component is calcium carbonate. Depending on the potential, magnesium hydroxide can also precipitate. This mixed deposit is generally called "calcareous deposit." This layer functions as a barrier against the corrosive environment, leading to a decrease in current demand. Hence, the importance of calcareous deposits for the effective, efficient operation of marine cathodic protection systems is recognized by engineers and scientists concerned with cathodic protection in submerged marine environments. Calcareous deposit formation on a marine structure depends on the potential, current, pH, temperature, pressure, sea-water chemistry, flow, and time; deposit quality is significantly influenced by these factors. This study determines how calcareous deposits form in sea water, and assesses the interrelationship of formation conditions (such as the sea water temperature and surface condition of steel), deposited structure, and properties and the effectiveness of the cathodic protection.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.877-885
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• 2013

A seawater pipe of the engine room in the ships is being surrounded with severely corrosive environments caused by fast flowing of the seawater, containing aggressive chloride ion and high conductivity etc.. Therefore, the leakage of the seawater from its pipe have been often occurred due to its local corrosion by aggressive chloride ions. Subsequently, its leakage area is usually welded by AC shielded metal arc welding with various electrodes. In this study, when the sea water pipe is welded with several types of electrodes such as E4301, E4311, E4313 and E4316, a difference of the corrosion resistance on the welding metal zones was investigated using an electrochemical method, observing microstructure, measuring polarization behaviors and hardness. The weld metal zone welded with E4313 electrode exhibited the lowest value of hardness compared to other weld metal zones. In addition, its zone indicated also the best corrosion resistance than those of other weld metal zones. Furthermore, all of the weld metal zones revealed a relatively better corrosion resistance than those of the base metal zones. and also showed higher hardness than the base metal zones.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.839-854
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• 2018

This study was performed to evaluate the performance of GFRP plate reinforced segments for TBM tunnel support. Recently, the SFRC segment has been applied to prevent local damage such as reduction of the amount of reinforcing bars of the segment, crack control and breakage. However, the steel fiber used in the SFRC segment has a problem of durability deterioration due to fiber corrosion. Compared with the RC segment, the maximum flexural load reduction of the SFRC segment hinders the broad application range of the TBM tunnel segment. Therefore, GFRP plate was considered as a stiffener for the maximum load increase of SFRC segment, and structural synthetic fiber without corrosive concern was used as a substitute for steel fiber. The flexural performance of the segment was evaluated by using the type of reinforcing fiber and GFRP plate thickness as the main parameters. As a result, the maximum load and the flexural toughness were increased by 21.78~23.03% and 0.5~7.96%, respectively, as compared with the segments reinforced with reinforcing fiber and GFRP plate of 3 mm thickness.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.23-28
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• 2015

This paper is to identify the dynamic phenomenon of the marine pollution management that is connected directly or indirectly by using system dynamics analysis. The method used herein is based on system dynamics analysis that analyzed the sub-systems for marine pollution management. Furthermore designed feedback loop between system elements. And made total casual map of marine pollution management. The main results of the paper are the following : 1. It's necessary to equipments and technology development and law revision for feedback loop slump of initial measures delay in oil spill. 2. It should be come up with partnerships and new business for community corrosion non-proliferation caused by social conflicts. 3. Marine pollution management should be an obligation that must be minimized to include social conflicts in the community and national levels besides oil spill response on-site. This model confirmed the hidden cause of delay by existing response plans, manuals and programs. And oil spill response in broader sense is more important from now on. The result can be useful in the guidance of marine pollution and management.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.155-162
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• 2012

When RC (Reinforced Concrete) structures are exposed to sea water, steel corrosion can occur and this leads a degradation of structural performance. Referring the electro-deposition system with sea water from the 1st step research, durability and structural performance are evaluated in coated steel and RC members containing it in the 2nd research. In the durability performance test, Half Cell Potential test is performed and the coated steel is evaluated to have the high resistance to corrosion, which shows only 35% of corrosion velocity in normal (bare) steel. In the structural performance test, tensile strength, adhesive strength, and flexural/shear in RC member are performed. For the electro-deposit coated steel, increasing ratios of 3.2% and 8.8% are evaluated in the test of tensile strength and adhesive strength, respectively. For the structural test in RC member, there is no big difference between RC members with coated and non-coated steel in ultimate load and failure pattern It is evaluated that the chemical compound with $CaCO_3$ and $Mg(OH)_2$ from electro-deposition causes slightly increased structural performance. The electro-deposit coated steel can be more widely applied after performance verification from several tests like fatigue, resistance to impact, and long term-submerging test.

• Journal of Conservation Science
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• v.30 no.1
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• pp.1-11
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• 2014

Stabilization of iron artifacts is focused on desalination than corrosion inhibitors. However artifacts are not condition of desalination treatment must be applied to corrosion inhibitors. But iron artifacts is not representative of inhibitors which drug is most effective qualities have not been identified. Therefore in this study validates the effectiveness of existing inhibitors and its purpose is to suggest corrosion inhibitors for iron artifacts. In this study, Comparative experiment of corrosion inhibitors is selected BTA, DAN and MEA, TEA. This study was studied using Corrosion resistance test, Contact angle, XPS. As a result, all the samples treated with corrosion inhibitors was formed hydrophobic coating and was rising corrosion resistance. Also, the concentration of corrosion inhibitors was 3% better than 0.3%. BTA in the XPS experiment, the corrosive material to block the CH bond of the peak concentration was highly. This is considered corrosion potential is very high to see out the effect in the polarization experiment. Ethanolamine was superior to the MEA rather than in the TEA. MEA is likely to be appropriate in an outdoor iron artifacts seem to be suitable as corrosion inhibitors.