• Title/Summary/Keyword: 부식모델

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Electrochemical Characterization of Anti-Corrosion Film Coated Metal Conditioner Surfaces for Tungsten CMP Applications (텅스텐 화학적-기계적 연마 공정에서 부식방지막이 증착된 금속 컨디셔너 표면의 전기화학적 특성평가)

  • Cho, Byoung-Jun;Kwon, Tae-Young;Kim, Hyuk-Min;Venkatesh, Prasanna;Park, Moon-Seok;Park, Jin-Goo
    • Journal of the Microelectronics and Packaging Society
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    • v.19 no.1
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    • pp.61-66
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    • 2012
  • Chemical Mechanical Planarization (CMP) is a polishing process used in the microelectronic fabrication industries to achieve a globally planar wafer surface for the manufacturing of integrated circuits. Pad conditioning plays an important role in the CMP process to maintain a material removal rate (MRR) and its uniformity. For metal CMP process, highly acidic slurry containing strong oxidizer is being used. It would affect the conditioner surface which normally made of metal such as Nickel and its alloy. If conditioner surface is corroded, diamonds on the conditioner surface would be fallen out from the surface. Because of this phenomenon, not only life time of conditioners is decreased, but also more scratches are generated. To protect the conditioners from corrosion, thin organic film deposition on the metal surface is suggested without requiring current conditioner manufacturing process. To prepare the anti-corrosion film on metal conditioner surface, vapor SAM (self-assembled monolayer) and FC (Fluorocarbon) -CVD (SRN-504, Sorona, Korea) films were prepared on both nickel and nickel alloy surfaces. Vapor SAM method was used for SAM deposition using both Dodecanethiol (DT) and Perfluoroctyltrichloro silane (FOTS). FC films were prepared in different thickness of 10 nm, 50 nm and 100 nm on conditioner surfaces. Electrochemical analysis such as potentiodynamic polarization and impedance, and contact angle measurements were carried out to evaluate the coating characteristics. Impedance data was analyzed by an electrical equivalent circuit model. The observed contact angle is higher than 90o after thin film deposition, which confirms that the coatings deposited on the surfaces are densely packed. The results of potentiodynamic polarization and the impedance show that modified surfaces have better performance than bare metal surfaces which could be applied to increase the life time and reliability of conditioner during W CMP.

Corrosion Fatigue Reliability-Based Life Cycle Cost Analysis of High-Speed Railway Steel Bridges (고속철도 강교량의 부식 피로신뢰성 기반 생애주기비용 분석)

  • Cho, Hyo-Nam;Jeon, Hong-Min;Sun, Jong-Wan;Youn, Man-Keun
    • Journal of the Korean Society for Railway
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    • v.11 no.1
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    • pp.107-113
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    • 2008
  • As it recently appears that LCC (Life Cycle Cost) analysis may be considered as an essential method for economic evaluation of infrastructures. Many researches have been made to assess LCC of each facility based on reasonable methods. However, expected maintenance repair cost must be reasonably estimated to enhance the reliability of LCC analysis through systematic and rational methods. This study is intended to propose a rational approach to reliability-based LCC analysis of high-speed railway steel bridges considering lifetime corrosion and fatigue damage. However in Korea, since high speed railway steel bridges are only recently constructed, no direct statistical data are available for the account of the maintenance cost and thus their maintenance characteristics are not clear yet. In this paper, for the assessment of expected maintenance/repair cost, the fatigue system reliability analysis incorporating the corrosion effect is proposed by considering the corrosion and fatigue damage using measured data of high speed railway steel bridges. A model proposed by Rahgozar, of at for fatigue notch factor considering the corrosion effect is used in order to incorporate the corrosion effect into the fatigue strength reduction and S-N curve. Finally, the effectiveness of LCC model proposed for high-speed railway steel bridges is demonstrated by a numerical example.

Assessment of Gas Generation in Underground Repository of Low-Level Waste (저준위 방사성폐기물 처분장에서의 기체 발생 평가)

  • Cho, Chan-Hee;Kim, Chang-Lak;Lee, Myung-Chan;Park, Heui-Joo
    • Nuclear Engineering and Technology
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    • v.28 no.1
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    • pp.79-92
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    • 1996
  • In a repository containing low-level waste, gas generation will occur principally by the coupled processes of metal corrosion and microbial degradation of cellulosic waste. This paper describes a mathematical model designed to address gas generation by these mechanisms and assesses the potential effects of gas generation on the performance of a radioactive waste repository. The metal corrosion model incorporates a three-stage process encompassing aerobic and anaerobic corrosion regimes ; the microbial degradation model simulates the activities of eight different microbial populations, which are maintained as functions both of pH and of the concentrations of particular chemical species. A prediction is made for gas concentrations and generation rates over an assessment period of ten thousand years in a radioactive waste repository. The results suggest that H$_2$will be the principal gas generated within the radioactive waste cavern.

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Remaining Service Life Prediction of Concrete Structures under Chloride-induced Loads (염해환경하의 콘크리트 구조물의 잔존수명 예측)

  • Song, Ha-Won;Luc, Dao Ngoc The
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.1037-1040
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    • 2008
  • In order to predict the remaining life of marine concrete structures under climatic loads, it is necessary to develop an analytical approach to predict the time and space dependent deterioration of concrete structures due to mainly chloride attack up to corrosion initiation and additional deterioration like cracking of cover concrete. This study aims to introduce FEM model for life-time simulation of concrete structures subjected to chloride attack. In order to consider uncertainties in materials as well as environmental parameters for the prediction, Monte Carlo Simulation is integrated in that FEM modeling for reliability-based remaining service life prediction. The paper is organized as follows: firstly general scheme for reliability-based remaining service life of concrete structures is introduced, then the FEM models for chloride penetration, corrosion product expansion and cover cracking are briefly explained, finally an example is demonstrated and the effects of localization of chloride concentration and corrosion product expansion on service life using above model are discussed.

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Analysis of Carbonation for Harbor Concrete Structure (항만 콘크리트 구조물에 대한 탄산화 해석)

  • Han, Sang-Hun;Park, Woo-Sun
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.20 no.6
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    • pp.575-582
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    • 2008
  • Carbonation is one of major factors influencing on the durability of concrete structure. This paper investigates the effect of carbonation on the soundness of harbor concrete structure and quantifies the influence of carbonation based on in-situation data tested at 369 points in 69 harbor facilities. The relationships between carbonation depth and cover depth, and between carbonation depth and compressive strength are studied and the failure probability of durability, that is the initiation probability of steel corrosion, is evaluated on the basis of reliability concept. The in-situation test results showed that the ratio of carbonation depth to cover depth was less than 0.2, and the carbonation depth increased with age. In most cases, the failure probability of durability by carbonation was less than 10%. Therefore, it can be concluded that the influence of carbonation on the durability of harbor concrete structure is smaller than other factors deteriorating the durability of harbor concrete structure.

A Study on Resistance of Chloride Ion Penetration in Ground Granulated Blast-Furnace Slag Concrete (고로슬래그 미분말 콘크리트의 염화물 침투 저항성에 관한 연구)

  • Song, Ha-Won;Kwon, Seung-Jun;Lee, Suk-Won;Byun, Keun-Joo
    • Journal of the Korea Concrete Institute
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    • v.15 no.3
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    • pp.400-408
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    • 2003
  • Chloride ion inside concrete destroys the so-called passive film surrounding reinforcing bars inside concrete so that the so-called salt attack accelerates corrosion which is the most critical factor for durability as well as structural safety of reinforced concrete structures. Recently, as a solution of the salt attack, the ground granulated blast-furnace slag(GGBFS) have been used as binder or blended cement more extensively. In this paper, characteristics of chloride ion diffusion for the GGBFS concrete, which is known to possess better resistance to damage due to the chloride ion penetration than ordinary portland cement(OPC) concrete possesses, are analyzed and a chloride ion diffusion model for the GGBFS concrete is proposed by modifying an existing diffusion model for the OPC concrete. The proposed model is verified by comparing diffusion analysis results using the model accelerated chloride penetration test results for concrete specimens as well as field test results for an RC bridge pier. Then, an optimal resistance condition to chloride penetration for the GGBFS concrete is obtained according to degrees of fineness and replacement ratios of the GGBFS concrete. The result shows that the GGBFS concrete has better resistance to chloride ion penetration than OPC concrete has and the resistance is more affected by the replacement ratio than the degree of fineness of the GGBFS.

Evaluation of Liquid Droplet Impingement Erosion through Prediction Model and Experiment (예측모델 및 실험을 통한 액적충돌침식 손상 평가)

  • Yun, Hun;Hwang, Kyeong-Mo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.10
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    • pp.1105-1110
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    • 2011
  • Flow-accelerated corrosion (FAC) is a well-known phenomenon that may occur in piping and components. Most nuclear power plants have carbon-steel-pipe wall-thinning management programs in place to control FAC. However, various other erosion mechanisms may also occur in carbon-steel piping. The most common forms of erosion encountered (cavitation, flashing, Liquid Droplet Impingement Erosion (LDIE), and Solid Particle Erosion (SPE)), have caused wall thinning, leaks, and ruptures, and have resulted in unplanned shutdowns in utilities. In particular, the damage caused by LDIE is difficult to predict, and there has been no effort to protect piping from erosive damage. This paper presents an evaluation method for LDIE. It also includes the calculation results from prediction models, a review of the experimental results, and a comparison between the UT data in the damaged components and the results of the calculations and experiments.

Mathematical Modeling on the Corrosion Behavior of the Steel Casing and Pipe in Cathodic Protection System (음극방식 시스템에서의 압입관과 배관의 부식거동에 관한 수학적 모델링)

  • Kim Y.S.;Li S.Y.;Park K.W.;Jeon K.S.;Kho Y.T.
    • Journal of the Korean Institute of Gas
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    • v.2 no.1
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    • pp.40-46
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    • 1998
  • Mathematical modeling on the corrosion of the steel casing and main pipe due to the protection current resulting from a cathodic protection system was carried out using boundary element method. The model is consisted of Laplace's equation with non-linear boundary conditions(Tafel equations) and the iterative technique to determine the miexed potential of the steel casing. The model is applied to the normal steel casing section as well as abnormal one with defects such as metal touch and insulation defects. From the modeling procedure, we can calculate the potential distributions and current density distributions of the system. The theoretical results of the qualitatiive corrosion aspect along the steel casing and main pipe agree well with the experimental results within the experimental conditions studied.

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Modeling of stress corrosion crack growth and lifetime of pipe grade high density polyethylene by using crack layer theory (Crack Layer 이론을 이용한 배관용 고밀도 폴리에틸렌의 응력부식균열 진전 및 수명 예측 모델)

  • Wee, Jung-Wook;Choi, Byoung-Ho
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.2
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    • pp.45-50
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    • 2015
  • In many cases, the field fracture mechanism of the thermoplastic pipe is considered as either brittle or environmental fractures. Thus the estimation of the lifetime by modeling slow crack growth considering such fracture mechanisms is required. In comparison of the some conventional and empirical equations to explain the slow crack growth rate such as the Paris' law, the crack layer theory can be used to simulate the crack and process zone growth behaviors precisely, so the lifetime of thermoplastic pipe can also be accurately estimated. In this study, the modified crack layer theory for the stress corrosion cracking (SCC) of high density polyethylene is introduced with detailed algorithm. The oxidation induction time of the HDPE is also considered for the reduction of specific fracture energy during exposed to chemical environments. Furthermore, the parametric study for an important SCC parameter is conducted to understand the slow crack growth behavior of SCC.

Theoretical Considerations of Numerical Model for Hydrogen Diffusion Behavior of High-Strength Steel Under Combined Action of Tensile Stress and H2S Corrosion (인장응력과 H2S 부식의 복합조건 하에서 고강도 강재의 수소확산 거동 분석을 위한 Numerical 확산모델과 이론적 고찰)

  • Kim, Sung Jin
    • Corrosion Science and Technology
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    • v.18 no.3
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    • pp.102-109
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    • 2019
  • The hydrogen diffusion and trapping model with a numerical finite difference method (FDM) was modified and extended to accommodate $H_2S$ corrosion and scale forming processes of high-strength steel under tensile stress condition. The newly proposed diffusion model makes it possible to clearly understand combined effect of tensile stress and $H_2S$ corrosion process on hydrogen diffusion behaviors. The core concept of this theoretical approach is that overall diffusion behavior is separated into diffusion process through two respective layers: an outer sulfide scale and an inner steel matrix. Diffusion coefficient values determined by curve-fitting permeation data reported previously with the newly proposed diffusion model indicate that the application of tensile stress can contribute to continual increase in the diffusivity in the sulfide scale with a high density of defect. This suggests that the scale with a lower stability under the stress condition can be a key parameter to enhance hydrogen influx in the steel matrix. Consequently, resistance to hydrogen assisted cracking of the steel under tensile stress can be decreased significantly.