• Title/Summary/Keyword: Surface corrosion

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A wireless impedance analyzer for automated tomographic mapping of a nanoengineered sensing skin

  • Pyo, Sukhoon;Loh, Kenneth J.;Hou, Tsung-Chin;Jarva, Erik;Lynch, Jerome P.
    • Smart Structures and Systems
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    • v.8 no.1
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    • pp.139-155
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    • 2011
  • Polymeric thin-film assemblies whose bulk electrical conductivity and mechanical performance have been enhanced by single-walled carbon nanotubes are proposed for measuring strain and corrosion activity in metallic structural systems. Similar to the dermatological system found in animals, the proposed self-sensing thin-film assembly supports spatial strain and pH sensing via localized changes in electrical conductivity. Specifically, electrical impedance tomography (EIT) is used to create detailed mappings of film conductivity over its complete surface area using electrical measurements taken at the film boundary. While EIT is a powerful means of mapping the sensing skin's spatial response, it requires a data acquisition system capable of taking electrical impedance measurements on a large number of electrodes. A low-cost wireless impedance analyzer is proposed to fully automate EIT data acquisition. The key attribute of the device is a flexible sinusoidal waveform generator capable of generating regulated current signals with frequencies from near-DC to 20 MHz. Furthermore, a multiplexed sensing interface offers 32 addressable channels from which voltage measurements can be made. A wireless interface is included to eliminate the cumbersome wiring often required for data acquisition in a structure. The functionality of the wireless impedance analyzer is illustrated on an experimental setup with the system used for automated acquisition of electrical impedance measurements taken on the boundary of a bio-inspired sensing skin recently proposed for structural health monitoring.

The Effect of Oxide Compound on Electrical Resistivity and Oxidation Stability in High-temperature for Ferritic P/M Stainless Steel (산화물 혼합상이 페라이트계 P/M스테인리스강의 고온산화 및 전기저항 안정성에 미치는 영향)

  • Park, Jin-Woo;Ko, Byung-Hyun;Jung, Woo-young;Park, Dong-Kyu;Ahn, In-Shup
    • Journal of Powder Materials
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    • v.23 no.3
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    • pp.240-246
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    • 2016
  • In order to improve the high-temperature oxidation stability, sintered 434L stainless steel is studied, focusing on the effect of the addition of metallic oxides to form stable oxide films on the inner particle surface. The green compacts of Fecralloy powder or amorphous silica are added on STS434L and oxidized at $950^{\circ}C$ up to 210 h. The weight change ratio of 434L with amorphous silica is higher than that of 434L mixed with Fecralloy, and the weight increase follows a parabolic law, which implies that the oxide film grows according to oxide diffusion through the densely formed oxide film. In the case of 434L mixed with Fecralloy, the elements in the matrix diffuse through the grain boundaries and form $Al_2O_3$ and Fe-Cr oxides. Stable high temperature corrosion resistance and electrical resistivity are obtained for STS434L mixed with Fecralloy.

ELECTROSLAG STRIP OVERLAY OF PIPE, FITTINGS, AND PRESSURE VESSELS

  • Dan, Capitanescu
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.355-360
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    • 2002
  • ElectroSlag Strip Overlaying (ESSO) process has been around since 1970. ESSO process had limited acceptance due to a few problems associated with the use of this process in its very early stage. Limited knowledge and, most significantly, poor quality of the equipment and welding flux gave the ESSO process a bad name. However, this process is well accepted today and used in North America, Europe and Japan. The ESSO process provides low dilution overlays at high deposition rates, excellent and consistent deposit chemistry with excellent surface quality, and virtually no defects. Capitan has taken this process one step further through extensive research and development of the process itself as well as the equipment. The improvement brought to the process warranted the issuance in May 2000 of an US patent. This study demonstrates the feasibility of this process with immediate positive production results. The main achievements of this work are as follows: $\textbullet$ Development of six various strip-flux combinations on three different base materials: carbon steel, $\frac{1}{4}$ Cr/.5 Mo and 2 $\frac{1}{4}$ Cr/l Mo, fully tested with: penetrant, ultrasound, bends, hardness, overlay chemistry, corrosion and hydrogen disbonding. $\textbullet$ 12" dia. 90 hot formed elbows from straight pipe electroslag overlayed with "1 layer" and "2 layer" Alloy 625 $\textbullet$ a very unique development of miniaturized overlaying equipment able to perform overlay in pipe with diameters as low as 10" (254 mm). This development has large applications in the field of offshore, petrochemical, refining, pulp and paper and power generation industries. The aftermath of this development was its immediate acceptance by major end users with the completion of four projects of overlayed pipe in the USA and Far East Asia.

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Electrodeposition of Nano TiO2 Powder Dispersed Nickel Composite Coating (전기도금법을 이용한 나노 산화티타늄 니켈 복합도금에 관한 연구)

  • Park, So-Yeon;Lee, Jae-Ho
    • Journal of the Microelectronics and Packaging Society
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    • v.19 no.4
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    • pp.65-69
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    • 2012
  • Composite coating can be manufactured during the electroplating with the bath containing a suspension of particles: ceramic, polymer, nanopowders. Improvement of hardness, wear resistance, corrosion resistance and lubrication properties are well-known advantage of composite coating. In this study, nano $TiO_2$ powder dispersed Ni composite plating was investigated. The improvement of surface hardness and photo decomposition effects can be expected in this coating. Zeta potential was measured with pH. The effect of ultrasonication time and types of ultrasonicator were studied to minimize the agglomeration of $TiO_2$ nanopowders in the electrolyte. Optimum conditions for nano $TiO_2$ dispersed Ni composite coating were $40mA/cm^2$ of current density, pH 3.5, and $50^{\circ}C$. At these conditions, $TiO_2$ nanoparticles contents in the Ni deposit was 15-20 at.%.

Local Bond Stress-Slip Model of GFRP Rebars (GFRP 보강근의 부착응력-미끄럼 모델)

  • Cheong, Yeon-Geol;Yi, Chong-Ku;Lee, Jung-Yoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.133-136
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    • 2008
  • The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Glass Fiber Reinforced Polymer (GFRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of GFRP. However, there remain various aspects of GFRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between GFRP and concrete. In this study, the bond-behavior of GFRP bars in concrete is investigated via the pullout test with varying parameters: surface condition of GFRP bars and concrete compression strength. And the local bond-stress model of GFRP rabars with applying monotonc load was also derived from the present test.

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The Study on Development of Plating Technique on Electroless Ni/Au (무전해 니켈/금도금 기술 개발에 관한 연구)

  • Park Soo-Gil;Park Jong-Eun;Jung Seung-Jun;Yum Jae-Suk;Jun Sae-ho;Lee Ju-Seong
    • Journal of the Korean Electrochemical Society
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    • v.2 no.3
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    • pp.138-143
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    • 1999
  • Recently, miniaturization of large scale integrated circuits (LSI) and printed circuit board (PCB) have become essential with the downsizing of electronic devices. Gold electroplating is applied of conductivity wiring or terminals for improvement of conductivity and corrosion resistance. However, electroplating is not applicable since the circuits are becoming finer and denser. Accordingly, electroless plating is recently highly attractive method because of the simplicity of the operation requiring no external source of current and no elaborate equipment. In this work, we tried to develop a plating technique on electroless Ni/Au plating. First, the electroless Ni plating was deposited on the PCB with agitation in the bath at $85^{\circ}C$. Then the Au layer was deposited on the Ni layer surface by same method at $90^{\circ}C$. The bonderability were tested in order to evaluate the stability of the electroless Ni/Au by gold wire or solder ball test.

Study on Enhancement for Interfacial Energy Release Rate of Adhesive Layer in Fiber Metal Laminates using Taguchi Method (다구찌 기법을 적용한 섬유금속적층판 접착층의 에너지 해방률 강화에 대한 연구)

  • Kil, Min-Gyu;Park, Eu-Tteum;Song, Woo-Jin;Kang, Beom-Soo
    • Composites Research
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    • v.29 no.5
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    • pp.249-255
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    • 2016
  • The fiber metal laminates have been widely used at aerospace industry due to outstanding fatigue characteristic, corrosion resistance and impact resistance and so forth. The objective of this research is to establish the proper manufacturing variables for enhancing the interfacial energy release rate of fiber metal laminates using Taguchi method. The major variables of the manufacturing process are surface treatment, pre-specified temperature holding time and additional pressure. In order to determine the interfacial adhesive strength, the double cantilever beam and end-notched flexure tests were conducted. Afterward, Mode I and II energy release rates at various conditions were introduced signal-to-noise ratio with respect to each condition. Finally, the most efficient manufacturing variables are recognized using larger-the-better characteristic.

Evaluation of the $\sigma$-Phase Degradation for Cast Stainless Steel CF8M by the Electrochemical Method (전기화학적 방법에 의한 주조 스테인리스강 CF8M $\sigma$상 열화평가)

  • Gwon, Jae-Do;Kim, Jung-Hyeong;Park, Jung-Cheol;Byeon, Jang-Hwan;Lee, U-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.11 s.170
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    • pp.2014-2021
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    • 1999
  • The present investigation is concerned with the degradation characteristics of cast stainless steel(CF8M), exposed to the $\sigma$-phase degradation at $700^{\circ}C$. In the present paper, the degradation of CF8 M at $700^{\circ}C$ is evaluated by a non-destructive test, DL-EPR(double loop electrochemical potentiokinetic reactivation). The surface of specimens is observed by using scanning electron microscopy after DL-EPR test. Also. chromium contents of matrix, grain boundary and ferrite phase are analyzed by electron probe X-ray micro analyzer. Through the experiments, the following results are obtained 1) The degree of sensitization(DOS) of CF8M aged up to 15hr at $700^{\circ}C$ is increased with acing time while that is decreased with aging time from 15hr to 150hr. 2) The impact energy decreases with increase of $\sigma$-phase while DOS increases with $\sigma$-phase until aging time reaches to 15hr. After the aging time. 15hr, the $\sigma$-phase and the rate of impact energy with respect to aging time decreases. Therefore the degradation behavior of the CF8M can be evaluated by comparing SEM micrographs and the value of DOS.

Mechanical and Thermal Analysis of Oxide Fuel Rods

  • Ilsoon Hwang;Lee, Byungho;Lee, Changkun
    • Nuclear Engineering and Technology
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    • v.9 no.4
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    • pp.223-236
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    • 1977
  • An integral computer code has been developed for a mechanical and thermal design and performance analysis of an oxide fuel rod in a pressurized water reactor. The code designated as FROD 1.0 takes into account the phenomena of radial power depression within the pellet, cracking, densification and swelling of the pellet, fission gas release, clad creep, pellet-clad contact, heat transfer to coolant and buildup of corrosion layers on the clad surface. The FROD 1.0 code yields two-dimensional temperature distributions, dimensional changes, stresses, and internal pressure of a fuel rod as a function of irradiation time within a reasonable computation time. The code may also be used for the analyses of oxide fuel rods in other thermal reactors. As an application of FROD 1.0 the behavior of fuel rod loaded in the first core of Go-ri Nuclear Power Plant Unit 1 is predicted for the two power histories corresponding to steady state operation and Codition II of the ANS Classification. The results are compared with the design criteria described in the Final Safety Analysis Report and a discrepancy between these two values is discussed herein.

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Electrochemical Studies of Lithium Ion Battery Current Collector in the Aprotic Electrolytes: I. Al Current Collector (비수용성 전해질내 리튬이온전지용 집전체의 전기화학적 특성 연구: I. Al 집전체)

  • Park, Heai-Ku
    • Applied Chemistry for Engineering
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    • v.10 no.4
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    • pp.620-627
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    • 1999
  • Electrochemical properties of the Al current collector being used in lithium ion batteries have been studied in the 4 different aprotic electrolytes(1 M $LiBF_4$ EC : DMC, 1 M $LiBF_4$ EC : EMC. 1 M $LiPF_6$ EC : DMC. 1 M $LiPF_6$ EC : EMC) employing cyclic voltammetry and impedance measurement. Al electrode showed a wide range of the electrochemical window(0.5~4.1 V vs. $Li/Li^{+}$). However, solid interfacial materials has been formed on the Al surface due to reduction of impurities($H_2O$, $O_2$, etc), lithium salts, and electrolytes at low applied potentials, and aluminum oxides in the highly oxidizing potential as well. Especially, Al current collector was susceptible to localized in consequence of impurities in electrolytes.

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