• Nuclear Engineering and Technology
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• v.39 no.3
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• pp.231-236
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• 2007

Due to the occasional occurrences of stress corrosion cracking(SCC) in steam generator tubing(Alloy 600), degraded tubes are removed from service by plugging or are repaired for re-use. Since electrodeposition inside a tube does not entail parent tube deformation, residual stress in the tube can be minimized. In this work, tube restoration via electrodeposition inside a steam generator tubing was performed after developing the following: an anode probe to be installed inside a tube, a degreasing condition to remove dirt and grease, an activation condition for surface oxide elimination, a tightly adhered strike layer forming condition between the electro forming layer and the Alloy 600 tube, and the condition for an electroforming layer. The reliability of the electrodeposited material, with a variation of material properties, was evaluated as a function of the electrodeposit position in the vertical direction of a tube using the developed anode. It has been noted that the variation of the material properties along the electrodeposit length was acceptable in a process margin. To improve the reliability of a material property, the causes of the variation occurrence were presumed, and an attempt to minimize the variation has been made. A Ni alloy electrodeposition process is suggested as a primary water stress corrosion cracking(PWSCC) mitigation method for various components, including steam generator tubes. The Ni alloy electrodeposit formed inside a tube by using the installed assembly shows proper material properties as well as an excellent SCC resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2116-2124
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• 2001

It's required mechanical properties of in-service facilities to maintain safety operation in power plants as well as chemical plants. In this studdy the four classes of the thermally aged 1Cr-lMo-0.25V specimens were prepared using an artificially accelerated aging method at 630$\^{C}$. Ultrasonic tests, tensile tests, K$\_$IC/ tests and hardness tests were performed in order to evaluate the degree of degradation of the material. The mechanical properties were decreased as degraded, but the attenuation coefficient and the harmonic generation level of a ultrasonic signal were increased. Expecially the nonlinear parameter derived from the harmonic generation level is sensitive and will be a good parameter to evaluate the material degradation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.25-28
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• 1998

Lithiated cobalt and nickel oxides are becoming very attractive as active cathode materials for secondary lithium ion secondary battery. $LiCoO_2$ is easily synthesized from lithium cobalt salts, but has a relatively high oxidizing potential on charge. LiNiOz is synthesized by a more complex procedure and its nonstoichiometry significantly degraded the charge-discharge characteristics. But $LiNiO_2$ has a lower charge potential which increases the system stability. Lithiated cobalt and nickel oxides are iso-structure which make the preparation of solid solutions of $LiNi_{1-x}Co_xO_2$ for O$LiCoO_2 and LiNiO_2$ electrode. The aim of the presentb paper is to study the electrochemical behaviour, as weU as the possibilities for practical application of layered Iithiated nickel oxide stabilized by $Co^{3+}$ substitution as active cathode materials in lithium ion secondary battery.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.36-40
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• 2007

Inorganic layers, such as SiOxNy and SiOx deposited using plasma sublimation method, were tested as passivation layer for organic thin-film-transistors (OTFTs). OTFTs with bottom-gate and bottom-contact structure were fabricated using pentacene as organic semiconductor and an organic gate insulator. SiOxNy layer gave little change in characteristics of OTFTs, but SiOx layer degraded the performance of OTFTs severely. Inferior barrier properties related to its lower film density, higher water vapor transmission rate (WVTR) and damage due to process environment of oxygen of SiOx film could explain these results. Polyurea and polyvinyl acetates (PVA) were tested as organic passivation layers also. PVA showed good properties as a buffer layer to reduce the damage come from the vacuum deposition process of upper passivation layers. From these results, a multilayer structure with upper SiOxNy film and lower PVA film is expected to be a superior passivation layer for OTFTs.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.187-187
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• 1997

Silicon nitride is the most excellent materials among structural ceramics. It has been reported that fracture toughness was improved with adding second phase particles, whisker, fiber etc. However, containing of second phase particles enhanced fracture toughness, however flexural strength was degraded. As adding nanosize SiC particles into silicon nitride, the physical properties of fluxural strength, fracture toughness, the modulus of elasticity. In this study, 2wt% $Al_2$O$_3$ and 4 wt% $Y_2$O$_3$ were added into UBE E-10 and 0, 10, 20, 30, 40, 50 vol% nano-SiC powder (Sumitomo T1 powder) were added, respectively. It is hot pressed at 185$0^{\circ}C$ for 1 hour. Most of structural ceramics for engineering application are wear resistance. In this study, wear behaviors (in water) of silicon nitride with varying the amount of nano-size silicon carbide were investigated, and was compared to physical properties. Simultaneously wear mechanism will be found out.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.53-53
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• 2009

Charge trap flash memory devices with modified tunneling barriers were fabricated using the tunneling barrier engineering technique. Variable oxide thickness (VARIOT) barrier and CRESTED barrier consisting of thin $SiO_2$ and $Si_3N_4$ dielectric layers were used as engineered tunneling barriers. The VARIOT type tunneling barrier composed of oxide-nitride-oxide (ONO) layers revealed reliable electrical characteristics; long retention time and superior endurance. On the other hand, the CRESTED tunneling barrier composed of nitride-oxide-nitride (NON) layers showed degraded retention and endurance characteristics. It is found that the degradation of NON barrier is associated with the increase of interface state density at tunneling barrier/silicon channel by programming and erasing (P/E) stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.7-7
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• 2009

In this paper, we investigated the dependence of HCI (Hot Carrier Immunity) degradation and device performance on channel orientation in sub-micron PMOSFET. Although device performance ($I_{D.sat}$ vs. $I_{Off}$) was improved as the transistor angle increased HC immunity was degraded. Therefore, consideration of reliability characteristics as well as dc device performance is highly necessary in channel stress engineering of next generation CMOSFETs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.480-481
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• 2009

In the paper we study for the ubiquitous networking based on power line communication technology with digital signal transmission. The necessity of research for using resources in the network effectively is being increase as network to use the PLC with smart grid networking. The data rate has compared with implemented modem 250Mbps in the pixel resolution and bandwidth, which has degraded with 80%. We also proposed for design of high-definition digital signal transceiver, which has used in the network between digital multimedia with PLC. Using resources in the network effectively can be also verified with this research.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1368-1374
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• 2004

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with in-service exposure time in high temperatures. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, nondestructive techniques are needed to evaluate the degradation. In this study, test materials with several different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. The DC potential drop method and destructive methods such as tensile and fracture toughness were used in order to evaluate the degradation of 1Cr-1Mo-0.25V steels. In this result, we can see that tensile strength and fracture toughness can be calculated from resistivity and it is possible to evaluate material degradation using DC potential drop method, non-destructive method.

• Journal of Welding and Joining
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• v.16 no.6
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• pp.86-96
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• 1998

This study proposes the analysis method of time series ultrasonic signal using the chaotic feature extraction for degradation extent evaluation. Features extracted from time series data using the chaotic time series signal analyze quantitatively degradation extent. For this purpose, analysis objective in this study is fractal dimension, lyapunov exponent, strange attractor on hyperspace. The lyapunov exponent is a measure of the rate at which nearby trajectories in phase space diverge. Chaotic trajectories have at least one positive lyapunov exponent. The fractal dimension appears as a metric space such as the phase space trajectory of a dynamical system. In experiment, fractal correlation) dimensions, lyapunov exponents, energy variation showed values of 2.217∼2.411, 0.097∼ 0.146, 1.601∼1.476 voltage according to degardation extent. The proposed chaotic feature extraction in this study can enhances precision ate of degradation extent evaluation from degradation extent results of the degraded materials (SA508 CL.3)