• Journal of Adhesion and Interface
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• v.4 no.2
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• pp.1-9
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• 2003

Epoxy-amine liquid prepolymers are extensively applied onto metallic substrates and cured to obtain painted materials or bonded joint structures. Overall performances of such systems depend on the created interphase between the organic layer and the substrate. When epoxy-amine liquid mixtures are applied onto more or less hydrated metallic oxide layer, concomitant amine chemical sorption and hydroxide dissolution appear lending to the chelate formation. As soon as the chelate concentration is higher than the solubility product, these species crystallize as sharp needles. Moreover, intrinsic and thermal residual stresses are developed within painted or bonded systems. When residual stresses are higher than the organic layer/substrate adhesion, buckling, blistering, debonding may occur leading to a catastrophic drop of system performances. Practical adhesion can be evaluated with either ultimate parameters (Fmax or Dmax) or the critical strain energy release rate, using the three point flexure test (ISO 14679-1997). We observe that, for the same system, the ultimate load decreases while residual stresses increase when the liquid/solid time increases. Ultimate loads and residual stresses depend on the metallic surface treatment. For these systems, the critical strain energy release rate which takes into account the residual stress profile and the Young's modulus gradient remains quite constant whatever the metallic surface treatment was. These variations will be discussed and correlate to the formation mechanisms of the interphase.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.338-342
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• 2003

Adhesion between Cu and low-k films has been investigated. Low-k films deposited using a mixture of hexamethyldisilane(HMDS) and Para-xylene had a dielectric constant as low as 2.7, showing the thermally stable properties up to $400^{\circ}C$. In this study, Ti glue layer, boron dopant, and $N_2$plasma treatment were used to improve adhesion property of between Cu and low-k films. Ti glue layer slightly improved adhesion property. After $N_2$plasma treatment, the adhesion property was significantly improved due to the increased roughness and the formation of new binding states between Ti and plasma-treated PPpX : HMDS. However, $300^{\circ}C$ annealing of $N_2$plasma treated sample caused the diffusion of Cu into the PPpX : HMDS, degrading the low-k properties. In the case of Cu(B)/Ti/PPpX : HMDS, the adhesion was remarkably increased. This enhanced adhesion was attributed to formation of Ti-boride at the Cu-Ti interface. It is because the formed Ti-boride prevented the diffusion of Cu into the PPpX : HMDS and the Cu-Ti reaction at the Ti interface.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.2
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• pp.112-120
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• 1996

The effects of ${\varepsilon}$ martensite content and strain amplitude on damping capacity of an Fe-17%Mn alloy have been studied to establish damping mechanism of Fe-Mn system corresponding to the magnitude of strain amplitude. In a range of $1{\times}10^{-4}{\sim}3{\times}10^{-4}$ strain amplitude, the damping capacity is linearly proportional to the ${\varepsilon}$ martensite content, which suggests that stacking faults and ${\varepsilon}$ martensite variant boundaries are the principal damping sources. In the range of $4{\times}10^{-4}{\sim}6{\times}10^{-4}$ strain amplitude, however, a maximum damping capacity is observed around 68 vol.% ${\varepsilon}$. This behavior is very similar to dependence of relative area of ${\gamma}/{\varepsilon}$ interface on ${\varepsilon}$ martensite content. This means that in this strain range, ${\gamma}/{\varepsilon}$ interface acts as damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.

• Journal of Ocean Engineering and Technology
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• v.4 no.2
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• pp.94-99
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• 1990

This paper deals with investigating experimentally the effects of PWHT on the weld quality such as strength, toughness, hardness and micro-structure of the welded joints in friction welding of torsion bar material SUP9A bar to bar. The results obtained are summarized as follows; 1) It was certified that the condition of the post-weld heat treatment(PWHT) for the friction welded joints was very satisfactory because both strength and toughness of the joints were improved as almost same as those of the base metal or better by the PWHT. 2) The peak of hardness distribution of the friction welded joints can be eliminated by PWHT, resulting in being almost equalized at the weld interface, the HAZ(heat affected zone) and the base metal. 3) The micro-structure of the base meta., HAZ and weld interface(WI) of friction welded joints welded at the optimum welding condition consists of the same sorbite structure obtained by PWHT and fined sorbite at WI, resulting in increasing toughness as well as strength, and no micro structural defect has been found at the friction welded zone.

• Journal of Ocean Engineering and Technology
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• v.4 no.2
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• pp.244-244
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• 1990

This paper deals with investigating experimentally the effects of PWHT on the weld quality such as strength, toughness, hardness and micro-structure of the welded joints in friction welding of torsion bar material SUP9A bar to bar. The results obtained are summarized as follows; 1) It was certified that the condition of the post-weld heat treatment(PWHT) for the friction welded joints was very satisfactory because both strength and toughness of the joints were improved as almost same as those of the base metal or better by the PWHT. 2) The peak of hardness distribution of the friction welded joints can be eliminated by PWHT, resulting in being almost equalized at the weld interface, the HAZ(heat affected zone) and the base metal. 3) The micro-structure of the base meta., HAZ and weld interface(WI) of friction welded joints welded at the optimum welding condition consists of the same sorbite structure obtained by PWHT and fined sorbite at WI, resulting in increasing toughness as well as strength, and no micro structural defect has been found at the friction welded zone.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.147-148
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• 2005

In this work, recovery of semiconductive silicone rubber on oxygen plasma treatment was investigated in terms of X-ray photoelectron spectroscopy(XPS). The adhesion characteristics of semiconductive-insulating interface layer of silicone rubber were studied by measuring the T-peel strengths. As a result, surface methyl groups is removed and an oxidized layer containing Si atoms bound to 3 or 4 oxygens appears. The surface is later covered by a very thin layer due to migration of low-molecular-weight components from the bulk, resulting in decreasing the degree of adhesion of the semiconductive-insulating interface layer of silicone rubber these results are probably due to reorientation of polar groups or migration of low-molecular-weight.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.170-172
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• 2014

$CO_2$ sensor was used only one solid electrolyte in many cases. To improve the sensing characteristics of $CO_2$ sensors, solid electrolyte $CO_2$ sensor has been developed by bi-electrolyte type sensor using Na-Beta-alumina and YSZ. However, in many further studies, bi-electrolyte type sensor was made by pellet pressed by press machine and additional treatment for formation of interface. In the aspect of mass production, using thick film and additional treatment is not suitable. In this study, $CO_2$ sensor was fabricated by bi-electrolyte structure which was made by an NBA paste layer deposited on YSZ pellet and fired at $1650^{\circ}C$ for 2 hour. The formation of stable interface between YSZ and NBA were confirmed by SEM image. When the type IV electrochemical cell arrangement represented by $CO_2,O_2,Pt{\mid}Li_2CO_3-CaCO_3{\parallel}NBA{\parallel}YSZ{\mid}O_2,Pt$ is used to measure the $CO_2$ concentration in air. This sensor EMF should depend only on the concentration of $CO_2$ by logarithmic. Also, sensor shows $P_{CO_2}$ and EMF relationship like nerstian reaction at a temperature of $450^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.3
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• pp.148-158
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• 2003

In this study, a user oriented CFD program for optimum design of a regenerative combustion furnace, REBURN was developed. For user's convenience, user friendly Graphic User Interface was made and the renumbering interface program was developed in order to directly input any generated mesh system from ICEM CFD/FEA. Also an automatic processing system for switching mode was developed. The program was verified through compahng with commercial CFD code about regenerative combustion furnace. Then, numerical simulation of real walking beam furnace used in real industry was performed and the parametric analysis was studied about the arrangement mode. As a results, the uniform temperature was appeared in the cross mode.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.287-291
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• 2002

We fabricated the crosslinked films using p-hexadecoxyphenol (p-HP), which is amphiphilic and can form polyion complexes with formaldehyde at the air-water interface. The behavior of polyion complexation at the air-water interface and the surface structure of LB films was investigated by Brewster angle microscope(BAM) and scanning Maxwell-stress microscope (SMM), respectively. Also, the electrical properties for crosslinking in phenol-formaldehyde LB films were investigated by measuring conductivity and dielectric constant. The conductivities of p-HP LB films are as follows: heat-treatment of 1% formaldehyde subphase(3.76$\times$10$^{-15}$ ~4.76$\times$10$^{-1}$5[S/cm])$\times$10$^{-14}$ ~1.74$\times$10$^{-14}$ [S/cm]). Also, relative dielectric constants of p-HP LB films were reduced from 6.76~7.84 (pure water) to 2.97~3.25 (heat-treatment of 1% formaldehyde subphase))

• 연구논문집
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• s.28
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• pp.219-227
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• 1998

In order to investigate the interfacial structure between TiN and iron nitride, an AISI 4140 steel was nitrided to form a layer of thickness 15$\mum$ by DC ion nitriding, then the surface was bombarded with Ti ions and subsequently coated a TiN film of 5$\mum$ by arc ion plating method. The interfacial microstructure between TiN and iron nitride was characterized by optical microscope, SEM and XRD. So called black layer was observed in the duplex treatment. It was resulted from the decomposition of iron nitride during the bombardment. Its thickness was increased with increasing bombardment time at high bias voltage. But the thickness was greatly decreased when the iron nitride was bombarded with a nitrogen gas or at a reduced bias voltage. The adhesion strength of the top TiN coating was decreased with increasing thickness of the black layer. Furthermore, the reduced adhesion strength in this system was discussed in view of the interfacial structural relationship between TiN and iron nitride.