• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.399-406
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• 2020

Pd nanogap hydrogen sensors were developed using an elastomeric substrate and operated through an on-off mechanism. A 10 nm thick Pd thin film was formed on a polydimethylsiloxane (PDMS) substrate, and 50% of the physical strain was applied in the longitudinal direction to fabricated uniform nanogaps. The initial concentration of the hydrogen gas for the PDMS/Pd films was controlled, and subsequently, the on-off switching response was measured. We found that the average nanogap was less than 50 nm, and the Pd nanogap hydrogen sensors operated over a wide range of temperatures. In particular, the sensors work properly even at a very low temperature of -40℃ with a fast response time of 2 s. In addition, we have investigated the relative humidity and annealing effects.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.352-356
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• 2007

The Ni/Cr/Al/Cu (51/41/4/4 wt%) thin films were deposited by using DC magnetron sputtering method for the application of the resistors having low TCR (temperature coefficients of resistance) and high resistivity from the former printed-results[3]. The TCR values measured on the as-deposited thin film resistors were less than ${\pm}10\;ppm/^{\circ}C$ and $-6{\sim}+1\;ppm/^{\circ}C$ after annealing and packaging process. The TCR values were $-3{\sim}1\;ppm/^{\circ}C$ (ratio of variation : about 0.02 %) and $-30{\sim}20\;ppm/^{\circ}C$ (ratio of variation : about $0.5{\sim}1\;%$) for the thermal cycling and PCT (pressure cooker test), respectively. It was confirmed that the reliability properties of the thin film resistor were good for electronic components.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.6
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• pp.296-302
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• 2020

Magnesium alloys have been rapidly attracting as lightweight structural material in various industry fields because of having high specific strength and low density. It is well known that the crystallographic texture plays an important role in improvement of poor room temperature ductility of magnesium alloys. In this study, high-temperature plane strain compression deformation was conducted on extruded AZ80 magnesium alloy at 723K by varying the strain rates ranging from 5.0×10^-3s^-1 to 5.0×10^-2s^-1 in order to investigate the behaviors of texture formation. It was found that texture formation behaviors in three kinds of specimens were affected by continuous and discontiuous deformation mechanism.

• Nuclear Engineering and Technology
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• v.34 no.2
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• pp.132-141
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• 2002

The effects of microstructure on fretting wear were investigated in Inconel 690 tube. The microstructure observation indicated that the solution annealing temperature and time affected the grain size of the Inconel 690 tubes. The carbide morphology, along grain boundaries, was mainly affected by thermal treatment time and temperature. The wear test results showed that specimens with larger grain size and with coarse carbides along grain boundaries had better wear resistance. Cracks were found in specimens with carbides along the grain boundary, while few cracks were found in carbide free specimens. It seemed that the carbides on grain boundary assisted crack formation and propagation in carbide containing specimens. On the other hand, the micro-hardness of specimen did not have a major role in fretting wear. It could be inferred from the SEM images of worn surfaces that the main wear mechanism of carbide containing specimen was delamination, while that of carbide free specimen was abrasion.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.31-37
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• 1999

In this study, the thermal property and adhesion of the electroless-deposited Cu thin film were investigated. The multilayered structure of Cu /TaN /Si was fabricated by electroless-depositing the Cu thin layer on the TaN diffusion barrier which was deposited by MOCVD on the Si substrate. The thermal stability was investigated by measuring the resistivity as post-annealing temperature for the multilayered Cu /TaN /Si specimen which was annealed at atmospheres of $H_2$and Ar gases, respectively. The adhesion strength of Cu films was evaluated by the scratch test. The adhesion of the electroless-deposited Cu film was compared with other deposition methods of thermal evaporation and sputtering. The scratch test showed that the adhesion of electroless plated Cu film on TaN was better than that of sputtered Cu film and evaporated Cu film.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.47-53
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• 2013

We have investigated the traits of clad metals in hot-rolled clad steel plates, including the sensitization and mechanical properties of STS 316 steel plate and carbon steel (A516), under various specific circumstances regarding post heat treatment, multilayered welds, and thick or repeated welds for repair. For evaluations, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by micro vickers hardness, tensile, and etching tests the results were compared with those of EPR tests. The clad steel plates were butt-welded using FCAW and SAW with the time of heat treatment as the variable, a that was conducted at $625^{\circ}C$, for 80, 160, 320, 640, and 1280 min. Then, the change in corrosion resistance was evaluated in these specimens. With carbon steel (A516), as the heat treatment time increased, the annealing effect caused the tensile strength to decrease. The micro-hardness gradually increased and decreased after 640 min. The elongation and contraction of the area also increased gradually. The oxalic acid etch test and EPR test on STS316 and the clad metal showed STEP structure and no sensitization. From the test results on multi-layered and repair welds, it could be concluded that there is no effect on the corrosion resistance of clad metals. The purpose of this study was to suggest some considerations for developing on-site techniques to evaluate the sensitization of stainless steels.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.585-588
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• 2005

Titanium and Titanium alloys are widely used as an orthopedic and dental implant material because of their excellent biocompatibility and mechanical strength. In this study, ECAP Cp-Ti and Cp-Ti were heat treated for different annealing time of 30 min, 90 min and 3 hours. The grain size for each condition was studied. The micro-Vicker hardness test was carried out f3r each different heat treated samples. The micro-Vicker hardness test for ECAP Cp-Ti, Cp-Ti and Cp-Ti (3hr) revealed hardness values of 239.5, 182 and 144 Hv, respectively. The grain size was increased from approximately $70{\mu}m\;to\;300{\mu}m$ with the increase in heat treatment time from 30 min to 3 hours. The heat treated samples were tested for their biocompatibility in simulated body fluid (SBF) and corrosion rates was determined using Polarization Curve test (PCT). The PCT results showed Cp-Ti with comparatively high corrosion potential of -0.18 V and corresponding corrosion current of $2\times10^{-6}$ A, while the corrosion rate in ECAP Cp-Ti and Cp-Ti (30 min annealed) showed very similar results of corrosion potential about -0.47 V with corresponding corrosion current of $7\times10^{-8}$ A.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.41-47
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• 2020

The effect of Co interlayer on the interfacial reliability of SiN_x/Co/Cu thin film structure for advanced Cu interconnects was systematically evaluated by using a double cantilever beam test. The interfacial adhesion energy of the SiN_x/Cu thin film structure was 0.90 J/㎡. This value of the SiN_x/Co/Cu thin film structure increased to 9.59 J/㎡.Measured interfacial adhesion energy of SiN_x/Co/Cu structure was around 10 times higher than SiN_x/Cu structure due to CoSi₂ reaction layer formation at SiN_x/Co interface, which was confirmed by X-ray photoelectron spectroscopy analysis. The interfacial adhesion energy of SiN_x/Co/Cu structure decreased sharply after post-annealing at 200℃ for 24 h due to Co oxidation at SiN_x/Co interface. Therefore, it is required to control the CoO and Co₃O₄ formation during the environmental storage of the SiN_x/Co/Cu thin film to achieve interfacial reliability for advanced Cu interconnections.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1405-1410
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• 2015

In this study we designed the radiation-hardened sensor signal processing modules that can be commonly used for a variety of sensors during normal operation and even in high-radiation environments caused by an accident. First development module was designed to receive the change of the R and C value from the sensors and to process the signal as a PWM modulation scheme. This module was assessed to have ± 10% error to the Full-Scale in the radiation test in the range of 12 kGy TID. The main cause of the error was analyzed as the annealing of the common circuit in the switching element and the consequent increase in the duty ratio of the pulse width modulation circuit according to the radiation dose increasement. The redesigned module for higher radiation resistivity with Stub transistor circuit was found to have less than 5% error to the Full-scale from the radiation test results for 20.7 kGy TID range.

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.139-150
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• 1996

The objective of this study is to provide the information on the manufacturing and exper- , ructures. imental techniques of small scale modeling of precast concrete(P.C.) large panel :-t The ad~~pted scale was one-fifth. 4 types of experiments were performed : nlaterial tests for model concrete and model reinforcement, compressive test of horizontal joint, shear test of vertical joint and cyclic static test of 2-story subassemblage structure. Based on the experimental results, the following conclusions are drawn : i 1) Model concrete had in general larger compressive strength than expected. (2) Model reinforcement showed less ductility if the annealing processes were performed without using vaccuum tube. 131 Failure niotles of horizontal and vertical joints were almost same for both prototype and model. But the strength of model appears to be higher than required by similitude law. (41 Hysteretic behavior of 1 /T, scale subassemblage model can be made quite similar to that of prototype if the ductility of model reinforcement and compressive strength of model concrete could be representative of those of prototype.