발간논문

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Copper electrodeposits annealed at 80 ℃ were investigated by electrical resistance measurement, X-ray diffraction and electron backscattered diffraction analyses. The decrease of electrical resistivity had a linear relationship with the re-crystallized area. Interestingly, the texture coefficient of (200) orientation increased as the re-crystallization occurred. Such appearance of (200) texture during annealing seemed to be related to the residual strain in the copper electrodeposits. It is possible to evaluate the progress of grain growth by measuring the electrical resistivity or texture coefficient in copper electrodeposits. (Received July 23, 2013)

keyword : copper electrodeposits, crystallography, grain growth, electrical resistivity, electron backscattered diffraction

Mg alloys with unique characteristics, such as high specific strength, low density, high corrosion rate, and so on, are regarded as functional and also structural materials. In particular, Mg alloys have attractive points as metal implants due to their good biocompatibility and biodegradability in the bio- environment and similar elastic modulus to that of bone tissue. The purpose of this work was to investigate the mechanical properties and bio-corrosion properties of extruded Mg-2Zn-1Mn-xCaO (x = 0.5, 1.0, and 1.5) alloys. To evaluate the bio-corrosion properties, electrochemical tests were conducted in Hanks` solution at 37 ℃. The results of tensile and in vitro corrosion tests indicated that the mechanical and biodegradable properties of Mg-2Zn-1Mn-xCaO alloys could be adjusted by controlling the CaO content. (Received September 24, 2013)

keyword : biomaterials, extrusion, corrosion, CaO

In this work, TaF5 was chosen as an additive to enhance the hydriding and dehydriding rates of Mg. Samples with the compositions of Mg-x wt% TaF5 (x=0, 5, and 10) were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of the samples were then examined. At 593 K under 12 bar H2 at the first cycle, Mg-5TaF5 absorbed 3.24 wt% H for 2.5 min, 3.95 wt% H for 5 min, 4.50 wt% H for 10 min, and 5.00 wt% H for 30 min. At 593 K under 1.0 bar H2 at the first cycle, Mg-5TaF5 desorbed 0 wt% H for 2.5 min, 0.61 wt% H for 5 min, 1.58 wt% H for 10 min, 3.82 wt% H for 30 min, and 4.93 wt% H for 60 min. Mg-5TaF5 has an effective hydrogen storage capacity of larger than 5 wt%. The reactive mechanical grinding of Mg with TaF5, which formed MgF2 and Ta2H by the reaction of 10Mg + 4TaF5 + H2 → 10MgF2 + 2Ta2H, is believed to facilitate nucleation and reduce the diffusion distances of hydrogen atoms. A higher hydriding rate and larger quantity of hydrogen desorbed for 60 min of Mg-5TaF5 than of Mg-10TaF5 suggest that these effects are stronger in Mg-5TaF5 than in Mg-10TaF5. (Received November 5, 2013)

keyword : hydrogen absorbing materials, mechanical alloying/milling, microstructure, X-ray diffraction, Mg-x wt% TaF5