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Transformation behavior and shape-memory characteristics of Ti-50.2 at%-Ni alloy were investigated after solution-treatment followed by cold working. The B2 → R → B19’ transformation occurred when the cold-worked samples were cooled, while the B2 → B19’ transformation occurred in the solution-treated sample. M* (the DSC peak temperature corresponding to the R → B19’ transformation) decreased with increase in the amount of cold working, while R* (the DSC peak temperature corresponding to the B2 → R transformation) kept almost constant. Negligible transformation-elongation occurred under the stress of 10 MPa applied to the solution-treated sample, while that was dramatically increased up to 3 % when the equal level stress was applied to the cold-worked(9% area reduction) sample. The residual elongation increased with increase in the amount of cold-working under applied stress less than about 70 MPa, while it decreased under applied stress higher than about 70 MPa.

keyword : transformation behavior, cold working, shape memory characteristics, X-ray diffraction, transformation elongation

The localized corrosion behavior associated with microstructure of F53 super duplex stainless steel (SDSS) was investigated using a potentiodynamic polarization test, a critical crevice temperature test, an electron probe micro-analyzer analysis, and scanning electron microscopy-energy dispersive spectroscopy analyses. Crevice corrosion was initiated at the α/γ phase boundaries, MOx inclusions (where M is Cr, Mn, Al, Fe, or Ti), as well as Cr and Mo depleted areas adjacent to the σ-phases precipitated in the F53 SDSS alloy. This alloy had been annealed at 1050 ℃ followed by improper water-cooling, and the corrosion was propagated into the α-phases because the pitting resistance equivalent number (PREN) of the α-phase was smaller than that of the γ-phase. As cooling rate increased, the variation of the α-phases decreased, and the content of the Cr and Mo rich σ-phases decreased, thereby increasing the corrosion resistance.

keyword : alloys, annealing, corrosion resistance, scanning electron microscopy, microstructure

For the formation of cemented Tic composite, Co or Ni is added as a binder. However, the high cost and low hardness of Co or Ni as binder and the low corrosion resistance of Tic-Co and Tic-Ni composite have generated interest to find alternative binder materials. It has been reported that FeAl show higher oxidation resistance and hardness as well as low cost compared to Co or Ni. Highly dense nanocrysatlline Tic and Tic-FelAl with a relative desity of up to 100% were obtained within 2 min by PCAS(pulsed current activated sintering) under the condition of 80MPa and up to 1300. The effect of FeAl addition of FeAl on the consolidation, the microstructure and the mechanical properties (hardness and fracture toughness) of TiC were investigated. The fracture toughness of TiC greatly increases without great decrease of the hardness by addition of FeAl. Not only fracture toughness but also hardness values of TiC-10vol.%FeAl were higher than those of TiC-10vol.%Fe, TiC-10vol.%Ni and TiC-10vol.%Co.

keyword : Composites, Nanostructured materials, Sintering, X-ray diffraction, Mechanical properties

Cold cracking is one of the most common catastrophic defects in welds. In this study, we investigated the effect of the shield gas composition (specifically Ar+5 ~ 20% CO2) on the cold-crack ratio on the preheating temperature of 20℃~100℃ in flux-cored arc welds. Critical assessment of the cold-crack ratio was achieved by observing the weld cross-section, appearance of surface cracks, and fractography. The cold-crack ratio decreased as the preheating temperature increased from 20 to 100℃. For the preheating temperature of 50℃, the shield gas (containing 20% CO2) provided higher oxygen content in the weld metal and increased the number of nucleant inclusions for acicular ferrite; thereby eliminating cold cracks. The shield gas with 15% CO2 produced welds that had nearly the same amount of acicular ferrite as compared with the 5% and 10% CO2 cases. However, the 15% CO2 shield gas produced the greatest hardness and largest amount of non-nucleant inclusions in the weld metal, therefore exhibiting the largest cold-crack ratio. If the volume fraction of acicular ferrite remains unchanged, hardness and non-nucleant inclusions should be considered roughly for assessment of the cold-crack ratio.

keyword : metals, welding, microstructure, transmission electron microscopy, TEM, cold crack

Since there are few ores containing indium, it is very important to recover indium from secondary sources, which is essential substance requested in the manufacture of liquid crystal displays. In order to investigate the possibility of developing a process to recover indium from indium-tin-oxide scrap, solvent extraction experiments were done using a synthetic chloride solution containing indium and tin. In these experiments, the concentration of indium and tin was fixed at 1.0 and 0.1 g/L, respectively. In the HCl concentration range from 0.5 to 4M, amines (Aliquat 336, TOA, TEHA) and TBP were employed. The use of TBP and TEHA resulted in the selective extraction of tin over indium, while it was difficult to separate the two elements by extraction with Aliquat 336 and TOA. TEHA was recommend as a potential extractant for the separation of the two metals because only tin could be selectively extracted from the solution at low HCl concentration.

keyword : Indium, Tin, ITO, separation, solvent extraction, metals, purification, recovery

A Cu pillar bump was fabricated by consecutive plating of Cu and Sn. Here, we investigated the change in shape of Sn, and the formation of intermetallic compound during the reflow process. At first, we made a cylindrical shape of Sn in various thickness and then, the Sn was changed into a truncated sphere (Sn bump) on a Cu pillar through the reflow process. When the Sn thickness was a third of the Cu pillar diameter, the reflowed bump radius had a minimum value and the bump-height change at that time had a maximum value. Such results were well understood based on the truncated sphere model.

keyword : electroplating, wetting, soldering, electron backscattering diffraction, EBSD

A sample [named Zn(BH4)2(+NaCl)] was synthesized by milling ZnCl2 and NaBH4 at 400 rpm under argon gas for 2 h. And Zn(BH4)₂(+NaCl)+MgH₂ sample was prepared by milling MgH₂ in a planetary ball mill and mixing with the Zn(BH₄)₂(+NaCl) synthesized by milling for 4 h in a mortar with a pestle. Then the gas-release characteristics of the two samples were investrigated. Analyses of XRD patterns and FT-IR spectra, as well as TGA, DTA, and SEM observations, were also performed. After heating the samples to 400 ℃, the weight losses of Zn(BH4)2(+NaCl) and Zn(BH4)2(+NaCl)+MgH2 were 11.2 and 8.2 wt%, respectively, with respect to the sample weight. The DTA results for the two samples showed a decomposition peak for Zn(BH4)2 at about 61 ℃. The DTA result of Zn(BH4)2(+NaCl) + MgH2 showed a decomposition peak for MgH2 at about 374 ℃. A sample of Zn(BH4)2(+NaCl)+MgH2 to which Ni, and Ti were added, with a composition of 90 wt% MgH2-5 wt% Zn(BH4)2(+NaCl)-2.5 wt% Ni-2.5 wt% Ti, in which a large amount of MgH2 is contained in order to make a large quantity of hydrogen be absorbed and released reversibly, was also prepared. The experimental results showed that addition of Zn(BH4)2(+NaCl), Ni, or Ti increased the dehydriding rate of MgH2, while decreased its initial hydriding rate.

keyword : hydrogen absorbing materials, mechanical alloying/milling, microstructure, X ray diffraction, Zn, BH4, 2, Ni or Ti addition to MgH2

Three-dimensional (3D) wrinkles and folds as periodic structures allow us to improve optical and mechanical characteristics of various optoelectronic devices by controlling light propagation or by inducing stress release capability into optoelectronic devices. Here, I explore visible light diffraction by 3D wrinkles and folds with different wrinkle wavelengths and fold fractions, expecting to increase their applicability for optoelectronic devices, especially where visible light (wavelength: 400~700 nm) is most important, such as organic light emitting diodes (OLED) and organic solar cells (OSC). Contrary to unidirectional periodic structures, 3D wrinkles and folds generated diffraction rings instead of diffraction spots due to their directional randomness. Moreover, when increasing wrinkle wavelength, diffraction angle decreased and diffraction efficiency increased. Maximum diffraction efficiency achieved in this study was about 25%. Then, introducing folds into wrinkle surfaces induced additional diffraction rings with small diffraction angle, indicating folds also have periodicity. The periodicity generated by folds was 8.4-12.7 μm, depending on the fold fraction.

keyword : optoelectronic materials, semisolid processing, buckling, diffraction, 3D wrinkles and folds

In this study, cupric oxide (CuO) thin films were grown on fluorine doped tin oxide(FTO) substrate by using spin coating method. We investigated the effects of thermal annealing temperature and thermal annealing duration on the morphological, structural, optical and photoelectrochemical properties of the CuO film. From the results, we could find that the morphologies, grain sizes, crystallinities and photoelectrochemical properties were dependent on the annealing conditions. As a result, the maximum photocurrent density of -1.47 mA/cm2 (vs. SCE) was obtained from the sample with the thermal annealing conditions of 500 ℃ and 40 min.

keyword : photoelectrochemical, PEC, cupric oxide, spin coating, photocurrent density, thermal annealing

Effects of Mo (1~7%) or Cr (2.3~8.3%) content on the friction and wear characteristics of Fe-based bulk metallic glasses (BMGs) were investigated using a pin-on-disc-type tribo-tester, micro-hardness tester, optical microscope (OM) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). Tribo-oxidational behavior of a worn surface was also analyzed by X-ray photoelectron spectroscopy (XPS). The friction coefficient was found to be less than 0.4 for Cr-containing BMG, which is lower than that of Mo-containing BMG. As Mo content increased, the mass loss of BMG decreased gradually. In the case of Cr content, the friction coefficient showed minimal change up to 6.3% composition, but significant reduction at 8.3%. EDS and XPS results indicate the formation of an oxide film on the worn surface. This film was identified as various iron oxides in all compositions, but as molybdenum at high composition and chromium oxides at 2.3% and 8.3% compositions.

keyword : amorphous materials, casting, micro structure, wear, X ray photoelectron spectroscopy analysis