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The matrix part of aged STS304 has been irradiated up to 5.4 dpa at 673 K using 1,250 keV highvoltage electron-microscopy (HVEM) connected with an ion accelerator, to study the effect of He pre-injection on microstructural evolution. Two types of irradiation modes were used in this study. The first mode used single electron-beam irradiation and the second mode used electron-beam irradiation after He pre-injection. Thin-disc samples were prepared from the matrix part of STS304 aged at 673 K for 1,000 h. Irradiationinduced- segregation analyses were carried out by an energy-dispersive X-ray analyzer (EDX) in a 200 keV field- emission transmission electron microscopy (FE-TEM) with a beam diameter of about 0.5 nm. The mean size of voids increased considerably and their distribution was bi-modal, when the electron-beam was used after He-injection. Void-number density, sink strength and swelling percentage of samples subjected to electron-beam irradiation after He-injection were larger than those subjected to single electron-beam irradiation. Compared to single electron-beam irradiation, the amount of grain boundary segregation was suppressed for electron-beam irradiation after He-injection. †(Received October 29, 2013)

keyword : alloys, aging, He pre-injection, radiation, transmission electron microscopy, TEM

To investigate the effects of hydrogen on the rupture behavior and mechanical property of ballooned-zirconium cladding after a loss-of-coolant accident, simulated loss-of-coolant-accident tests were carried out using pressurized-zirconium-tube samples with and without hydrogen pre-charging. A prehydrided cladding sample showed lower deformation in the ballooned area and lower rupture temperature than the as-received cladding sample. Ballooned cladding without hydrogen charging showed no significant difference in mechanical property, in spite of a wide range of values for circumferential strain and of a different balloon shape caused by a different heating rate. Pre-hydrided cladding, however, showed an increase in maximum load with increasing heating-rate. The strong relationship between hydrogen content and burst behavior during the loss-of-coolant accident was analyzed and the mechanism by which hydrogen hardens zirconium alloy was explained. †(Received August 2, 2013)

keyword : alloys, deformation, mechanical properties, hardness test, zirconium fuel cladding

Commercially pure (CP) titanium shows low wear resistance and scratch resistance in spite of high specific strength and toughness. In order to improve these problems, the effect of holding time on surface hardening of CP titanium by thermo-chemical treatment (TCT) process was investigated. The surface hardening processes were conducted as a function of treatment holding time for 0.5 hr, 1hr and 2 hrs under nitrogen gas atmosphere at 800 ℃ (thermo-chemical nitriding temperature). The hardness of TCTtreated CP titanium was increased more than the as-received CP titanium by 3 to 4 times, which this layer had continuously gradient hardness distribution from surface to substrate. As the holding time was increased, the whole hardened layer also be came thicker and the depth of Ti2N+TiNx layer was higher. Ball-on-disk tests showed that wear resistance of the samples was improved significantly compared to CP titanium. From these results, the TCT process has proven to be an attractive inner-layered surface hardening process by reducing unnecessary process. †(Received December 9, 2013)

keyword : Surface hardening, Wear resistance, CP titanium, Thermo-chemical treatment

In fossil-fuel-fired power plants, a variety of pollutants are produced from the combustion of conventional fuels such as coal, oil and gas. Major component of such pollution are ash and corrosive chemicals, which also destroy pumps and piping; by causing erosion/corrosion, pitting, and wear. In order to over come such damage, materials with high hardness and high corrosion resistance are needed. In this work, we melted super-cast-iron with excellent corrosion resistance and high hardness. To elucidate the effect of heat treatment, microstructural analysis, hardness measurement, and corrosion tests were performed. Test results revealed that the super-cast-iron had several tens better corrosion resistance than 316 L stainless steel, and it also had a high surface hardness (> HRC45). High hardness, in spite of its low carbon content (0.74%C), could resulted from a hardening heat treatment to precipitate sufficient Cr7C3 and Cr23C6. Also, it was concluded that the excellent corrosion resistance of the super-cast-iron was due to the increase of the relative chromium content by minimizing the carbon content, and by the enhancement of passive film by the addition of Cr, Mo, Cu, and W. †(Received August 22, 2013)

keyword : metals, annealing, corrosion, hardness test, super cast iron, super cast iron

During refining of stainless-steel melt using the AOD (Argon Oxygen Decarburization) process, slag composition and melt stirring can significantly affect the decarburization behavior and reduction of Cr2O3 in slag. An 18 wt%Cr-8 wt%Ni stainless-steel melt containing 0.2 wt%C was decarburized at 1650 ℃ by different types of slag containing Cr2O3. Melt stirring by Ar or Ar+O2 gas bubbling through a submerged nozzle enhanced the decarburization rate significantly. Pure solid Cr2O3 and liquid slag containing Cr2O3 were far more effective than a solid CaO-Cr2O3 mixture for decarburization. The formation of a stable CaO? Cr2O3 phase in the slag was confirmed by XRD analysis after the decarburization experiment with CaOCr2O3 slag. Therefore, in order to improve the decarburization of stainless-steel melt in low-carbon-content regions, it is essential to increase the liquid fraction of slag. †(Received September 24, 2013)

keyword : stainless steel, decarburization, slag, Cr2O3, calcium chromite

A new hydrometallurgical route was investigated for improvement in the recycling of valuable metals from electrodes of lithium batteries. The recycling process involves reductive acid leaching, doublesolvent extraction, and direct electro-winning in an organic solution. The dissolution rate of metal from the electrodes was up to 90% in 2 M sulfuric acid with hydrogen peroxide (10 vol%) at 75 ℃, within 60 min. The improvement of dissolution by hydrogen peroxide seems to be due to reduction of Co(III) to Co(II), which can readily be dissolved. Cobalt and lithium were extracted into Cyanex 272 and a room-temperature ionic liquid of [EMIM] TFSI, respectively, whereas most nickel and manganese did not move to the organic phases. Lithium in the [EMIM] TFSI could be directly reduced as a form of metal by non-aqueous electrowinning. The dense electrodeposits were composed of metallic lithium and an alloy with a gold substrate. †(Received September 26, 2013)

keyword : Lithium ion battery, recycling, solvent extraction, electrolysis, non-aqueous solution

Zone refining, using a locally-melted zone by high-frequency induction heating, was utilized to purify neodymium (Nd) metal. The traveling rate of the molten zone was set as a parameter during zone refining process. The purification efficiency for each impurity (Al, Cu, Fe, Mn, Se, Ti) in the Nd specimen was analyzed using ICP, and experimental results were compared with the numerical zone refining model. In addition, the effect of the impurity migration on the hardness of Nd was investigated. The result showed that a slower traveling rate of the molten zone was more effective for purification. The distribution coefficient, k, of Al and Mn was 0.87, and the k values of Cu, Fe, and Ti were 0.82, 0.83 and 0.68, respectively. These elements were effective for purification of Nd by zone refining. On the other hand, the k value of Se was greater than 1, thus Se migrated in the same direction as the molten zone traveling. The obtained k values of impurities can be used as guidelines for the purification of Nd by zone refining. The trend of hardness with respect to location was similar to the concentration distribution: low at the starting region and high at the end of specimen for the molten zone traveling. The redistribution of impurities resulted from the formation of the eutectic phase during freezing, and the hardness was proportional to the amount of eutectic phase formation. Therefore, the purification efficiency of the zone-refined Nd can be indirectly estimated by measuring the hardness. †(Received October 18, 2013)

keyword : metals, zone refining, solidification, hardness test, neodymium, impurity

Composite nanowires (NWs) mainly consisted of tin oxide (SnO2) and sodium titanate were prepared by the facile hydrothermal method. In this way, the composite crystalline phase was changed to mainly TiO2, and 1-dimensional (1-D) NWs were modified by the deposition of nano-branches to form flower-shaped NWs. The photo-electrochemical properties of both kinds of NW electrodes were tested by fabricating dye-sensitized solar cells (DSSCs). This revealed that the composite NWs exhibited a very low efficiency of 0.011% as a result of sodium titanate insulating the SnO2 photo-electrode. However, the nanobranched NWs exhibited an enhanced conversion efficiency of 0.8%, which is attributed to phase transformation to photoactive TiO2, and to the substantial dye uptake made possible by the large surface area available. Accordingly, the nano-branched NWs were prepared using phase and structural transformation of composite NWs and that showed more than 15-fold enhancement of the photo-conversion efficiency. †(Received July 11, 2013)

keyword : composite, nanostructured materials, phase transformation, scanning electron microscopy, SEM

Metamaterials composed of an electric ring resonator (ERR) and cut wire (CW) were investigated for thin microwave absorbers in an X-band frequency range of 8-12 GHz. S parameters (reflection S11 and transmission S21) were simulated with a variation of material parameters of the substrate (dielectric constant) and dimensions of periodic conducting elements using commercial simulation software. The anti-symmetric plasmon mode of magnetic resonance was predicted between the ERR-CW conducting pairs from the current density distribution and frequency profile of the S parameters. At the magnetic resonance frequency, reflection loss and transmission loss were minimum, resulting in almost 100% power absorption of the incident electromagnetic wave. It is also verified that the magnetic resonance frequency (therefore, the absorbing frequency band) was inversely proportional to the inductance (L) and capacitance (C) of an equivalent circuit, which was, in turn, influenced by the dimension and material parameters of the ERR-CW metamaterials. †(Received October 22, 2013)

keyword : Metamaterials, Electric properties, Magnetic materials, Computer simulation, Coating

In order to improve energy-conversion efficiency using a Cu/Pt bilayer on a flat-glass substrate of a counter electrode (CE), a 0.45 cm2 dye-sensitized solar-cell (DSSC) device (with glass/FTO/blocking layer/ TiO2/N719 (dye)/electrolyte/50 nm-Pt/50 nm-Cu/glass) was prepared. For comparison, 100-nm thick Cu and Pt CEs were also prepared on flat-glass substrates using the same method. The photovoltaic properties of the DSSC device, such as short-circuit current-density (Jsc), open-circuit voltage (Voc), fill factor (FF), energy-conversion efficiency (ECE), and impedance, were checked using a solar simulator and potentiostat. The sheet resistance was examined using a four point probe. The phases of the bi-layered films were examined using X-ray diffraction. The measured energy-conversion efficiency of the DSSC devices with only Pt and Cu/Pt bilayer counter electrodes was 4.60% and 5.72%, respectively. The sheet resistance and interface (CE/electrolyte) resistance of a Cu/Pt bilayer were smaller than those of a Pt-only layer. The phases of the Cu/Pt bi-layered films were identified in pure Cu and Pt without any intermetallic layer. We concluded that the increase in the efficiency of DSSCs employing Cu/Pt, resulted from employing the low-resistive Cu layer. †(Received August 20, 2013)

keyword : solar cells, sputtering, optical properties, solar simulator, bilayer