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One of the major reasons for utilizing Zr-base alloys in nuclear reactors is its good resistance to creep. Tension and creep deformation behaviors of Zr-1Nb-1Sn-0.1Fe alloy (0%Mo alloy) and Zr-1Nb-1Sn-0.1Fe-0.5Mo (0.5%Mo alloy) were evaluated to investigate the effect of Mo addition on mechanical properties and anisotropy. The addition of Mo increased the tensile strength through solid solution hardening. Room and high temperature tensile strength of TD(transverse direction) specimens were higher than those of RD(rolling direction) specimens. The TD specimen of 0.5Mo alloy showed higher elongation at room temperature than the RD specimen due to lattice rotation resulted from twin deformation. The stress exponent, n, obtained in creep test lied between 2.3 and 4.5 in both RD and TD specimens and the viscous glide was the predominant mechanism in creep deformation. The 0.5%Mo alloy showed higher creep resistance than the one without Mo.

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Tungsten carbide was synthesized by SHS process using highly exothermic mixture [Mg+ {-C₂F_(4-)}] as an activate additive and tungsten, carbon elements as starting raw materials. The tungsten carbide was obtained at 2500K combustion temperature. In the final product, MgF₂ and small amount of W₂C , which were byproducts, were completely removed by acidic leaching. The purity of tungsten carbide was 99%, after leaching.

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Rapidly solidified flakes of 7075 aluminum alloys with the addition of 0.5-2.5 wt.%Mn were fabricated by atomizing the alloy and subsequently splat quenched on a rotating water-cooled copper drum. Consolidation of these flakes was done by cold pressing, degassing and hot extrusion at a reduction ratio of 25 to 1. A typical flake was approximately 10 ㎜ in diameter, and its thickness is about 25 ㎛ at center and increased near the edge. Effect of manganese on the aging behavior was examined by DSC(differential scanning calorimetry) and TEM(Transmission electron microscopy). The aging heat treatment of the extrusions investigated the solution treatment at 490℃ during two hours followed by the aging at 120℃ and the peak hardness time showed at 1300 minute. The cooling rate of the apparatus was estimated as 1.8×10^6∼5.5×10^6℃/sec from the measurement of interlamellar spacing Al-33 wt.%Cu eutectic alloy. The microstructure of splat quenched flakes showed microscopic α-Al phase and eutectic compounds. Microhardness of flakes increased with the addition of manganese due to fine particle of their eutectic compounds. P/M materials also containes fine dispersion of eutectic compounds and showed higher hardness even after annealed at high temperatures. P/M materials showed higher hardness at T6. However, addition of manganese appreciable reduced the age hardening of 7075 alloy. As results of observing the microstructure of Mn added extrusions, the dispersoid of fine Mn compounds(Al_(24)Mn_5Zn) which have 0.2 ㎛ or less than it were observed and also these Mn compounds made the Precipitation(η`(MgZn₂)) quantity lower.

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WC-Co composite powders were prepared by reduction of Co^(++) from ammoniacal cobalt solution on WC core by hydrogen gas at hydrothermal environment. The reduction rate and the porperties of cobalt layer were investigated by SEM, size and chemical analysis. The reduction of Co^(++) showed the maximum value when the molar ratio of NH₃/Co^(++) was 2. Optimum condition obtained in this study was reduction temperature 175℃, stirring speed 700 rpm, hydrogen partial pressure 350 psi and reduction time 45 min. Cobalt layer was continuously coated on WC particles and the prepared cobalt coated WC powder was uniformly distributed.

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In the development of the advanced spent fuel management process based on the molten salt technology, it is essential to choose the optimum material for the process equipment handling molten salt. The corrosion behavior of SUS 304L, SUS 316L, More 1 and Super 22H in molten salts was investigated in the temperature range of 650-850℃. In a melton salt of LiCl, a dense protective oxide scale of LiCrO₂ was formed, following growth of oxide scale with parabolic kinetics. But in a mixed molten salt of LiCl-Li₂O, a porous non-protective scale of Li_x(Cr, Ni, Fe)_(2-X)O₂ was formed, following growth of oxide scale with linear kinetics. As the increase of the temperature up to 850℃, the corrosion rate increased slightly in molten salt of LiCl. But in a mixed molten salt of LiCl-Li₂O, the corrosion rate increased rapidly above 750℃. The corrosion behaviors of SUS 304L. and SUS 316L was similar to those of More 1 and Super 22H. But SUS 304L and SUS 316L showed higher corrosion resistance than More 1 and Super 22H.

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In order to develop the new zirconium alloys for cladding materials, the effects of Nb addition and the final heat treatment on the microstructure and corrosion characteristics of Zr-xNb(x = 0.2, 1.0 wt.%) alloys were investigated. The 1.0Nb alloy showed higher corrosion resistance than 0.2Nb alloy at 360℃, 70 ppm LiOH solution. The microstructure of oxide films that having equal oxide thickness has been characterized by TEM. The oxide of 1.0Nb alloy was mainly composed of columnar grains but the oxide of 0.2Nb alloys was mainly composed of equiaxed grains. From the XRD analysis of equal oxide thickness, the oxide of 1.0Nb alloy has higher tetra-ZrO₂ volume fraction than 0.2Nb alloys. Also when hydrogen pick-up content and fraction were measured with the corroded specimens of 0.2, 1.0Nb alloy at pre and post transition region, the hydrogen pick-up content and fraction were lower in 1.0Nb than 0.2Nb alloy. From the final heat treatment effect, the 1.0Nb alloy was affected annealing temperature but the 0.2Nb alloy was not.

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The functional gradient material of p-type (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te with the segment ratio of 1.3 : 1 was fabricated by hot pressing of the mechanically alloyed (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te powders. The power generation characteristics of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te were measured and compared with those of the (Bi_(0.2)Sb_(0.8))₂Te₃and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys. With the temperature difference (ΔT) higher than 300℃ at both ends of the specimen, the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te exhibited larger output power than those of the (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys. The maximum output power of the (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te predicted with the measured Seebeck coefficient and the estimated electrical resistivity was in good agreement with the measured values.

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Thermoelectric properties of the n-type (Bi₂Te₃)_(0.9)(Sb₂Te₃)_(0.05)(Sb₂Se₃)_(0.05) alloy prepared by melting/grinding and hot pressing, were investigated with variation of the doping amount of SbI₃and excess Te. With increasing the doping amount of SbI₃ and excess Te, the Seebeck coefficient and electrical resistivity of the hot-pressed (Bi₂Te₃)_(0.9)(Sb₂Te₃)_(0.05)(Sb₂Te₃)_(0.05) alloy were lowered due to the increase in the electron concentration. When SbI₃ and excess Te were doped within 0.1 wt%, SbI₃ exhibited doping effect, i.e., increase in the electron concentration, 2.8 times larger than that of excess Te. The hot-pressed (Bi₂Te3)_(0.9)(Sb₂Te3)_(0.05)(Sb₂Se₃)_(0.05) alloy exhibited maximum figure-of-merits of 2.02×10^(-3)/K and 2.22×10^(-3)/K with doping of 0.025 wt% SbI₃ and 0.2 wt% excess Te, respectively.

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In order to investigate the origin of capacity fading with charge/discharge cycling in LiMn₂O₄ thin film battery, impedance studies have been performed as function of cycling in Li₂MnO₄/Lipon/1M LiClO₄/Li cells using the Lipon layer as blocking electrolyte for Mn dissolution into liquid electrolyte. The fitted values obtained from impedance analysis shows good agreements with the experimental results. The Warburg resistance of LiMn₂O₄ steadily increase with increasing the charge/discharge cycles, which can explain that capacity fading of LiMn₂O₄ thin film by cycling originated from the structural instability of LiMn₂O₄ due to Jahn-Teller distortion.

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In order to investigate the effects on cycling rechargeability and capacity retention by Co added spinel LiMn₂O₄, the cyclic tests were peformed on the LiMn_(2-x)Co_xO₄ (x=0.05, 0.1, 0.2) cathode thin films fabricated by RF magnetron sputtering. Though the initial discharge capacity of LiMn_(2-x)Co_xO₄ were slightly lowered with increasing the Co contents in comparison with that of LiMn₂O₄, irreversible capacity loss greatly decreased and its stability on cycling was noticeably improved. The LiMn_(2-x)Co_xO₄, x=0.05, retained 97% of its initial capacity after 100 cycles while LiMn₂O₄ retains 88% of the initial capacity. Especially, discharge capacity of the composition LiMn_(2-x)Co_xO₄, x=0.05, after the 100 cycles is 49 ㎂h/㎠-㎛, which was superior to that of LiMn₂O₄, 46㎂h/㎠-㎛. These results indicated that the Co addition into LiMn₂O₄ improved the structure stability of spinel LiMn₂O₄.

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