발간논문

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For the CuBr-doped 85% Bi₂Te₃-15% Bi₂Se₃ single crystals, the temperature dependences of Seebeck coefficient, electrical resistivity, thermal conductivity, and ftgure-of-merit have been characterized at temperatures ranged from 77K to 600K. Comparing to 85% Bi₂Te₃ 15% Bi₂Se₃, the (m^*/m_0)^(3/2). μc of the CuBr-doped 85% Bi₂Te₃ - 15% Bi₂Se₃ specimens was higher than that of the undoped specimens indicating that the addition of CuBr was effective for the improvement of figure-of-merit. Electron concentration was increased with increasing CuBr content, decresing the Seebeck coefficient and electrical resistivity, and shifting the maximum of figure-of-merit to higher temperatures. A maximum figure-of-merit obtained in these experiments was 2.2×10^(-3)/K for the 0.03 wt% CuBr-doped 85% Bi₂Te₃ 15% Bi₂Se₃ single crystal.

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A new process was proposed to control the defects in the ZMR-SOI thin film. Thermoelectric phenomena were adopted to the conventional lamp-ZMR. The effect of the new process was verified by the experimental examination and analyzed by the computer simulation. It was possible to control the defects by the ZMR with thermoelectric phenomena. The negative direct current density decreased the inter-defect spacing, while the positive current increased the defects spacing. It was shown by the computer simulation that the Peltier effect was the most dominant among the thermoelectric phenomena. The experimental results were correlated with the width of undercooling. A model was proposed to explain the mechanism of defect generation.

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Metal matrix composites reinforced with shape memory alloys induce compressive residual stresses in the matrices and result in improved tensile properties of the composite. In the present study. Al/TiNi_p shape memory composites were fabricated by powder metallurgical method, so called Plasma Activated Sintering method (PAS). Strengthening effect due to TiNi particle reinforcement as well as compressive residual stresses in A1 matrix were investigated. Fairly good matrix/reinforcement bonding was observed in the Al/TiNi_p composites. It was found that the yield strength of the composites is increased with increasing the volume fraction of TiNi particles and the amount of prestrain applied to the composites. For example, yield strength increases from 64㎫ to 114㎫ with reinforcement of 8% TiNi_p shape memory particles to the Al matrix when 4% prestrain is applied to the composite.

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