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        검색결과 607

        230.
        2006.04 구독 인증기관·개인회원 무료
        We report on the mechanical and structural properties of nanocrystalline 8% and 10% mol yttria stabilized zirconia (YSZ) obtained using mechanical alloying (MA). The as-milled powders show a body-centered cubic structure with grain sizes in the nanometer scale. After uniaxial pressing and sintering the compacts exhibit good mechanical properties. We discuss the correlation of these enhanced properties with the microstructural changes induced by heat treatment.
        231.
        2006.04 구독 인증기관·개인회원 무료
        The influence of doping on the structural and morphological properties of the phosphor system, obtained ultrasonically via Spray Pyrolysis from common gadolinium and europium nitrate solutions, was studied. The particle morphology, crystalline and chemical structure were studied by XRD, SEM and EDS. TEM was applied in order to identify the structure and growth of "primary nanoparticles" and determine the presence of domains locally affected by "Moires Frames" and "Crystallite Size". The SADP allows determining the presence of a polycrystalline material with two phases in the "as-prepared" samples, and only an Ia3 phase along the thermal treatment.
        232.
        2006.04 구독 인증기관·개인회원 무료
        This paper presents a study of large grains by transmission electron microscopy in two WC-Co alloys, one W rich and one C rich. In the W rich alloy, some large grains are found in contact with the phase. The C content influences the morphology of large grains: they are flatter in the C rich alloy with smoother interfaces. Whatever the C content, they contain few dislocations compared to matrix grains except often in a small area. Small WC grains are often found inside the large grains. They have likely been engulfed during the growth of the large grains owing to the low boundary energy.
        233.
        2006.04 구독 인증기관·개인회원 무료
        Based on the comparison of structures and properties of the HS6-5-2 high speed steels made with the powder injection moulding method, pressureless forming, compacting and sintering, and commercial steels made with the ASEA-STORA method, fine carbides spread evenly in the steel matrix were found in the structure of all tested high-speed steels in the sintered state. The steels made with the pressureless forming method are characteristic of the lowest sintering temperature and the highest density, resulting from the high carbon concentration coming from the binding agent degradation.
        234.
        2006.04 구독 인증기관·개인회원 무료
        Due to the increasing use that the stainless steel is getting recently in the nuclear industry, this document proposes the study of the stainless steel 316L with boron addition. With the final product, the properties of the stainless steel 316L (good mechanical properties and high corrosion resistance) with the boron neutron absorption properties are claimed to unify. The P/M technologies allow adding higher boron quantities than with the solidification conventional technologies, where segregation is produced.
        235.
        2006.04 구독 인증기관·개인회원 무료
        The corrosion performance of a powder metallurgical aluminum alloy in aeronautical environments was studied for both as sintered and heat treated states. Sintered samples were obtained by uniaxial pressing of an Al-Cu-Mg prealloyed powder followed by liquid phase sintering. The heat treatments applied were T4 and T6. Corrosion behaviour was assessed by means of potentiodynamic polarization. Results for the equivalent commercial wrought counterpart, AA2024-T3, are also presented for comparison. Similar corrosion performance was observed for both as sintered and AA2024-T3 samples, while corrosion resistance of the PM materials was improved by the heat treatment, especially in the T4 state.
        236.
        2006.04 구독 인증기관·개인회원 무료
        The n-type compound was newly fabricated by gas atomization and hot extrusion, which is considered to be a mass production technique of this alloy. The effect of powder size on thermoelectric properties of 0.04% doped alloy were investigated. Seebeck coefficient and Electrical resistivity increased with increasing powder size due to the decrease in carrier concentration by oxygen content. With increasing powder size, the compressive strength of alloy was increased due to the relative high density. The compound with size shows the highest power factor among the four different powder sizes. The rapidly solidified and hot extruded compound using powder size shows the highest compressive strength.
        237.
        2006.04 구독 인증기관·개인회원 무료
        Several titanate powders (, etc.) were synthesized by an ethylene glycol solution route. Titanium isopropoxide and nitrate salts were dissolved in stoichiometric proportions in liquid-type ethylene glycol without any precipitation. The parent precursor sols were dried to porous gels, and then the gels were calcined and crystallized. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after a simple ball-milling process. A three-component PZT powder was also synthesized successfully by the ethylene glycol method. In this study, the characteristics of the multi-component titanate powders by the ethylene glycol method are examined.
        240.
        2006.04 구독 인증기관·개인회원 무료
        We present a systematic study of the heating and pre-sintering behavior of porous copper powder metal compacts. We employ a TE102 single mode microwave system to position the samples in the separated electric field (E) or magnetic field (H) anti-node of the cavity. We observe significant differences in the heating, pre-sintering, and microstructure evolution of the samples due to the individual fields. We note that sample history (whether heated first in the E-field or H-field) greatly effects a difference in heating trends and subsequent heating behavior and does not appear to be solely a thermal process.