Browsing by Author "Chen, Yun-Tien"

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Effects of microwave heating on dielectric and piezoelectric properties of PZT ceramic tapes
(2008-04-01)
Chen, Yun-Tien
;
Sheu, Ching-Iuan
;
Lin, Shih-Chin
;
Cheng, Syh-Yuh
;
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Commercial lead zirconate titanate (PZT) perovskite powders were used to fabricate ceramic tape and then sintered by microwave and conventional methods. Both dielectric and piezoelectric properties of PZT ceramic tapes were studied in terms of sintering process. X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) show the PZT perovskite phase with smaller grain size and dense microstructure can be obtained at a lower sintering temperature by microwave process. It was also observed that shrinkage ratio and bulk density of the tapes sintered at 800 degrees C were obtained about 19% and 7.46 g/cm(3) by the microwave heating method, respectively, that is corresponding to those values of sintered PZT tapes at 950 degrees C by conventional process. Moreover, the dielectric constant and maximum permittivity are increased about 30% as compared with conventional processing method. The experimental results demonstrated that the characteristics of the PZT tapes could be significantly improved by microwave heating method. These results demonstrate that such a simple approach can upswing the piezoelectric and dielectric properties of these tapes by using microwave process with a short heating time. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Electrochemical fabrication and magnetic properties of highly ordered silver-nickel core-shell nanowires
(2008-01-31)
Lin, Shih-Chin
;
Chen, San-Yuan
;
Chen, Yun-Tien
;
Cheng, Syh-Yuh
;
交大名義發表
Ordered silver-nickel core-shell nanowire arrays were successfully fabricated by electrodeposition. The ordered silver nanowire arrays embedded in a porous alumina template were first fabricated from an aqueous solution of Ag(NO3)(2) and Ac(NH3). After removing out the template, the obtained silver nanowire arrays were subsequently electrodeposited with nickel at 1.6-2.6 V and 60 degrees C using the electrolyte composed of NiSO4, NiCl2 and H3BO3. Transmission electron microscopy observation revealed that a similar to 15 nm thick nickel film was coated on the surface of the silver nanowires with about 200 nm in diameter. It was found that the silver nanowires with nickel coating showed enhanced magnetic properties in comparison to that of pure silver nanowires. The magnetic force microscope image of silver-nickel core-shell nanowires showed magnetic domain state. In addition, the hysteresis loops of the silver-nickel nanowire arrays showed a coercive field of 180 Oe, almost independent of the applied magnetic field. However, it was observed that a larger magnetic domain was found in parallel direction than that in perpendicular direction. (c) 2007 Elsevier B.V. All rights reserved.