Browsing by Author "Kuo, CG"

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Characterization of lead-bismuth eutectic nanowires
(2005-04-01)
Kuo, CG
;
Hsu, YY
;
Wu, MK
;
Chao, CG
;
材料科學與工程學系
In this work, lead-bismuth eutectic alloy nanowires were fabricated by a novel vacuum melting method and centrifugal process. An anodic aluminum oxide (AAO) template was used to produce an array of ordered, dense, and continuous Pb-Bi nanowires. Scanning electron microscopy and transmission electron microscopy investigations reveal that nanowires with a diameter of 80 nm are composed of Pb7Bi3 and Bi phases, and have a single orientation of growth. Magnetic susceptibility and hysteresis measurements have been used to characterize the superconductive and magnetic properties of the nanowires. The results show that Pb-Bi nanowires have a slightly lower superconducting transition temperature than Pb-Bi eutectic alloy bulk, and only about 1% superconductivity volume fraction in magnetic fields both perpendicular and parallel to the plate. In magnetization curves, a fairly large hysteresis is observed for both field orientations.
Fabrication of isolated alloy nanoballs and nanowires using centrifugal force
(2005-02-01)
Kuo, CG
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Lead-bismuth alloy nanoballs and nanowires were fabricated using a process based on centrifugal forces. An AAO template with a molten Pb-Bi alloy was sealed in a titanium tube in vacuum at a pressure of 10(-6) Torr, controlled using a molecular turbo-pump. When various centrifugal forces were generated in the titanium tube, nanoscalar alloy balls and wires were formed. During centrifugation, the sealed titanium tube could prevente the oxidation of the Pb-Bi alloy at the interface between the molten alloy and the AAO template. The repulsive force between the nanotube and the molten alloy, and the force applied to the molten alloy inside the AAO template were calculated using the surface tension of the ultrafine tube and centrifugal forces.
Nanoparticles of Pb-Bi eutectic nucleation and growth on alumina template
(2004-12-01)
Chen, CC
;
Kuo, CG
;
Chen, JH
;
Chao, CG
;
材料科學與工程學系
A novel and convenient method of thermo-immersion was used to fabricate of a large of lead-bismuth (Pb-Bi) eutectic nanoparticles on an uniform size anodic aluminum oxide (AAO) template. The AAO with a 60 nm pore diameter was used as a template for nanoparticles nucleation and growth. Both Pb-Bi and AAO were placed in a glass tube in vacuum at 10(-6) Torr, controlled by a molecular turbo pump then heated up to the melting point of the alloy. Nanoparticles nucleated and grew on the AAO template when the molten Pb-Bi solidified. The nanoparticles nucleated on the pore corners of the AAO template initially, grew simultaneously and assembled into a big nanoparticle on top of the AAO template later. Additionally, the size diameters of the initial nanoparticles were approximately 15 nm on the pore corners of the AAO template, and 80 nm when the initial nanoparticles formed a large nanoparticle. Latent heat was released when the molten Pb-Bi solidified to form nanoparticles. The size diameters distribution of nanoparticles was observed by scanning electron microscopy (SEM) such that, the diameters of the nanoparticles were 80 nm on top of the AAO template, and 200 nm in depths of the concave.
Template assisted fabrication of tin nanospheres by thermal expansion and rapid solidification process
(2005-03-01)
Chen, CC
;
Kuo, CG
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Tin (Sn) nanospheres with diameters ranging from 100 to 300nm were fabricated by thermal expansion and rapid solidification process. The Sn melt was injected into an anodic aluminum oxide (AAO) template to form Sn nanowires. The Sn nanowire and AAO composite was then heated to the Sn melting temperature (similar to 232 degrees C) and quenched to low temperature (8 degrees C). The Sn melt exhibits high surface tension and AAO has nanoscale roughness on its surface. These two properties caused Sn nanospheres to form easily on the AAO surface when the partial Sn melt expanded out from AAO channels and rapidly solidified on the AAO surface.