Browsing by Author "Ying, Kuo-Liang"

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Colloidal dispersion of nano-scale ZnO powders using amphibious and anionic polyelectrolytes
(2009-04-01)
Ying, Kuo-Liang
;
Hsieh, Tsung-Eong
;
Hsieh, Yi-Feng
;
材料科學與工程學系
;
Department of Materials Science and Engineering
This article describes the dispersion of aqueous suspensions containing nano-scale ZnO powder by utilizing a hybrid of chemical dispersant and mechanical mixing/grinding process. The chemical dispersants included anionic or amphibious polyelectrolytes, i.e., sodium salt of polymethylacrylic acid (PMAA-Na) or polyacrylamide/(alpha-N, N-dimethyl-N-acryloyloxyethyl) ammonium ethanate (PDAAE). The optimum critical concentrations for each dispersants to achieve the lowest viscosity, smallest final sediment volume and particle size (d(50)) for the nano-ZnO suspensions, 3 wt.% for PMAA-Na and 5 wt.% for PDAAE, were identified. The finely dispersed nano-ZnO powders were transferred to prepare sputtering target. The root-mean-square roughness (R(Rms)) of thin films deposited by utilizing such a target was found to be 2.05 nm, which was lower than the RRMS of the film (approximate to 27.57 nm) deposited by using a commercial ZnO target comprised of micro-scale granules. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Dispersion of nanoscale BaTiO3 suspensions by a combination of chemical and mechanical grinding/mixing processes
(2007-11-05)
Ying, Kuo-Liang
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The colloidal stability of aqueous nanometer- and micrometer-scale barium titanate (BaTiO3) utilizing poly (methacrylic acid) (PMAA-Na) and polyacrylamide/(alpha-N,N-dimethyl-N-acryloyloxyethyl)ammonium ethanate (PDAAE) was investigated. In addition to chemical dispersants, the effects of mechanical milling using either conventional ball milling or nanogrinding/-mixing on the dispersion of BaTiO3 suspensions were also studied. Characterization of the particle size distribution (d(50)), viscosity, and morphology of BaTiO3 particles in the suspensions revealed that a sole chemical dispersant or mechanical milling was insufficient to achieve nanometer-scale dispersion. The best dispersion results were obtained with a combination of PMAA-Na dispersant and nanogrinding/-mixing, which could provide sufficient electronic repulsive force and shear force to disperse the 80-nm BaTiO3 powders uniformly in the aqueous suspension. (C) 2007 Wiley Periodicals, Inc.
Sintering Behavior, Microstructure, and Dielectric Properties of Nano-Ba(0.7)Sr(0.3)TiO(3) Ceramics
(2008-10-01)
Ying, Kuo-Liang
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Nanoscale Ba(0.7)Sr(0.3)TiO(3) (BST) powders were synthesized by solid-state reaction, chemical dispersion, and mechanical grinding. Capacitor samples based on the nano-BST powders were then prepared; their sintering behaviors at different temperatures, dielectric properties, and correlations to microstructure were investigated accordingly. It was found that specific sintering conditions are essential for achieving high-density (>= 95%) BST samples with a desired microstructure. Dielectric property measurements revealed that the best result was achieved in samples sintered at 1200 degrees C for 6h (dielectric constant = 9700; dielectric loss = 0.04) or at 1300 degrees C for 1 h (dielectric constant = 9800; dielectric loss = 0.075). The BST samples exhibited a lower Curie point (T(C)) than conventional BaTiO(3) (BTO) and BST systems. The improvement of dielectric properties and phase transition temperature were attributed to the fine grain structure in BST samples.
Sintering Behavior, Microstructure, and Dielectric Properties of Nano-Ba0.7Sr0.3TiO3 Ceramics
(2008-10-01)
Ying, Kuo-Liang
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Nanoscale Ba0.7Sr0.3TiO3 (BST) powders were synthesized by solid-state reaction, chemical dispersion, and mechanical grinding. Capacitor samples based on the nano-BST powders were then prepared; their sintering behaviors at different temperatures, dielectric properties, and correlations to microstructure were investigated accordingly. It was found that specific sintering conditions are essential for achieving high-density (>= 95%) BST samples with a desired microstructure. Dielectric property measurements revealed that the best result was achieved in samples sintered at 1200 degrees C for 6h (dielectric constant = 9700; dielectric loss = 0.04) or at 1300 degrees C for 1 h (dielectric constant = 9800; dielectric loss = 0.075). The BST samples exhibited a lower Curie point (T-C) than conventional BaTiO3 (BTO) and BST systems. The improvement of dielectric properties and phase transition temperature were attributed to the fine grain structure in BST samples.
Sintering behaviors and dielectric properties of nanocrystalline barium titanate
(2007-04-15)
Ying, Kuo-Liang
;
Hsieh, T.-E.
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Nanometer-scale barium titanate (BaTiO3) Powders were prepared via a process consisting of chemical dispersion and physical grinding/mixing. Sintering behaviors, microstructures as well as their correlations to dielectric properties of nano-BaTiO3 sintered at the temperatures ranging from 1100 to 1300 degrees C for various time spans were investigated. It was found that specific control on sintering condition is required for the nano-BaTiO3 powders to achieve desired microstructure, crystalline phase and dielectric properties of devices. The BaTiO3 sample sintered at 1100 degrees C for 6 h possesses relatively small grain sizes (about 140 nm), high density (about 95% T.D.) and distinct room-temperature dielectric properties (dielectric constant = 8000; dielectric loss = 5 x 10(-3)). Hence, in addition to the saving of thermal budget, the adoption of nano-scale ceramic powders in conjunction with appropriate sintering process may dramatically improve the dielectric properties of devices. (C) 2007 Elsevier B.V. All rights reserved.