Chi-Yun Kuan

Wetting Characteristics on Micro/Nanostructured Zinc Oxide Coatings

© The Electrochemical Society, Inc. [2009]. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in [Journal of The Electrochemical Society, Vol.156, No.2, pp.J32-J36].

A complementary electrochromic device based on W18O49 nanowire arrays and Prussian blue thin films

Tungsten oxides (W18O49) nanowire arrays as effective electrochromic working electrodes were fabricated on seed-free FTO glasses through a facile solvothermal process. XRD, FESEM and TEM were used to characterize the phase, morphology and nanostructure. Uniform monoclinic W18O49 nanowire arrays can be obtained at 180 °C for 5 h. In the assembled electrochromic device the W18O49 nanowire array films show a fast response and switching time, extracted for a 50% transmittance change of 10.8 s for coloration (tc) and 3.1 s for bleaching (tb), which surpass current traditional devices using monoclinic tungsten oxide (WO3) as the electrochromic material. The reasons can be attributed to their large specific surface area, special tunnel structure and non-stoichiometry characteristics. A complementary electrochromic device combining the W18O49 nanowire arrays with Prussian blue film shows a higher optical contrast (59.05% at 632.8 nm) and a faster switching response with a coloration time of 6.9 s and a bleaching time of 1.2 s, superior to the single layer W18O49 nanowire device. The complementary device with excellent electrochromic performance demonstrates a great potential for practical application.

Preparation of WO3 nanorods by a hydrothermal method for electrochromic device

Uniform WO3 nanorods were prepared by a hydrothermal process, and the synthesis was accomplished by using NaCl as the capping agent and Na2WO4 as the inorganic precursor. Scanning electron microscopy, X-ray diffractometer, transmission electron microscopy and UV–visible spectroscopy were used to characterize the morphology, phase, and nanostructure of the resulting nanorods. The effects of pH and the amount of NaCl capping agent on the morphology of the WO3 nanorods were investigated. Uniform and regular aligned WO3 nanorod films can be achieved by self-assembly in a drop coating process. Moreover, the electrochromic devices based on WO3 nanorods display a deep blue color and have low transmittance (<2%) in the colored state, especially in the infrared range, which may provide a promising platform for energy-saving smart windows, and other electro-optical applications.

Hydrothermal synthesis of Li4Ti5O12 nanosheets as anode materials for lithium ion batteries

Spinel Li4Ti5O12 (LTO) has the advantages of superior cycling performance, long and stable voltage plateau, enhanced safety, low cost, and environmental friendliness. LTO nanosheets were synthesized by a hydrothermal method using Ti(OC4H9)4 and LiOH as the raw materials, followed by a subsequent heat treatment to get the desired phase. The effects of the reactant concentration and heat treatment temperature on the phase structure were studied to optimize process parameters for preparing the LTO nanosheets. The results demonstrate that the LTO nanosheets obtained by a hydrothermal method with 2 M LiOH and a subsequent heat treatment at 550 °C exhibit an outstanding stable capacity of 175 mA h g−1 at 0.1 C to 20 C for 40 cycles. The ameliorated electrode-performance is ascribed to the nanostructure of the materials, which provides shorter diffusion-paths and a faster migration rate for both ions and electrons. The newly synthesized nanostructured LTO materials can offer good high rate performance and stability. Li4Ti5O12 nanosheets were developed in this paper for use as anode materials for lithium-ion power batteries with high-rate applications.