g-Ho Chen

Electrochromic Devices Based on Copolymers of 2,5-Dimethoxyaniline-Diphenylamine

Electrochemical copolymerization of diphenylamine (DPA) with 2,5-dimethoxyaniline (DMA) was performed in 4 M H 2 SO 4 aqueous solution for different feed ratios of DPA using cyclic voltammetry. The deposition rate of DPA-DMA copolymer is higher than that of homopolymers (PDPA and PDMA). (DMA-co-DPA) film was deposited using electrochemical polymerization as conducting film on indium tin oxide (ITO) electrode and used as an electrode in an electrochromic device. From the deconvoluted results of X-ray photoelectron spectroscopy, an azeotrope composition of DPA-DMA copolymers exists at DPA feed ratio of 0.5. Poly(3, 4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was spin-coated on ITO as the other electrode. Polyurethane ionomer (PUI) blended with LiClO 4 was used as solid polymer electrolyte. A total solid electrochromic device was assembled as follows: ITO P(DMA-co-DPA) ||LiClO 4 -PUI|| PEDOT:PSS ITO. The columbic efficiency of the devices reached 84% for P(DMA-co-DPA) film with azeotrope composition. The optical contrast (AT,%) of the single electrode and the device were determined by UV-visible spectroelectrochemical studies. A value (31%) of AT in color upon switching the potential from -1.0 to + 1.0 V (vs PEDOT) was noticed for this device. The device was pale yellow at -1.0 V and blue at +1.0 V.

pH Effects on Formation of Cerium-Doped Terbium Aluminum Garnet ( Tb2.95Al5O12 : Ce0.05 ) Phosphor Powder

Terbium aluminum garnet (TAG) was successfully synthesized by a solid-state reaction method in this study. Before calcining, the mixing powder of terbium oxide (Tb 4 O 7 ), boehmite (AlOOH), and cerium chloride (CeCl 3 ·7H 2 O) was aged at pH 1, 2, and 3, respectively. Experimental results revealed that the better process for the formation of TAG powder was aged at pH 1. The effects of pH on the formation of TAG powder were further studied. The diffusion distance between terbium oxide and boehmite was reduced by aging the mixed slurry at pH 1. A pure phase of TAG powder was obtained after the aged mixture of boehmite, terbium oxide, and cerium chloride was heated at 1200°C for 2 h and then calcined at 1500°C for 20 h. The particle size of pure TAG powders is the agglomerate morphology through scanning electron microscopy observation. The formed TAG powder in this work had a maximum emission peak in 553 nm as exciting at 470 nm.