Innovation in Ceramic Science and Engineering

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Authors: Taro Shimonosono, Go Hiramatsu, Yoshihiro Hirata, Soichiro Sameshima, Naoki Matsunaga, Toshiya Doi, Teruhisa Horita
Abstract: Electrochemical properties (terminal voltage, ohmic resistance and overpotential) were measured for the cell of indium tin oxide cathode (ITO, 90 mass% In2O3-10 mass% SnO2) or perovskite-type oxide cathode La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) / Gd-doped ceria electrolyte (Ce0.8Gd0.2O1.9, GDC, 600-700 μm thick)/Ni-GDC anode using 3 vol% H2O-containing H2 fuel at 873 and 1073 K. The maximum power densities for the cell with ITO cathode at 873 and 1073 K were 21 and 71 mW/cm2, respectively. Similarly, the maximum power density with LSCF was 12 and 113 mW/cm2 at 873 and 1073 K, respectively. The voltage drop was larger for the cathode than for the electrolyte or anode. The overpotential of the LSCF cathode was comparable to the ohmic resistance.
Authors: Hiroaki Wada, Ryo Sakurai, Norio Nihei, Itsuo Tanuma, Yoshitomo Masuda
Authors: Lian Meng Zhang, Guo Qiang Luo, J. Li, Dong Ming Zhang, Qiang Shen
Abstract: In this study, SnO2-based ceramics, with 0.5%CuO as sintering aid and Sb2O3 as activator of the electrical conductivity, was obtained by pressureless sintering at 1450°C for 5 h. Densification behavior and microstructure development strongly depend on Sb2O3. The characteristization of microstructures on Sb2O3 concentrations are analyzed by SEM. A small amount of CuO improves densification; Sb2O3 retards the densification of SnO2-based ceramic. The electrical resistivities of SnO2-based ceramics with different contents of Sb2O3 are measured by the standard four probe method and varied in a wide range. The electrical resistivity arrives the minimal value of 4.964×10-2 0·cm for 99%SnO2+0.5%CuO +0.5%Sb2O3. More content of Sb2O3 than that of CuO causes the degression of density and the increasing of electrical resistivity of ceramics.
Authors: Kazuhiro Kusukawa, Yohei Shiozaki
Abstract: Fatigue damage behavior under repeated electric loading was investigated on two kinds of PZT ceramics with discontinuous electrodes. Intergranular cracking was observed at the electrode edge in soft PZT under electric fields greater than ±400 V/mm. However, under the same loading conditions, no damage was observed in hard PZT. When cracking occurred, permittivity of specimens decreased with the number of cycles corresponding to the amount of mechanical damage. FEM analyses of the electroelastic field of the specimens showed that cracking due to cyclic electric loading was related to 180˚ domain switching caused by concentrated electroelastic field.
Authors: E. Haemmerle, M. Leung, K.A. Razak, M. Hodgson, Wei Gao
Abstract: This paper describes a new optical switching concept using the deflection of a piezoelectric tube manufactured by an electrophoretic deposition process. A prototype optical switch has been assembled and some of the performance characteristics have been measured, such as an insertion loss of 0.9dB, crosstalk of -47dB and switching speed from 5-15ms. The system for measuring deflection has been custom-designed and built with a measurement accuracy of 1μm. Future work involves the improvement of the piezoelectric tube performance characteristics and combining all switching components in one case so that the switch can be tested in a real network environment.
Authors: Xin Yan Yue, Rong Tu, Takashi Goto
Abstract: b-axis oriented SrO substituted BaTi2O5 (Ba1-xSrxTi2O5) was prepared by arc-melting. The effect of SrO substitution on the dielectric properties of BaTi2O5 (BT2) was investigated by A.C. impedance spectroscopy. The Cole-Cole plot of Ba1-xSrxTi2O5 showed a distorted semi-circle which was deconvoluted into two semicircles corresponding to the bulk BT2 and a second phase. The complex impedance, modulus and capacitances from the ferroelectric bulk matrix and the paraelectric second phase of Ba1-xSrxTi2O5 were simulated by a Maxwell-Wagner model.
Authors: P. Sujaridworakun, Supatra Jinawath, W. Panpa, Akira Nakajima, Masahiro Yoshimura
Abstract: Photocatalyst materials were prepared as a hybrid between TiO2 /SiO2 via low temperature hydrothermal method (150oC) without further heat treatment. Porous silica from rice husk ash was used as a support for fine TiO2 particles which acted as a photocatalyst when radiated with a UV light. TiO2-deposited SiO2 was successfully prepared through hydrolysis of TiOSO4 solution by controlling synthesis parameters such as pH ,concentration of TiOSO4, temperature and time under hydrothermal treatment. The obtained products were characterized for physical and chemical properties by means of XRD, XRF, BET and TEM . It was found that pH had an influence on the crystallization of TiO2, and under an appropriated pH, only anatase presented along with amorphous phase. High crystallinity of nano-crystalline anatase ( about 5 nm) deposited on silica surface was observed through TEM. Adsorption and photocatalytic performances of the prepared catalyst were evaluated in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Due to the synergetic functions of adsorption by porous substrate and decomposition by TiO2 photocatalyst, an enhancing of photocatalytic activity for decomposition of organic pollutants in water under UV rays was obtained.
Authors: Akihiko Suda, Kae Yamamura, Akira Morikawa, Yasutaka Nagai, Hideo Sobukawa, Yoshio Ukyo, Hirofumi Shinjo
Abstract: Ceria-zirconia solid solution is one of the most important components of three way catalyst (TWC) for cleaning automotive exhaust. Ceria-zirconia solid solution has a function as an oxygen storage material, which keeps air to fuel ratio (A/F) at the surface of TWC on a stoichiometric composition. The dissolved zirconia into ceria lattice makes cerium ions to be reduced easier and enhances especially bulk oxygen to release. However, there is a large difference of oxygen storage capacity (OSC) between a theoretical value and that of the prior ceria zirconia solid solutions. The cause of the large difference of OSC might be come from the inhomogeneous dispersion of Zr ions in ceria lattice. Atmospheric pressure solvothermal (APS) process was applied to ceria-zirconia solid solutions in this study. The APS ceria-zirconia showed excellent OSC. The excellent OSC performance was presumed to come from further uniformity of zirconium ions in the ceria lattice.
Authors: Tsugio Sato, Ahmed Mohamed El-Toni, Shu Yin, Hisao Hidaka
Abstract: White nanoparticles of calcia-doped ceria were prepared from the precipitate by reacting CeCl3-CaCl2 mixed solution with NaOH solution at pH 12 and the oxidation with hydrogen peroxide solution at 40oC, followed by the calcination at 700oC for 1 h. Ceria particles generated far less singlet oxygen and caused far less damage to the DNA plasmids upon UV illumination than either the titania or the zinc oxide reference pigments.
Authors: Toshikazu Akahori, Mitsuo Niinomi, Masaaki Nakai
Abstract: Titanium and its alloys have been widely used as biomaterials for hard tissue replacements because of their excellent mechanical properties and biocompatibility. However, the bonding between their surfaces and bone is not enough after implantation. The bioactive surface modification such as a hydroxyapatite (HAp) coating on their surfaces has been investigated. Recently, a simple method for forming HAp layer on the surfaces of titanium and its alloys has been developed. This method is called as alkaline treatment process. In this method, HAp deposits on the surfaces of titanium and its alloys by dipping into simulated body fluid (SBF) after an alkaline solution treatment that is followed by a baking treatment (alkaline treatment). This process is applicable to newly developed beta-type Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) for biomedical applications achieving bioactive HAp modification. In this study, the morphology of the HAp layer formed on the surface of TNTZ was investigated after various alkaline treatments followed by dipping in SBF. The formability of HAp on the surface of TNTZ was then discussed. The formability of HAp on TNTZ is much lower than that of commercially pure Ti, Ti-6Al-4V ELI and Ti-15Mo-5Zr-3Al alloys, which are representative metallic biomaterials. The formability of HAp on TNTZ is improved by increasing the amount of Na in the sodium titanate gels formed during an alkaline solution treatment where the NaOH concentrations and the dipping time are over 5 M and 172.8 ks, respectively. The formability of HAp on TNTZ is considerably improved by dipping in a 5 M NaOH solution for 172.8 ks. This condition for alkaline solution treatment process is the most suitable for TNTZ.

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