Journal of the Ceramic Society of Japan
Online ISSN : 1348-6535
Print ISSN : 1882-0743
ISSN-L : 1348-6535
123 巻, 1440 号
(August)
選択された号の論文の17件中1~17を表示しています
Special Articles: The 69th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
  • Koichiro FUKUDA
    2015 年 123 巻 1440 号 p. 623-629
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    The author will briefly review the recent progress and future perspective on the research topics of (i) highly c-axis-oriented polycrystals of lanthanum silicate oxyapatite in the pseudo-binary system La2SiO5–La2Si2O7, (ii) homologous layered carbides in the system Zr–Y–Si–Al–C, (iii) layered oxycarbonitrides in the system Al–Si–O–C–N, (iv) crystal structures and ordered atom arrangements in SiAlON polytypoids, and (v) disordered crystal structure of Al3O3.5C0.5. The crystal structures were necessarily expressed by the split-atom models for the layered oxycarbonitrides and SiAlON polytypoids, indicating that each of these compounds was composed of domains related by merohedral twinning. With Al3O3.5C0.5 the antiphase domains (APDs) were observed, which were formed by the high-low phase transition involving loss of translational symmetry elements. The formation mechanisms of merohedral and pseudo-merohedral twin domains as well as APDs will be discussed in detail.
Special Articles: The 69th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Articles: The 69th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
  • Naoto KITAMURA
    2015 年 123 巻 1440 号 p. 637-642
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Since a high ionic conduction in a crystal can be achieved by tailoring point defects generally, an investigation on a defect structure is of much importance in the field of the solid-state electrochemistry. Due to a non-periodic nature of a defect distribution, however, a typical atomic-configuration analysis with the Bragg reflections is insufficient to gain deep understanding on defects in a crystal. In order to get a clear snapshot of an atomic configuration of a crystal with defects, this paper pays special attention on advanced analytical methods using the pair distribution function (PDF) combined with theoretical calculations. The PDF analyses on some ion-conducting oxides succeed in revealing mobile-ion trappings by specific cations. Especially, the reverse Monte Carlo modeling with both the Bragg reflections and convolved structure factors S(Q) enables us to discuss an intermediate-range atomic configuration with a couple of hundreds of atoms, and then visualize mobile-ion distribution in a crystal as a snapshot. An electronic structure computed by the density functional theory can explain well the trapping mechanism of the mobile ions. Such a strategy will shed new light on the defect chemistry and give a breakthrough for discovering a novel ion-conducting crystal.
Papers
  • Weixia DONG, Qifu BAO, Xingyong GU, Gaoling ZHAO
    2015 年 123 巻 1440 号 p. 643-648
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    CaTiO3 structure with flower-like morphology was prepared by a template-free and surfactant-free solvothermal process in an ethanol-H2O mixed solvent. The possible growth of flower-like structure was discussed based on the experimental results. During this process, PVP and NaOH affected drastically the kinetics of crystal growth and morphology of CaTiO3. NaOH played a crucial role in the formation of CaTiO3 flower-like structure without surfactant. A diffusion-limited and etching growth mechanism was proposed to elucidate the formation of CaTiO3 flower-like structure. Experiment results indicated that the as-synthesized flower-like morphology exhibited higher photocatalytic activities for RhB evolution than those of the “cross” cubic and prism-like structures, which was attributed to the special flower-like structure morphology. The electrochemical property of flower-like morphology was investigated through the cyclic voltammogram (CV) measurement.
  • Hibiki SAIGYO, Hiroki HORI, Takuma TSUKAMOTO, Ryota YAMASE, Kensuke HA ...
    2015 年 123 巻 1440 号 p. 649-655
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Hagi ware originally consists of a mixture of two raw materials: Daido clay and Mishima clay. During its firing process, we observed a change in the magnetic properties of the iron oxide, Fe2O3. The magnetic moment of the Daido clay (which only contains a small amount of the Fe2O3 γ-phase) attains a maximum at a firing temperature of approximately 600°C, where a minor amount of the poorly crystallized Fe2O3 temporarily changes to the ferromagnetic γ-phase. Furthermore, the magnetic moment of the Mishima clay (which contains a large amount of the Fe2O3 γ-phase) decreases as the firing temperature increases, whereas the coercive field rapidly increases at firing temperatures above 1000°C. The magnetization curve of the Mishima clay that was fired at temperatures above 1200°C is characteristic of a two-component system consisting of a minor γ-phase and a major α-phase. The above-mentioned phenomena were also confirmed by XRD analyses. A series of experiments indicated that the firing of Hagi ware can be characterized as a transformation from the γ-phase of Fe2O3 to the α-phase of Fe2O3. This transformation is considered to contribute to the change from soft magnetism to hard magnetism of Hagi ware.
  • Jang-Hoon HA, Jongman LEE, In-Hyuck SONG
    2015 年 123 巻 1440 号 p. 656-661
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Recently, porous ceramic membranes have become a subject of significant interest due to their outstanding thermal and chemical stability. To reduce the high manufacturing costs of these porous ceramic membranes, recent research has focused on the utilization of low-cost natural materials. Therefore, in this paper, we report the results of an attempt to prepare a diatomite-kaolin composite support layer that could effectively filter the ISO 12103-1 A3 test dust while exhibiting acceptable water permeability. The pore characteristics of the specimens were studied by scanning electron micrography, mercury porosimetry, capillary flow porosimetry, and a dead-end microfiltration system with particle counters.
  • Min-Ho LEE, Woo-Sik JUNG
    2015 年 123 巻 1440 号 p. 662-666
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    The reaction mechanism of β-gallium oxide (β-Ga2O3) to gallium nitride (GaN) under flowing ammonia was examined by observing the change in morphology according to the conversion of nanostructured β-Ga2O3 to GaN by ammonolysis. The morphology of the β-Ga2O3 nanostructures after ammonolysis was dependent on the experimental conditions (i.e. oxygen-rich and -deficient gas flow) for their growth. The surface of the β-Ga2O3 nanostructures grown in the oxygen-rich gas flow was striated after ammonolysis. On the other hand, the morphology of the β-Ga2O3 nanostructures grown in the oxygen-deficient gas flow was changed remarkably and diversely with maintaining their contour. These microstructural observations can be explained by the reaction mechanism, in which the ammonolysis of β-Ga2O3 to GaN consists of two successive reactions, the reduction of β-Ga2O3 to gaseous Ga2O and the nitridation of Ga2O(g) to GaN. The relative rates of the two reactions affect the morphology of the nitridated β-Ga2O3 nanostructures.
  • Takayuki MURAKAMI, Iwao NODA, Atsushi NAKAHIRA, Hiroshi MIYAMOTO, Masa ...
    2015 年 123 巻 1440 号 p. 667-671
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    In orthopedic surgery, infection after implantation is a serious complication. Silver (Ag) exhibits antibacterial activity and a broad antibacterial spectrum and is considered to exhibit low toxicity in the human body. In our previous work, we developed an Ag-containing hydroxyapatite (Ag–HA) coating process in which the coatings were applied to substrates using a thermal spraying system and subsequently evaluated the antibacterial properties of the coatings. In this study, we investigated the structure of Ag–HA coatings, especially the microstructure of Ag. Hydroxyapatite powder containing silver oxide (Ag2O) was used as a thermal spraying powder. The coatings were applied onto pure titanium disks by the thermal spraying method, followed by a vacuum heat treatment to crystallize the hydroxyapatite phase of the coatings. X-ray diffraction (XRD) patterns indicated that the Ag–HA coatings consisted primarily of hydroxyapatite and a small amount of Ag metal and that the amount of Ag metal increased with increasing amount of Ag2O in the thermal spraying powder. XANES spectra of the coatings were compared with the spectrum of Ag metal as a reference material, and the peaks associated with the Ag–HA coatings were similar to those of Ag metal; however, the edge peaks shifted to the low-energy side. These results suggested that the Ag in the Ag–HA coatings existed primarily as Ag metal.
  • Hongjuan ZHENG, Kazumichi YANAGISAWA, Ayumu ONDA, Kongjun ZHU
    2015 年 123 巻 1440 号 p. 672-676
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    電子付録
    The spindle-like architectures consisting of Tb(OH)3 nanowires were successfully prepared from Tb2O3 powder by hydrothermal treatments in acetic acid solutions without adding other surfactants. The products were characterized by XRD, FE-SEM and FT-IR. The influence of the concentration of acetic acid, reaction temperature and reaction time on the crystalline phases and morphologies of the products was investigated. The concentration of acetic acid plays a key role in determining the morphology of the Tb(OH)3 products. The effect of acetic acid on the morphologies of the products was systematically discussed.
  • Akio SAYANO, Hiroshi KANNO, Shuichi INAGAKI, Masashi TAKAHASHI, Mitsua ...
    2015 年 123 巻 1440 号 p. 677-684
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Most heating apparatuses include Cr-containing metals and heat-insulating materials that are often placed in contact with each other. It was observed that hexavalent chromium [Cr(VI)] oxide occurred at the contact interface between Cr-containing metals and heat-insulating materials at elevated temperatures. Yellowish reaction products were confirmed on the contact surfaces of the heat-insulating materials and were identified as Cr(VI) compounds. The effect of heat-treatment temperature, time and metal Cr content on the amount of Cr(VI) was investigated. The amount of Cr(VI) compound increased as the heat-treatment temperature, time and metal Cr content increased. The compounds that occurred as a result of the reaction were CaCrO4 and Na2CrO4 for heat-insulating materials containing Ca and Na, respectively. The sol–gel coating technique was used to prevent the formation of Cr(VI) compounds. Al2O3-based coating films were formed on the surfaces of SUS304 metals by a dipping process. The coated metals were placed on the heat-insulating materials and these specimens were heat-treated at 873 K for 5,000 h. As a result, the formation of Cr(VI) was almost completely prevented by the coating film. It was concluded that the Al2O3-based coating films effectively suppressed the diffusion of Cr.
Technical report
  • Takaaki NAGAOKA, Ken’ ichiro KITA, Naoki KONDO
    2015 年 123 巻 1440 号 p. 685-689
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Hot corrosion tests of alumina (Al2O3) and carbon silicate (SiC) ceramics exposed to KCl–NaCl molten salt were performed at high temperatures (700 and 800°C) and for long times (100–400 h) in order to improve the reliability of tanks and heat exchangers for molten salts. The samples were tested by being immersed in molten salt and under salt vapor. Basic corrosion data, such as the corrosion product, surface conditions, and 4-point bending strength were acquired. In the case of the Al2O3 ceramics, neither corrosion products nor a significant roughness of the Al2O3 particles was observed. In the case of the SiC ceramics, the observed corrosion product was SiO2, and considerable roughness was found at the surface of the immersed sample. The surface roughness became more pronounced as the corrosion temperature and time increased. On the other hand, a SiO2 thin film was observed on the surface of the sample that was exposed to salt vapor. A significant strength decrease was not observed for the two types of Al2O3 and SiC ceramics. Therefore, Al2O3 ceramics are expected to represent a suitable container material for molten salts. On the other hand, predicting the lifetime of the material is necessary if SiC ceramics are intended to be used.
Express letter
  • Nan XU, Takahiro TAKEI, Akira MIURA, Nobuhiro KUMADA
    2015 年 123 巻 1440 号 p. 690-694
    発行日: 2015/08/01
    公開日: 2015/08/01
    ジャーナル フリー
    Ag-intercalated and Bi-intercalated layered perovskite were fabricated by ion-exchanged process. The XRD and XPS confirm the phase transformation of the Ag-ion exchanged layered perovskite from Dion–Jacobson to Ruddlesden–Popper phase by heating at higher than 200°C. In the case of Bi ion-exchange perovskite, the product remained Dion–Jacobson phase during the heat treatment. For the Ag-intercalated sample, Ruddlesden–Popper type photocatalyst by heating at 500°C can degrade 20 ppm phenol solution to 6 ppm in 3 h under Xe light, which has superior photocatalytic activity to Dion–Jacobson phase Ag0.67H0.33LaNb2O7. For the Bi-intercalated sample, Dion–Jacobson type photocatalyst can degrade phenol from 20 to 12 ppm in 3 h. From first principle DFT simulation, high photocatalytic activity may be due to the new Ag 4d, O 2p and Nb 4d hybridized band at the highest of the valence band for Ag-included, and to the new Bi 6p band at the lowest of the conduction band for Bi-included samples.
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