Journal of the Ceramic Society of Japan
Online ISSN : 1348-6535
Print ISSN : 1882-0743
ISSN-L : 1348-6535
最新号
(February)
選択された号の論文の12件中1~12を表示しています
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  • Naoki KAWANO, Daisuke NAKAUCHI, Fumiya NAKAMURA, Takayuki YANAGIDA
    2020 年 128 巻 2 号 p. 57-61
    発行日: 2020/02/01
    公開日: 2020/02/01
    ジャーナル フリー

    We synthesized a Dy-doped CaF2 translucent ceramic by the spark plasma sintering method, and investigated its scintillation and dosimetric properties compared with those of the single crystal. Both the samples showed sharp peaks across 480–670 nm due to the 4f–4f transitions of Dy3+, and a broad peak approximately at 300 nm due to the self-trapped excitons. The decay time constants of both the samples in scintillation were approximately 5 ms, which was close to those for the 4f–4f transitions of Dy3+. Regarding thermally-stimulated luminescence, the translucent ceramic exhibited higher sensitivity than the single crystal, and the dynamic range was at least 0.01–100 mGy. In addition, both the samples showed optically stimulated luminescence due to the 4f–4f transitions of Dy3+ during 590 nm stimulation light, but the lowest detection limit of both the samples was approximately 10 mGy.

Express letter
Full papers
  • Zhanjiang LI, Chenglong ZHU, Bingjie CAI, Fa CHANG, Xiaoqiang LIU, Muh ...
    2020 年 128 巻 2 号 p. 66-74
    発行日: 2020/02/01
    公開日: 2020/02/01
    ジャーナル フリー

    Composite cermets with different mass ratios of Ti (C,N)/TiB2 and 10 wt % FeCoCrNiAl high-entropy alloys (HEAs) binder were fabricated by mechanical alloying and vacuum hot press sintering. The effect of the TiB2 content on the microstructure and mechanical properties of the Ti (C,N)–TiB2–HEAs cermets was systematically examined and is discussed in detail. The microstructure was analyzed by X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM). The results of this study show that a small amount of Fe2B phase was detected in the XRD patterns besides the Ti(C,N) and TiB2 phase. The TEM observation shows the presence of a HEAs binder phase, which was tightly bound to Ti(C,N) and TiB2 phases. The grain size of the composite cermets gradually decreased with increasing TiB2 content increased from 0 to 45 wt %. The relative density of the composite cermets first increased and then decreased with increasing TiB2 content from 11.25 to 45 wt %. When the TiB2 content reached 22.5 wt %, the composite cermets exhibited excellent comprehensive performance. The grain size, relative density, and hard phase of the composite cermets were the dominating factors that determined the mechanical properties with increasing TiB2 content. The relative density, Vickers hardness, bending strength, and fracture toughness of the Ti (C,N)–22.5 wt % TiB2–10 wt % HEAs composite cermets reached 98.86 ± 0.20%, 1954.4 ± 20 HV10, 727 ± 20 MPa, and 7.9 ± 0.1 MPa m1/2, respectively.

  • Chika MATSUNAGA, You ZHOU, Dai KUSANO, Hideki HYUGA, Kiyoshi HIRAO
    2020 年 128 巻 2 号 p. 75-79
    発行日: 2020/02/01
    公開日: 2020/02/01
    ジャーナル フリー

    Sintering of reaction-bonded silicon nitride (SRBSN) is a method of preparing Si3N4 ceramics with high thermal conductivity and good mechanical properties. In the present study, by using a high purity silicon powder as the starting material and 2 mol % of Y2O3 and 5 mol % of MgO as sintering additives, the phenomena including phase transformation, grain growth, densification, and pore size evolution occurred in the SRBSN process were studied. It was found that the α- to β-Si3N4 phase transformation could complete at 1700°C. Obvious grain growth started at around 1700°C. Substantial densification took place at temperatures between 1800 and 1900°C. When sintered at 1900°C for 30 min, not only the total number of pores drastically decreased as a result of the shrinkage of the compact, but also a fraction of open pores turned to be closed pores due to microstructural changes such as grain growth and pore coalescence.

  • Miho AKO, Jun-ichi FUJISAWA, Minoru HANAYA
    2020 年 128 巻 2 号 p. 80-83
    発行日: 2020/02/01
    公開日: 2020/02/01
    ジャーナル フリー

    Formation of solid solutions was examined in a wide miscibility gap system of Ba1−xCaxZrO3 by preparing film samples having amorphous structures with the help of rf magnetron sputtering and then annealing the amorphous film samples at a moderate temperature condition. Ba1−xCaxZrO3 solid solutions were successfully formed as monophasic products over the entire Ca composition range, indicating the usefulness of the method for the formation of solid solutions in perovskite-type oxides, and Ca composition dependence of the permittivity was revealed in the solid-solution system.

  • Takuya EHIRO, Kazuaki KATAGIRI, Shimpei YAMAGUCHI, Yayoi YOSHIOKA
    2020 年 128 巻 2 号 p. 84-91
    発行日: 2020/02/01
    公開日: 2020/02/01
    ジャーナル フリー

    MgO-modified mesoporous silicas (MgO/SBA-15) were prepared in a one-pot synthesis method. In the present study, a silica precursor was rapidly hydrolyzed and condensed together with a Mg source under mild conditions without a hydrothermal treatment. It was confirmed that N2 adsorption–desorption isotherms of the prepared MgO/SBA-15s were classified as type IV, which is characteristic of SBA-15. The X-ray diffraction (XRD) patterns at low diffraction angle also indicated that MgO/SBA-15s retained the ordered mesoporous structure of SBA-15, in spite of a high Mg content. On the other hand, no diffraction peaks due to Mg species were confirmed in the XRD patterns at high diffraction angle, suggesting that Mg species were dispersed on mesopores. After MgO/SBA-15s were impregnated with Co and Mo, the obtained CoMo/MgO/SBA-15 catalysts were tested for ammonia decomposition. It was revealed that the MgO content greatly influenced the catalytic activities of the CoMo-based catalysts. Although a small or large additive amount of MgO decreased the catalytic activity of CoMo/SBA-15, the modification of SBA-15 with 15 wt % of MgO resulted in the highest catalytic performance for ammonia decomposition. Moreover, the present one-pot synthesis method was more favorable for the enhancement of the catalytic activity, compared with the conventional impregnation method.

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