Journal of the Ceramic Society of Japan (日本セラミックス協会学術論文誌)
Online ISSN : 1882-1022
Print ISSN : 0914-5400
ISSN-L : 0914-5400
112 巻, 1309 号
(September)
選択された号の論文の10件中1~10を表示しています
第58回日本セラミックス協会学術賞受賞研究総説
  • 前川 尚
    2004 年 112 巻 1309 号 p. 467-471
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    Multi-component silicate glasses containing alumina and alkaline earth metal oxides have been used for optical glasses. In these glasses competitive reactions between various kinds of network-forming and network-modifying oxides occur, so that it is effective to differentiate these reactions in terms of an acid-base concept. In this report the reactivities of alkali or alkaline earth oxide with P2O5, Al2O3, B2O3 and SiO2 are discussed based on the result of high-resolution solid state NMR. In alkali aluminoborosilicate glasses the population of four-coordinated boron atom, N4 are expressed well by r/(1-r). However, in the case of alkaline earth aluminoborosilicate glasses, the deviation from the line of r/(1-r) increases in the order of BaO<SrO<CaO<MgO, where r=([M2O] or [MO]-[Al2O3])/([M2O] or [MO]-[Al2O3]+[B2O3]). Alkaline earth oxide reacts with Al2O3 first. Subsequently, residual one reacts with B2O3 or SiO2. Weak base such as MgO reacts mainly with weak acids such as SiO2 rather than B2O3. On the other hand, a strong base such as BaO reacts mainly with B2O3. The equilibrium constant of the reaction, Si (Q3)+B(Q3)=Si(Q4)+B(Q4), can be determined. When K2O and CaO are contained in aluminoborosilicate glasses, it is possible to predict the distribution of the structural units by using the equilibrium constant of individual basic oxide.
  • 若井 史博
    2004 年 112 巻 1309 号 p. 472-476
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    A ceramic material can be elongated extensively in tension above approximately half the absolute melting point provided it has a fine (<1 μm diameter) equiaxed grain size that is stable during deformation. The discovery of superplasticity in ZrO2-based ceramics triggered numerous research activities on ceramics superplasticity, because of potential applications to superplastic forming. Micrograins move past one another by grain boundary sliding during deformation. The analysis of grain boundary dynamics provides insight on the role of grain boundary in superplasticity and grain growth. Here, we review the current knowledge on ceramics superplasticity with a focus on how the grain boundary affects deformation behavior.
  • 伊藤 節郎
    2004 年 112 巻 1309 号 p. 477-485
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    Mechanical behavior and structure of glass under pressure and stress were investigated to seek a guiding principle for obtaining a less brittle glass. A new simple method for measurement of brittleness was proposed by using the concept of brittleness defined from deformation and fracture behaviors. Using this method, brittleness was measured for various kinds of glasses. It was found that in the case of normal glasses, the brittleness decreased monotonically with decreasing density, while in the case of anomalous glasses, the brittleness increased with decreasing density. As a result, in most silicate glass systems, a minimum brittleness appeared at a certain density in the transition region from normal glass to anomalous glass. The glasses in the minimum region showed easier deformation and higher cracking-resistance. A 50% decrease in brittleness resulted in the increase of crack initiation load by about 15 times. To clarify structural change during deformation and fracture, molecular dynamics simulation was carried out for glasses with different brittleness. When the glasses were subjected to relatively low pressure and stress, they showed mostly elastic deformation caused by changing bond angle of Si-O-Si. With increasing pressure and stress, they showed inelastic deformation due to flow and densification besides elastic deformation. The inelastic deformation resulted from the movement of modifier ions and the rearrangement of network structure. Finally, the glasses fractured, forming cavities in the network. It was concluded that a higher polymerized network and an easier movement of modifier ions were important for lower brittleness, which can be related to easier deformation and more difficult cavitation, namely, more difficult cracking.
論文
  • 森本 繁樹
    2004 年 112 巻 1309 号 p. 486-490
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    The formation mechanism, optical absorption and emission spectra of Cr4+ ions-containing Li2O-SiO2 system transparent glass-ceramics were investigated. In this material, the main crystalline phase was Li2O•2SiO2, and the percent crystallinity and crystal size were 67-72 and 20-33 nm, respectively. The remarkable change in color and absorption spectra was observed upon crystallization. The characteristic emission of tetrahedrally coordinated Cr4+ ions was identified in the near infrared region, 1000-1600 nm. It was found that tetrahedrally coordinated Cr4+ ions exist in this transparent glass-ceramics from absorption and emission measurement. The Cr4+ ions exist in residual high SiO2 glassy phase, and their ligand field parameters are estimated to be: 10Dq=10,610 cm-1, B=690 cm-1 and Dq/B=1.54. This Dq/B value is just below the crossing point of 3T2 and 1E levels (Dq/B=1.6). The Cr4+ ions in Li2O-SiO2 system transparent glass-ceramics occupy the little stronger ligand field sites than those in aluminate glass reported previously (Dq/B=1.2). It is considered that the Cr4+ ions can be formed by the reduction of Cr6+ ions (chromate ion [CrO4]2-) associated with decreasing the basicity of residual glassy phase during crystallization. In this process the behavior of Li+ ions plays a significant role. The [CrO4] formed is equivalent to [SiO4] and substitutes [SiO4] sites in the residual high SiO2 glassy phase.
  • 冨田 由美子, 高橋 亮治, 佐藤 智司, 袖澤 利昭, 乙田 真
    2004 年 112 巻 1309 号 p. 491-495
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    Humidity control ability of monolithic bimodal porous silica gel prepared from water glass in the presence of poly (acrylic acid) was investigated from the viewpoints of both equilibrium and kinetic aspects. The humidity, at which adsorption-release of water vapor occurred reversibly, was systematically controlled by changing the mesopore size. The equilibrium adsorption amount of water was as high as 0.7 g per gram of silica. In addition, the presence of macropores made it possible to quickly response for humidity change by the adsorption-release cycle because of rapid gas diffusion in monolithic gel body. These features are quite attractive as a material for humidity control in the airtight buildings.
  • 唐 安江, 橋本 忠範, 西田 哲也, 那須 弘行, 神谷 寛一
    2004 年 112 巻 1309 号 p. 496-501
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    The 70TiO2•30P2O5 (mol%) glass was prepared by the sol-gel method. Its structure was examined by means of IR, Raman spectroscopy and X-ray radial distribution function analysis, and was compared with the corresponding melt-derived glass. It was found that average coordination number of Ti4+ ions was almost 6 and Ti4+ ions formed predominantly TiO6 octahedra in the sol-gel-derived glass, while Ti4+ ions were present in the 4, 5 and/or 6-fold coordination states to give average coordination number in-between 4 and 5 in the melt-glass. The preference of high coordination state of Ti4+ ions in the sol-gel glass was consistent with higher refractive index and density than the melt-glass.
  • —リン酸八カルシウム (Ca8H2(PO4)6•5H2O)—
    西野 忠, 井上 宏一, 永井 正幸
    2004 年 112 巻 1309 号 p. 502-506
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    The dissolution process of octacalcium phosphate (Ca8H2(PO4)6•5H2O, OCP) using a strongly acidic ion exchange resin with a hydrogen form (H-R) suspended in water was examined in detail to confirm the formation of CaHPO4•2H2O (DCPD) as an intermediate. The reactivity of OCP, α- or β- tricalcium phosphate (α- or β-TCP), or tetracalcium phosphate (Ca4(PO4)2O, TetCP), with Ca(H2PO4)2 solution to form DCPD was compared using calorimetry and chemical analysis. The reactivity increased in the order of TetCP=α-TCP»OCP≥β-TCP. The structure of OCP consists of “apatite layer” and “hydrated layer.” The “apatite layer” of OCP was examined by comparing the reactivity of DCPD+hydroxyapatite (HAp) and DCPD+β-TCP with H-R where HAp and β-TCP imitated the “apatite layer.” The results suggested that the “apatite layer” in OCP would be similar to β-TCP rather than HAp in terms of the reactivity.
  • 石川 剛
    2004 年 112 巻 1309 号 p. 507-510
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    The hydroxapatite coloring phenomenon after high-temperature firing was caused by the kinds of atmosphere gasses and the pressure. Especially the influence of oxygen on the coloring was strong. X-ray diffraction measurement showed that the hydroxapatite coloring phenomenon corresponded to the crystal phase transition of hydroxapatite. The crystal system of white and red hydroxapatite was monoclinic and reddish-brown hydroxapatite was hexagonal. From the measurement of the spectrophotometer, red hydroxapatite had an absorption band near 537 nm. This absorption band was considered to be due to the color center.
ノート
  • 張 健, 高橋 雅英, 徳田 陽明, 横尾 俊信
    2004 年 112 巻 1309 号 p. 511-513
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    A CaGa2S4-CaS composite doped with Eu2+ has been prepared by cooling the corresponding melt of the composition of 65CaS•35Ga2S3 containing 1 mol% EuS in order to obtain an efficient bicolor phosphor applicable to white light emitting diode. Efficient green and red fluorescence were simultaneously observed at around 555 and 645 nm, respectively, under 476 nm excitation. Especially, the red emission was about three times as intense as a simple mixture of CaGa2S4: Eu2+ and CaS: Eu2+ powders with the same composition. It was also found that the post heat-treatment doubled the red fluorescence. The obtained CaGa2S4-CaS composite doped with Eu2+ showed more intense fluorescence rich in color rendering than a commercially available Y3Al5O12: Ce phosphor.
  • 森坂 英昭, 谷 孝夫, 加賀 久, 鷹取 一雅
    2004 年 112 巻 1309 号 p. 514-516
    発行日: 2004年
    公開日: 2004/09/01
    ジャーナル フリー
    Zirconia nanoparticles were made from zirconium propionate (ZP) by flame spray pyrolysis (FSP). The ZP was dessolved in 2-propanol, 2-propanol/2,2,4-trimethylpentane or propionic acid, to prepare precursor solutions. The 2-propanol, 2-propanol/2,2,4-trimethylpentane solutions gave low specific surface area (SSA) powders (∼20 m2/g), suggesting evaporation of the precursor was limited. Using propionic acid as a solvent resulted in a mixture of nano- and sub-micron particles (60 m2/g). The evidences suggest that an innovative preparation of precursor solution of the ZP and propionic acid could enhance the gas phase reaction during the FSP, resulting in high SSA zirconia particles.
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