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2005 Fiscal Year Final Research Report Summary

Research for abnormal mechanical properties in nano-structured ceramics

Research Project

Project/Area Number 16560588
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Inorganic materials/Physical properties
Research InstitutionTokyo Institute of Technology

Principal Investigator

AKATSU Takashi  Tokyo Institute of Technology, Materials and Structures Laboratory, Associate Professor, 応用セラミックス研究所, 講師 (40231807)

Co-Investigator(Kenkyū-buntansha) WAKAI Fumihiro  Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (30293062)
SHINODA Yutaka  Tokyo Institute of Technology, Materials and Structures Laboraty, Research Associate, 応用セラミックス研究所, 助手 (30323843)
Project Period (FY) 2004 – 2005
KeywordsStructural・Functional Materials / Ceramics / Nano Materials
Research Abstract

The aim of this research work is to investigate the mechanical properties of nano-structured ceramics which show superior mechanical performance. We obtained important results as follows,
1. The hardness of cubic zirconia polycrystals with average grain size of 100nm was observed to be the same as that of cubic zirconia single crystals. This means that there is no grain size dependence in the hardness of cubic zirconia, which is quite different from metal materials.
2. In tetragonal zirconia, extremely high hardness was found in polycrystals with the average grain size of 60nm, which was almost two times larger than the hardness observed in ordinal tetragonal zirconia with average grain size of submicron. The high hardness is attributed to the inhibition of stress-induced transformation from tetragonal to monoclinic phase, which was experimentally confirmed through laser raman spectra.
3. In monoclinic zirconia, the hardness of polycrystals with average grain size of 60nm was found to be … More 1.5 times larger than that of polycrystals with average grain size of submicron. The plastic deformation due to twinning seems to occur hardly in polycrystals when the average grain size becomes smaller than 100nm.
4. In alumina, it was rather difficult to obtain polycrystals with average grain size smaller than 100nm, because the rate of grain growth in alumina was very fast in comparison with zirconia. Alpha alumina polycrystals with average grain size of 600nm was fabricated two-step sintering by utilizing hot-pressing and HIP technique. The hardness of the polycrystals was observed to be the same as that of alpha alumina single crystals. This means that there is no grain size dependence in the hardness of alpha alumina.
5. Extremely high hardness was found in cubic magnesia polycrystals with the average grain size of 100nm, which was almost two times larger than the hardness observed in ordinal magnesia with average grain size of the order of micron. This seems to be due to the difficulty of dislocation slip and/or glide in very small grains of the order of 100nm.
6. Indentation size effect of hardness, i.e. hardness increases with the decrease in indentation depth, was, for the first time, found in ceramic materials although ISE has been predicted to be difficult to observe for hard materials according to the theory of the strain gradient plasticity. Less

  • Research Products

    (3 results)

All 2006 2005

All Journal Article (2 results) Book (1 results)

  • [Journal Article] Indentation Size Effect on the Hardness of Zirconia Polycrystals2005

    • Author(s)
      Takashi AKATSU, Shingo NUMATA, Michiyuki YOSHIDA, Yutaka SHINODA, Fumihiro WAKAI
    • Journal Title

      Fracture Mechanics of Ceramics 14

      Pages: 13-20

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Indentation Size Effect on the Hardness of Zirconia Polycrystals2005

    • Author(s)
      Takashi AKATSU, Shingo NUMATA, Michiyuki YOSHIDA, Yutaka SHINODA, Fumihiro WAKAI
    • Journal Title

      Fracture Mechnics of Ceramics 14

      Pages: 13-20

    • Description
      「研究成果報告書概要(欧文)」より
  • [Book] ケミカル・エンジニアリング2006

    • Author(s)
      吉田道之, 赤津 隆, 若井史博
    • Total Pages
      80 13-17(5)
    • Publisher
      (株)化学工業社
    • Description
      「研究成果報告書概要(和文)」より

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Published: 2007-12-13  

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