高温・長時間の使用を目的とするHIP焼結窒化ケイ素材料の機械的特性
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概要
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The influence of small addition of selected oxide additives and brittle SiC-phases of various morphologies on the mechanical behavior of high-purity Si_3N_4 has been investigated. Dense monolithic (doped with SiO_2, Y_2O_3 or Yb_2O_3) and composite bodies (containing SiC whiskers or platelets) were obtained by hot-isostatic-press (HIP) sintering via glass-encapsulation and tested from room-temperature to 1400℃ in comparison with the additive-free Si_3N_4. A remarkable increase in toughness was obtained only by doping with 1.7 vol% Y_2O_3 or Yb_2O_3 (the largest amount added in the present investigation), or by dispersing 25 vol% of SiC platelets. The mechanical performance at 1400℃ was evaluated with emphasis on the time-dependent strength and deformation behavior. Two different trends were recognized: (1) the materials containing only SiO_2 at grain boundaries including composites showed linear strength behaviors and the critical phenomenon for strength degradation at 1400℃ was the subcritical crack growth from pre-existing defects. (2) doping with oxide additives led to significant reduction of flaw sensitivity due to crack-tip blunting/healing mechanism concurrently, however, with marked degradation of the deformation resistance. Among the tested materials, the one containing 25 vol% SiC platelets showed a combination of properties convenient for long-term high-temperature applications: a fracture resistance comparable with that of materials containing additives as well as a superior time-dependent strength and deformation behaviors up to 1400℃.
- 社団法人日本セラミックス協会の論文
- 1993-08-01
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関連論文
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- Si3N4系セラミックスの微構造と破壊挙動
- 高温・長時間の使用を目的とするHIP焼結窒化ケイ素材料の機械的特性
- イルテック CNR ファエンツァ