Role of Zr(OH)4 hard agglomerates in fabricating porous ZrO2 ceramics and the reinforcing mechanisms
✍ Scribed by Zhen-Yan Deng; You Zhou; Yoshiaki Inagaki; Motohide Ando; Tatsuki Ohji
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 429 KB
- Volume
- 51
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
Porous ZrO 2 ceramics were fabricated by adding Zr(OH) 4 hard agglomerates to ZrO 2 powder, followed by pressureless sintering. The mechanical properties of porous ceramics sintered from pure ZrO 2 powder were poor. The addition of Zr(OH) 4 increased the strength and fracture toughness of the porous ZrO 2 ceramics for sintered specimens containing lower porosity. However, the Young's modulus had little change so that the strain to failure of porous ZrO 2 ceramics increased with the incorporation of Zr(OH) 4 . Scanning electron microscopy (SEM) observations revealed that microstructures of the green compacts prepared from pure ZrO 2 powder were nonuniform due to the ZrO 2 soft agglomeration, which resulted in a localized nonuniform shrinkage during densification. The localized nonuniform shrinkage led to a weaker grain bonding and degraded the mechanical properties of porous ZrO 2 ceramics. In this work, we found that this microstructure nonuniformity could be eliminated by the addition of Zr(OH) 4 , because the bimodal particle size distribution confined the formation of ZrO 2 soft agglomerates due to a space constraint and an internal friction between the Zr(OH) 4 hard agglomerates during compaction. As Zr(OH) 4 decomposed into ZrO 2 grains during heating, the Zr(OH) 4 hard agglomerates disappeared before sintering occurred. The present study indicates that Zr(OH) 4 hard agglomerate is a unique agent to improve the mechanical properties of porous ZrO 2 ceramics.