Processing and Characterization of ZrB₂-based Monolithic and Fibrous Monolithic Ceramics
Zirconium diboride (ZrB2) based ultra-high temperature ceramics either unmodified or with SiC particulate additions of 10, 20, or 30 volume percent were prepared by conventional hot pressing. The ZrB2-SiC compositions had improved four-point bend strength compared to the ZrB2 prepared in our laboratory as well as other reported ZrB2 or ZrB2-SiC materials. Strength and toughness increased as the amount of SiC increased. Measured strengths ranged from sim550 MPa for ZrB2 to over 1000 MPa for ZrB2-30% SiC. Likewise, toughness increased from 3.5 MPa to more than 5 MPa over the same composition range. The addition of SiC also improved oxidation resistance compared to pure ZrB2. Co-extrusion processing was used to produce ZrB2-based ultra-high temperature ceramics with a fibrous monolithic structure. Samples had dense ZrB2-30 vol% SiC cells approximately 100 mgrm in diameter surrounded by porous ZrB2 cell boundaries approximately 20 mgrm thick. ZrB2-based fibrous monoliths had four point bend strength of sim450 MPa, about half of a conventional ZrB2-SiC ceramic with the cell composition. Preliminary analysis of fracture behavior found that ZrB2-based fibrous monoliths did not exhibit graceful failure because the difference in strength between the cell and cell boundary of the current materials was not sufficient.
W. Fahrenholtz et al., "Processing and Characterization of ZrB₂-based Monolithic and Fibrous Monolithic Ceramics," Journal of Materials Science, Springer Netherlands, Jan 2004.
Materials Science and Engineering
Keywords and Phrases
ZrB2-Based Monolithic; Co-Extrusion Processing; Fibrous Monolithic Ceramics; Fracture; Hot Pressing; Oxidation Resistance; Strength
Article - Journal
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