Abstract
Self-toughening ZrB2–SiC based composites are fabricated by in-situ reactive hot pressing. The effect of sintering additive content on the microstructure and mechanical properties of the composites is investigated. Microstructure observation found that the in-situ reactive hot pressing could promote the anisotropic growth of ZrB2 grains and the formation of interlocking microstructure. Such microstructure could improve the mechanical properties, especially, for the fracture toughness. The improved mechanical properties could be attributed to the self-toughening structure related to the ZrB2 platelets and the formed interlocking microstructure, which could trigger various toughening mechanisms such as grain pull-out, crack bridging, crack deflection, and crack branching, providing the main contribution to the high fracture toughness.
Highlights
In recent decades, ultrahigh temperature ceramics (UHTCs) are attracting more and more attention with the development of space and industrial applications
The formation of trace ZrO2 should be attributed to the surface oxidation of the ZrSi2 powders, which may be occurred in the starting powder and handling after the ball-milling
Self-toughening ZrB2–SiC based composites were fabricated via in-situ reactive hot pressing using ZrSi2, B4C, and C as the raw materials
Summary
Ultrahigh temperature ceramics (UHTCs) are attracting more and more attention with the development of space and industrial applications. As a special class of highly refractory materials, UHTCs have been accepted for potential use as thermal protection structures in next-generation space vehicles, as well as in critical ground-based applications such as refractory linings and cutting tools [1,2]. By adding SiC to ZrB2, the sintering ability, Considerable research efforts have been prompted to improve the toughness of ZrB2–SiC based ceramics. Nanotubes, graphene, or fibers with high strength and high elastic modulus into the ceramic matrix, the fracture toughness of ZrB2–SiC based composites has been effectively improved [8,9,10,11]. The application of these reinforcements was still limited to some extent due to the low volume fraction of introduction, difficulties in densification, dispersion in the matrix, and high cost [12]
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