In Situ Observation of Fracture along Twin Boundaries in Boron Carbide.
basic_science · Level V
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- Record sourced from PubMed, PMID 36099908.
- Also identified by DOI 10.1002/adma.202204375.
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Abstract
The observation of fracture behaviors in perfect and twinned B<sub>4</sub> C crystals via in situ transmission electron microscopy (TEM) mechanical testing is reported. The crystal structure of the synthesized B<sub>4</sub> C, composed of B<sub>11</sub> C icosahedra connected by boron-deficient C-▫-C chains in a chemical formula of B<sub>11</sub> C<sub>3</sub> , is determined by state-of-the-art aberration-corrected scanning TEM. The in situ TEM observations reveal that cracking is preferentially initiated at the twin boundaries (TBs) in B<sub>4</sub> C under both indentation and tension loading. The cracks then propagate along the TBs, thus resulting in the fracture of B<sub>4</sub> C. These results are consistent with the theoretical calculations that show that TBs have a softening effect on B<sub>4</sub> C with amorphous bands preferentially nucleated at the TBs. These findings elucidate the atomic arrangement and the role of planar defects in the failure of B<sub>4</sub> C. Furthermore, they can guide the design of advanced superhard materials via planar defect control.