PSI - Issue 68

Kotrechko Sergiy et al. / Procedia Structural Integrity 68 (2025) 47–52 K. Sergiy et al. / Structural Integrity Procedia 00 (2025) 000–000

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due to the formation of a defect in atomic structure of the graphene sheet near the contact bond (Fig. 4). This defect is similar to half of the known Stone-Wales graphene defect, as it consists of one pentagon and one heptagon (Fig. 4b). The second half of this defect is absent, since the defect formation occurs at the edge of graphene sheet. After that, the bond adjacent to the defect are broken and the carbyne chain lengthens (Fig. 4c). Further CGN stretching gives rise to the chain elongation due to pulling of atoms from the graphene sheet (Fig. 4f). This requires less force, since the bonds breaking occurs in the region where the graphene structure is broken (Fig. 5). Possibility of such atomic rearrangements is confirmed by the DFT calculations data (Hobi et al., 2010).

Fig. 1. A cell of a carbyne-graphene nanoelement. "Y" is the stretching direction.

It should be noted that similar rearrangements which accompany pulling of the carbyne chain from the graphene sheet were observed experimentally by Chuvilin et al. (2009). Unfortunately, the microscope resolution was not sufficient to identify the neighboring defects of the graphene sheet (pentagon and heptagon). Thus, at temperatures higher than 1000 K, there is a transition from the CGN instability due to the contact bond break to instability as a result of the formation of a Stone-Wales-like defect with subsequent unravelling. According to the obtained data, the maximum fall in strength over the temperature range from 0 K up to 1000 K doesn't exceed 25%. At room temperature, this decrease is only 10%. This enables the use of CGN within this temperature range in straintronics devices. On the other hand, heating these elements to temperatures above 1000 K allows the carbyne chains to be pulled from graphene sheets. This phenomenon may be employed in relevant technologies.