The results of the high-field technique for obtaining and testing the carbyne strength in situ are presented. By using molecular dynamics simulation and ab initio calculations, a comprehensive analysis of the results is executed. High-field technique for experimental measurement of the carbyne strength in situ is briefly described. It is shown that the technique used gives a lower estimation for strength of carbyne, which equals 251 GPa at T = 77 K. This value is close to the strength 7.85 nN (250 GPa) of contact atomic bond between carbyne and graphene sheet, from which the monatomic chain is pulled. The strength of carbyne itself is determined by strength of an edge atomic bond and it is ≈ 12.35 nN (393 GPa) at T = 0 K. For carbynes containing more than 10 to 12 atoms, the coefficient of elasticity (kY = 145.40 nN) and the elastic modulus (Y = 4631 GPa) are ascertain.
An approach is developed to predict stability of carbyne-based nanodevices. Within this approach, the thermo-fluctuation model of instability and break of contact bond in nanodevices, containing carbyne chains and graphene sheets, is offered. Unlike the conventional models, it does not include empirical constants. The results of DFT calculations are used as initial data for this model. Possibility of synergistic effect of temperature and mechanical load on stability and value of service time of carbyne-based nanodevices is predicted. It is ascertained, that this synergism results in a significant (by many orders of magnitude) decrease in the lifetime of nanodevices containing carbyne chains. The atomic mechanism of this phenomenon is outlined. Conditions of thermo-force loading are predicted at which a service time of these devices is sufficient for applications.
A relative contribution to irradiation hardening caused by dislocation loops and solute-rich precipitates is established for RPV steels of WWER-440 and WWER-1000 reactors, based on TEM measurements and mechanical testing at reactor operating temperature of 563 K. The pinning strength factors evaluated for loops and precipitates are shown to be much lower than those obtained for model alloys based on the room temperature testing as well as those evaluated by means of atomistic simulations in the temperature range of 300 to 600 K. This discrepancy is explained in the framework of a model of thermally activated dislocation motion, which takes into account the difference in temperature and strain rate employed in atomistic simulations and in mechanical testing.
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