584
H. Yu. Mykhailova et al.
This fact underscores the complex nature of the effect of radiation defects generated in CNTs under the action of electron irradiation on the elastic properties of
the CNT array. Perhaps at some irradiation dose, the concentration of point defects
(vacancies and adsorbed atoms) reached saturation in the CNT.
As the radiation dose increased, the subsequent accumulation of structural defects
did not occur but the role of their “healing” effects and the reorganization of carbon–
carbon bonds under radiation loading increased. Both effects could have contributed
to an increase in the coefficient of elasticity ε at the maximum dose D = 2.21 · 10
17
e/cm
2 compared to the value of ε at the dose D = 0.89 · 10
17 e/cm
2 .
For CNTs irradiated with electrons with E = 2 MeV and E = 21 MeV and γquanta (E = 1.2 MeV), there is an increase in the Seebeck coefficient α with increasing
dose D up to 38 μV/K, 44 μV/K for 2 MeV and 21 MeV, respectively, and up to
62 μV/K for γ-irradiation. Such an increase in the coefficient α is associated with the
appearance of radiation defects in the acceptor type under the action of high-energy
electrons.
Research showed that irradiation of an array of multilayer carbon nanotubes by
electrons with an energy of 2 and 21 MeV and a dose up to 2.21 · 10
17 e/cm
2 affects
its electrical and elastic properties. The irradiation leads to a noticeable decrease in
its elastic limit but contributes to a significant (approximately twofold) increase in
the electrical conductivity of the material, as well as the Seebeck.
These results are due to the complex nature of the interaction of primary and
radiation defects: primary defects compensate for the effects of radiation defects on
the electrical properties of the array but do not change their effect on the elasticity
of the material. A stronger decrease in the elastic limit of the CNT was observed
at a lower dose of radiation, which was explained by the effects of the “healing”
of structural defects generated in the CNT and the rearrangement of carbon–carbon
bonds under radiation irradiation.
Therefore, controlled changes in the concentration of primary defects in CNTs
by thermal and mechanical treatment can offset the influence of radiation on the
conductivity of the CNT array, which is important for their practical application.
1 Conclusion
It is established that after irradiation of the MCNT array by high-energy (2 and
21 MeV) electrons with a dose up to 2 · 10
17 e/cm
2 , their elastic properties decrease by
2–3 times, the conductivity changes significantly, and by two times the Seebeck coefficient increases the formation of acceptor-type defects that reduce the concentration
of conduction electrons. It is shown that by a controlled change in the concentration
of defects in thermal and mechanical treatment, it is possible to compensate for the
influence of radiation irradiation on electrical conductivity, which is important for
the use of the CNT array in the long term as sensitive sensors and energy converters
in the conditions of radiation exposure: at cosmic, radioactive states, waste, etc.
H. Yu. Mykhailova et al.
This fact underscores the complex nature of the effect of radiation defects generated in CNTs under the action of electron irradiation on the elastic properties of
the CNT array. Perhaps at some irradiation dose, the concentration of point defects
(vacancies and adsorbed atoms) reached saturation in the CNT.
As the radiation dose increased, the subsequent accumulation of structural defects
did not occur but the role of their “healing” effects and the reorganization of carbon–
carbon bonds under radiation loading increased. Both effects could have contributed
to an increase in the coefficient of elasticity ε at the maximum dose D = 2.21 · 10
17
e/cm
2 compared to the value of ε at the dose D = 0.89 · 10
17 e/cm
2 .
For CNTs irradiated with electrons with E = 2 MeV and E = 21 MeV and γquanta (E = 1.2 MeV), there is an increase in the Seebeck coefficient α with increasing
dose D up to 38 μV/K, 44 μV/K for 2 MeV and 21 MeV, respectively, and up to
62 μV/K for γ-irradiation. Such an increase in the coefficient α is associated with the
appearance of radiation defects in the acceptor type under the action of high-energy
electrons.
Research showed that irradiation of an array of multilayer carbon nanotubes by
electrons with an energy of 2 and 21 MeV and a dose up to 2.21 · 10
17 e/cm
2 affects
its electrical and elastic properties. The irradiation leads to a noticeable decrease in
its elastic limit but contributes to a significant (approximately twofold) increase in
the electrical conductivity of the material, as well as the Seebeck.
These results are due to the complex nature of the interaction of primary and
radiation defects: primary defects compensate for the effects of radiation defects on
the electrical properties of the array but do not change their effect on the elasticity
of the material. A stronger decrease in the elastic limit of the CNT was observed
at a lower dose of radiation, which was explained by the effects of the “healing”
of structural defects generated in the CNT and the rearrangement of carbon–carbon
bonds under radiation irradiation.
Therefore, controlled changes in the concentration of primary defects in CNTs
by thermal and mechanical treatment can offset the influence of radiation on the
conductivity of the CNT array, which is important for their practical application.
1 Conclusion
It is established that after irradiation of the MCNT array by high-energy (2 and
21 MeV) electrons with a dose up to 2 · 10
17 e/cm
2 , their elastic properties decrease by
2–3 times, the conductivity changes significantly, and by two times the Seebeck coefficient increases the formation of acceptor-type defects that reduce the concentration
of conduction electrons. It is shown that by a controlled change in the concentration
of defects in thermal and mechanical treatment, it is possible to compensate for the
influence of radiation irradiation on electrical conductivity, which is important for
the use of the CNT array in the long term as sensitive sensors and energy converters
in the conditions of radiation exposure: at cosmic, radioactive states, waste, etc.