Electrophysical Properties and Heat Capacity of Activated Carbon Obtained from Coke Fines

Aigul T. Ordabaeva
Zainulla M. Muldakhmetov
Sergey V. Kim
Shuga B. Kasenova
Zhenisgul I. Sagintaeva
Arstan M. Gazaliev

Abstract: This paper studies the dependence of the specific heat capacity (Cp) of activated carbon
obtained by the activation of coke fines on temperature (T, K) and the dependence of electrical resistance
(R, Om) on temperature (T, K). In the course of the work, it was found that in the temperature
range of 298.15–448 K on the curve of dependence Cp ???? f (T) at 323 K there is a jump in heat capacity,
associated with a phase transition of the second kind. Measurements of the temperature dependence
of electrical resistance on temperature were also carried out, which showed that activated carbon in
the temperature range of 293–343 K exhibits metallic conductivity, turning into a semiconductor in the
temperature range of 343–463 K. The calculation of the band gap showed that the resulting activated
carbon is a semiconductor with a moderately narrow band gap. The satisfactory agreement of the
phase transition temperatures on the curves of the temperature dependences of the heat capacity on
temperature (323 K) and on the curves of the dependences of electrical resistance and the relative
permittivity on temperature (343 K) indicates the nature of this phase transition, i.e., at a temperature
of 323 K, the change in heat capacity is associated with the transition from semiconductor conductivity
to metallic.
Keywords: activated carbon; heat capacity; electrical resistance; the relative permittivity