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

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.