The power factor of carbon fibers

The chemical composition and thermoelectric properties of carbon fiber bundles (CF) have been studied. It is shown that the change in the sign of thermopower after modification of CF can be explained by the formation of additional bonds of oxygen-containing complexes on the branched surface of CF. The temperature dependences of thermal $(S)$ and resistivity $(\rho)$ of $n$- and $p$-type carbon fibers were measured. In the temperature range from 300 to 600 K in both types of CF, an increase in thermal EMF is observed with an increase in temperature and a decrease in resistivity in the initial and modified CF, which leads to a rapid increase in the thermoelectric factor $(S^2/\rho)$ of fiber power in the specified temperature range. The combination of high mechanical and thermal stability of the fibers with temperature-increasing thermoelectric efficiency opens up the possibility of using such materials for thermoelectric converters at extremely high temperatures.