Electrical conductivity of carbon blacks under compression

A study was made of the electrical conductivity of six commercial carbon blacks under compression. The influence of the applied pressure, sample volume, mechanical work, and density of the carbons was investigated. The conductivity was measured at room temperature by impedance spectroscopy over the frequency range 20-106 Hz with a voltage of 1 V. The decrease in volume under compression depended significantly on each particular carbon and on the applied pressure, and for a larger number of carbons it was only important at low pressures. The patterns of variation of the conductivity with pressure and mechanical work were similar. Of the pressure and volume effects comprised in the influence of mechanical work on the conductivity, that of the pressure appeared to predominate. The increase in conductivity with decreasing sample volume was greater for the carbons in which the volume under compression was smaller. The total increase in conductivity was greater for the densest carbons and least for the lightest one. Both the conductivity and its variation under compression were positively related to the density of the carbons.