Influence of Atmosphere on Electric Resistance of Various Carbon Powders

Abstract

The electric resistance of carbon powders freely heaped between two electrodes was measured around 250 C in several atmoSpheres. Polyvinylchloride cokes, heat-treated at 700Nf2400 C, and various commerCial carbons W ere used as samples th and influence of atmospere on electric resistance wes discussed with respeet to the structure of carbons.
In hydrogen gas, the resistance of carbon powders increased with time. ln air, the change of resistance with time depended strongly on the degree of graphitization, which was measured fr, m lattice distance. and crystalline sizes, The resistance, for s7gr I e4 carbQ s ncreased with time, , but that of well-graphitized ones decreatted with tinie. The effect seemed to be explained by simplified assumption the co. ntact r. esistance concerned with peripheral carbons of net plane increases and the one concemed u with carborts in, net pl ane dereasesi wit-h oxygen.