On the flexibility of the carbon skeleton

Abstract

The rigid matrix of amorphous carbon which is composed of disperse graphitic layers responsible for both constrictions and wider pores is found to be somewhat flexible. Nitrogen which is a non-swelling molecule could easily dilate critical constrictions in low-activated carbons. Low-pressure hystereses are observed for nitrogen isotherms at 77 K on these carbons. Study of the nitrogen hystereses of gradually activated ultramicroporous carbon fibres shows that air at 400 °C activates the carbon much more vigorously than CO₂ and steam at 800 °C. It is shown that air activation produces heterogeneous carbon with unactivated regions inside the fibres, while CO₂ and steam homogeneously activate all the carbon matrix.