Characterisation of carbon fibres grown from carbonaceous gases by measurements of their density and oxidation resistance

In the present work it has been demonstrated, by measurements of their density and air oxidation resistance, that different sorts of carbon fibres grown from a gaseous stage, vapour grown carbon fibres (VGCF), present a duplex structure. By means of these two experimental techniques, structural differences between both constituent phases of this kind of fibres have been determined. It has been proved that the catalytic phase or nucleus presents higher level of crystalline perfection than the pyrolytic or cortical phase. This is corroborated by the fact that thin VGCF show better mechanical properties than thick fibres.

In this way, it has been possible to determine the mean nucleus diameter of a batch of VGCF, and to established a mathematical expression, of the rule of mixtures type, for their density.