Fluorination of carbon blacks: An x-ray photoelectron spectroscopy study .3. Fluorination of different carbon blacks with gaseous fluorine at temperatures below 100 degrees C influence of the morphology, structure and physico-chemical characteristics of the carbon black on the fluorine fixation

Furnace, thermal and a high electrical conductive blacks were submitted to fluorination at room temperature using a gaseous mix of fluorine and nitrogen. The weight uptake of the samples and their elemental composition were determined and compared to the composition of the outer surface and subsuperficial zone of the particles as determined by XPS. Analysis of the XPS spectra indicates that F is merrily fixed at the surface and in a subsuperficial layer of limited thickness and covalently bonded to C. In the furnace blacks, a minor amount of F-2 is trapped in micropores. When the blacks are activated (air oxidation at 450 degrees C), the amount of fluorine fixed by the furnace and thermal blacks increases due to a slight increase of the density of reactive sites consecutively to the development of porosity. The high conductive black, made of empty carbon shells shows a peculiar behavior as the activation does not lead to an augmentation of the F fixation. (C) 1997 Elsevier Science Ltd.