Physicochemical properties of debris ejected from C/C brakes with different structural orders

Debris samples from braking tests carried out with carbon/carbon discs, mounted in a reduced-scale bench, have been studied by X-ray diffraction, thermogravimetry coupled with mass spectrometry, and N2 physisorption at −196 °C. The tests were carried out at low temperature with a high friction coefficient. Two materials with different structural orders (d002 = 338 and 344 nm, respectively) were studied. Debris samples from both materials are similar: they are essentially amorphous and contain up to 10% of oxygen. The specific surface areas are about 180 m2/g. However, a careful examination of the experimental results clearly shows some differences depending on the starting materials. Debris from the less ordered material contains fewer carboxylic groups, the specific surface areas of debris obtained from the more ordered material are systematically larger, and debris samples from both materials may be differentiated by the XRD pattern of the small fraction of starting material they contain. Thus, materials with different structural orders yielded similar debris resulting from the severe mechanico-chemical processes involved but retained a slight but clear memory of the material from which they came.