TY - JOUR A1 - Ă–sterle, Werner A1 - Urban, Ingrid T1 - Friction layers and friction films on PMC brake pads N2 - A rather new tool, the focused ion beam (FIB) technique, was used to characterise superficial layers at micro-contact areas of a commercial brake pad. The friction material was a polymer matrix composite (PMC) with approximately 50% metal content (semi-metallic) and the counter part was a cast iron rotor. Though the contact areas were not visible as topographic features, they could be identified with the aid of their increased secondary electron emission during FIB-scanning of the surface after tribological activation. Target preparation of micron-sized cross-sections with the FIB enabled the study of superficial layers at predetermined sites at high magnification. Depending on the constituent of the pad, one, two or three layers were identified. The three layer structure comprised: (i) a 100 nm thick friction film containing nanocrystalline metal oxides and an amorphous phase which was enriched with sulphur, (ii) a nanocrystalline friction layer of compacted wear debris accommodating surface roughness and (iii) a severely deformed layer if the supporting constituent was a metal particle. Though the majority of loose wear particles was iron oxide, the friction film which adhered tightly to the pad surface contained a large amount of copper and sulphur, whereas zinc was transferred to the cast iron rotor. KW - Brake KW - Friction film KW - Friction layer KW - Oxidational wear KW - FIB PY - 2004 U6 - https://doi.org/10.1016/j.wear.2003.12.017 SN - 0043-1648 VL - 257 IS - 1-2 SP - 215 EP - 226 PB - Elsevier CY - Amsterdam AN - OPUS4-7645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -