Ultralow wear PTFE composites filled with beryllia and germania particles

Nanosized α-phase alumina has been one of the few inorganic fillers that could induce 10 −7 mm 3 /Nm ultralow wear rates of PTFE for the past two decades. We report here two additional oxide fillers, beryllia (BeO) and germania (GeO 2 ) particles, that exhibit comparable wear reduction ability when filled in PTFE. Particle size and surface chemistry analysis revealed that the beryllia and germania particles had different structure and size from the alumina fillers used in this study whereas their composites shared similar ultralow wear rates and carboxylate salt rich tribofilms to the alumina PTFE system. Results in this study support both a particle structure driven and a tribochemistry driven wear reduction hypothesis for the alumina PTFE composite as previously suggested; whereas more systematic investigations are needed to elucidate wear resistance mechanisms in the beryllia and germania filled PTFE composites.