Nanomechanical Filler Functionality Enables Ultralow Wear Polytetrafluoroethylene Composites.

Surprisingly, certain α-phase alumina filler particles at one to five weight percent can reduce the wear rate of polytetrafluoroethylene (PTFE) by 10,000 times, while other, seemingly comparable α-phase alumina particles provide only modest─by PTFE composite standards─100 times improvements. Detailed studies reveal that size, porosity, and composition of the particles play important roles, but a quantitative metric to support this mechanism is yet to be developed. We discovered the mechanistic importance of friability of the particles, for example, the ability of the particles to fragment at the sliding interface.

Impact of Microstructure on MoS Oxidation and Friction.

This work demonstrates the role of microstructure in the friction and oxidation behavior of the lamellar solid lubricant molybdenum disulfide (MoS). We report on systematic investigations of oxidation and friction for two MoS films with distinctively different microstructures-amorphous and planar/highly-ordered-before and after exposure to atomic oxygen (AO) and high-temperature (250 °C) molecular oxygen. A combination of experimental tribology, molecular dynamics simulations, X-ray photoelectron spectroscopy (XPS), and high-sensitivity low-energy ion scattering (HS-LEIS) was used to reveal new insights about the links between structure and properties of these widely utilized low-friction materials.

Wear biomechanics in the slicing dentition of the giant horned dinosaur Triceratops.

Herbivorous reptiles rarely evolve occluding dentitions that allow for the mastication (chewing) of plant matter. Conversely, most herbivorous mammals have occluding teeth with complex tissue architectures that self-wear to complex morphologies for orally processing plants. Dinosaurs stand out among reptiles in that several lineages acquired the capacity to masticate.