Wear resistance of nanostructured metal-polymer self-lubricating powder composites

Tribotechnical tests and microstructural studies were carried out. Wear mechanism of nanostructured metalpolymer self-lubricating composite materials has been established. This mechanism involves in the formation of separating polymer layers on the friction surface, which reduces the coefficient of friction and running-in period of parts of friction units. Carbon nanoparticles move along the friction surface, hinder the development of seizure processes during the interaction of microroughnesses of the contacting surfaces of the material and the counterbody during the destruction of the separating polymer layers. It was found that the polymer filler is displaced from the friction zone, carbon nanoparticles are pressed into the open areas of the surface of the copper matrix of the composite when the pressure in the tribocontact is higher than 1.5 MPa. The temperature in the tribocontact increases, the polymer filler degrades, the carbon nanoparticles are removed from the friction zone, the strength properties of the composite decrease, the friction coefficient and the wear rate increase at a sliding speed above 1.5 m/s. The obtained research results can be used in mechanical engineering, transportation industry and power engineering.

Matrix-trapped viruses can prevent invasion of bacterial biofilms by colonizing cells

Bacteriophages can be trapped in the matrix of bacterial biofilms, such that the cells inside them are protected. It is not known whether these phages are still infectious and whether they pose a threat to newly arriving bacteria. Here we address these questions using Escherichia coli and its lytic phage T7. Prior work has demonstrated that T7 phages are bound in the outermost curli polymer layers of the E. coli biofilm matrix. We show that these phages do remain viable and can kill colonizing cells that are T7-susceptible. If cells colonize a resident biofilm before phages do, we find that they can still be killed by phage exposure if it occurs soon thereafter. However, if colonizing cells are present on the biofilm long enough before phage exposure, they gain phage protection via envelopment within curli-producing clusters of the resident biofilm cells.