Friction coefficient dependence on electrostatic tribocharging

Abstract

Friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The literature presents a wealth of information on the electronic contributions to friction in metals and semiconductors but the effect of triboelectricity on friction coefficients of dielectrics is as yet poorly defined and understood. In this work, friction coefficients were measured on tribocharged polytetrafluoroethylene (PTFE), using three different techniques. As a result, friction coefficients at the macro- and nanoscales increase many-fold when PTFE surfaces are tribocharged, but this effect is eliminated by silanization of glass spheres rolling on PTFE. In conclusion, tribocharging may supersede all other contributions to macro- and nanoscale friction coefficients in PTFE and probably in other insulating polymers.

Spreading of triboelectrically charged granular matter

“…This is consistent with our observation that the crossover time for glass ( W F = 5 eV)9 particles in polystyrene ( W F = 4.2 eV)10 vials is shorter than that in polypropylene vials ( W F = 4.9 eV)9. The data presented in the paper are also sensitive to the humidity in the atmosphere11 and the protocol used for cleaning the surfaces12 implying the importance of the surface charges in the observed phenomenon.…”

Vibrational contributions to intrinsic friction in charged transition metal dichalcogenides

“…At q = 0, the sliding modes are Γ(4-7), Γ(8-9), A(1-4), A(7-10), while the compressive modes are Γ(10-11), Γ(12), A(5-6), A (11)(12), where we grouped the modes with degenerate frequencies. We want here to notice that, according to the usual convention, the IBZ A point relative to the hexagonal space group 194 corresponds to the Z point of the IBZ relative to the space groups 63, 40, 15, 8, 5, 2 and 1, and to the Y point of the IBZ relative to the space groups 12 and 6; all the three A, Y and Z high symmetry points correspond to the direction (0, 0, 1 /2) of the respective reciprocal lattice.…”

“…); it then originates from the atomic type and the geometric arrangement of the atoms forming the pristine compound, together with the resulting electronic features. In tribological conditions, non-null net charges can arise [11][12][13][14] and redistribute in the neighbourood of the volume where they originated; this corresponds to a charge injection across several layers, and to a perturbation of their charge neutrality. Such perturbation influences the intrinsic frictional properties, the latter being highly relevant in the micromanupulation of free-standing atomic layers, 15 hence in the final design of TMD-based nanostructured materials.…”

Mechanically driven luminescence in a ZnS:Cu-PDMS composite

“…In general, the frictional contact led to a large surface potential of the order of few kV in similar materials such as polytetrafluoroethylene (PTFE)-polyethylene (PE), polymethylmethacrylate (PMMA)-PE, and (PTFE)-glass beads. 21,22 In present case, particle size of ZnS:Cu was around 2.5−40 µm (2.4 × 10 −4 −4 × 10 −3 cm) as observed from the SEM micrograph. Thus the resultant electric field (E = V/d) around the ZnS:Cu particle should be roughly approximated to 10 6 − 10 7 V/cm.…”