Polyelectrolyte multilayer thin films [poly(diallyl dimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA)] for the synthesis of CuS and ZnS nanoparticles were prepared. The CuS/ZnS nanoparticles in situ synthesised by immersing the PDDA/PAA polyelectrolyte multilayer thin films into Cu 2z (or Zn 2z ) and Na 2 S aqueous solutions alternately, which were characterised in detail by UV visible absorption spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) analysis. The CuS and ZnS nanoparticles doped polyelectrolyte multilayer thin films were synthesised by the layer-by-layer molecular deposition technology and in situ synthesis method. The coefficient of friction (COF) decreased with the in situ synthesis CuS and ZnS nanoparticles doped into the polyelectrolyte layers. The in situ nanoparticles exhibited enhanced wear resistance performance of the plain polyelectrolyte multilayers.
The tension-tension fretting fatigue tests of steel wires were performed on a self-made fretting fatigue test equipment under contact loads ranging from 40 to 70 N and a strain ratio of 0?8. The results showed that when the contact load increased, the fretting regime of steel wires transformed from gross slip regime to mixed fretting regime. The fretting fatigue life in the mixed fretting regime was significantly lower than that in the gross slip regime. The main fretting wear mechanisms in the gross slip regime, where there were serious fretting damage and a lot of wear debris, were abrasive wear and fatigue wear. Microcracks were observed in the fretting scar of the mixed fretting regime, and the main fretting wear mechanisms were adhesive and fatigue wears. The fretting wear scar was the fatigue source region, and the fatigue fracture surface could be divided into three regions.
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