Boron-doped carbon coatings have been produced by a method combining the deposition of a pulsed carbon plasma coating and a boron flow formed as a result of the evaporation of a boron target by pulsed YAG: Nd3+ laser irradiation. Phase, chemical composition, structure, and mechanical properties of composite boron-carbon coatings have been determined. Changes in the coatings’ roughness depending on the boron concentration have been established using atomic force microscopy. It has been shown that the grain size is on the rise with increasing boron concentration. Raman spectroscopy has revealed that at a boron concentration of 43.2 at. %. There is a sharp increase in the ID/IG ratio, which indicates the carbon component’s graphitization. Low ID/IG ratios are observed in the coating at low boron concentrations (no more than 17.4 at. %), suggesting a high content of carbon atoms with sp3 bond hybridization. The coating studies, carried out by X-ray photoelectron microscopy, showed that boron could be in a free state or in the form of carbide or oxide depending on the concentration in the coating. In this case, with an increase in boron concentration, there is a decrease in the concentration of carbon atoms in the state with sp3 bond hybridization, accompanied by an increase in the number of B-C bonds and a reduction in the boron concentration not associated with carbon and oxygen. These coating and chemical composition features determine the boron concentration’s established non-monotonic nature on their microhardness, elastic and mechanical properties.
Keywords: composite carbon coatings, boron-doped, atomic force microscopy, X-ray photoelectron microscopy, Raman spectroscopy, microhardness, scratch.
Polylactic acid (PLA)-based ciprofloxacin (Cip) antibacterial films with mass ratio PLA:Cip=1:1 were prepared by low-electron beam dispersion (EBD). The molecular structure, chemical composition and morphology of PLA-based ciprofloxacin antibacterial films were investigated by XPS, FTIR, liquid NMR and SEM. The antibacterial activity of composite films was tested against E. coli ATCC 25922 and S. aureus ATCC 12600 using the agar diffusion method on the solid LB agar medium. XPS and FTIR analysis showed the presence of an antibacterial ingredient in the composite films. Using NMR, it has been shown that the molecular structure of a monolayer of ciprofloxacin is fully consistent with the molecular structure of the initial ciprofloxacin powder. High antibacterial activity of the composite films has been also established and the layers still possess antibacterial activity with regard to S. aureus even after 7 days of leaching in an isotonic solution. The thermal treatment indicates that the composite films can withstand temperatures of 180 °C and keep its structure unchanged.
Polytetrafluoroethylene (PTFE) composite coatings doped with copper acetate and polyethylene (PE) were fabricated on rubber substrate by electron beam dispersion technique. The effects of dopant nature and glow discharge treatment on morphology, structural and tribological properties of the coatings were investigated. The results showed that Cu and PE doping change the surface structure of PTFE-based composite coatings due to the chemical reactions between the dispersion products. Cu-PE-PTFE coatings show the columnar and layered growth models without and with discharge treatment. Cu adding decreases the crystallinity, branched degree and unsaturated degree of PE coatings, but increases the branched degree and unsaturated bonds in the PE-PTFE coatings. Glow discharge enhances the crystallinity and ordering degree of composite coatings. Friction experiments indicated the significant difference of composite coatings in the nature of their destruction during friction. PE-PTFE coating is characterized of the brittle fracture with clear failure boundaries but Cu-PE-PTFE coating shows a rough surface without cracking and delaminating after friction. Cu doping increases the dynamic coefficient of friction of PE and PE-PTFE composite coatings, but discharge plasma decreases the dynamic coefficient of friction. Cu-PE-PTFE composite coating after discharge treatment has the decreased dynamic coefficient of friction and improved wear resistance. POLYM. ENG. SCI., 58:103-111, 2018.
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