Interfacial adhesion in the “MWCNT/Ti” system and its improvement using ion beam treatment: a comparative analysis of the effects of argon and helium ions

A comparative study of the adhesion of multi-walled carbon nanotubes (MWCNTs) to a titanium surface, depending on the modes of irradiation with He$^+$ and Ar$^+$ ions of the “MWCNT/Ti” system, was carried out using atomic force microscopy and X-ray photoelectron spectroscopy. A quantitative assessment of the adhesion force at the interface, performed using atomic force microscopy, demonstrated its significant increase as a result of the treatment of “MWCNT/Ti” with high-energy helium and argon ions. This increase in adhesion force was found to depend on the time of ion irradiation and the type of ions. The nature of chemical bonding between MWCNTs and the surface of a titanium substrate, which causes an increase in the adhesion of nanotubes to titanium during ion irradiation, was studied using X-ray photoelectron spectroscopy. It has been established that this bonding is mainly the result of the formation of chemical C–O–Ti bonds between titanium and carbon atoms with the participation of oxygen atoms of oxygen-containing functional groups, which are localized on defects in the tube walls formed during ion irradiation. With long-term (30 min) irradiation with argon ions, weak effects of direct bonding between titanium and carbon atoms are observed in the photoelectron spectra, which also enhances interfacial adhesion.