Investigation of the microstructure and tribological properties of CNTs/Ni composites prepared by electrodeposition

Abstract

Here, numerous oxygen-containing functional groups were grafted onto the surface of CNTs to improve their dispersibility in an electrolyte. The CNTs were characterized by FT-IR, Raman, XPS, FE-SEM, and TEM. The results revealed that the dispersibility of the functionalized CNTs in the composites was better than unfunctionalized CNTs. CNTs/Ni composites were deposited on a copper plate by pulsed electrodeposition and ultrasonic dispersion using an electrolytic bath with CNTs concentrations from 0 to 2 g l ^−1 . The friction and wear behavior of the composite coatings were assessed using two different methods. In the first method, the coatings were scratched with a progressively higher load from 0–100 N, and the results demonstrate a 10 percent reduction in the coefficient of friction (COF) of the composite compared to pure nickel. The other method involved applying a constant load of 30 N, the COF and microscopic wear mechanism were investigated at different carbon nanotube contents, and the results confirmed that the COF of the composites was gradually reduced with the increase of carbon nanotube mass concentration, and the COF was only 0.343 when the carbon nanotube content was increased to 2 g l ^−1 . According to the XRD results, increasing the CNTs contents changed the preferred growth orientation. Moreover, the FE-SEM images of the wear surface of the 1 g l ^−1 CNTs/Ni sample indicated that it had the best wear resistance and showed the smoothest wear trace without apparent cracks. The addition of CNTs enhanced the wear resistance of the nickel matrix due to the superior mechanical strength and lubricating effect of the CNTs. CNTs exposed to the matrix surface reduced the direct contact between the Ni matrix and the friction pair, acted as lubricants, and reduced the wear rate.

Keywords

• carbon nanotubes (CNTs)
• functionalization
• electrodeposition
• friction