Effect of anodic oxidation of single crystal boron doped diamond on tribocurrent and macroscopic friction force with metals

• Published in: Diamond and related materials 2013-06, Vol.36, p.8-15
• Main Authors: Escobar, Juan V., Chakravarty, Avik, Putterman, Seth J.
• Format: Article
• Language: English
• Subjects: Amontons-Coulomb law; Anodic Oxidation; Anodizing; Boron doped diamond; Condensed matter: structure, mechanical and thermal properties; Contact; Cross-disciplinary physics: materials science; rheology; Diamonds; Electric current; Electric power generation; Exact sciences and technology; Friction; Fullerenes and related materials; diamonds, graphite; Materials science; Mechanical and acoustical properties; Needles; Nickel; Physical properties of thin films, nonelectronic; Physics; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tribocurrent; Tribology
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2013.04.001

Electric currents generated when two solids are forced to move in mechanical contact (tribocurrents) can give information about the fundamental processes involved in triboelectrification and friction. In this paper, we study the effect of anodic oxidation of a natural type boron doped diamond single crystal (100) surface on both the tribocurrent and macroscopic friction force (~mN) when a nickel-coated steel needle slides on it with different normal forces. We find that oxidation leads to significantly larger tribocurrents and higher kinetic friction. The tribocurrent is proportional to the 1/3 power of the load, indicating that the deformation of the tip obeys Hertz law and that the real area of contact is proportional to the 2/3 power of the load. However, the excess friction depends linearly on the load, and does not affect the adhesion term of the two term friction model for nickel and gold needles. Finally, we find that when a small electric current is made to flow transiently in the forward direction across the sliding contact of the oxygen terminated surface, friction decreases down to the value of the original low friction diamond surface, suggesting that the friction increase after anodic oxidation may be electronic in nature. •Macroscopic (~mN) friction and tribocurrent are measured simultaneously.•The substrate is single crystal boron doped diamond. Needles are made of Fe and Au.•Both friction and tribocurrent increase after anodic oxidation.•Area grows as load^(2/3), but excess friction is proportional to the load.•Amontons–Coulomb law applies but friction is not proportional to real contact area.