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Lubricants 2018, 6(2), 56;

Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends

Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA
Authors to whom correspondence should be addressed.
Received: 20 May 2018 / Revised: 5 June 2018 / Accepted: 13 June 2018 / Published: 18 June 2018
(This article belongs to the Special Issue Wear Resistant Materials)
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Nanodiamonds are known to improve tribological performance when added to lubricants, but their impact on additives that may already be present in the lubricant is poorly documented. Here, we report on a study of their effects on thermal reaction films formed from tricresyl phosphate (TCP) on Fe substrates immersed in a dibasic ester basestock when blended with TCP. Thermal reaction film formation temperatures were recorded in-situ by monitoring the reaction film formation on both Fe and air baked Fe surfaces using a quartz crystal microbalance (QCM). The nanodiamonds were found to raise the thermal reaction film formation temperature by 18 °C, possibly by raising the activation energy for the reaction, but they were not observed to affect the thickness or rate of formation of the films. The nanodiamonds, moreover, were observed to trigger thermal reaction film formation on air baked Fe surfaces that otherwise were highly resistance to reaction film formation. The surface morphology, roughness, and thickness of the thermal reaction films, as measured by atomic force microscopy (AFM), are reported as well as their chemical compositions, as studied with Electron Dispersive X-ray Spectroscopy (EDS). The coefficients of friction measured on the thermal reaction films during dry solid–solid contact are also reported. View Full-Text
Keywords: phosphate esters; nanodiamonds; TCP; anti-wear; QCM phosphate esters; nanodiamonds; TCP; anti-wear; QCM

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Acharya, B.; Avva, K.S.; Thapa, B.; Pardue, T.N.; Krim, J. Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends. Lubricants 2018, 6, 56.

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