Nanodiamond-based Nanolubricants: Experiment and Modeling
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Nanodiamond-based Nanolubricants: Experiment and Modeling D.Brenner1, Z. Mahbooba1, F. Saberi-Movahed1, J.Krim1, Z.Liu1, M.G. Ivanov2, E.Osawa3, O. Shenderova4 1
North Carolina State University; 2Ural Federal University, Yekaterinburg, Russia; 3NanoCarbon Research Institute, Tokita, Japan; 4International Technology Center, Raleigh, NC, USA ABSTRACT Our recent efforts using primarily nanodiamonds as lubricant additives are discussed. For traditional high performance engine oils, our results show a reduction in friction for steel surfaces for both laboratory experiments under controlled conditions and in a pilot study of passenger cars under typical driving conditions. Examination of the surfaces suggests that surface polishing at the sub-micron scale may be responsible for these results. A separate set of experiments using a quartz crystal microbalance to measure dissipation and drag due to friction has shown that when added to water the charge of the nanodiamond acquired from surface functionalization can have a large influence on uptake and friction at the water-metal interface. More importantly, these results suggest the possibility of creating nanodiamonds with controllable frictional drag at the solid-liquid interface through surface processing. Companion simulation results for nanodiamonds in water sliding between diamond surfaces are also presented. Future possibilities for further understanding and tuning the properties of nanodiamonds as lubricant additives through synergistic experiments and modeling are also discussed. INTRODUCTION Improving lubrication efficiency will have a significant impact on global efforts in sustainable manufacturing and energy conservation. Efficient lubricants, for example, increase the lifetimes of industrial machines, which means more efficient material use since these machines need to be remanufactured less often. Efficient lubricants also reduce energy use in transportation, where for example frictional losses in typical diesel engines can account for greater than 10% of the total fuel energy. There are also environmental issues related to the development of new lubricants. Petroleum-based lubricants used today, for example, were developed during a time at which wear elimination was emphasized over environmental and frictional considerations. Because of this, lubricants commonly used today tend to rely heavily on additives containing sulfur, phosphorous and/or chlorine. These additives have a propensity for bioaccumulation and environmental toxicity, which together with metal oxide powder from use makes waste oil a major environmental hazard.[1] Using traditional lubricants can also limit progress toward developing new structural materials and higher efficiency operating conditions. Tricresyl phosphate, for example, is an effective lubricant additive for iron-containing materials, but is ineffective on stronger crack resistant chrome-based materials.[2-5] It is also a known neurotoxin. A number of recent studies have looked at the effect of adding various classes of nanoparti
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