Research Article Experimental Evaluation of Oxide Nanoparticles as Friction and Wear Improvement Additives in Motor Oil Nicholaos G. Demas, Robert A. Erck, Cinta Lorenzo-Martin, Oyelayo O. Ajayi, and George R. Fenske Argonne National Laboratory, ES 212, 9700 South Cass Ave., Argonne, IL 60439, USA Correspondence should be addressed to Nicholaos G. Demas; ndemas@anl.gov Received 16 October 2016; Revised 21 December 2016; Accepted 4 January 2017; Published 30 January 2017 Academic Editor: Simo-Pekka Hannula Copyright © 2017 Nicholaos G. Demas et al. Tis 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. Te efect of two nanoparticle oxides on friction and wear was studied under laboratory test conditions using a reciprocating test machine and two test confgurations. Te addition of these nanoparticles in base stock oil under certain conditions reduced the coefcient of friction and improved wear, but that depended on the test confguration. Examination of the rubbed surfaces showed the pronounced formation of a triboflm in some cases, while polishing on the surface was also observed in other cases. Contact confguration is important when oxide nanoparticles are being evaluated and the conclusions about their efcacy can be vastly diferent. 1. Introduction Fuel economy improvement and lower emissions are major goals of the automotive industry and are driven, in part, by regulation and, in part, by market forces. With the introduc- tion of low-viscosity oils, component surfaces operate more in the boundary and/or mixed lubrication regimes, and wear can become accelerated. In recent years, nanoparticles have been considered as friction modifers and antiwear additives [1–12]. Studies have shown that the addition of nanoparticles to base stock lubricating oil can reduce friction and wear and have concluded that nanoparticles might be benefcial lubricant additives, even though some might be hard and could be abrasive [1, 2, 4–10]. Various hypotheses have been ofered about how nanoparticles reduce friction and wear. Tese include the ball-bearing or rolling efect [2], the formation and removal of layered-structure protective triboflms [3], penetration into the rubbing surfaces that, in turn, changes the material properties at the contact points between mating surfaces (the “mending efect”) [13], and the polishing efect [2]. Most of the evidence found in the open literature was collected from tests performed under laboratory conditions and may not indicate whether the benefts will occur under conditions experienced in an actual engine. For example, contact confgurations such as the ball-on-fat, pin-on-fat, four-ball, cylinder-on-fat, and block-on-ring have been used to evaluate oils containing nanoparticles. Te use of these test confgurations is widespread due to their simplicity, low cost, and the availability of standard samples. Most laboratory-scale test rigs are limited in their ability to simulate actual engine conditions. Useful information can be extracted as long as prototypical materials are used, and there is some agreement between loads, speeds, temperatures, contact pressures, and surface parameters. In this work, the efect on friction and wear of two nanoparticle oxides (TiO 2 and Al 2 O 3 ) dispersed in a lubricant was determined under laboratory test conditions using reciprocating motion and two test confgurations (52100 steel ball-on-52100 steel fat and PVD CrN ring-on-gray cast iron liner) at speeds up to 5 Hz and temperature of 100 ∘ C. Te results indicate that the nanoparticle additives tested under ball-on-fat conditions can improve the friction and wear of a base stock oil but can have a detrimental efect on the tribological behavior of realistic materials under conditions that simulate an engine environment. More importantly, the results show that very diferent results are obtained for diferent contact confgura- tions. Hindawi Journal of Nanomaterials Volume 2017, Article ID 8425782, 12 pages https://doi.org/10.1155/2017/8425782