Carmichael’s Concise Review


Coming Events 2015


SMMS 2015: Single-Molecule Microscopy


and Spectroscopy September 14–16, 2015 London, UK


www.rsc.org/conferencesandevents/rscconferences/fd/ molecule-fd2015/index.asp


SPIE Scanning Microscopies September 29–October 1, 2015 Monterey, CA


http://spie.org/x104030.xml North American Molecular Beam


Conference (NAMBE 2015) October 4–7, 2015 Mayan Riviera, Mexico


www2.avs.org/conferences/nambe/2015/index.htm


Materials Science & Technology 2015 October 4–8, 2015 Columbus OH http://matscitech.org


Neuroscience 2015 October 17–21, 2015 Chicago, IL


Sponsor: Society for Neuroscience www.sfn.org


American Vacuum Society October 18–23, 2015 San Jose, CA


www.avs.org/symposium


Frontiers in Light Microscopy Symposium November 17, 2015


National Institutes of Health, Bethesda, MD https://ncifrederick.cancer.gov/events/ LightMicroscopy


2015 MRS Fall Meeting & Exhibition November 29–December 4, 2015 Boston, MA


Sponsor: Materials Research Society (MRS) www.mrs.org/fall2015


American Society for Cell Biology (ASCB)


2015 Annual Meeting December 12–16, 2015 San Diego, CA


http://ascb.org/future-ascb-annual-meetings 2016


Microscopy & Microanalysis 2016 July 24–28, 2016 Columbus, OH www.microscopy.org


2017


Microscopy & Microanalysis 2017 July 23–27, 2017 St. Louis, MO


www.microscopy.org 2018


Microscopy & Microanalysis 2018 August 5–9, 2018 Baltimore, MD www.microscopy.org


2019


Microscopy & Microanalysis 2019 August 4–8, 2019 Portland, OR


www.microscopy.org 2020


Microscopy & Microanalysis 2020 August 2–6, 2020 Milwaukee, WI www.microscopy.org


More Meetings and Courses Check the complete calendar near the back of this magazine.


8


Figure 1 : Periodically acquired 2 µm × 2 µm AFM images of an iron oxide surface using a DLC-coated silicon AFM tip (single-asperity) immersed in ZDDP containing base stock, acquired at a non-perturbative load of 20.0 ± 0.1 nN. The central 1 µm × 1 µm regions were scanned at a signifi cantly higher load of 340 ± 2 nN (4.2 ± 0.5 GPa). The images demonstrate progressive tribofi lm growth where the higher load was applied.


doi: 10.1017/S1551929515000772 2015 September


Additives are used in lubricant oils for many important applications such as internal combustion engines and other machine components with moving parts. Among other things, these additives are crucial for improving the lubricant’s ability to reduce friction and wear. A widely used additive is zinc dialkyldithiophosphate (ZDDP), which is one of the most successful anti-wear additives. However, due to the presence of P, S, and Zn, ZDDP has the disadvantage of degrading catalytic converters in automobiles. It is known that ZDDP acts by forming a thin, solid layer called a “tribofi lm” that grows at the interface of the sliding surfaces in contact with each other in the engine, and so it prevents direct metal-to-metal contact. T is reduces wear dramatically. In spite of the fact that ZDDP has been used and studied for decades, the mechanisms governing tribofi lm growth are not well understood, and this limits development of alternative lubricants that won’t harm catalytic converters. T is could all be changed by a recent study by Nitya Nand Gosvami, Jason Bares, Filippo Mangolini, Andrew Konicek, Dalia Yablon, and Robert Carpick [ 1 ]. Using atomic force microscopy (AFM), they monitored the growth and properties of ZDDP-derived tribofi lms under conditions simulating the normal use of these lubricant additives.


It is known that ZDDP forms patchy films with pad-like features during the sliding process, but the mechanism behind the observation that they form a graded structure (with the composition changing with height) and stop growing at a certain thickness has been a mystery. On microscopic length scales, engineering surfaces are made of asperities, which resemble mountain peaks. So far, only macroscopic multi-asperity contacts had been analyzed, and most of the studies


Stephen W. Carmichael Mayo Clinic , Rochester , MN 55905 carmichael.stephen@mayo.edu


AFM Solves the Mystery of the Slippery Slope


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