Insights into tribology from in situ nanoscale experiments

Jacobs, Tevis D. B.; Greiner, Christian; Wahl, Kathryn J.; Carpick, Robert W.

doi:10.1557/mrs.2019.122

Cited by 37 publications

(25 citation statements)

References 101 publications

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“…Piezo/triboelectric applications are also important energy applications for the transfer of kinetic energy into electricity, and the conversion of sea wave motions to electricity can be regarded as blue energy . In situ TEM has been reported to reveal the physics of piezoelectric phenomena, but one may expect more triboelectric experiments to be performed by in situ TEM in the nearest future …”

Section: Conclusion and Trendsmentioning

confidence: 99%

Recent Progress of In Situ Transmission Electron Microscopy for Energy Materials

et al. 2019

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replacing gasoline, diesel, or other types of fuels with electricity, it is expected that our world will become more environmentally friendly by storing energy directly from sustainable sources, such as solar, wind, geothermal, bioenergy, and the ocean. Even Australia, as a country with abundant energy resources, has identified energy as one of the key scientific research priorities. It is clear that the efficiency of energy harvesting and consumption must be improved, emissions must be reduced, and the integration of various energy sources into the electricity grid and chemical storage must be implemented. A desirable outlook is one with a variety of energy sources and mechanisms that significantly reduces carbon emissions and is economical for consumers and society. Recent fast-growing research should boost the development of reliable, highly efficient, low-cost, and sustainable energy materials that are effective for new technologies and that satisfy the growing demand for energy storage and climate change solutions.The progress in energy materials is indeed significant, however, as the expectations of energy materials research are always quite high, it is not sufficient. Particularly, the material performances are always theoretically predicted but are limited by the underlying mechanisms in real applications. As a wellknown example, silicon is expected to deliver a high theoretical capacity of 4200 mAh g −1 in the form of Li 4.4 Si, and is thought to replace the currently commercial graphite with a capacity of 372 mAh g −1 . However, in real applications, it is found that Si exhibits more than 360% of volume expansion during lithiation, which leads to battery anode failure. In the last few years, TEM, especially in situ TEM, has provided exceptional advantages in investigating the lithiation process of silicon anodes: direct imaging, full crystallography information, and real-time recording have all become possible. By directly observing the charge/discharge processes of Si anodes, the dynamics of expansion have been well understood. The research has then been focused on structural designs of composites containing Si to overcome the expansion. The Si composites (for instance, carbon-wrapped Si nanoparticles with different sizes) were directly analyzed by in situ TEM to determine the best structural design. [12] From 2012, in situ TEM became an essential tool to review and evaluate structural designs for high-capacity anodes with significant volume expansions. The same scenarios apply to similar research topics. In situ transmission electron microscopy (TEM) is one of the most powerfulapproaches for revealing physical and chemical process dynamics at atomic resolutions. The most recent developments for in situ TEM techniques are summarized; in particular, how they enable visualization of various events, measure properties, and solve problems in the field of energy by revealing detailed mechanisms at the nanoscale. Related applications include rechargeable batteries such as Li-ion, Na-ion, Li-O 2 , Na-O 2 , Li...

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Section: Conclusion and Trendsmentioning

confidence: 99%

Recent Progress of In Situ Transmission Electron Microscopy for Energy Materials

et al. 2019

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“…Insights into nanotribology from in situ experiments have enabled identification of physical processes occurring at and below a wear surface. In their article in this issue, Jacobs et al 31 describe key advances in in situ nanotribology that have enabled direct observations of processes in the sliding contact, including tribochemistry and subsurface deformation. For example, in situ TEM nanotribology has revealed a number of material transformations in layered materials typically used as lubricants such as MoS 2 32 and graphite.…”

Section: Nanotribologymentioning

confidence: 99%

“…Subsurface dislocation processes in metal contacts during in situ nanotribology demonstrate the impact of in situ testing, and surface adhesion phenomena are readily observed with in situ TEM. As Jacobs et al 31 discuss, breakthroughs in in situ nanotribological characterization have the potential to impact a wide array of applications and technologies.…”

Section: Nanotribologymentioning

confidence: 99%

Advances in in situ nanomechanical testing

Minor

Dehm

2019

MRS Bull.

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“…17 Gosvami et al 29 suggested that wear became significant above 5 GPa in their experiments, but it is quite likely that some of the tribofilm is removed by the hard AFM tip during the early stages of tribofilm formation (where the film is less durable 22 ) even at lower pressures. Although AFM experiments allow topographic images to be obtained frequently during the tribofilm growth process, 28 direct asperity contact may remove some material even within a single scanning cycle. If the tribofilm is being both formed and partially removed during the rubbing process, this clearly complicates any subsequent kinetic analysis.…”

Section: Introductionmentioning

confidence: 99%

Mechanochemistry of Zinc Dialkyldithiophosphate on Steel Surfaces under Elastohydrodynamic Lubrication Conditions

Zhang

Ewen

Ueda

et al. 2020

ACS Appl. Mater. Interfaces

172

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Zinc dialkyldithiophosphate (ZDDP) is added to engine lubricants to reduce wear and ensure reliable operation. ZDDP reacts under rubbing conditions to form protective zinc/iron phosphate tribofilms on steel surfaces. Recently, it has been demonstrated that this process can be promoted by applied stresses in lubricated contacts, as well as temperature, and is thus mechanochemical in origin. In this study, a tribology test rig capable of applying very high loads has been developed to generate ZDDP tribofilms under full-film elastohydrodynamic lubrication (EHL) conditions in steel/steel ball-on-disk contacts. This provides a well-defined temperature and stress environment with negligible direct asperity contact in which to study mechanochemical processes. ZDDPs with branched primary and secondary alkyl substituents have been studied in three base oils, two with high EHL friction and one with low EHL friction. In the high EHL friction base oils, the tribofilm growth rate increases exponentially with shear stress and temperature for both ZDDPs, as predicted by a stress augmented thermal activation model. Conversely, under otherwise identical conditions, negligible ZDDP tribofilm formation takes place in the low EHL friction base oil. This confirms that the ZDDP reaction is driven by macroscopic shear stress rather than hydrostatic pressure. The secondary ZDDP forms tribofilms considerably faster than the primary ZDDP under equivalent conditions, suggesting that the initial decomposition reaction is the rate determining step for tribofilm formation. The rate of tribofilm growth is independent of ZDDP concentration over the range studied, indicating that this process follows zero-order kinetics. Under full-film EHL conditions, ZDDP tribofilm formation is promoted by macroscopic shear stress applied through the base oil molecules, which induces asymmetric stress on adsorbed ZDDP molecules to promote their decomposition and initiate rapid phosphate polymerisation.

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Insights into tribology from in situ nanoscale experiments

Abstract: Abstract

Cited by 37 publications

References 101 publications

Recent Progress of In Situ Transmission Electron Microscopy for Energy Materials

Recent Progress of In Situ Transmission Electron Microscopy for Energy Materials

Advances in in situ nanomechanical testing

Mechanochemistry of Zinc Dialkyldithiophosphate on Steel Surfaces under Elastohydrodynamic Lubrication Conditions

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