Tag Archives: materials science

Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys

Although catalysis is a popular explanation for tribopolymer generation, the interplay of catalysis, mechanochemistry, and electrostatic interactions remain incompletely understood. There is consensus, however, that the mechanisms for forming a frictional polymer in situ require at least three conditions: the presence of organics, a catalytically-active substrate, and shear between surfaces (i.e., sliding contacts). *

The formation of these highly lubricious tribofilms at low temperature from ambient hydrocarbon species is novel and of significant practical interest, given the simple requirements to activate the process. *

In their article “Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys” Morgan R. Jones, Frank W. DelRio, Thomas E. Beechem, Anthony E. McDonald, Tomas F. Babuska, Michael T. Dugger, Michael Chandross, Nicolas Argibay and John F. Curry describe how low shear strength (30 MPa) organic films were grown in situ on Pt0.9Au0.1 surfaces via cyclic sliding contact in dry N2 with trace concentrations of ambient hydrocarbons. *

The nanocrystalline Pt0.9Au0.1 alloy (also termed a Pt-Au thin film in the article) used in their study is likely catalytically-active while exhibiting high hardness (~ 7 GPa) and exceptional wear resistance. *

They then continue to present a systematic investigation of the stress- and time-dependent film formation. *

Atomic force microscopy (AFM) was used to study the formation and growth of films at the nanoscale. *

The authors’ AFM experiments confirm the increase in surface coverage (volume) with pressure, but also highlight a transition from film growth to wear at a threshold contact pressure near 1.2 GPa. *

With time-dependent AFM experiments they demonstrate a sublinear increase in film volume with time, suggesting that the efficacy of the catalytic process decreased as the number of cycles increased. *

NANOSENSORS Diamond Coated PointProbe® Plus AFM probes of the DT-CONTR type were used for the nanoscale tribology experiments with Atomic Force Microscopy. *

Figure 5 from Morgan R. Jones et al. Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys: Tribofilm formation as a function of number of cycles as determined from the nanoscale experiments. (a) Intermittent-contact mode topography images (3 µm × 3 µm area) of the contact region at a contact pressure of 1.2 GPa after 0 cycles, 500 cycles, 1000 cycles, 2000 cycles, 3000 cycles, and 4000 cycles. (b) Tribofilm volume as a function of cycles for contact pressures up to 3.1 GPa. For all P, tribofilm volume increased asymptotically to a steady-state value at large numbers of cycles. NANOSENSORS Diamond Coated PointProbe Plus AFM probes DT-CONTR were used for the nanoscale tribology with atomic force microscopy.
Figure 5 from Morgan R. Jones et al. Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys:
Tribofilm formation as a function of number of cycles as determined from the nanoscale experiments. (a) Intermittent-contact mode topography images (3 µm × 3 µm area) of the contact region at a contact pressure of 1.2 GPa after 0 cycles, 500 cycles, 1000 cycles, 2000 cycles, 3000 cycles, and 4000 cycles. (b) Tribofilm volume as a function of cycles for contact pressures up to 3.1 GPa. For all P, tribofilm volume increased asymptotically to a steady-state value at large numbers of cycles.

*Morgan R. Jones, Frank W. DelRio, Thomas E. Beechem, Anthony E. McDonald, Tomas F. Babuska, Michael T. Dugger, Michael Chandross, Nicolas Argibay and John F. Curry
Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys
JOM The Journal of The Minerals, Metals & Materials Society (TMS), 73, pages 3658–3667 (2021)
DOI: https://doi.org/10.1007/s11837-021-04809-5

Please follow this external link to read the full article: https://rdcu.be/cPDfl

Open Access: The article “Stress- and Time-Dependent Formation of Self-Lubricating In Situ Carbon (SLIC) Films on Catalytically-Active Noble Alloys” by Morgan R. Jones, Frank W. DelRio, Thomas E. Beechem, Anthony E. McDonald, Tomas F. Babuska, Michael T. Dugger, Michael Chandross, Nicolas Argibay and John F. Curry is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Temperature effects on the nano-friction across exposed atomic step edges

In the article “Temperature effects on the nano-friction across exposed atomic step edges” Wen Wang, Ashu Wang and Lingyan Zeng describe how they used friction force microscopy ( FFM ) under ultrahigh vacuum ( UHV) conditions to study the temperature dependence of nanoscale friction between a silicon AFM tip ( NANOSENSORS™ PointProbe® Plus PPP-LFMR AFM probe for lateral/friction force microscopy ) and a freshly cleaved HOPG surface with exposed single- and double-layer step edges.*

They present experimental measurements as well as theoretical calculations of the temperature effects on atomic friction across HOPG surface step edges.*

Among other things the authors found that the resistive force for the double-layer step edge was twice as large as that of the single-step edge, and simultaneously, the assistive force that resulted from the horizontal component of the total force acting on the AFM tip seemed to be less influenced by the height of the step edges.*

Their experimental results also showed that temperature had very little effect on the friction coefficients at the step edges, which is inconsistent with the thermal activated friction where friction should decrease with temperature.*

Based on the theoretical studies, this observation can be explained by a process where the temperature effect is very small compared with the edge Schwoebel–Ehrlich barrier.*

The authors hope that their findings will contribute to understanding the temperature effects on macroscopic friction having a lot of step edges at the interface.*

Figure 1 from “Temperature effects on the nano-friction across exposed atomic step edges” by Wen Wang et al.:
 Experimental setup and the topographic image of the HOPG surface with step edges used in our measurements. (a) Illustration of the experimental setup. All experiments have been performed using a conventional friction force microscope on a freshly cleaved HOPG sample which was in contact with the temperature control stage under UHV conditions. (b) The typical topographic image of the HOPG surface with a single- and double-layer step edge obtained at T = 297.7 K using the contact mode operation with an applied normal force of 13.1 nN and a scan velocity of 1.25 μm/s. (c) The cross-section height profile across the step edges highlighted in (b). The black arrows in (b) and (c) indicate the scanning direction.  NANOSENSORS PointProbe Plus PPP-LFMR AFM probes for lateral force microscopy and friction force microscopy were used.
Figure 1 from “Temperature effects on the nano-friction across exposed atomic step edges” by Wen Wang et al.:
 Experimental setup and the topographic image of the HOPG surface with step edges used in our measurements. (a) Illustration of the experimental setup. All experiments have been performed using a conventional friction force microscope on a freshly cleaved HOPG sample which was in contact with the temperature control stage under UHV conditions. (b) The typical topographic image of the HOPG surface with a single- and double-layer step edge obtained at T = 297.7 K using the contact mode operation with an applied normal force of 13.1 nN and a scan velocity of 1.25 μm/s. (c) The cross-section height profile across the step edges highlighted in (b). The black arrows in (b) and (c) indicate the scanning direction.

*Wen Wang, Ashu Wang and Lingyan Zeng
Temperature effects on the nano-friction across exposed atomic step edges
AIP Advances 10, 085322 (2020)
DOI: https://doi.org/10.1063/5.0019196

Please follow this external link to read the full article: https://aip.scitation.org/doi/10.1063/5.0019196

Open Access The article “Temperature effects on the nano-friction across exposed atomic step edges” by Wen Wang, Ashu Wang and Lingyan Zeng is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes

Solid state electrolytes (SSEs) are interesting materials that could potentially replace the currently used organic electrolytes in lithium‐ion batteries (LIBs). *

Electrochemical strain microscopy (ESM), a research technique based on atomic force microscopy (AFM), was developed to locally probe ion movement in electrodes based on electro-chemo-mechanical coupling measure through the AFM cantilever deflection. It can be used to characterize Li-ion mobility in energy materials with extremely high spatial resolution. *

The main challenge with ESM is its nonquantitative nature due to complex AFM cantilever dynamics in contact mode when performed on resonance as well as signal contribution that are not necessarily related to ions such as electrostatic forces.*

In the article “ Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes “ Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke and Florian Hausen investigate the exact signal formation process of electrochemical strain microscopy (ESM) when it is applied on sodium super ionic conductor (NASCIO)-type solid state electrolytes containing Na- and Li-ions.*

In their research the authors correlatively use various scanning probe microscopy (SPM) based microscopy techniques together with scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy ( EDX ) at identical positions of the solid state electrolyte LATP.*

They find that changes in the dielectric properties are responsible for the detected contrast in the deflection of the AFM cantilever instead of a physical volume change as a result of Vegard’s Law. The AFM cantilever response is strongly reduced in areas of high sodium content which is attributed to a reduction of the AFM tip-sample capacitance in comparison with areas with high lithium content.*

This is the first time a direct link between electrostatic forces in contact mode and local chemical information is demonstrated on SSEs. The results presented in the article open up the possibility to learn more since dielectric properties are sensitive to subtle changes in local chemical composition.*

NANOSENSORS conductive Platinum-Iridium coated PointProbe® Plus PPP-EFM AFM probes were primarily used in the research for this article.

Figure 1 from Nino Schön et al. «Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes”:
a) Topography, b) deflection error, and c) corresponding cantilever deflection change (Dac) map of a 30 µm × 30 µm area of LATP. d) Noncontact EFM amplitude map in the same area.
NANOSENSORS conductive platinum-iridium coated PointProbe Plus PPP-EFM AFM probes were used.
Figure 1 from Nino Schön et al. «Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes”:
a) Topography, b) deflection error, and c) corresponding cantilever deflection change (Dac) map of a 30 µm × 30 µm area of LATP. d) Noncontact EFM amplitude map in the same area.

*Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke, Florian Hausen
Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes
Small Methods, Early View, Online Version of Record before inclusion in an issue 2001279
DOI: https://doi.org/10.1002/smtd.202001279

Please follow this external link to read the full article: https://onlinelibrary.wiley.com/doi/10.1002/smtd.202001279

Open Access The article “Signal Origin of Electrochemical Strain Microscopy and Link to Local Chemical Distribution in Solid State Electrolytes” by Nino Schön, Roland Schierholz, Stephen Jesse, Shicheng Yu, Rüdiger‐A. Eichel, Nina Balke, Florian Hausen is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.