Nanoscale Friction

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 3999 Experts worldwide ranked by ideXlab platform

Bharat Bhushan - One of the best experts on this subject based on the ideXlab platform.

  • Friction model for the velocity dependence of Nanoscale Friction
    Nanotechnology, 2005
    Co-Authors: Nikhil Subhashchandra Tambe, Bharat Bhushan
    Abstract:

    The velocity dependence of Nanoscale Friction is studied for the first time over a wide range of velocities between 1 microm s(-1) and 10 mm s(-1) on large scan lengths of 2 and 25 microm. High sliding velocities are achieved by modifying an existing commercial atomic force microscope (AFM) setup with a custom calibrated nanopositioning piezo stage. The Friction and adhesive force dependences on velocity are studied on four different sample surfaces, namely dry (unlubricated), hydrophilic Si(100); dry, partially hydrophobic diamond-like carbon (DLC); a partially hydrophobic self-assembled monolayer (SAM) of hexadecanethiol (HDT); and liquid perfluoropolyether lubricant, Z-15. The Friction force values are seen to reverse beyond a certain critical velocity for all the sample surfaces studied. A comprehensive Friction model is developed to explain the velocity dependence of Nanoscale Friction, taking into consideration the contributions of adhesion at the tip-sample interface, high impact velocity-related deformation at the contacting asperities and atomic scale stick-slip. A molecular spring model is used for explaining the velocity dependence of Friction force for HDT.

  • a new atomic force microscopy based technique for studying Nanoscale Friction at high sliding velocities
    Journal of Physics D, 2005
    Co-Authors: Nikhil Subhashchandra Tambe, Bharat Bhushan
    Abstract:

    Tribological studies on the micro/Nanoscale conducted using an atomic force microscope (AFM) have been limited to low sliding velocities (< 250 µm s−1) due to inherent instrument limitations. Studies of tribological properties of materials, coatings and lubricants that find applications in micro/nanoelectromechanical systems and magnetic head-media in magnetic storage devices that operate at high sliding velocities have thus been rendered inadequate. We have developed a new technique to study nanotribological properties at high sliding velocities (up to 10 mm s−1) by modifying the commercial AFM set-up. A custom calibrated nanopositioning piezo stage is used for mounting samples and scanning is achieved by providing a triangular input voltage pulse. A capacitive sensor feedback control system is employed to ensure a constant velocity profile during scanning. Friction data are obtained by processing the AFM laser photo-diode signals using a high sampling rate data acquisition card. The utility of the modified set-up for Nanoscale Friction studies at high sliding velocities is demonstrated using results obtained from various tests performed to study the effect of scan size, rest time, acceleration and velocity on the Frictional force for single crystal silicon (100) with native oxide.

  • Nanoscale Friction-induced phase transformation of diamond-like carbon
    Scripta Materialia, 2005
    Co-Authors: Nikhil Subhashchandra Tambe, Bharat Bhushan
    Abstract:

    Abstract Tribological behavior of diamond-like carbon (DLC) is believed to be controlled by an interfacial transfer layer of low shear strength, formed by a Friction-induced transformation of the top layer of the DLC film. Nanoscale Friction, adhesion, durability and wear studies indicating such a phase transformation in DLC films are discussed.

  • fundamentals of tribology and bridging the gap between the macro and micro Nanoscales
    2001
    Co-Authors: Bharat Bhushan
    Abstract:

    Preface. Group Photo. Author Index. Subject Index. Participants list. 1: History. History of Tribology and Its Industrial Significance K. Ludema. 2: Adhesion and Friction. Friction, Wear, Lubrication, and Materials Characterization Using Scanning Probe Microscopy B. Bhushan. Atomic Scale Origin of Adhesion and Friction: Viscoelastic Effects in Model Lubricant Monolayers M. Salmeron, et al. Atomic-Scale Stick Slip R. Bennewitz, et al. Dissipation Mechanisms Studied by Dynamic Force Microscopies E. Meyer, et al. Frictional-Force Imaging and Friction Mechanisms with a Lattice Periodicity S. Morita, et al. Atomic Scale Origins of Force Interaction S. Morita, et al. Dynamic Friction Measurement with the Scanning Force Microscope O. Marti, H.-U. Krotil. Towards the Ideal Nano-Friction Experiment J.W.M. Frenken, et al. Investigation of the Mechanics of Nanocontacts Using a Vibrating Cantilever Technique U.D. Schwarz, et al. A Scanning Probe and Quartz Crystal Microbalance Study of C60 on Mica and Silver(111) Surfaces T. Coffey, et al. Interactions, Friction and Lubrication Between Polymer-Bearing Surfaces J. Klein. Effect of Electrostatic Interactions on Frictional Forces in Electrolytes L.I. Daikhin, M. Urbakh. Adsorption of Thin Liquid Films on Solid Surfaces and its Relevance J. Colchero, et al. Theory and Simulations of Friction Between Flat Surfaces Lubricated by Submonolayers M.H. Muser. Friction Mechanisms and Modeling on the Macroscale P.J. Blau. Experimental Aspects of Friction Research on the Macroscale P.J. Blau. The Anisotropic Friction Characteristics of Crystalline Materials: A Review B.L. Weick, B. Bushan. Relationship Between Structure and Internal Friction inCoPt and FePd Alloys E. Klugmann. Direct Measurement of Surface and Interfacial Energies of Glassy Polymers and PDMS L. Li, et al. A Model for Adhesive Forces in Miniature Systems A.A. Polycarpou, A. Suh. Simple Model for Low Friction Systems M. D'Acunto. Ultra-Low Friction Between Water Droplet and Hydrophobic Surface K. Hiratsuka, et al.AFM as a New Tool in Characterisation of Mesoporous Ceramics as Materials to Tribological Applications I. Piwonski, J. Grobelby. Discussion Forum Report: Bridging the Gap Between Macro- and Micro/Nanoscale Adhesion and Friction M. Tirrell, E. Meyer. 3: Wear. Modeling (and) Wear Mechanisms K. Ludema. Surface Damage Under Reciprocating Sliding S. Fouvry, Ph. Kapsa. Wear Particle Life in a Sliding Contact Under Dry Conditions: Third Body Approach J. Denape, et al. Fretting Wear Behaviour of a Titanium Alloy V. Fridrici, et al. Wear Measurements and Monitoring at Macro- and- Microlevel N.K. Myshkin, et al. Slurry Erosion: Macro- and Micro-Aspects H.McI. Clark. Macro- and Micro Kelvin Probe in Tribological Studies A.L. Zharin. Thermomechanics of Sliding Contact: When Micro Meets Macro A. Soom, et al. Nanostructuring of Calcite Surfaces by Tribomechanical Etching with the Tip of an Atomic Force Microscope M. Muller, et al. Atomic-Scale Processes of Tribomechanical Etching Studied by Atomic Force Microscopy on the Layered Material NbSe2 R. Kemnitzer, et al. Determining the Nanoscale Friction and Wear Behavior of Si, SiC and Diamond by Microscale Environmental Tribology M.N. Gardos. On Some Similarities of Structural Modification in Wear and Fatigue L. Palaghian, et al. The Mesostructure of Surfac

  • fundamentals of tribology and bridging the gap between the macro and micro Nanoscales
    2001
    Co-Authors: Bharat Bhushan
    Abstract:

    Preface. Group Photo. Author Index. Subject Index. Participants list. 1: History. History of Tribology and Its Industrial Significance K. Ludema. 2: Adhesion and Friction. Friction, Wear, Lubrication, and Materials Characterization Using Scanning Probe Microscopy B. Bhushan. Atomic Scale Origin of Adhesion and Friction: Viscoelastic Effects in Model Lubricant Monolayers M. Salmeron, et al. Atomic-Scale Stick Slip R. Bennewitz, et al. Dissipation Mechanisms Studied by Dynamic Force Microscopies E. Meyer, et al. Frictional-Force Imaging and Friction Mechanisms with a Lattice Periodicity S. Morita, et al. Atomic Scale Origins of Force Interaction S. Morita, et al. Dynamic Friction Measurement with the Scanning Force Microscope O. Marti, H.-U. Krotil. Towards the Ideal Nano-Friction Experiment J.W.M. Frenken, et al. Investigation of the Mechanics of Nanocontacts Using a Vibrating Cantilever Technique U.D. Schwarz, et al. A Scanning Probe and Quartz Crystal Microbalance Study of C60 on Mica and Silver(111) Surfaces T. Coffey, et al. Interactions, Friction and Lubrication Between Polymer-Bearing Surfaces J. Klein. Effect of Electrostatic Interactions on Frictional Forces in Electrolytes L.I. Daikhin, M. Urbakh. Adsorption of Thin Liquid Films on Solid Surfaces and its Relevance J. Colchero, et al. Theory and Simulations of Friction Between Flat Surfaces Lubricated by Submonolayers M.H. Muser. Friction Mechanisms and Modeling on the Macroscale P.J. Blau. Experimental Aspects of Friction Research on the Macroscale P.J. Blau. The Anisotropic Friction Characteristics of Crystalline Materials: A Review B.L. Weick, B. Bushan. Relationship Between Structure and Internal Friction inCoPt and FePd Alloys E. Klugmann. Direct Measurement of Surface and Interfacial Energies of Glassy Polymers and PDMS L. Li, et al. A Model for Adhesive Forces in Miniature Systems A.A. Polycarpou, A. Suh. Simple Model for Low Friction Systems M. D'Acunto. Ultra-Low Friction Between Water Droplet and Hydrophobic Surface K. Hiratsuka, et al.AFM as a New Tool in Characterisation of Mesoporous Ceramics as Materials to Tribological Applications I. Piwonski, J. Grobelby. Discussion Forum Report: Bridging the Gap Between Macro- and Micro/Nanoscale Adhesion and Friction M. Tirrell, E. Meyer. 3: Wear. Modeling (and) Wear Mechanisms K. Ludema. Surface Damage Under Reciprocating Sliding S. Fouvry, Ph. Kapsa. Wear Particle Life in a Sliding Contact Under Dry Conditions: Third Body Approach J. Denape, et al. Fretting Wear Behaviour of a Titanium Alloy V. Fridrici, et al. Wear Measurements and Monitoring at Macro- and- Microlevel N.K. Myshkin, et al. Slurry Erosion: Macro- and Micro-Aspects H.McI. Clark. Macro- and Micro Kelvin Probe in Tribological Studies A.L. Zharin. Thermomechanics of Sliding Contact: When Micro Meets Macro A. Soom, et al. Nanostructuring of Calcite Surfaces by Tribomechanical Etching with the Tip of an Atomic Force Microscope M. Muller, et al. Atomic-Scale Processes of Tribomechanical Etching Studied by Atomic Force Microscopy on the Layered Material NbSe2 R. Kemnitzer, et al. Determining the Nanoscale Friction and Wear Behavior of Si, SiC and Diamond by Microscale Environmental Tribology M.N. Gardos. On Some Similarities of Structural Modification in Wear and Fatigue L. Palaghian, et al. The Mesostructure of Surfac

Sriram Sundararajan - One of the best experts on this subject based on the ideXlab platform.

  • Nanoscale Friction switches Friction modulation of monomolecular assemblies using external electric fields
    Langmuir, 2009
    Co-Authors: K Kanaga S Karuppiah, Yibo Zhou, Keith L Woo, Sriram Sundararajan
    Abstract:

    This paper presents experimental investigations to actively modulate the Nanoscale Friction properties of a self-assembled monolayer (SAM) assembly using an external electric field that drives conformational changes in the SAM. Such "Friction switches" have widespread implications in interfacial energy control in micro/Nanoscale devices. Friction response of a low-density mercaptocarboxylic acid SAM is evaluated using an atomic force microscope (AFM) in the presence of a DC bias applied between the sample and the AFM probe under a nitrogen (dry) environment. The low density allows reorientation of individual SAM molecules to accommodate the attractive force between the -COOH terminal group and a positively biased surface. This enables the surface to present a hydrophilic group or a hydrophobic backbone to the contacting AFM probe depending upon the direction of the field (bias). Synthesis and deposition of the low-density SAM (LD-SAM) is reported. Results from AFM experiments show an increased Friction response (up to 300%) of the LD-SAM system in the presence of a positive bias compared to the Friction response in the presence of a negative bias. The difference in the Friction response is attributed to the change in the structural and crystalline order of the film in addition to the interfacial surface chemistry and composition presented upon application of the bias.

  • the effect of anisotropic wet etching on the surface roughness parameters and micro Nanoscale Friction behavior of si 1 0 0 surfaces
    Sensors and Actuators A-physical, 2005
    Co-Authors: S Chandrasekaran, Sriram Sundararajan, J Check, Pranav Shrotriya
    Abstract:

    Abstract Etching processes can affect the surface roughness and hence the tribological properties of silicon surfaces. In this paper, we evaluate the surface roughness parameters and micro/Nanoscale Friction behavior of Si(1 0 0) surfaces etched using 8 M KOH and tetramethyl ammonium hydroxide (TMAH) solution with and without isopropyl alcohol (IPA) additive. Amplitude and spatial parameters were evaluated using atomic force microscopy (AFM) and profilometry at scan sizes ranging from 1 to 500 μm. Results showed that TMAH and KOH produced comparable roughness up to 5 μm scan size and that at larger scan sizes, TMAH produced rougher surfaces than KOH. The use of IPA additive caused enhancement of sub-micron roughness features as well as a reduction in the long-range roughness of the surfaces resulting in smoother surfaces than the pure etchants. All etched surfaces exhibited pit like features with TMAH producing slightly larger pits than KOH. Surface roughness evolution spectroscopy (SRES) showed that using IPA resulted in an increase in the maximum pit size. Single asperity Friction behavior correlated well with the adhesive forces for the various surfaces—KOH and TMAH showed comparable behavior and the use of IPA resulted in lower Friction forces. However the use of IPA resulted in surfaces with higher real area of contact, which was responsible for higher Friction forces in multiple asperity contacts on the microscale. This study demonstrates that the choice of etchants and additives affect the surface roughness and microscale Friction behavior of the resulting surfaces.

  • micro Nanoscale Friction and wear mechanisms of thin films using atomic force and Friction force microscopy
    Acta Materialia, 1998
    Co-Authors: Bharat Bhushan, Sriram Sundararajan
    Abstract:

    Abstract Atomic force microscopy/Friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales ranging from atomic and molecular to microscales. At most solid–solid interfaces of technological relevance, contact occurs at numerous asperities; a sharp AFM/FFM tip sliding on a surface simulates just one such contact. However, asperities come in all shapes and sizes. To study the effect of tip radius, experiments are conducted using an AFM tip with radii ranging from about 50 nm to 14.5 μm. The effect of the radius on adhesive forces and coefficient of Friction at different relative humidities is measured. It is found that adhesive forces at low humidities do not change with tip radius whereas these increase with tip radius at high humidities. Coefficient of Friction increases with the tip radius at all humidities. Samples coated with perfluoropolyether lubricant, which are hydrophobic in nature, are less sensitive to the environment and the tip radius. It appears that hydrophobicity of liquid films can be studied using large radii tips. Another objective of this study is to understand material removal mechanisms on microscale. Silicon surfaces are micromachined using a sharp diamond tip in an AFM. It is found that wear rate as well as the coefficient of Friction is negligible up to a certain load and these increase rapidly above this load. The critical load corresponds to the local hardness of the silicon implying that the wear rate is negligible and the coefficient of Friction is very low if the deformation is primarily elastic. The range of scanning velocity used in this study has little effect on the wear rate. SEM studies show that at light loads used in AFM, material is removed by ploughing and fine particulate debris is observed. At higher loads, cutting type including ribbon-like debris is observed. SEM and TEM studies of the wear region suggest that the material is removed in a brittle manner or chipping without major dislocation activity and crack formation. Evolution of wear of thin films also has been studied. Wear is found to be initiated at nano-scratches. These fundamental studies have provided insight to molecular origins of Friction and wear mechanisms.

Izabela Szlufarska - One of the best experts on this subject based on the ideXlab platform.

  • Friction laws at the Nanoscale
    Nature, 2009
    Co-Authors: Yifei Mo, Kevin T Turner, Izabela Szlufarska
    Abstract:

    For large objects sliding over one another, the Friction force is proportional to the true contact area between the two bodies — which is smaller than the apparent contact area because the surfaces are rough, consisting of a large number of smaller features (asperities) that actually make the contact. The situation for nanomaterials, however, has been unclear, since the continuum contact theory that can account for macroscale effects has been predicted to break down at the Nanoscale. Using large-scale molecular dynamics simulations of scanning force microscopy experiments, Yifei Mo et al. show that, despite this, simple Friction laws do apply at the Nanoscale: the Friction force depends linearly on the number of atoms, rather than the number of asperities, that are chemically interacting across the sliding interfaces. For large objects sliding over one another, the Friction force is proportional to the true contact area between the two bodies — this is smaller than the apparent contact area as the surfaces are rough, consisting of a large number of smaller features (asperities) that actually make contact. Here a related idea holds for contacts at the Nanoscale: the Friction force depends linearly on the number of atoms (rather than asperities) chemically interacting across the sliding interfaces. Macroscopic laws of Friction do not generally apply to Nanoscale contacts. Although continuum mechanics models have been predicted to break down at the Nanoscale1, they continue to be applied for lack of a better theory. An understanding of how Friction force depends on applied load and contact area at these scales is essential for the design of miniaturized devices with optimal mechanical performance2,3. Here we use large-scale molecular dynamics simulations with realistic force fields to establish Friction laws in dry Nanoscale contacts. We show that Friction force depends linearly on the number of atoms that chemically interact across the contact. By defining the contact area as being proportional to this number of interacting atoms, we show that the macroscopically observed linear relationship between Friction force and contact area can be extended to the Nanoscale. Our model predicts that as the adhesion between the contacting surfaces is reduced, a transition takes place from nonlinear to linear dependence of Friction force on load. This transition is consistent with the results of several Nanoscale Friction experiments4,5,6,7. We demonstrate that the breakdown of continuum mechanics can be understood as a result of the rough (multi-asperity) nature of the contact, and show that roughness theories8,9,10 of Friction can be applied at the Nanoscale.

  • Friction laws at the Nanoscale
    Nature, 2009
    Co-Authors: Kevin T Turner, Izabela Szlufarska
    Abstract:

    Macroscopic laws of Friction do not generally apply to Nanoscale contacts. Although continuum mechanics models have been predicted to break down at the Nanoscale, they continue to be applied for lack of a better theory. An understanding of how Friction force depends on applied load and contact area at these scales is essential for the design of miniaturized devices with optimal mechanical performance. Here we use large-scale molecular dynamics simulations with realistic force fields to establish Friction laws in dry Nanoscale contacts. We show that Friction force depends linearly on the number of atoms that chemically interact across the contact. By defining the contact area as being proportional to this number of interacting atoms, we show that the macroscopically observed linear relationship between Friction force and contact area can be extended to the Nanoscale. Our model predicts that as the adhesion between the contacting surfaces is reduced, a transition takes place from nonlinear to linear dependence of Friction force on load. This transition is consistent with the results of several Nanoscale Friction experiments. We demonstrate that the breakdown of continuum mechanics can be understood as a result of the rough (multi-asperity) nature of the contact, and show that roughness theories of Friction can be applied at the Nanoscale.

Nicholas D. Spencer - One of the best experts on this subject based on the ideXlab platform.

  • polymer brushes under shear molecular dynamics simulations compared to experiments
    Langmuir, 2015
    Co-Authors: Manjesh K Singh, Martin Kroger, Rosa M Espinosamarzal, Nicholas D. Spencer
    Abstract:

    Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (Friction) obtained via nonequilibrium MD is contrasted with Nanoscale Friction studies employing col...

  • Polymer Brushes under Shear: Molecular Dynamics Simulations Compared to Experiments
    2015
    Co-Authors: Manjesh K. Singh, Patrick Ilg, Rosa M. Espinosa-marzal, Martin Kröger, Nicholas D. Spencer
    Abstract:

    Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (Friction) obtained via nonequilibrium MD is contrasted with Nanoscale Friction studies employing colloidal-probe lateral force microscopy. We find good agreement in the hydrodynamic regime and explain the observed leveling-off of the Friction forces in the boundary regime by means of an effective polymer–wall attraction

Jeong Young Park - One of the best experts on this subject based on the ideXlab platform.

  • In-Situ Nanotribological Properties of Ultrananocrystalline Diamond Films Investigated with Ambient Pressure Atomic Force Microscopy
    'American Chemical Society (ACS)', 2021
    Co-Authors: Jae-eun Kim, Joong Il Jake Choi, Jeongjin Kim, Bongjin Simon Mun, Ki-jeong Kim, Jeong Young Park
    Abstract:

    © 2021 American Chemical Society.The relationship between Nanoscale Friction and the surrounding environment has long been a critical issue in the field of nanotribology. Here, we utilized ambient pressure-atomic force microscopy to investigate the effect of environmental gas on Nanoscale Friction of ultrananocrystalline diamond (UNCD) films. The Frictional forces were measured in an atomic force microscopy (AFM) chamber in the environmental range from an ultrahigh vacuum to near ambient pressure in the presence of oxygen, nitrogen, and water. We observed that Friction increased with the pressure of the oxygen responsible for the oxidation of the surface of the UNCD, while that in nitrogen gas remained unchanged. Interestingly, Friction decreased in water, due to the tribochemical reaction caused by surface passivation. When two diamond materials come into contact under water conditions, the water molecules are dissociated because of normal pressure between the AFM tip and diamond surface, and the dissociative water molecule adsorption passivates the surfaces of the diamond-coated tip and UNCD, resulting in a reduction of Friction force. The chemical state of the UNCD surface in various environmental conditions was confirmed using near ambient pressure X-ray photoelectron spectroscopy. This result elucidates the role of vapor-phase oxygen and water in the tribological properties of carbon-based materials.11Nsciescopu

  • Nanoscale Friction on Confined Water Layers Intercalated between MoS2 Flakes and Silica
    2019
    Co-Authors: Hyunsoo Lee, Hochan Jeong, Joonki Suh, Won Hui Doh, Jaeyoon Baik, Hyun-joon Shin, Yong-hyun Kim, Jeong Young Park
    Abstract:

    Frictional energy dissipation at the interfaces of two-dimensional (2D) materials through the excitation and transfer processes of kinetic energy into the bulk can be easily influenced by an intercalated water film. An enhancement of Friction on water-intercalated graphene has been observed. Is this Frictional enhancement by confined water a general phenomenon? We address this issue by investigating the Frictional behavior of confined water layers intercalated between single-layer molybdenum disulfide (MoS2), synthesized using chemical vapor deposition, and a silica substrate. The icelike water was intercalated by exposure to high-humidity air. We found that the intercalated water molecules morphologically deform the 2D MoS2 sheet, forming distinct subdomains after the exposure to high humidity. We found that the adsorption of the icelike water layer between the MoS2 and the silica leads to Friction enhancement, compared with a pristine MoS2/silica sample, which is associated with additional phononic Friction energy dissipation at the solid–liquid interface, as indicated by the phonon distribution analysis from the empirical force-field calculations. Moreover, the atomic stick–slip behavior shows that the lattice orientation of the hydrophilic MoS2 affects water molecule diffusion at the interface of the MoS2/silica substrate. Chemical mapping of the water-intercalated MoS2 on silica using scanning photoelectron microscopy and vacuum annealing processes shows water intercalation without changing the intrinsic composition of the MoS2 on silica

  • Nanoscale Friction on Confined Water Layers Intercalated between MoS 2 Flakes and Silica
    AMER CHEMICAL SOC, 2019
    Co-Authors: Hyunsoo Lee, Hochan Jeong, Joonki Suh, Won Hui Doh, Jaeyoon Baik, Hyun-joon Shin, Yong-hyun Kim, Jeong Young Park
    Abstract:

    © 2019 American Chemical Society. Frictional energy dissipation at the interfaces of two-dimensional (2D) materials through the excitation and transfer processes of kinetic energy into the bulk can be easily influenced by an intercalated water film. An enhancement of Friction on water-intercalated graphene has been observed. Is this Frictional enhancement by confined water a general phenomenon? We address this issue by investigating the Frictional behavior of confined water layers intercalated between single-layer molybdenum disulfide (MoS 2 ), synthesized using chemical vapor deposition, and a silica substrate. The icelike water was intercalated by exposure to high-humidity air. We found that the intercalated water molecules morphologically deform the 2D MoS 2 sheet, forming distinct subdomains after the exposure to high humidity. We found that the adsorption of the icelike water layer between the MoS 2 and the silica leads to Friction enhancement, compared with a pristine MoS 2 /silica sample, which is associated with additional phononic Friction energy dissipation at the solid-liquid interface, as indicated by the phonon distribution analysis from the empirical force-field calculations. Moreover, the atomic stick-slip behavior shows that the lattice orientation of the hydrophilic MoS 2 affects water molecule diffusion at the interface of the MoS 2 /silica substrate. Chemical mapping of the water-intercalated MoS 2 on silica using scanning photoelectron microscopy and vacuum annealing processes shows water intercalation without changing the intrinsic composition of the MoS 2 on silic

  • Shape-dependent adhesion and Friction of Au nanoparticles probed with atomic force microscopy
    IOP PUBLISHING LTD, 2018
    Co-Authors: Youngji Yuk, Hong J.w., Hyunsoo Lee, Sang Woo Han, Jeong Young Park
    Abstract:

    The relation between surface structure and Friction and adhesion is a long-standing question in tribology. Tuning the surface structure of the exposed facets of metal nanoparticles is enabled by shape control. We investigated the effect of the shape of Au nanoparticles on Friction and adhesion. Two nanoparticle systems, cubic nanoparticles with a low-index (100) surface and hexoctahedral nanoparticles with a high-index (321) surface, were used as model nanoparticle surfaces. Atomic force microscopy was used to probe the Nanoscale Friction and adhesion on the nanoparticle surface. Before removing the capping layers, the Friction results include contributions from both the geometric factor and the presence of capping layers. After removing the capping layers, we can see the exclusive effect of the surface atomic structure while the geometric effect is maintained. We found that after removing the capping layer, the cubic Au nanoparticles exhibited higher adhesion and Friction, compared with cubes capped with layers covering 25% and 70%, respectively. On the other hand, the adhesion and Friction of hexoctahedral Au nanoparticles decreased after removing the capping layers, compared with nanoparticles with capping layers. The difference in adhesion and Friction forces between the bare Au surfaces and Au nanoparticles with capping layers cannot be explained by geometric factors, such as the slope of the nanoparticle surfaces. The higher adhesion and Friction forces on cubic nanoparticles after removing the capping layers is associated with the atomic structure of (100) and (321) (i.e., the flat (100) surfaces of the cubic nanoparticles have a larger contact area, compared with the rough (321) surfaces of the hexoctahedral nanoparticles). This study implies an intrinsic relation between atomic structure and nanomechanical properties, with potential applications for controlling Nanoscale Friction and adhesion via colloid chemistry. © 2015 IOP Publishing Ltd3

Related terms

Nanoscale Friction - 15 days free trial to Access Experts & Abstracts