Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session D33: Focus Session: Friction, Fracture and Deformation I |
Hide Abstracts |
Sponsoring Units: DMP GSNP Chair: H.G.E. Henstchel, Emory University Room: Baltimore Convention Center 336 |
Monday, March 13, 2006 2:30PM - 3:06PM |
D33.00001: Tribochemical studies at the nanometer scale: synergisms of mechanical and chemical forces Invited Speaker: The manipulation of matter on small size scales dominates a number of potential applications in nanoscience and nanotechnology. The forces and potentials available to break and reestablish bonds between ions, atoms, and molecules becomes greatly expanded when we consider combining stimuli. Our efforts on combining (mechanical + chemical) or (mechanical + radiative) stimulation aims at understanding the resulting synergisms in, for example, dissolution and/or deposition of material. We show that we can measure the kinetics of chemical mechanical wear (e.g., polishing) with a single asperity (the tip of an Atomic Force Microscope) on substrates of single crystals, amorphous materials such as silicate glasses,polymers, crystalline silicon, and on polycrystalline oxides, nitrides, and carbides in controlled chemical media. We find that although the mechanics are relatively straight forward to model, the \textit{dependence} on the applied normal force, the applied stress, the solution composition, the solution temperature, the duration time of the wear experiment, and the relative velocity of the AFM tip and substrate can be complex. With care, we have been able to properly measure and model the tribochemical wear on model systems. We present these studies and include new results on technologically interesting materials such as single crystal Si(100). We also present results on the use of an AFM tip to localize layer-by-layer growth of single crystals of inorganic carbonates, sulfates, and phosphates in saturated aqueous solutions. [Preview Abstract] |
Monday, March 13, 2006 3:06PM - 3:18PM |
D33.00002: Elucidation of the Atomic-Scale mechanisms of Friction in Model SAMs and DLC films Judith Harrison, Paul Mikulski, Guangtu Gao, Kevin Van Workum, J. David Schall, Ginger Chateauneuf The development of micron-sized devices for terrestrial and space applications has prompted the need for protection of the surfaces of these devices. Amorphous carbon films, diamondlike carbon, and SAMs are all possible candidates for the passivation and lubrication of these devices. The fundamental problem associated with controlling friction is a lack of understanding of the underlying atomic-scale processes that govern it. Over the past several years, we have performed extensive molecular dynamics simulations aimed at understanding the atomic-scale mechanisms of friction. We have examined the contact forces present at the interface of a tip and SAMs during sliding. Compression- and shear-induced polymerization have also been modeled in SAMs. In addition, we have done simulations that analyzed the tribological properties of amorphous carbon films with various compositions and of diamondlike carbon films. Some of our recent results will be discussed. [Preview Abstract] |
Monday, March 13, 2006 3:18PM - 3:30PM |
D33.00003: Relating structure and friction: Energy dissipation during the lateral manipulation of antimony nanoparticles U.D. Schwarz, C. Ritter, M. Heyde, K. Rademann Despite its daily-life importance, the fundamentals of friction are still insufficiently understood. In particular, the interplay between friction, ``true'' contact area, and crystalline structure at the interface is an issue of current debate. Recently, a new technique had been introduced that allows determining the threshold energy dissipated during the lateral displacement of small nanoparticles on suitable substrates as a function of the particle-substrate contact area [Ritter et al., PRB \textbf{71}, 085405 (2005)]. Here, we present results of an extensive study of antimony nanoparticles 1000 nm$^{2}$ to 100000 nm$^{2}$ in size moved in air on graphite substrates. Complementary studies by electron microscopy reveal the internal structure of the islands, showing a transition from amorphous to crystalline of the island's cores at about 10000-15000~nm$^{2}$ size, while the surface layers are composed of amorphous antimony oxide in all cases. However, despite the similarities of the amorphous surface layer, islands with crystalline core show significantly higher energy dissipation during motion than the ones with amorphous core. Possible reasons for this effect are discussed. [Preview Abstract] |
Monday, March 13, 2006 3:30PM - 3:42PM |
D33.00004: Relationship between friction and quasicrystallinity; friction anisotropy in a decagonal Al-Ni-Co quasicrystal surface Jeong Young Park, D. F. Ogletree, M. Salmeron, R. A. Ribeiro, P. C. Canfield, C. J. Jenks, P. A. Thiel We investigated the nanoscale tribological properties of a decagonal quasicrystal using a combination of atomic force microscopy (AFM) and scanning tunneling microscopy (STM) in ultrahigh vacuum. This combination permitted a variety of in situ measurements, including atomic- scale structure, friction and adhesion force, tip-sample current, and topography. We found that thiol-passivated tips can be used for reproducible studies of the tip-quasicrystal contact while non-passivated probes adhere irreversibly to the clean quasicrystalline surface causing permanent modifications. The most remarkable results were obtained on the 2-fold surface of the Al-Ni-Co decagonal quasicrystal where atoms are arranged periodically along the 10-fold axis and aperiodically in the perpendicular direction. Strong friction anisotropy was observed on this surface, with high friction along the periodic direction, and low friction in the aperiodic direction. These results reveal a strong connection between interface atomic structure and the mechanisms by which energy is dissipated, which likely include electronic or phononic contributions, or both. [Preview Abstract] |
Monday, March 13, 2006 3:42PM - 3:54PM |
D33.00005: New Phenomena in High Temperature Nanofriction on Nonmelting Surfaces: NaCl(100) Tatyana Zykova-Timan, Davide Ceresoli, Erio Tosatti High temperature nanofriction is a difficult and so far unexplored area whwere we made an initial attack by means of simulation. Alkali halide (100) surfaces were chosen as they would not automatically liquefy under a sliding tip, even at temperatures very close to the melting point. We conducted sliding friction molecular dynamics simulations of hard tips on NaCl(100),both in the heavy ploughing, wear-dominated regime, and in the light grazing, wearless regime. Ploughing friction shows for increasing temperature a strong frictional drop near the melting point. Here the tip can be characterized as ``skating'' over the hot solid, its apex surrounded by a local liquid halo, which moves along with the tip as it ploughs on. At the opposite extreme, we find that grazing friction of a lightly pressed flat-ended tip behaves just the other way around. Starting with an initially very weak low temperature frictional force, there is a surge of friction just near the melting point, where the surface is still solid, but not too far from a vibrational instability. This frictional rise can be envisaged as an analog of the celebrated ``peak effect'' found close to Hc2 in the mixed state critical current of type II superconductors. [Preview Abstract] |
Monday, March 13, 2006 3:54PM - 4:06PM |
D33.00006: Nanotribological studies of Temperature Rise in a Sliding Adsorbed Film Matthew Walker, Cherno Jay, Jacqueline Krim Theoretical predictions of friction-induced temperature increases at sliding interfaces in general show a wide variation, with little opportunity for experimental verification. In order to explore temperature rise in a particularly simple geometry, we have recorded isotherms of sliding Kr layers adsorbed on graphene (a one-atom thick layer of graphite) and compared them to those recorded in the past in static conditions[ J.A. Venables, \textit{Introduction to surface and Thin Film Processes}. Cambridge University Press, Cambridge, (2000) p. 116]. We synthesize graphene on a Ni(111), which has a lattice spacing stretched approximately 2{\%} beyond that of graphite. The Ni(111) was prepared as an electrode on the surface of a quartz crystal microbalance (QCM) so that friction measurements in sliding conditions could be recorded [J. Krim and A. Widom, Phys. Rev. B, \textbf{38}, 12184 (1988)]. Superposition of the isotherms recorded for this system were superimposed on the static volumetric phase diagrams to infer a temperature increase of approximately 15K above the temperature at which the experiments were performed. Work funded by the NSF. [Preview Abstract] |
Monday, March 13, 2006 4:06PM - 4:18PM |
D33.00007: The Temperature Dependence of Macroscopic Sliding Friction J.C. Burton, P. Taborek, J.E. Rutledge We present measurements of the static and kinetic coefficients of friction of gold-plated copper on gold-plated copper and sapphire on sapphire as a function of temperature from 10K to 400K. The measurements were done by sliding a block down a controllable incline plane and using high-speed video to extract the acceleration. The large size of our optical cryostat allowed linear motion of 7.5 cm over which to measure the acceleration. Surfaces were baked under high vacuum at 400K, and data was taken as they cooled. Preliminary results indicate that the coefficient of friction for gold plated copper surfaces change by 10 percent from room temperature to 10K. [Preview Abstract] |
Monday, March 13, 2006 4:18PM - 4:30PM |
D33.00008: Measurements of Coefficients of Kinetic Friction Using a Driven Harmonic Oscillator M. G. Aggleton, P. Taborek, J. E. Rutledge We have developed a method of measuring the kinetic coefficient of friction of various materials. Instead of the standard pin-on-disc tribometer, we have developed a driven harmonic oscillator at frequencies around 50Hz to measure friction at the millimeter to centimeter scale. The system is driven by a magnetic field and measured by a linear variable differential transducer (LVDT). Contact between a plate attached to the oscillator and a sphere provides damping due to friction. We will present results for various material combinations, as well as perform a comparison between these results and those of other researchers using a variety of techniques. This apparatus was designed with the intention of being vacuum and low temperature compatible in order to explore the temperature dependence of friction in the cryogenic regime. [Preview Abstract] |
Monday, March 13, 2006 4:30PM - 4:42PM |
D33.00009: Free-standing micro locomotive structures driven by the thermal modulation Onejae Sul, Michael Falvo, Lloyd Caroll, Timothy O'Brien, Richard Superfine, Russell Taylor, Jr., Sean Washburn As the sizes of Microelectromechanical(MEMS) devices and also the sizes of their contact to environment shrink down to micrometers, the role of contact becomes more critical in understanding and applying it for realization of mobile devices. Since the dominating forces between objects under micro regime are attractive forces such as van der Walls and capillary force, any motion will be mainly influenced by the surface forces rather than inertia. The greatest barrier to actuation is to overcome such forces while achieving net motion. This necessitates smallest contact area. Our research pushed the limits of the contact area to nanometers for minimized friction against the substrate, thus small friction requires lesser thrust and enables faster actuation. We made the inch-worm style bimorph thin film devices standing on the graphite and they are non-umbilical by design. We will first discuss the estimation of thrust, friction of a device on the graphite. We will then discuss the walking mechanism of coordinating three contact tips upon repeated heating and cooling thermal cycles. Additionally we will present predictions and measurements on various properties of our devices such as deflection depending on temperature, time constant of heat/cooling, and contact sliding speeds. [Preview Abstract] |
Monday, March 13, 2006 4:42PM - 4:54PM |
D33.00010: Superconductivity Dependent Friction in Superheated He Films M. Highland, J. Krim We report a quartz crystal microbalance (QCM) study of sliding friction levels in N$_{2}$, H$_{2}$O and superheated He films adsorbed on Pb(111) above and below its superconducting transition temperature. Our findings establish firmly that superconductivity dependent friction is present in a wide range, if not all, of adsorbed film systems that remain unpinned at 7K, and that on and off cycling of an externally applied magnetic field may impact friction. Changes in friction at the superconducting transition are observed to be greater for H$_{2}$O and N$_{2}$ than for the He films, consistent with a recent theory that attributed differences in electronic friction levels to the polarity of the adsorbate [L.W. Bruch, Phys. Rev. B. \textbf{61}, 16201 (2000)] . This work was supported by NSF and AFOSR. [Preview Abstract] |
Monday, March 13, 2006 4:54PM - 5:06PM |
D33.00011: Friction between Polymer Brushes Jeffrey Sokoloff A polymer brush consists of a surface with a fairly concentrated coating of polymer chains, each one of which has one of its ends tightly bound to the surface. They serve as extremely effective lubricant, producing friction coefficients as low as 0.001 or less! Polymer brushes are a promising way to reduce friction to extremely low values. They have the disadvantage, however, that they must be immersed in a liquid solvent in order to function as a lubricant. The presence of a solvent is believed to result in osmotic pressure which partially supports the load. The density profile of a polymer brush (i.e., the density of monomers as a function of distance from the surface to which the polymers are attached) is well established. What is not understood is how the interaction of polymer brush coated surfaces in contact with each other is able to account for the details of the observed low friction. For example, molecular dynamics studies generally do not predict static friction, whereas surface force apparatus measurements due to Tadmor, et. al., find that there is static friction. This is the topic of the present presentation. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700