Friction between single-grain Al70Pd21Mn9 quasicrystal surfaces

Ko, Jeff S.; Gellman, Andrew J.; Lograsso, Thomas A.; Jenks, Cynthia J.; Thiel, Patricia A.

doi:10.1016/s0039-6028(98)00911-x

Cited by 52 publications

(47 citation statements)

References 27 publications

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“…Tribological properties are of particular interest in quasicrystals, materials with atoms arranged in patterns with rotational symmetry but no translational periodicity, 15 because low coefficients of friction and low adhesion to polar liquids have been reported for surfaces in air [16][17][18][19] and also in vacuum studies. [20][21][22][23] The relationship between these anomalous surface properties and the surface atomic structure, however, is unclear. One basic issue is the relative importance of elastic versus inelastic deformation processes to the relatively low friction coefficient, because of the high intrinsic hardness of quasicrystals.…”

Section: Introductionmentioning

confidence: 99%

Elastic and inelastic deformations of ethylene-passivated tenfold decagonalAl−Ni−Coquasicrystal surfaces

et al. 2005

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The adhesion and friction force properties between a tenfold Al-Ni-Co decagonal quasicrystal and a titanium nitride (TiN)-coated tip were investigated using an atomic force microscope in ultrahigh vacuum. To suppress the strong chemical adhesion found in the clean quasicrystal surfaces, the sample was exposed to ethylene that formed a protective passivating layer. We show that the deformation mechanism of the tip-substrate junction changes from elastic to inelastic at a threshold pressure of 3.8 to 4.0 GPa. Images of the indentation marks left above the threshold pressure indicate the absence of new steps, and indicate that surface damage is not accompanied by formation of slippage planes or dislocations, as found in plastically deforming crystalline materials. This is consistent with the lack of translational periodicity of quasicrystals. The work of adhesion in the inelastic regime is five times larger than in the elastic one, plausibly as a result of the displacement of the passivating layer. In the elastic regime, the friction dependence on load is accurately described by the Derjaguin-Müller-Toporov (DMT) model, consistent with the high hardness of both the TiN tip and the quasicrystal sample. Above the threshold pressure, the friction versus load curve deviates from the DMT model, indicating that chemical bond formation and rupture contribute to the energy dissipation. The adhesion and friction force properties between a tenfold Al-Ni-Co decagonal quasicrystal and a titanium nitride ͑TiN͒-coated tip were investigated using an atomic force microscope in ultrahigh vacuum. To suppress the strong chemical adhesion found in the clean quasicrystal surfaces, the sample was exposed to ethylene that formed a protective passivating layer. We show that the deformation mechanism of the tip-substrate junction changes from elastic to inelastic at a threshold pressure of 3.8 to 4.0 GPa. Images of the indentation marks left above the threshold pressure indicate the absence of new steps, and indicate that surface damage is not accompanied by formation of slippage planes or dislocations, as found in plastically deforming crystalline materials. This is consistent with the lack of translational periodicity of quasicrystals. The work of adhesion in the inelastic regime is five times larger than in the elastic one, plausibly as a result of the displacement of the passivating layer. In the elastic regime, the friction dependence on load is accurately described by the Derjaguin-Müller-Toporov ͑DMT͒ model, consistent with the high hardness of both the TiN tip and the quasicrystal sample. Above the threshold pressure, the friction versus load curve deviates from the DMT model, indicating that chemical bond formation and rupture contribute to the energy dissipation.

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Section: Introductionmentioning

confidence: 99%

Elastic and inelastic deformations of ethylene-passivated tenfold decagonalAl−Ni−Coquasicrystal surfaces

et al. 2005

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“…AES shows that exposure to O 2 results in the formation of a thin film of aluminum oxide that passivates the surface against further oxidation. This is similar to the oxidation of the surface of aluminum itself [ 101,102]. These films have an influence on the frictional properties of the surface.…”

Section: Tribology Of Quasicrystalsmentioning

confidence: 71%

Surface chemistry in tribology

Gellman

Spencer²

2002

Proceedings of the Institution of Mechanical Engineers, Part J:

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IntroductionIn general, the twentieth century marked the first major incursion of chemists into the world of tribology. Driven partly by the need for improved lubricants for new machines developed in the first few decades of the century, and partly by new analytical capabilities, lubricant chemists and tribochemists were to become full partners in the science of tribology. In this review we cover a number of topics in surface chemistry in tribology, which serve both to illustrate some of the successes in tribochemical research over the past decades, and also to show that much work remains to be done before true, first-principles tribochemistry-based lubricant and tribopair design can begin. Boundary Lubrication and Oiliness AdditivesIn an ideal world, lubricated sliding surfaces are separated by a stable fluid film of lubricant, which effectively lowers friction and prevents wear, holding the surfaces apart by virtue of its fluid-mechanical properties. The friction coefficient in such a hydrodynamically lubricated bearing is proportional to ηU/W, where U is the relative sliding speed of the surfaces, W the normal load supported by the bearing and η the Newtonian viscosity [1]. At low sliding speeds (e.g upon startup) and/or higher forces, however, the friction coefficient varies in a more complex way (Figure 1) and at the lowest speeds and friction forces can be 2 orders of magnitude higher than under hydrodynamic lubrication conditions. This is the regime of "boundary lubrication", where fluid films have given way to thin layers that serve as the active lubricants, and the realm of pure engineering (hydrodynamic lubrication) has given 2 way to the complex world of surface chemistry under confinement. Boundary lubrication is clearly of vital importance, since it is the mechanism in operation under the most extreme of tribological conditions. Understanding boundary lubrication, however, has been a challenge to tribochemists over the last century, with light appearing at the end of the tunnel only quite recently. Monolayers, Multilayers and soapsIt was noticed in the 1920s that certain lubricants possessed a quality designated "oiliness", which, independent of their viscosity, led to better lubrication at low sliding speeds [2][3][4]. Generally, these oily lubricants tended to be those of natural origin, such as castor oil, containing long-chain oxygenated organic compounds (esters and acids), which have surfactant properties, and are not usually present in their mineral oil counterparts. It was shown that these oxygenated molecules could, by themselves, reduce friction considerably between sliding surfaces, their effectiveness depending on their molecular weight [5] (Figure 2). Hardy developed a monolayer theory of boundary lubrication (Figure 3), whereby he postulated that, under boundary conditions, the sliding surfaces were held apart by adsorbed, oriented monolayers of polar molecules, which form a plane of low shear strength, thus lowering friction and affording protection of the surfaces.3 Figure 2. Depe...

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“…In addition the chamber was equipped with a unique device for measurement of friction between pairs of well-defined surfaces, both of which have been subjected to the same preparation and analysis procedures. The original work with the Al 70 Pd 21 Mn 9 quasicrystal surfaces has been described in another paper which includes a fairly detailed description of the apparatus [29]. Briefly, it is an UHV chamber pumped into the low 10 -10 Torr pressure range using an ion pump and a titanium sublimation pump.…”

Section: Methodsmentioning

confidence: 99%

“…In previous work we have measured friction coefficvrÃsÃ s = 0.11± 0.02 between the surfaces of Al 70 Pd 21 Mn 9 quasicrystals in air and prior to any UHV cleaning [29]. These surfaces were, of course, coated with carbon and with an oxide film.…”

Section: Frictional Properties Of Quasicrystal and Approximant Surfacesmentioning

confidence: 99%

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Comparative Study of the Tribological and Oxidative Properties of AlPdMn Quasicrystals and Their Cubic Approximants

Mancinelli

Jenks

et al. 2000

MRS Proc.

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An experimental comparison has been made between the properties of the surfaces of an Al 70 Pd 21 Mn 9 quasicrystal and its Al 48 Pd 42 Mn 10 approximant. The Al 70 Pd 21 Mn 9 sample was a single grain icosahedral quasicrystal cut to expose its five-fold symmetric (000001) surface. The approximant was polycrystalline β-phase Al 48 Pd 42 Mn 10 , which has a CsCl-type cubic structure. Surfaces of both were prepared under ultra-high vacuum (UHV) conditions and then used for comparative measurements of their frictional properties and oxidation rates. Both materials are oxidized by reaction with O 2 to form a thin film of aluminum oxide that ultimately passivates their surfaces. The interesting difference between the two is that the rate of oxidation of the approximant is significantly higher than that of the quasicrystal in spite of the fact that the bulk Al concentration of the approximant is lower than that of the quasicrystal. Friction measurements were made under UHV conditions between pairs of quasicrystals and pairs of approximants whose surfaces were either clean or oxidized to varying degrees. The friction between pairs of the approximant surfaces is significantly higher than that measured between the quasicrystal surfaces under all conditions of surface oxidation. sample was a single grain icosahedral quasicrystal cut to expose its five-fold symmetric (000001) surface. The approximant was polycrystalline β-phase Al 48 Pd 42 Mn 10 , which has a CsCl-type cubic structure. Surfaces of both were prepared under ultra-high vacuum (UHV) conditions and then used for comparative measurements of their frictional properties and oxidation rates. Both materials are oxidized by reaction with O 2 to form a thin film of aluminum oxide that ultimately passivates their surfaces. The interesting difference between the two is that the rate of oxidation of the approximant is significantly higher than that of the quasicrystal in spite of the fact that the bulk Al concentration of the approximant is lower than that of the quasicrystal. Friction measurements were made under UHV conditions between pairs of quasicrystals and pairs of approximants whose surfaces were either clean or oxidized to varying degrees. The friction between pairs of the approximant surfaces is significantly higher than that measured between the quasicrystal surfaces under all conditions of surface oxidation. Keywords

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Friction between single-grain Al70Pd21Mn9 quasicrystal surfaces

Cited by 52 publications

References 27 publications

Elastic and inelastic deformations of ethylene-passivated tenfold decagonalAl−Ni−Coquasicrystal surfaces

Elastic and inelastic deformations of ethylene-passivated tenfold decagonalAl−Ni−Coquasicrystal surfaces

Surface chemistry in tribology

Comparative Study of the Tribological and Oxidative Properties of AlPdMn Quasicrystals and Their Cubic Approximants

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