Tribological properties of quasicrystals: Effect of aperiodic versus periodic surface order

Abstract

We investigated the nanoscale tribological properties of a decagonal quasicrystal using a combination of atomic force microscopy and scanning tunneling microscopy in ultrahigh vacuum. This combination permitted a variety of in situ measurements, including atomic-scale structure, friction and adhesion force, tipsample current, and topography. We found that thiol-passivated tips can be used for reproducible studies of the tip-quasicrystal contact while nonpassivated probes adhere irreversibly to the clean quasicrystalline surface causing permanent modifications. The most remarkable results were obtained on the twofold surface of the Al-Ni-Co decagonal quasicrystal where atoms are arranged periodically along the tenfold 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. We investigated the nanoscale tribological properties of a decagonal quasicrystal using a combination of atomic force microscopy and scanning tunneling microscopy 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 nonpassivated probes adhere irreversibly to the clean quasicrystalline surface causing permanent modifications. The most remarkable results were obtained on the twofold surface of the Al-Ni-Co decagonal quasicrystal where atoms are arranged periodically along the tenfold 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.

Friction Anisotropy with Respect to Topographic Orientation

“…Friction anisotropy probed in different motion direction is widely observed in interactions of various surfaces, such as single crystal surfaces456, quasicrystal surfaces78, organic molecular monolayers91011, monolayer graphene12, and textured surfaces1314. It even exists in the presence of lubrication151617.…”

Factors influencing deformation stability of binary glasses

“…We observe an average ␥ cr Ϸ 30% in single component glasses. 12 As is evident the size ratio has a very strong influence on the deformation stability. With increasing solute concentration x ͑for = 1.03 and m ജ 12͒ we observe a drop in f c .…”

“…[1][2][3][4][5][6][7][8][9] Deformation induced crystallization of glasses is also observed in atomistic simulations. [10][11][12] Deformation induced crystallization is a possible mechanism for large scale strain accommodation in glasses, and a possible cause for the high toughness of metallic glasses. 13 In an earlier work, 12 we have studied deformation induced crystallization using atomistic simulations to identify the microscopic parameters ͑such as "potential energy barrier"͒ that control crystallization of glasses.…”

“…[10][11][12] Deformation induced crystallization is a possible mechanism for large scale strain accommodation in glasses, and a possible cause for the high toughness of metallic glasses. 13 In an earlier work, 12 we have studied deformation induced crystallization using atomistic simulations to identify the microscopic parameters ͑such as "potential energy barrier"͒ that control crystallization of glasses. The propensity of the glasses to crystallize during the deformation is seen to decrease with the increase of the energy barrier for the atoms to "cross" each other.…”

The surface science of quasicrystals

“…Friction is a complex phenomenon, with many channels contributing to energy dissipation. Park and co-workers used atomic force microscopy (AFM) and STM to study the twofold surface of d-Al-Ni-Co which contains both periodic and quasiperiodic directions [51,75,120]. By measuring the torsional response of the AFM cantilever, they could directly compare frictional effects along the periodic and aperiodic directions on the same surface.…”