title: Size Dependence of Nanoscale Wear of Silicon Carbide.
abstract: Nanoscale, single-asperity wear of single-crystal silicon carbide (sc-SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native oxide layers. We discovered a transition in the relative wear resistance of the SiC samples compared to that of Si as a function of contact size. With larger nanoindenter tips (tip radius ≈ 370 nm), the wear resistances of both sc-SiC and nc-SiC are higher than that of Si. This result is expected from the Archard's equation because SiC is harder than Si. However, with the smaller AFM tips (tip radius ≈ 20 nm), the wear resistances of sc-SiC and nc-SiC are lower than that of Si, despite the fact that the contact pressures are comparable to those applied with the nanoindenter tips, and the plastic zones are well-developed in both sets of wear experiments. We attribute the decrease in the relative wear resistance of SiC compared to that of Si to a transition from a wear regime dominated by the materials' resistance to plastic deformation (i.e., hardness) to a regime dominated by the materials' resistance to interfacial shear. This conclusion is supported by our AFM studies of wearless friction, which reveal that the interfacial shear strength of SiC is higher than that of Si. The contributions of surface roughness and surface chemistry to differences in interfacial shear strength are also discussed.
authors.affiliation: Department of Materials Science & Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Chaiyapat
authors.initials: C
authors.lastname: Tangpatjaroen
authors.affiliation: Department of Materials Science & Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: David
authors.initials: D
authors.lastname: Grierson
authors.affiliation: Department of Nuclear Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Steve
authors.initials: S
authors.lastname: Shannon
authors.affiliation: Forest Biopolymers Science and Engineering, USDA Forest Service, Forest Products Laboratory , One Gifford Pinchot Drive, Madison, Wisconsin 53726, United States.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Jakes
authors.affiliation: Department of Materials Science & Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Izabela
authors.identifier: http://orcid.org/0000-0002-5895-8620
authors.initials: I
authors.lastname: Szlufarska
keywords: atomic force microscopy; nanoscale friction; nanoscale wear; silicon; silicon carbide