Nanomechanical Properties and Nanowear Characterization of Thin Solid Films and Engineering Surfaces

"Reliable nanomechanical property and nanowear measurements have recently drawn significant attention, as thin solid films have been routinely used in various applications, such as semiconductor, magnetic storage and microelectromechanical systems, and their thickness has shrunk from as low as a couple of nanometers to tens of nanometers thick. In this work, nanomechanical properties and nanowear behavior were investigated analytically, numerically and experimentally. Since traditional methods to measure mechanical properties are not readily applicable to such thin films, techniques to measure their nanomechanical properties were developed in this study. First, a method to determine the shear strength of a material from nanoscratch experiments was analytically derived and the model was validated using finite element analysis. Nanomechanical properties of thin solid films that are related to functional performance, such as shear strength and hardness, were measured based on nanoscratch experiments with constant and ramp load profiles. The results were in good agreement with measurements performed using a different method, namely nanoindentation with a high resolution transducer and extremely sharp diamond tip. Finite element analysis was also used to obtain hardness values for elastic perfectly plastic materials with different properties to validate an earlier proposed model for obtaining hardness from nanoscratch experiments. Even though the measurement of nanomechanical properties is useful, it can not provide complete information on the nanowear performance of sliding interfaces, thus, nanowear measurements were also performed. Techniques to characterize nanowear using a nanoscratch apparatus were presented and experiments were performed using a sub-10 nm thick carbon overcoat found in magnetic storage samples as well as engineering rail steel samples. In the case of engineering ""macro-scale systems,"" the contact occurs on the surface and the most drastic material property changes are limited to the topmost surface and sub-surface. The results show that reliable nanowear measurements could be performed and are in good agreement with the nanomechanical property measurements. Also finite element analysis was performed to simulate repeated sliding contacts, which was able to show that nanowear performance as well as the changes that occur due to work hardening."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Lee, Ki Myung

Contributors dc:contributor

• Polycarpou, Andreas A.

• Engineering, Mechanical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3223644

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83846