Structure and Low-temperature Tribology of Lubricious Nanocrystalline ZnO/Al2O3 Nanolaminates and ZrO2 Monofilms Grown by Atomic Layer Deposition

• Main Author: Romanes, Maia Castillo
• Other Authors: Scharf, Thomas W.
• Format: Others
• Language: English
• Published: University of North Texas 2008
• Subjects: ZnO; nanocrystalline; oxide ceramics; atomic layer deposition; Tribology.; solid lubricant; nanolaminate; ZrO2; Solid lubricants.; Lubrication and lubricants > Effect of temperature on.; Thin films > Surfaces.; Oxides.; Nanostructured materials.
• Online Access: https://digital.library.unt.edu/ark:/67531/metadc9741/

Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures, they would be excellent solid lubricants for a wide range of conditions. Atomic layer deposition (ALD) is a growth technique capable of depositing highly uniform and conformal films in challenging applications that have buried surfaces and high-aspect-ratio features such as microelectromechanical (MEMS) devices where the need for robust solid lubricants is sometimes necessary. This dissertation investigates the surface and subsurface characteristics of ALD-grown ZnO/Al2O3 nanolaminates and ZrO2 monofilms before and after sliding at room temperature. Significant enhancement in friction and wear performance was observed for some films. HRSEM/FIB, HRTEM and ancillary techniques (i.e. SAED, EELS) were used to determine the mechanisms responsible for this enhancement. Contributory characteristics and energy dissipation modes were identified that promote low-temperature lubricity in both material systems.