Nanostructurally designed ultra-hydrophilic hard coating of ceramic oxides.

Renat Sabirianov
Dept. Physics, University of Nebraska at Omaha

Fereydoon Namavar
Department of Orthopaedic Surgery and Rehabilitation, University of Nebraska, Medical Center, Omaha

C.L. Cheung
Dept. Chemistry, University of Nebraska Lincoln

W.N. Mei
Dept. Physics, University of Nebraska at Omaha

X.C. Zeng
Dept. Chemistry, University of Nebraska Lincoln

Chuck Blatchley
Physics Department,Pittsburg State University,

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     Last modified: February 15, 2006

Abstract
Designer ultrahydrophilic nanocrystalline coatings of ceramic oxides, such as pure cubic ZrO2 (diamond simulant) and TiO2, have been produced by ion beam assisted deposition (IBAD) processes. IBAD combines physical vapor deposition with concurrent ion beam bombardment (from an ion gun), in a high vacuum environment, to produce films with superior properties that are then “stitched” to any substrate. Oxygen and argon gases are used as source materials to generate energetic ions to produce these coatings with differential nanoscale (7 to 70 nm grain size) characteristics that affect the wettability, roughness, mechanical and optical properties of the coating.

These materials are important catalysts, or substrates for catalysts, and therefore offer potential applications both for industrial processes and environmental remediation, air purification, self-cleaning surfaces, as well as for sensors of important atmospheric pollutants, such as NOx. The cubic zirconia coating is particularly novel, because it was made without the addition of any stabilizing oxide, such as calcia, yttria or ceria, resulting in greater hardness (16 GPa) and fracture toughness. The as-synthesized film exhibits complete water wetting behavior. Excellent wetting properties and smaller Young’s contact angle of nanostructurally stabilized cubic ZrO2 is partially due to a large apparent tetrahedral surface area yields a hydrophilic surface with complete wetting and can be explained by Wenzel’s model.
This combination of hardness, wetting ability and high temperature stability of pure cubic ZrO2 films could also have important implications for tribology and wear resistance for industrial applications.