Role of surface oxygen-to-metal ratio on the wettability of rare-earth oxides
Name
Varanasi_Role of.pdf
Size
1019.5 KB
Format
Adobe PDF
Checksum (MD5)
f867bdfa7adfd8c52a53ec14fb79fbd0
Author(s)
Khan, Sami
Azimi, Gisele
Yildiz, Bilge
Varanasi, Kripa
Date Issued
February 2015
Journal
Applied Physics Letters
Publisher
American Institute of Physics (AIP)
Citation
Khan, Sami, Gisele Azimi, Bilge Yildiz, and Kripa K. Varanasi. “Role of Surface Oxygen-to-Metal Ratio on the Wettability of Rare-Earth Oxides.” Appl. Phys. Lett. 106, no. 6 (February 9, 2015): 061601. © 2015 AIP Publishing LLC
Version
Final published version
Abstract
Hydrophobic surfaces that are robust can have widespread applications in drop-wise condensation, anti-corrosion, and anti-icing. Recently, it was shown that the class of ceramics comprising the lanthanide series rare-earth oxides (REOs) is intrinsically hydrophobic. The unique electronic structure of the rare-earth metal atom inhibits hydrogen bonding with interfacial water molecules resulting in a hydrophobic hydration structure where the surface oxygen atoms are the only hydrogen bonding sites. Hence, the presence of excess surface oxygen can lead to increased hydrogen bonding and thereby reduce hydrophobicity of REOs. Herein, we demonstrate how surface stoichiometry and surface relaxations can impact wetting properties of REOs. Using X-ray Photoelectron Spectroscopy and wetting measurements, we show that freshly sputtered ceria is hydrophilic due to excess surface oxygen (shown to have an O/Ce ratio of ∼3 and a water contact angle of ∼15°), which when relaxed in a clean, ultra-high vacuum environment isolated from airborne contaminants reaches close to stoichiometric O/Ce ratio (∼2.2) and becomes hydrophobic (contact angle of ∼104°). Further, we show that airborne hydrocarbon contaminants do not exclusively impact the wetting properties of REOs, and that relaxed REOs are intrinsically hydrophobic. This study provides insight into the role of surface relaxation on the wettability of REOs.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Engineering Systems Division
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1063/1.4907756
