TY - JOUR
T1 - The apparent surface free energy of rare earth oxides is governed by hydrocarbon adsorption
AU - Oh, Junho
AU - Orejon, Daniel
AU - Park, Wooyoung
AU - Cha, Hyeongyun
AU - Sett, Soumyadip
AU - Yokoyama, Yukihiro
AU - Thoreton, Vincent
AU - Takata, Yasuyuki
AU - Miljkovic, Nenad
N1 - Funding Information:
The authors gratefully acknowledge funding support from the Office of Naval Research (ONR) under Grant No. N00014-16-1-2625, the National Science Foundation under Award No. 1554249, and the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology. The authors gratefully acknowledge Dr. Ryan Enright from Nokia Bell Labs for insightful discussions. D.O. acknowledges the support received from JSPS KAKENHI sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology with Grant No. JP16K18029 and JP18K13703. Scanning electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectroscopy were carried out in part in the Materials Research Laboratory Central Facilities, University of Illinois. N.M. conceived the idea and supervised the work. J.O. designed and conducted the experiments and prepared the manuscript. W.P. Y.Y. H.C. V.T. D.O. and S.S. carried out the experiments. D.O. Y.T. J.O. and N.M. reviewed and edited the manuscript. All authors discussed the results and provided comments on the manuscript. The authors declare that they have no conflicts of interest.
Funding Information:
The authors gratefully acknowledge funding support from the Office of Naval Research (ONR) under Grant No. N00014-16-1-2625 , the National Science Foundation under Award No. 1554249 , and the International Institute for Carbon-Neutral Energy Research ( WPI-I2CNER ), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology . The authors gratefully acknowledge Dr. Ryan Enright from Nokia Bell Labs for insightful discussions. D.O. acknowledges the support received from JSPS KAKENHI sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology with Grant No. JP16K18029 and JP18K13703 . Scanning electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectroscopy were carried out in part in the Materials Research Laboratory Central Facilities, University of Illinois.
Publisher Copyright:
© 2021 The Author(s)
PY - 2022/1/21
Y1 - 2022/1/21
N2 - The surface free energy of rare earth oxides (REOs) has been debated during the last decade, with some reporting REOs to be intrinsically hydrophilic and others reporting hydrophobic. Here, we investigate the wettability and surface chemistry of pristine and smooth REO surfaces, conclusively showing that hydrophobicity stems from wettability transition due to volatile organic compound adsorption. We show that, for indoor ambient atmospheres and well-controlled saturated hydrocarbon atmospheres, the apparent advancing and receding contact angles of water increase with exposure time. We examined the surfaces comprehensively with multiple surface analysis techniques to confirm hydrocarbon adsorption and correlate it to wettability transition mechanisms. We demonstrate that both physisorption and chemisorption occur on the surface, with chemisorbed hydrocarbons promoting further physisorption due to their high affinity with similar hydrocarbon molecules. This study offers a better understanding of the intrinsic wettability of REOs and provides design guidelines for REO-based durable hydrophobic coatings.
AB - The surface free energy of rare earth oxides (REOs) has been debated during the last decade, with some reporting REOs to be intrinsically hydrophilic and others reporting hydrophobic. Here, we investigate the wettability and surface chemistry of pristine and smooth REO surfaces, conclusively showing that hydrophobicity stems from wettability transition due to volatile organic compound adsorption. We show that, for indoor ambient atmospheres and well-controlled saturated hydrocarbon atmospheres, the apparent advancing and receding contact angles of water increase with exposure time. We examined the surfaces comprehensively with multiple surface analysis techniques to confirm hydrocarbon adsorption and correlate it to wettability transition mechanisms. We demonstrate that both physisorption and chemisorption occur on the surface, with chemisorbed hydrocarbons promoting further physisorption due to their high affinity with similar hydrocarbon molecules. This study offers a better understanding of the intrinsic wettability of REOs and provides design guidelines for REO-based durable hydrophobic coatings.
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U2 - 10.1016/j.isci.2021.103691
DO - 10.1016/j.isci.2021.103691
M3 - Article
AN - SCOPUS:85122539853
SN - 2589-0042
VL - 25
JO - iScience
JF - iScience
IS - 1
M1 - 103691
ER -