Wednesday 31 August 2016

Water-repellent coatings prepared by modification of ZnO nanoparticles

Published Date

August 2012, Vol.94:352–356, doi:10.1016/j.saa.2012.03.079

Short communication

Title

Water-repellent coatings prepared by modification of ZnO nanoparticles

Author

R.P.S. Chakradhar^,^,

V. Dinesh Kumar

Surface Engineering Division, CSIR-National Aerospace Laboratories, Bangalore 560017, India

Received 22 January 2012. Revised 18 March 2012. Accepted 25 March 2012. Available online 2 April 2012.

Abstract

Superhydrophobic coatings with a static water contact angle (WCA) > 150° were prepared by modifying ZnO nanoparticles with stearic acid (ZnO@SA). ZnO nanoparticles of size ∼14 nm were prepared by solution combustion method. X-ray diffraction (XRD) studies reveal that as prepared ZnO has hexagonal wurtzite structure whereas the modified coatings convert to zinc stearate. Field emission scanning electron micrographs (FE-SEM) show the dual morphology of the coatings exhibiting both particles and flakes. The flakes are highly fluffy in nature with voids and nanopores. Fourier transformed infrared (FTIR) spectrum shows the stearate ion co-ordinates with Zn²⁺ in the bidentate form. The surface properties such as surface free energy (γ_p) and work of adhesion (W) of the unmodified and modified ZnO coatings have been evaluated. The electron paramagnetic resonance (EPR) spectroscopy reveals that surface defects play a major role in the wetting behavior.

Graphical abstract

FE-SEM micrographs of superhydrophobic ZnO@SA coating with different magnification (a) 4k×, (b) magnified view of (zone A) 20k×, (c) magnified view of (zone B) 20k× and (d) 25k×.

Highlights

► Water repellent coatings were prepared by modifying ZnO nanoparticles. ► Surface properties of the coatings were evaluated. ► EPR spectroscopy reveals that surface defects play a major role in wetting behavior.