Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat Silicone/graphene oxide sheet-alumina nanorod ternary composite for superhydrophobic antifouling coating Mohamed S. Selim a,b , Sherif A. El-Safty a,c, ⁎ , Nesreen A. Fatthallah d , Mohamed A. Shenashen a,b a National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukubashi, Ibaraki-ken 305-0047, Japan b Petroleum Application Department, Egyptian Petroleum Research Institute (EPRI), Nasr City 11727, Cairo, Egypt c Faculty of Engineering and Advanced Manufacturing, University of Sunderland, St Peter’s Campus, St Peter’s Way, Sunderland SR6 0DD, UK d Processes Development Department, EPRI, Nasr City 11727, Cairo, Egypt ARTICLE INFO Keywords: Fouling release Eco-friendly Ternary nanocomposite Fillers Superhydrophobicity Coating materials ABSTRACT Superhydrophobic silicone fouling-release (FR) nanocomposite coatings have gained considerable interest as an eco-friendly and economic solution to combat biofouling problems of ship hulls. In this work, graphene oxide anchored with alumina nanorods (GO-Al 2 O 3 NRs) sheet hybrids were fabricated via a two-phase method. A ternary nanocomposite series of elastomeric silicone/GO-Al 2 O 3 hybrid NRs sheet coating was developed via solution-casting method. γ–Al 2 O 3 NRs of 150 nm in length and 20 nm in diameter were fastened between GO nanosheets and conformably coated with silicone layers. Different concentrations of GO-Al 2 O 3 hybrid NRs sheet fillers were inserted in the silicone composites to study the structure property relationship. Nanocomposites’ surface characteristics, such as superhydrophobicity, surface free energy (SFE), and rough topology were in- vestigated here. The physical and mechanical characteristics of the coating materials were also considered. Selected micro-foulants were used for the investigation of biological inertness. Laboratory assessments were performed on coated specimens for up to 28 days. A rigorous field trial was carried out for the fabricated model in natural marine water for 3 months. Well-dispersed GO-γ-Al 2 O 3 NRs sheets hybrids of up to 1 wt.% increased the contact angle (151°), decreased the SFE (13.25), and provided micro-nano roughness. Thus, a promising FR nanocomposite coating was approved with superhydrophobicity, high thermal stability, and economic savings for marine coating applications. 1. Introduction Superhydrophobic, nanostructured surfaces have caused a world- wide concern in various industrial applications [1]. These surfaces are candidates for various engineering applications, including self-cleaning, anti-biofouling, anticorrosion, and textiles [2]. Biofouling is a complex problem that causes serious negative economic and ecological impacts in the marine environment and shipping industry [3,4]. Biofouling on ship hulls results in the increase in drag resistance and hydrodynamic weight and thus causes the reduction of shipping velocity, increase in fuel consumption, and emission of harmful compounds to the en- vironment [5]. Substantial environmental toxicity issues and increased global restrictions on the applications of traditional biocidal antifouling (AF) paints have motivated research in an eco-friendly direction with a particular focus on silicone foul-release (FR) technology [6]. Non-stick polydimethylsiloxane (PDMS) FR paints rely on a technology that 1) inhibits fouling settlements and 2) weakens fouling adhesion strength by providing low friction and self-cleaning performance [7]. PDMS possesses several merits, such as its nonleaching property, low porosity, low surface free energy (SFE), high molecular mobility, repellency against water and dirt, and good thermal and UV stability [8]. The fabrication of PDMS surfaces with superhydrophobicity involves the controlled generation of a rough morphology with low-energy mole- cules [9]. High water contact angles (WCAs) > 150° and low sliding angle and self-cleaning effect result in the so-called superhydrophobic surfaces [10]. Superhydrophobic organic/inorganic hybrid nano- composites represent a creative solution to develop novel nanomater- ials with innovative self-cleaning and FR paints [11–13]. Carbonaceous nanofillers, especially graphene-based nanomaterials, play a promising role in the development of self-cleaning surfaces [14]. Among various shapes, sheet-like structures demonstrate the most outstanding barrier effects [15]. Graphene oxide (GO), one of the most important derivatives of graphene, is characterized by a layered structure with oxygen functional groups bearing on the basal planes and edges [16]. Many GO nanocomposites were reported because of the large and tortuous path produced by GO sheets and their reactions with https://doi.org/10.1016/j.porgcoat.2018.04.021 Received 13 December 2017; Received in revised form 1 April 2018; Accepted 14 April 2018 ⁎ Corresponding author at: National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukubashi, Ibaraki-ken 305-0047, Japan. E-mail addresses: sherif.elsafty@nims.go.jp, sherif.el-safty@sunderland.ac.uk (S.A. El-Safty). Progress in Organic Coatings 121 (2018) 160–172 0300-9440/ © 2018 Elsevier B.V. All rights reserved. T