Fabrication of superhydrophobic reduced-graphene oxide/nickel coating with mechanical durability, self-cleaning and anticorrosion performance

Nanocomposite Coatings for Anti-Corrosion Properties of Metallic Substrates

Nanocomposites are high-performance materials with exceptional characteristics that possess properties that their individual constituents, by themselves, cannot provide. They have useful applications in many fields, ranging from membrane processes to fuel cells, biomedical devices, and anti-corrosion protection. Well-tailored nanocomposites are promising materials for anti-corrosion coatings on metals and alloys, exhibiting simple barrier protection or even smart auto-responsive and self-healing functionalities. Nanocomposite coatings can be prepared by using a large variety of matrices and reinforcement materials, often acting in synergy. In this context, recent advances in the preparation and characterization of corrosion-resistant nanocomposite coatings based on metallic, polymeric, and ceramic matrices, as well as the incorporation of various reinforcement materials, are reviewed. The review presents the most important materials used as matrices for nanocomposites (metals, polymers, and ceramics), the most popular fillers (nanoparticles, nanotubes, nanowires, nanorods, nanoplatelets, nanosheets, nanofilms, or nanocapsules), and their combinations. Some of the most important characteristics and applications of nanocomposite coatings, as well as the challenges for future research, are briefly discussed.

A biomimetic beetle-like membrane with superoleophilic SiO2-induced oil coalescence on superhydrophilic CuC2O4 nanosheet arrays for effective O/W emulsion separation

It is highly attractive to develop highly efficient oil-in-water (O/W) emulsion separation technologies for promoting the oily wastewater treatment. Herein, a novel inversely Stenocara beetle-like hierarchical structure of superhydrophobic SiO₂ nanoparticle-decorated CuC₂O₄ nanosheet arrays were prepared on copper mesh membrane by bridging polydopamine (PDA) to make a SiO₂/PDA@CuC₂O₄ membrane for substantially enhanced separation of O/W emulsions. The superhydrophobic SiO₂ particles on the as-prepared SiO₂/PDA@CuC₂O₄ membranes were served as localized active sites to induce coalescence of small-size oil droplets in oil-in-water (O/W) emulsions. Such innovated membrane delivered outstanding demulsification ability of O/W emulsion with a high separation flux of 2.5 kL⋅m^-2⋅h^-1 and its filtrate's chemical oxygen demand (COD) being 30 and 100 mg⋅L^-1 for surfactant-free emulsion (SFE) and surfactant-stabilized emulsion (SSE), respectively, and also exhibited a good anti-fouling performance in cycling tests. The innovative design strategy developed in this work broadens the application of superwetting materials for oil-water separation and presents a promising prospect in practical oily wastewater treatment applications.

Study of the Corrosion of Nickel-Chromium Alloy in an Acidic Solution Protected by Nickel Nanoparticles

This study uses nickel nanoparticles coated on the nickel-chromium (Ni-Cr) alloy by the electrodeposition technique to protect the alloy against corrosion. An open-circuit potential and potentiodynamic and linear polarization resistance in a 1 M H₂SO₄ solution saturated with carbon dioxide were used to study the anticorrosion performance of nanoparticle coatings. When coated with nanomaterials, the corrosion rate of Ni-Cr alloy was lower than when it was bare, and the potential for corrosion increased from -0.433 V for uncoated Ni-Cr alloy to -0.103 V when the electrodes were exposed to saturated calomel. Electrochemical experiments show that nickel-coated Ni-Cr alloy corrosion in sulfuric acid media has high protective characteristics, with an efficiency of 83.69% at 0.165 mA/cm² current density when pH = 1 is used. As demonstrated by the results of this research, the nickel-chromium alloy can be protected from corrosion in acidic media by a low-acidity bath coating layer. Surface morphologies have shown that coatings at different acidic scales may be able to resist an acid attack because of their excellent adherence to the nickel-chromium alloy surface. Measures for determining and studying the composition of the alloy surface's protective covering were improved using X-ray diffraction (XRD).

Superhydrophobic Ni-Reduced Graphene Oxide Hybrid Coatings with Quasi-Periodic Spike Structures

Recently, sophisticated technologies are applied to design a certain surface nature that can have superhydrophobic properties. Thus, a simple spray technique was introduced to prepare a superhydrophobic surface using rGO with Ni-S system (rGO-Ni) by using NiSO₄ catalyst under microwave irradiation at various reaction times of 5, 10, 20, and 30 min. The GO reduction was conducted at a fixed Ar/H₂ ratio, a flow rate of 0.4 L/min, microwave power of 720 W, and a mass of 0.5 g. GO powder with nickel sulfate catalyst was treated under Ar/H₂ (4:1) mixture for GO reduction, where Ar and H₂ were expected to prevent the rebinding of oxygen released from GO. The result of XRD and Raman measurement confirms that rGO-Ni prepared at reaction time 20 min exhibit the highest reduction of GO and the presence of various Ni-S crystal structures such as NiS, NiS₂, Ni₃S₂, and Ni₃S₄ due to decomposition of NiSO₄. The rGO-Ni coating performance shows superhydrophobic nature with a contact angle of 150.1°. The AFM images show that the addition of nickel to rGO produces a quasi-periodic spike structure, which increases the superhydrophobicity of the r-GO-Ni coated glass with a contact angle of 152.6°. It is emphasized that the proposed simple spray coating using rGO-Ni provides a more favorable option for industry application in obtaining superhydrophobic surfaces.

Surface engineering of silica based materials with Ni-Fe layered double hydroxide for the efficient removal of methyl orange: Isotherms, kinetics, mechanism and high selectivity studies

Herein, low-cost diatomite (DE) and bentonite (BE) materials were surface modified with Ni-Fe layered double hydroxide (LDHs) (represented as NFD and NFB respectively), using a simple co-precipitation procedure for the removal of methyl orange (MO) dye from water. The adsorbents of both before and after MO adsorption have been studied by XRD, N₂ adsorption-desorption isotherm, FTIR, FESEM-EDX and XPS characterization. The zeta potential analysis was used to observe the surface charge of adsorbents within the pH ranges of 4-10. The MO removal efficiency was significantly improved after LDHs modification, showing a 94.7% and 92.6% efficiency for NFD and NFB at pH 6, respectively. Whereas bare DE and BE have shown removal efficiency of 15.5% and 4.9% respectively. The maximum adsorption capacities of NFD and NFB using the Langmuir isotherm model were found to be 246.9 mgg^-1 and 215.9 mgg^-1 respectively. The designed NFD showed high selectivity towards anionic-based dyes from water and also the effect of salts shows the dye removal percentage was increased and decreased for the addition of Na₂SO₄ and NaCl, respectively. The reusability of NFD and NFB have been studied for a maximum of five cycles and they can remove MO up to four cycles. Therefore, the designed adsorbents can be very effective towards the removal of MO from water and they may be useful for dye-based wastewater treatment.

Functional nanomaterials, synergisms, and biomimicry for environmentally benign marine antifouling technology

Marine biofouling remains one of the key challenges for maritime industries, both for seafaring and stationary structures. Currently used biocide-based approaches suffer from significant drawbacks, coming at a significant cost to the environment into which the biocides are released, whereas novel environmentally friendly approaches are often difficult to translate from lab bench to commercial scale. In this article, current biocide-based strategies and their adverse environmental effects are briefly outlined, showing significant gaps that could be addressed through advanced materials engineering. Current research towards the use of natural antifouling products and strategies based on physio-chemical properties is then reviewed, focusing on the recent progress and promising novel developments in the field of environmentally benign marine antifouling technologies based on advanced nanocomposites, synergistic effects and biomimetic approaches are discussed and their benefits and potential drawbacks are compared to existing techniques.

Synchronous removal of emulsions and soluble organic contaminants via a microalgae-based membrane system: performance and mechanisms

In this study, we applied a flexible strategy to manufacture a microalgal biochar-based membrane (MBCM). Due to the hierarchical surface topography on a micro-nano scale, the MBCM was found to have both underwater superoleophobic and underoil superhydrophobic properties. Combining an underoil superhydrophobic oil-containing region (OCR) with an underwater superoleophobic water-containing region (WCR) achieved the successive filtration of multiphase emulsions. The MBCM also served as a high-performance carbocatalyst for advanced oxidation processes (AOPs), due to the N functionalities (5.08%) of the graphene-like structure. This was caused by the high-temperature pyrolysis of rich proteins and alkaline salts in the algal residue. As a result, the MBCM/AOPs system achieved greater than 99.5% emulsions separation efficiency in different emulsion mixtures, while also achieving an outstanding degradation rate (99.8%) of soluble organic contaminants (SOCs). This in-depth exploration resulted in a low-cost and green strategy for developing multifunctional membranes to treat complex wastewater. The paper explains the mechanisms used by MBCM to synchronously remove emulsions and SOCs from wastewater.

A comparative study between two novel silicone/graphene-based nanostructured surfaces for maritime antifouling

Two novel superhydrophobic nanocomposite series of polydimethylsiloxane (PDMS) enriched with reduced graphene oxide (RGO) and graphene oxide/boehmite nanorods (GO-γ-AlOOH) nanofillers were synthesized as maritime fouling-release (FR) surfaces. Controlling the nanofillers' structures and distribution in the silicone matrix influenced the self-cleaning and antifouling properties. γ-AlOOH nanorods had a single crystallinity with an average diameter of 10-20 nm and < 200 nm length. A hydrothermal method was used to prepare RGO, while the chemical deposition method was used to synthesis GO-γ-AlOOH nanocomposites for use as fouling-release coating materials. For studying the synergetic effects of graphene-based materials on the surface, mechanical, and FR features, these nanofillers were dispersed in the silicone matrix using the solution casting method. The hydrophobicity and antifouling properties of the surface were studied using water contact angle (WCA), scanning electron, and atomic force microscopes (SEM and AFM). Coatings' roughness, superhydrophobicity, and surface mechanical properties all improved for the homogeneity of the dispersion of the nanocomposite. Laboratory assessments were carried out for 30 days using selected microorganisms to determine the antifouling effects of the coating systems. PDMS/GO-γ-AlOOH nanorod composite had better antibacterial activity than PDMS/RGO nanocomposite against different bacterial strains. This is caused by the high surface area and stabilizing effects of the GO-γ-AlOOH hybrid nanofillers. The PDMS/GO-γ-AlOOH nanorod composite (3 wt%) had the lowest biodegradability percentage (1.6%) and the microbial endurability percentages for gram-positive, gram-negative, and fungi were 86.42%, 97.94%, and 85.97%, respectively. A field trial in natural seawater was conducted to confirm the coatings' FR performance based on the screening process and image analysis for 45 days in a tropical area. The most profound superhydrophobic antifouling nanostructured coating was the homogeneity of the GO-γ-AlOOH (3 wt%) dispersion, which had a WCA of 151° and a rough surface.

Superhydrophobic Nanocoatings as Intervention against Biofilm-Associated Bacterial Infections

Biofilm formation represents a significant cause of concern as it has been associated with increased morbidity and mortality, thereby imposing a huge burden on public healthcare system throughout the world. As biofilms are usually resistant to various conventional antimicrobial interventions, they may result in severe and persistent infections, which necessitates the development of novel therapeutic strategies to combat biofilm-based infections. Physicochemical modification of the biomaterials utilized in medical devices to mitigate initial microbial attachment has been proposed as a promising strategy in combating polymicrobial infections, as the adhesion of microorganisms is typically the first step for the formation of biofilms. For instance, superhydrophobic surfaces have been shown to possess substantial anti-biofilm properties attributed to the presence of nanostructures. In this article, we provide an insight into the mechanisms underlying biofilm formation and their composition, as well as the applications of nanomaterials as superhydrophobic nanocoatings for the development of novel anti-biofilm therapies.