Ni-Graphene oxide (GO) composite coatings were electrodeposited over mild steel substrate. The coatings exhibited compact and crack free morphology. Incorporation of GO facilitated grain growth along low energy (111) and (200) atomic planes without any significant alteration in the crystallite size. Compositional analysis suggested uniform distribution of GO within the coating for lower GO concentration. Whereas for higher GO concentrations, agglomeration and non-uniform distribution of GO within the coating microstructure was noticed. Corrosion behaviour of coatings was studied by electrochemical impedance spectroscopy and potentiodynamic polarisation techniques. It was observed that the corrosion rate of the coating initially decreased with the addition of GO. After an optimum GO concentration which produced the lowest corrosion rate, further addition of GO resulted in increase in the corrosion rate. The initial decrease in the corrosion rate was attributed to the coating growth along the low energy low index planes and the impermeability of the GO to the electroactive media. The increase in the corrosion rate beyond the optimum was attributed to the GO agglomeration which caused inhomogeneous distribution of GO in the coating and relatively non-uniform coating morphology.

Ni-graphene oxide composite coatings: Optimum graphene oxide for enhanced corrosion resistance

This study examines the aggregation/agglomeration of layered clay in polymer nanocomposites and discusses their influences on nanoparticle characteristics and mechanical properties using appropriate equations. The effective volume fraction, specific surface area, and aspect ratio of layers are calculated in samples containing both single and aggregated/agglomerated nanoparticles. The Young’s modulus and yield strength of nanocomposites are predicted based on the effective characteristics of layers.
 The aggregation/agglomeration decreases the effective levels of volume fraction, aspect ratio, and specific surface area of nanoparticles.
 As a result, researchers should prevent the accumulation of clay layers in nanocomposites and encourage the exfoliation of single layers causing optimal properties.

A Simulation Work for the Influences of Aggregation/Agglomeration of Clay Layers on the Tensile Properties of Nanocomposites

Graphene oxide-chitosan-silver composite coating on Cu-Ni alloy with enhanced anticorrosive and antibacterial properties suitable for marine applications

The present paper reports the fabrication of efficient anticorrosion coating material on mild steel using epoxy phenolic novolac (EPN) polymer. The EPN was prepared by refluxing the mixture of phenol formaldehyde amine and epoxy in a 1:1 weight ratio and characterized by 1H NMR and FT-IR spectral studies. The graphene oxide (GO) was functionalized using 2-{4-[2-hydroxy-3-(propan-2-ylamino) propoxy] phenyl} acetamide and thoroughly characterized by FT-IR, Raman, and energy dispersive X-ray spectroscopies and TEM techniques. The anticorrosion performance of the coated mild steel (MS) samples was studied by electrochemical impedance spectroscopy and potentiodynamic polarization techniques in 3.5 wt% NaCl medium. The results revealed that the anticorrosion ability of EPN coating was significantly enhanced by the incorporation of functionalized graphene oxide (FGO). The corrosion inhibition efficiency of 99.99% is achieved with 0.2 wt% FGO-grafted EPN matrix.

Functionalized graphene oxide-epoxy phenolic novolac nanocomposite: an efficient anticorrosion coating on mild steel in saline medium

In this study, we used the Takayanagi model expanded by Loos and Manas-Zloczower for the tensile modulus to assess the tensile strength of polymer/carbon nanotube nanocomposites (PCNTs).
 The new model assumes the strengthening and percolating efficiencies of the interphase between the polymer matrix and the nanoparticles. We evaluated the suggested model with the experimental data of two PCNTs and found that this model successfully calculated the average levels of the percolation threshold, interphase thickness (t), and interphase strength (σiN). The percolation threshold > 0.004, interphase volume fraction   30 nm caused the lowest relative tensile strength, less than the strength of the polymer matrix. Among the studied variables, the t and σiN parameters most significantly affected the tensile strength of PCNTs; when t = 25 nm and σiN = 17 GPa, there was 1300% improvement in the strength of the PCNT. This model can be applied in future studies to accelerate the material design process.

Evaluation of the Tensile Strength in Carbon Nanotube-Reinforced Nanocomposites Using the Expanded Takayanagi Model

Optimum amount of graphene oxide for enhanced corrosion resistance by tin-graphene oxide composite coatings

Grain boundary engineering in Ni-carbon nanotube composite coatings and its effect on the corrosion behaviour of the coatings

In the present study, microstructure-electrochemical property correlation in electrodeposited SnBi-GO composite coatings containing different amounts of graphene oxide has been investigated. The SnBi-GO coatings exhibited uniform and compact morphology for lower GO concentrations, whereas for higher GO concentrations the morphological defects appeared. X-ray diffraction analysis showed the presence of Sn rich and a Bi rich phase in the coatings. Crystallite size of Bi-rich phase decreased whereas for Sn-rich phase it remained nearly unaffected with increasing GO addition. Growth texture analysis showed that the incorporation of GO enhanced growth along the low index planes for the Sn-rich grains and along the high index planes for the Bi-rich grains. Corrosion properties of coatings examined by the potentiodynamic polarisation and impedance spectroscopy methods revealed that the corrosion rate of the coatings decreased with increase in the GO content till an “optimum” addition of GO, after which the corrosion rate significantly increased with further GO addition. Microstructural analysis conducted using the electron backscatter diffraction (EBSD) technique showed that the coating with “optimum” GO amount which yielded the minimum corrosion rate contained highest fraction of low energy low angle grain boundaries which was due to the lowering of Bi dissolution in the Sn grains. Initial decrease in the corrosion rate was attributed to coating compactness, growth of grains along low energy index planes and GO impermeability. Increase in the corrosion rate after the optimum was attributed to increase in the morphological defects and possible galvanic coupling between the GO and the metals in the coatings. The enhanced corrosion properties of SnBi-GO coatings make them a viable material for interconnections used in the electronic components.

Correlation between microstructure and corrosion behaviour of SnBi-graphene oxide composite coatings

Nucleation and growth mechanism of tin electrodeposition on graphene oxide: A kinetic, thermodynamic and microscopic study

The inert and hydrophobic nature of carbon nanotubes (CNTs) makes them a potential material for corrosion protection coatings. In this work, a uniform coating of multi-walled CNTs (MWCNTs) was formed over a mild steel substrate by direct decomposition of a ferrocene–benzene mixture over the substrate which was kept inside a chemical vapor deposition setup at a temperature of 800°C. The MWCNTs formed over the substrate were characterized using x-ray diffraction, Raman spectroscopy and transmission electron microscopy techniques. Corrosion behavior of the bare and MWCNT-coated mild steel substrate was examined through potentiodynamic polarization and electrochemical impedance spectroscopy methods. A significant improvement in the corrosion resistance in terms of the reduction in corrosion current and corrosion rate and increase in polarization resistance was noted in the case of the MWCNT-coated mild steel plate. Corrosion resistance increased due to MWCNT coating.

Abhay Gupta

Papers

Optimum amount of graphene oxide for enhanced corrosion resistance by tin-graphene oxide composite coatings

Grain boundary engineering in Ni-carbon nanotube composite coatings and its effect on the corrosion behaviour of the coatings

Correlation between microstructure and corrosion behaviour of SnBi-graphene oxide composite coatings

Nucleation and growth mechanism of tin electrodeposition on graphene oxide: A kinetic, thermodynamic and microscopic study

High Corrosion Resistance Offered by Multi-Walled Carbon Nanotubes Directly Grown Over Mild Steel Substrate