High-Efficiency Preparation of Reduced Graphene Oxide by a Two-Step Reduction Method and Its Synergistic Enhancement of Thermally Conductive and Anticorrosive Performance for Epoxy Coatings

Abstract

Herein, a simple and high-efficiency two-step reduction method is developed to prepare graphene. Graphite oxide is reduced by Fe powder and microwave thermal reduction. The two-step microwave-assisted reduction method greatly shortens the preparation time of graphene. The obtained microwave-reduced graphene oxide (MrGO) possesses obvious graphene characteristics and high C/O atomic ratio. The thermal conductivity of epoxy coating incorporating 5 wt % MrGO-6 increases to 0.66 W/(m·K), an almost 267% enhancement compared with pure epoxy (0.18 W/(m·K)). Importantly, the coating resistance of epoxy/MrGO-6 is 2–3 times higher than that of epoxy after being immersed in 3.5 wt % NaCl aqueous solution. The MrGO/polymer composites have potential application prospects in the field of corrosion protection for heat exchange equipment due to its high thermal conductivity, excellent anticorrosion performance, and simple preparation method.

A New Understanding of Graphene Influencing the Protective Performance of Zinc-Rich Coatings

“…The equivalent circuits of R(QR) and R(Q(R(QR))) are suitable for impermeable coating and permeable coating, respectively. 37 For the coating with one time constant, R s is the solution resistance, while R c and CPE c represent the resistance and the constant phase element (CPE) of the coating, respectively. 38 For the coating with two time constants, there are additional double-layer capacitance (CPE dl ) and the charge transfer resistance (R ct ) in the corrosion process at the metal interface based on that of the coating with one time constant, where CPE is defined by admittance Y and power index number n, given by Y = Y 0 (j•w).…”

“…The equivalent circuits (Figure ) were employed to analyze the EIS data during the immersing process by quantitatively assessing the time dependence of the coating performance. The equivalent circuits of R­(QR) and R­(Q­(R­(QR))) are suitable for impermeable coating and permeable coating, respectively . For the coating with one time constant, R s is the solution resistance, while R c and CPE c represent the resistance and the constant phase element (CPE) of the coating, respectively .…”

“…Research on graphene in the field of corrosion protection has mainly focused on applying a complete graphene film directly to metal surfaces or dispersing graphene nanosheets in polymer coatings to prevent corrosion. However, due to their high electrical conductivity and thermodynamic stability, it is easy to induce and promote the corrosion of metal with the formation of galvanic microcells, once in contact with the metal. − The introduction of conductive fillers is expected to enhance the electrical connection and extend the protection life of the coating. However, it may also exacerbate the corrosion of zinc to a certain extent in the form of galvanic corrosion with zinc particles, thereby weakening the service life of the zinc particle as a sacrificial anode.…”

Ultra-thin freestanding graphene films for efficient thermal insulation and electromagnetic interference shielding

“…Although the dispersion of graphene can be signicantly improved, the introduced impurity ions tend to degrade the electrical, thermal, and magnetic properties of graphene lms. [7][8][9] In addition, the traditional preparation methods, such as the redox method, mechanical exfoliation method, and liquid deposition method, [10][11][12] have insurmountable problems such as being timeconsuming, easy environmental pollution and performance defects caused by hazardous chemicals. The chemical vapour deposition method 13 is a complex preparation process.…”