Herein described is a facile preparation protocol by which amino-alcohol derivatives of graphene oxide (GO) can be conveniently synthesized in high yield and a short time by an ultrasound treatment of ethanol-graphite-oxide suspensions and amines. Linear primary amines of different chain length rapidly react with graphite oxides prepared from powder and flakes, leading to the formation of GO amino-alcohol derivatives. Characterization of the amine-modified materials by XRD, TGA, FTIR, and Raman demonstrates the proposed derivatization; the findings are corroborated by SEM and TEM observations. Additionally, quantum-chemical investigations shed additional light on the reaction, suggesting an alcohol-accelerated SN2 mechanism where the initial step, the simultaneous formation of a C-N bond (GO-amine) and rupture of an epoxide bond in GO, is rate-determining. Energy barriers lower than 8 kcal/mol are estimated, which can be overcome with the energy supplied by the sonotrode tip (ca. 2 kcal) and the use of ethanol to facilitate it.
In this study, the effect of pure and modified hexagonal boron nitride (h-BN) nanosheet incorporation on the stability, viscosity, and electrochemical behavior of a waterborne emulsion acrylic coating was studied. The functionalization of h-BN nanoplatelets with polyacrylic acid (PAA) plasma polymerization was performed, and the successful surface modification was determined through water dispersion testing, Fourier transform infrared spectroscopy and thermogravimetric analysis, X-ray photoelectron spectroscopy, and also by transmission electronic microscopy. Later, the stability and viscosity properties of emulsion nanostructured acrylic coatings, which were previously prepared by an ultrasound-assisted mixing system, were analyzed using zeta potential and rheometry testing, respectively. The electrochemical behavior was analyzed by electrochemical impedance spectroscopy. The results prove an effective deposition of PAA films on the h-BN surfaces, which enhanced the stability and viscosity acrylic of nanostructured coatings due to the interactions between the h-BN nanoplatelets surface and emulsion acrylic paint and also with the thickener additives. On the other hand, the electrochemical analysis demonstrated a significant increase (two orders of magnitude) in corrosion resistance in the acrylic nanostructured coatings with 1 wt.% of unmodified and modified h-BN nanoplatelets concerning pure acrylic paint due to a barrier protection mechanism of corrosion inhibition. Therefore, the results demonstrate that the surface modification of h-BN by plasma polymerization (green technology) helped to solve the low dispersibility issue of BN nanosheet surfaces in a waterborne polymer matrix to obtained green nanostructured acrylic coatings with the right balance in in-can properties and corrosion inhibition of AISI 304 stainless steel.
In a Proton Exchange Membrane Fuel Cell (PEMFC), the bipolar plates are exposed to oxidant conditions on one side and reducing conditions on the other. The requirement of good electrical and thermal conductivity, good corrosion resistance, low weight, a good impermeability to the reactant gases and low cost restricts the choices of materials to manufacture bipolar plates. The objective of this research is to determine the corrosion resistance of candidate bipolar plate materials in the chemical environment encountered in PEM fuel cells. Several austenitic stainless steels (SS304 and SS316) and nickel alloys have been examined (Inconel 600, Inconel 601, Inconel 625, Incoloy 800H). The out-of-stack tests involved two types of electrochemical measurements, made in solutions that simulate the atmospheres of both the cathode and the anode chambers of a typical fuel cell, bubbled with O 2 and H 2 , respectively, at room temperature and at 50 °C.
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