The effect of single-layer graphene sheets (Gr) on the corrosion protection of zinc-rich epoxy primers (ZRPs) was investigated. Scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) were used to characterize morphology and composition of the coatings after immersion for 25 days. The cross-sectional SEM images and X-ray photoelectron spectroscopy (XPS) confirmed that the addition of single-layer graphene facilitated assembling of zinc oxides on the interface between the coating and the steel. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements revealed that both the cathodic protection and barrier performance of the ZRP were enhanced after addition of 0.6 wt. % Gr (Gr0.6-ZRP). In addition, the cathodic protection property of the Gr0.6-ZRP was characterized quantitatively by localized electrochemical impedance spectroscopy (LEIS) in the presence of an artificial scratch on the coating. The results demonstrate that moderate amounts of single-layer graphene can significantly improve corrosion resistance of ZRP, due to the barrier protection and cathodic protection effects.

The corrosion behavior of zinc-rich epoxy primers or paints (ZRPs) with different conducting polyaniline-grafted graphene (PANI/Gr) contents was investigated. Conductivity of the formed PANI/Gr nanosheets was significantly improved by employing the Gr as the inner template to synthesize the PANI. The protective properties and electrochemical behavior of coatings with artificial defects were investigated by monitoring the free corrosion potential versus time and by using localized electrochemical impedance spectroscopy (LEIS). A synergetic enhancement of the physical barrier role of the coating and the zinc sacrificial cathodic protection was achieved in the case of ZRP including PANI/Gr nanosheets. In addition, the ZRP mixed with the PANI/Gr at a content of 0.6% exhibited the best anticorrosion performance across the range of investigated PANI/Gr contents.

Na_0.67Ni_0.33Mn_0.67O₂ is a prospective layered cathode material for sodium-ion batteries owing to its low cost, ease of synthesis, and high specific capacity. However, due to direct contact with electrolytes during the cycling process, the cyclic stability is not satisfied. To address this issue, magnesium oxide (MgO) surface modification was performed in this study to improve the material’s cycling properties. MgO layers of various thicknesses were successfully coated onto the cathode, and their electrochemical performances were thoroughly investigated. Among the as-prepared samples, the 2 wt% MgO-coated sample demonstrated the best rate capability and cycling stability. It had an initial reversible discharge capacity of 105 mAh g⁻¹ in the voltage range from 2.0 to 4.5 V at 0.2 C with a high cycle retention of 81.5%. Electrochemical impedance spectroscopy (EIS) results showed that the 2 wt% MgO-coated electrode had the highest conductivity due to the smaller charge transfer resistance (Rct) value. All the test results show that the MgO modification improves the electrochemical properties of Na_0.67Ni_0.33Mn_0.67O₂ cathode material. This research could lead to the development of a promising strategy for improving the electrochemical performance of next-generation sodium-ion batteries.

A random metamaterial, carbon/alumina (C/Al₂O₃) composite, was prepared using a precursor infiltration and pyrolysis method, which has potential applications in novel antennas, microwave absorbing and shielding. The microstructures, radio-frequency dielectric property and conductivity behavior of the composites with different carbon contents were investigated in detail. It was found that the carbon membrane spread out on the pore walls of the alumina matrix. As the carbon content increased, the composites underwent a percolation phenomenon, and the conductive mechanism changed from hopping conduction to metal-like conduction due to the formation of conductive carbon networks. A negative permittivity behavior was observed in the composites above the percolation threshold, and this was ascribed to the low frequency plasmonic state produced by the carbon networks. The frequency dispersion of such negative permittivity efficiently agreed with the Drude model. The negative magnitude of permittivity in the testing frequency was small, ranging from −370 to −28, which originated from the lower carrier concentration in the conducting carbon networks. This work will greatly facilitate the practical application of random metamaterials with tunable electrical properties, and has great significance for the development of metamaterials.

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.