Theoretical and experimental investigations about the role of MXene nanosheets covered with ZnO quantum dots on barrier resistance of epoxy coatings

In this research, MXene nanosheets were covered by ZnO quantum dots with particle sizes of less than 10 nm. Then, the synthesized nanohybrid was modified with 3-aminopropyltriethoxy silane (APTES) and designed as Silane-MXene@ZnO QDs for application as a nanofiller into an epoxy polymer matrix. The results indicate that: (1) the presence of Silane-MXene@ZnO QDs in the coating structure creates a hydrophobic coating with a water contact angle of 112.7 ± 1.1 º. (2) The bonding strength at the interface of the coating with the steel substrate increases from 3.2 ± 0.7 to 4.4 ± 0.5 MPa by adding the nanofillers. (3) The barrier resistance against the diffusion of the NaCl solution increases, and the impedance modulus of the nanocomposite coating is 1.47 × 109 and 3.60 × 107 ohm.cm2 after 1 day and 56 days of immersion, respectively. The interactions and electronic properties in the novel corrosion-resistant matrix were investigated by density functional theory (DFT) calculations. It is found that the robust chemisorption of the ZnO QDs on the MXene nanosheets improves the dispersion quality and barrier effects. Moreover, the stable interface of the nanohybrid with the APTES effectively hinders the permeation of corrosive agents. In particular, the d-states of MXene significantly contributes to the conductivity and charge transfer with the APTES and improves the matrix stability. This study provides valuable insights for designing protective coatings.