jp6b10860_si_001.pdf (662.98 kB)
How Density Functional Theory Surface Energies May Explain the Morphology of Particles, Nanosheets, and Conversion Films Based on Layered Double Hydroxides
journal contribution
posted on 2016-12-28, 00:00 authored by Tiago L. P. Galvão, Cristina S. Neves, Mikhail L. Zheludkevich, José R. B. Gomes, João Tedim, Mário G.
S. FerreiraConversion films based on layered
double hydroxides constitute
an important and environmentally friendly technology for the corrosion
protection of aeronautical structures. Unfortunately, the morphology
of layered double hydroxide (LDH) conversion films is still not well
understood. In the present work, the structure and driving forces
behind the morphology of zinc–aluminum LDH conversion films
on aluminum alloy 2024 (AA2024) are explained from the perspective
of molecular modeling. Since LDH particles are the core structures
of LDH conversion films, the first step in this work was to understand
the relation between structure and morphology of the particles themselves
and the single-layer nanosheets that constitute them. Results regarding
LDH’s crystallites, particles, and conversion films obtained
using X-ray diffraction (XRD), dynamic light scattering (DLS), scanning
electron microscopy (SEM), and atomic force microscopy (AFM) are interpreted
using periodic model density functional theory (DFT) calculations.
On the basis of the understanding of the formation of LDH particles
and their exfoliation to obtain single-layer nanosheets, for the first
time, LDH conversion films have been modeled using periodic model
DFT. The results point to a preferential orientation of the cationic
layers perpendicular to the surface, thus explaining the film morphology
(SEM and AFM) and providing a rational for their crystallization process.