Sol–Gel Synthesis and Characterization of Coatings of Mg-Al Layered Double Hydroxides

Abstract

In this study, new synthetic approaches for the preparation of thin films of Mg-Al layered double hydroxides (LDHs) have been developed. The LDHs were fabricated by reconstruction of mixed-metal oxides (MMOs) in deionized water. The MMOs were obtained by calcination of the precursor gels. Thin films of sol–gel-derived Mg-Al LDHs were deposited on silicon and stainless-steel substrates using the dip-coating technique by a single dipping process, and the deposited film was dried before the new layer was added. Each layer in the preparation of the Mg-Al LDH multilayers was separately annealed at 70 °C or 300 °C in air. Fabricated Mg-Al LDH coatings were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was discovered that the diffraction lines of Mg3Al LDH thin films are sharper and more intensive in the sample obtained on the silicon substrate, confirming a higher crystallinity of synthesized Mg3Al LDH. However, in both cases the single-phase crystalline Mg-Al LDHs have formed. To enhance the sol–gel processing, the viscosity of the precursor gel was increased by adding polyvinyl alcohol (PVA) solution. The LDH coatings could be used to protect different substrates from corrosion, as catalyst supports, and as drug-delivery systems in medicine.

Highly Efficient Composite Flame Retardants for Improving the Flame Retardancy, Thermal Stability, Smoke Suppression, and Mechanical Properties of EVA

“…In recent years, layered double hydroxides (LDHs) and intumescent flame retardants (IFRs) have been used to increase the flame retardancy and smoke suppression of the EVA matrix [3,4]. The LDH is composed of positively charged brucite-like layers, meanwhile containing charge-compensating anions and water molecules in the interlayer gallery [5]. The general formula of LDH is [M 2+ 1−x M 3+ x (OH) 2 ] x+ [A n− ] x/n •mH 2 O [6], where M 2+ and M 3+ are divalent and trivalent cations that occupy octahedral positions in the hydroxide layers.…”

Duplex Coating Combing Vanadate-Intercalated Layered Double Hydroxide and Ce-Doped Sol–Gel Layers on Aluminum Alloy for Active Corrosion Protection

“…This approach can effectively improve the binding force between LDH and SG layers. However, uneven coverage at the top of LDH flower clusters may cause a lot of stress and cracks or other defects could form [ 33 ]. After dip-coating twice, as shown in Figure 1 d, the LDH-V/SG-Ce composite film has good uniformity, and the surface is flat without obvious defects.…”

Metal-sulfide/polysulfide functionalized layered double hydroxides – recent progress in the removal of heavy metal ions and oxoanionic species from aqueous solutions

“…76,77 While the layered cations vary from s, p, d, and f block metal ions, the interlayered anions vary to include halides, inorganic oxoanions, and organic anionic species. 78–80 The synthesis of such a robust class of chemically diverse compositions involves versatile synthetic approaches, including co-precipitation, 81 hydrothermal, 82 sol–gel, 83 electrodeposition 84 and others. 85–87…”