Nanocomposite dodecylsulfate-modified Mg-Al layered double hydroxide thin films deposited via laser technique

A. Vlad, R. Birjega, A. Matei, M. Dumitru, M. Dinescu, R. Zavoianu, O.D. Pavel, M.C. Corobea
National Institute for Lasers, Plasma and Radiation Physics, Romania,
Romania

Keywords: hydrotalcite, dodecylsulfate, thin films, PLD

Summary:

Layered double hydroxides (LDHs), also known as hydrotalcites or anionic clays having a brucite-like structure are a class of host-guest materials, which can be described by the formula [M2+1-xM3+x(OH)2]x+(An-)x/n•mH2O where M2+ and M3+ are divalent (Mg, Ni, Zn, Cu or Co) and trivalent (Al, Cr, Fe, or Ga) metal ions respectively. An- is an exchangeable anion, or an organic anion, compensating the positive charge of the hydroxide layers. Introducing the anions with specific functions in LDH structure, functional materials can be produced. Layered double hydroxides (LDHs) are regarded as potential nanocontainers of corrosion inhibitors in self-healing corrosion protection coatings. Their benefits are their cost-effective, non-toxic and large variety of compositions. The aim of this work is to investigate the properties of composite functional material organo-modified LDH thin films obtained by pulsed laser deposition (PLD). LDH based on Mg-Al (Mg/Al atomic ratio of 2.5) was used as host material, while dodecyl sulfate (DS) acted as organic surfactant guest material. The composite organo-LDH powders were synthesized by common co-precipitation in aqueous solutions and compare with pristine Mg-Al-LDH prepared similarly. The targets used for PLD were pressed pellets from these powders. Pulsed laser deposition (PLD) has gained worldwide acknowledgement as a reliable and inexpensive method for obtaining thin films of simple or complex compounds. The synthesis of all compounds described in this chapter relies on the use of classical PLD. The films were deposited using a Nd:YAG laser working at different wavelength (266 nm, 532 nm and 1064 nm) having a 10 Hz repetition rate. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were developed to investigate the topography of thin films. The degree of crystallinity of the powders and films was checked by X-ray diffraction, while spectral techniques (FT-IR, UV-VIS) were used to evidence the interlayer composition, in particular of the organic component for both powders and thin films. The chemical composition was determined by energy dispersive X-ray analysis (EDX) and secondary ion mass spectrometry (SIMS). The results evidenced the ability of PLD to produce composite LDH intercalated with an organic surfactant (DS) films with prospects to act as corrosion protective coatings.