Synthesis and characterization of gordaite, osakaite and simonkolleite by different methods: comparison, phase interconversion, and potential corrosion protection applications

Gordaite (NaZn4(OH)6SO4Cl·6H2O) is a mineral from the layered hydroxide salts (LHS) family that presents both cation- and anion-exchange properties, which is rare in this class of materials, having then called much attention lately due to its interesting potential applications. Sharing similar layered structure and composition, gordaite’s non-cation-exchanger analogous such as osakaite (Zn4(OH)6SO4·5H2O) and simonkolleite (Zn5(OH)8Cl2·H2O) show the possibility of interconversion reactions, in dynamics that might be of interest in technological applications such as corrosion protection. The materials can act as stimuli-responsive nanocontainers for storing corrosion inhibitors between the layers that might then be released on demand and avoid corrosion reactions on metals and alloys. In this work, we study the different methodologies for obtaining these LHS by synthesizing them by the oxide hydrolysis, co-precipitation by increasing pH and electrochemical methods, and comparing the obtained results.publishe

Layered materials as nanocontainers for active corrosion protection: A brief review

Over the past years, the use of layered materials such as clay minerals, layered double hydroxides, and layered hydroxide salts, as nanocontainers of corrosion inhibitors has grown, and these materials have proved to be very advantageous to improve the corrosion protection of metallic surfaces. The layered materials are especially advantageous for this application due to their capacity of not only releasing corrosion inhibitors on-demand to protect the metal but also capturing ionic aggressive species from the medium. The diversity of corrosion inhibitors species that can be intercalated in the interlayer space of these materials and the possibility to synthesize different layered materials (composition, structure, and morphology), using different methods, provide a high versatility to produce efficient protective systems, which are elucidated and discussed in this review. Moreover, a section on future perspectives is presented, indicating promising and still underexplored possibilities for future development trends in using layered materials for corrosion protection applications.publishe

Optical (DRUV-VIS) and magnetic (EPR) behavior of synthetic melanins

The properties of melanins prepared from L-dopa oxidation by both chemical and electrochemical methods are reported, searching for a material with more intense optical absorption in the visible region. The characterization of the samples have been done by cyclic voltammetry (CV), cronoamperometry (CA), Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR) and diffuse reflectance ultraviolet-visible spectroscopy (DRUV-VIS) techniques. The electrochemical method enhanced the organic free radical (spin) concentration and the absorption intensity in the visible region of the spectrum. The DRUV-VIS technique along with mathematical tools, such as the Kubelka-Munk remission function, were good options for the characterization of the final products