Influence of Embedded Nanocontainers on the Efficiency of Active Anticorrosive Coatings for Aluminum Alloys Part II: Influence of Nanocontainer Position

The present work contributes to the coating design of active anticorrosive coatings for the aluminum alloy, AA2024-T3. Part II is a continuation of Part I: Influence of Nanocontainer Concentration and describes further surprising aspects of the design of nanocontainer based active anticorrosive coatings, which influence their performance. The studied coating system consists of a passive sol–gel (SiO_<i>x</i>/ZrO_<i>x</i>) matrix and inhibitor (2-mercaptobenzothiazole) loaded mesoporous silica nanocontainers (MBT@NCs), which are dispersed only in half of the coating volume. Varying position and concentration of MBT@NCs the synergetic effect of inhibitor amount and path length on the metal surface were analyzed, considering the balance between optimum barrier properties, active protection and adhesion. The impact of MBT@NC position on passive and active corrosion resistance was investigated by electrochemical impedance spectroscopy and scanning vibrating electrode technique. Increasing the distance between MBT@NCs and metal surface led to better barrier properties but worse active corrosion inhibition. These findings improve the understanding of the factors influencing the overall performance of active anticorrosive coatings and enable the development of a coating system with optimum anticorrosion efficiency

Influence of Embedded Nanocontainers on the Efficiency of Active Anticorrosive Coatings for Aluminum Alloys Part I: Influence of Nanocontainer Concentration

This work presents an effective anticorrosive coating for the industrially important aluminum alloy, AA2024-T3. The protective coating was designed by dispersing mesoporous silica nanocontainers, loaded with the nontoxic corrosion inhibitor, 2-mercaptobenzothiazole, in a hybrid sol–gel (SiO_<i>x</i>/ZrO_<i>x</i>) layer. The concentration of the embedded nanocontainers was varied (0.04–1.7 wt %) to ascertain the optimum conditions for anticorrosion performance. Attaining high efficiency was found to be a compromise between delivering sufficient corrosion inhibitor and preserving the coating barrier properties. The impact of nanocontainer concentration on the thickness and adhesion of freshly cured coatings was also investigated. The barrier properties of the intact coatings were assessed by electrochemical impedance spectroscopy. The active corrosion inhibition was evaluated during a simulated corrosion process by the scanning vibrating electrode technique. This study has led to a better understanding of the factors influencing the anticorrosion performance and properties of active anticorrosive coatings with embedded nanocontainers

Ultrasonic Modification of Aluminum Surfaces: Comparison between Thermal and Ultrasonic Effects.

Ultrasound has become an increasingly popular tool in the modification of metal surfaces, imbuing them with various desired characteristics and functionalities. The exact role played by ultrasound in such processes remains largely speculative and thus requires clarification. In this study, aluminum was taken as a model metal to probe the nature of the surface modification, focusing on both chemical and physical changes. Using metal plates as substrates, the formation of a characteristic porous surface structure was ascertained to arise from a purely thermal mechanism, with the ultrasound providing an inhibitory influence when compared with controlled experiments matching the thermal conditions of sonication. No beneficial effect was observed through sonication, with regards to surface texture, porosity, and electrochemistry. However, for metal powders, a pronounced change in the phase composition was observed following ultrasonic exposure, largely attributed to the growth of bayerite from the surface. The immobilization of the powder on a thin epoxy film nullified such effects. This suggests that the changes in phase composition are due to the effect of ultrasound-induced mechanical stirring and high speed particle motion on the dissolution and reprecipitation of the metal oxide and hydrated oxide species. This work is of significant value to researchers both in materials science and in sonochemistry

Growth of Mesoporous Silica Nanoparticles Monitored by Time-Resolved Small-Angle Neutron Scattering

Since the first development of surfactant-templated mesoporous silicas, the underlying mechanisms behind the formation of their structures have been under debate. Here, for the first time, time-resolved small-angle neutron scattering (tr-SANS) is applied to study the complete formation of mesoporous silica nanoparticles. A distinct advantage of this technique is the ability to detect contributions from the whole system, enabling the visualization not only of particle genesis and growth but also the concurrent changes to the coexistent micelle population. In addition, using contrast-matching tr-SANS, it is possible to highlight the individual contributions from the silica and surfactant. An analysis of the data agrees well with the previously proposed “current bun” model describing particle growth: Condensing silica oligomers adsorb to micelles, reducing intermicellar repulsion and resulting in aggregation to form initial particle nuclei. From this point, the growth occurs in a cooperative manner, with condensing silica filling the gaps between further aggregating micelles. The mechanistic results are discussed with respect to different reaction conditions by changing either the concentration of the silica precursor or the temperature. In doing so the importance of in situ techniques is highlighted, in particular, tr-SANS, for mechanism elucidation in the broad field of materials science

Effect of Surface Functionalization of Metal Wire on Electrophysical Properties of Inductive Elements

The development of the microelectronics industry requires a new element basis with reduced size and increased functionality. The most important components in modern microelectronic integrated circuits are passive elements. One of the key challenges in order to improve the functionality of integrated circuits is to increase the quality of passive elements composing them. In this paper we suggest a novel approach to increase the quality factor Q of inductors by the surface modification and functionalization of the metal components. Ultrasound induced surface modification of metal wires led to the formation of a porous surface structure, which further can be functionalized with magnetite nanoparticles using layer-by-layer assembly technique. The surface modification and deposition of magnetite nanoparticles was investigated with SEM, XRD, and contact angle measurements. Additionally, inductance and resistance measurements, as the main parameters determining the Q-factor of inductors, were carried out. Samples with high number of magnetic nanoparticle–polyelectrolyte bilayers demonstrate a significant increase in inductance and a slight decrease in resistance in comparison to uncoated ones. The combination of these factors led to enhancement the Q-factor of the investigated inductive elements