3 research outputs found
Redox Responsive Release of Hydrophobic Self-Healing Agents from Polyaniline Capsules
Redox-responsive nanocapsules consisting
of conductive polyaniline
and polypyrrole shells were successfully synthesized by using the
interface of miniemulsion droplets as a template for oxidative polymerizations.
The redox properties of the capsules were investigated by optical
spectroscopies, electron microscopy, and cyclic voltammetry. Self-healing
(SH) chemicals such as diglycidyl ether or dicarboxylic acid terminated
polydimethylsiloxane (PDMS-DE or PDMS-DC) were encapsulated into the
nanocapsules during the miniemulsion process and their redox-responsive
release was monitored by <sup>1</sup>H NMR spectroscopy. The polyaniline
capsules exhibited delayed release under oxidation and rapid release
under reduction, which make them promising candidates for anticorrosion
applications
James Cook viaje al Polo Sur y alrededor del mundo (fragmento)
A new
generation of nanosensors based on mesoporous silica nanocapsules
with the ability to monitor the onset of metallic corrosion is successfully
developed and tested on 304 stainless steel. The core of the nanocapsules
contains water insoluble organic molecules that fluoresce during the
anodic dissolution of metallic substrates in the corrosion process.
The dispersion of the nanosensors in organic coatings applied on metal
substrate allows a very sensitive fluorescent detection of the initiation
of metal dissolution, close to defects in the substrate. This promising
concept offers therefore new perspectives for the development of smart
coatings for corrosion sensing
Initiation and Inhibition of Dealloying of Single Crystalline Cu<sub>3</sub>Au (111) Surfaces
Dealloying is widely utilized but is a dangerous corrosion process as well. Here we report an atomistic picture of the initial stages of electrochemical dealloying of the model system Cu<sub>3</sub>Au (111). We illuminate the structural and chemical changes during the early stages of dissolution up to the critical potential, using a unique combination of advanced surface-analytical tools. Scanning tunneling microscopy images indicate an interlayer exchange of topmost surface atoms during initial dealloying, while scanning Auger-electron microscopy data clearly reveal that the surface is fully covered by a continuous Au-rich layer at an early stage. Initiating below this first layer a transformation from stacking-reversed toward substrate-oriented Au surface structures is observed close to the critical potential. We further use the observed structural transitions as a reference process to evaluate the mechanistic changes induced by a thiol-based model-inhibition layer applied to suppress surface diffusion. The initial ultrathin Au layer is stabilized with the intermediate island morphology completely suppressed, along an anodic shift of the breakdown potential. Thiol-modification induces a peculiar surface microstructure in the form of microcracks exhibiting a nanoporous core. On the basis of the presented atomic-scale observations, an interlayer exchange mechanism next to pure surface diffusion becomes obvious which may be controlling the layer thickness and its later change in orientation