Smart coating with dual-pH sensitive, inhibitor-loaded nanofibers for corrosion protection

Smart coatings that provide corrosion protection on demand have received a lot of recent attention. In the present study, nanofibers containing a corrosion inhibitor were prepared by a coaxial electrospinning technique, which addresses the limitations of inhibitor-loaded microcapsules or nanocontainers. The as-prepared nanofibers have a core-shell structure with Ce(NO3)3 and the chitosan/polyacrylic acid polyelectrolyte coacervate as the core and shell materials, respectively. UV-vis spectroscopic analysis confirms that the nanofibers are pH-sensitive and able to release the enclosed Ce(NO3)3 at both low and high pH conditions, which are spontaneously generated during corrosion at local anodes and cathodes, respectively. A coating system consisting of such nanofibers within a polyvinyl butyral coating matrix exhibits improved corrosion protection of an AA2024-T3 substrate. Moreover, the embedded Ce(NO3)3-loaded nanofibers can persistently release Ce(NO3)3 to impede corrosion of AA2024-T3 when the artificially damaged coating sample is exposed to NaCl solution.

Effect of ZrB2 Functionalized Nanoparticles Growth on Microstructural and Corrosion Resistance on Mild Steel through Electrodeposition Route

In other to have a better performance of Ni-P-Zn multifunctional applications, crystallite-like Ni-P-Zn-ZrB2 composite was actively fabricated by electrodeposition principle. The corrosion, structural evolution and surface active phenomena were investigated by various techniques. The influence of ZrB2 particulate on the morphology and corrosion properties was examined. The outcomes show an inclusive flower-like doped ZrB2 phase constituent and is uniformly distributed Ni-P-Zn-ZrB2 improved strengthening effect. The corrosion progression of the developed metal alloy was compared with other coating matrix from 10-25 minutes interval. The integration of ZrB2 on Ni-P-Zn phase especially for 25 min deposits significantly enhances corrosion resistance due to good grain refinement. Keywords: Ni-based composite, electrodeposition, time difference, coating, corrosion

Laser Activated and Electroless Metalized Polyurethane Coatings Containing Copper(II) L-Tyrosine and Glass Microspheres

Polyurethane coatings containing copper(II) L-tyrosine and glass microspheres were laser irradiated and underwent electroless metallization. Various sizes of glass microspheres were incorporated into the polyurethane coating matrix in order to examine their effects on surface activation and electroless metallization. The surface of the coatings was activated by using ArF excimer laser emitting ultraviolet radiation (λ = 193 nm) using different number of laser pulses and their fluence. The effects of surface activation and metallization were evaluated mainly based on optical and scanning electron microcopies (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoelectron spectroscopy (XPS). It was found that the presence of glass microspheres enabled the reduction in copper complex content, intensified the ablation process (higher cone-like structures created) and resulted in higher content of copper metallic seeds. On the other hand, the glass microspheres concentration, which was higher for lower size microspheres, was advantageous for obtaining a fully metallized layer.

Effect of Heating on the Microstructure of NiAl + CrB2 Coatings Deposited by Mechanical Embedding in a Ball Mill

The thickness of NiAl + CrB2 coatings, produced by the mechanical embedding of powders, is limited due to the increasing brittleness of processed materials with milling time. Only the NiAl grain growth and resultant softening of the coating matrix could overcome this problem. Therefore, the effect of heating up to 750°C on the microstructure of NiAl + CrB2 coatings deposited in a ball mill rotating at 350 rpm was investigated through in situ TEM observations. The performed observations proved that defect annihilation starts at ~400°C in large intermetallic grains, which are first attached to the substrate. The growth in NiAl nanocrystallites forming most of the coating is activated only above ~600°C. The average crystallite size was measured to be 5, 14, and 19 nm at RT, 650°C, and 750°C, respectively. The first stage of nano-crystallite growth is relatively fast and connected with the reconstruction of crystallite boundaries using up the amorphous material accumulated in between them. The second stage is slower and involves the expansion of larger crystallites at the expense of smaller ones. The performed experiment proved that heating up to 750°C allows the microstructure recovery and grain coarsening of coatings to be activated.

Synthetic Analogue of Butenolide as an Antifouling Agent

Butenolide derivatives have the potential to be effective and environmentally friendly antifouling agents. In the present study, a butenolide derivative was structurally modified into Boc-butenolide to increase its melting point and remove its foul smell. The structurally modified Boc-butenolide demonstrated similar antifouling capabilities to butenolide in larval settlement bioassays but with significantly lower toxicity at high concentrations. Release-rate measurements demonstrated that the antifouling compound Boc-butenolide could be released from polycaprolactone-polyurethane (PCL-PU)-based coatings to inhibit the attachment of foulers. The coating matrix was easily degraded in the marine environment. The performance of the Boc-butenolide antifouling coatings was further examined through a marine field test. The coverage of biofouler on the Boc-butenolide coatings was low after 2 months, indicating the antifouling potential of Boc-butenolide.

The influence of Gum Arabic on the physicochemical and antimicrobial activity of the microencapsulated Mahkota Dewa (Phaleria macrocarpa) leaves

Mahkota Dewa (Phaleria macrocarpa) also known as God's Crown has been historically used as an indispensable alternative herbal medicine. Microencapsulation is a process whereby tiny particles or droplets are engulfed or enclosed in a coating matrix to produce small capsules. Generally, without microencapsulation, powders are fragile materials that could easily interfere with other components that are difficult to dissolve in water, lose their beneficial properties and decrease shelf life. It is hoped that the microencapsulation would increase the consistency of the powder during storage and maintain its beneficial properties. The goal of this research is to investigate the physicochemical and antimicrobial activity of Mahkota Dewa leaves encapsulated in different concentrations of gum Arabic (GA) and to determine the form of antioxidant and their role and properties. Mahkota Dewa leaves powders were microencapsulated in 0%, 2%, 4%, 6%, 8% and 10% gum Arabic using an ultrasonic spray dryer at 90οC. The microencapsulated Mahkota Dewa leaves (MMDL) samples were subjected to physicochemical and antimicrobial activity. The results showed that the 6% GA MMDL exhibited the highest yield (3.91%) while 0% GA was the lowest yield (1.64%). The highest total phenolic and flavonoid content was exhibited by 2% GA. The highest DPPH inhibition was depicted in 0% GA which indicates the highest antioxidant activity (54.9±0.01%) and is significantly (p<0.05) different from other samples. The highest inhibition was exhibited in 0% GA in the TBA method and FTC analysis. The encapsulated powders were identified to have weak antimicrobial activity against Bacillus cereus, Escherichia coli, Staphylococcus aureus, Salmonella and Listeria monocytogenes. The powders produced have an irregularly spherical structure and smooth surface with some dented spots on the surface. The different concentration of gum Arabic resulted in different antioxidant activity, flavonoid content and antimicrobial activity of MMDL.

Corrosion Resistance Evaluation of Self-Healing Epoxy Coating Based on Dual-Component Capsules Containing Resin and Curing Agent

In this study, a self-healing epoxy coating was prepared by incorporating a dual capsule healing system including epoxy resin and its amine-based curing agent. The emulsion electrospray technique was used for encapsulating the healing agents in poly(styrene co-acrylonitrile) (SAN) as shell material. Characterizing the prepared microcapsules (MCs) by Scanning Electron Microscopy (SEM) revealed their spherical morphology with the particle size of 827 nm and 749 nm for epoxy and amine cores, respectively. Fourier Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results confirmed successful encapsulation with no side chemical reaction between the encapsulated core and shell materials. The effects of embedding MCs on the physical and mechanical properties of the epoxy coating matrix were studied by pull-off adhesion, conical mandrel bending, and gloss tests. In addition, the prepared coatings’ self-healing performance was evaluated by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization (Tafel) experiments. The results revealed that the coating sample containing 1 wt% of core-shell MCs (a mixture of epoxy and amine-containing MCs with a 50 : 50 weight ratio) showed the best corrosion performance with 99% self-healing efficiency.

Bodipy-Loaded Micelles Based on Polylactide as Surface Coating for Photodynamic Control of Staphylococcus aureus

Decontaminating coating systems (DCSs) represent a challenge against pathogenic bacteria that may colonize hospital surfaces, causing several important infections. In this respect, surface coatings comprising photosensitizers (PSs) are promising but still controversial for several limitations. PSs act through a mechanism of antimicrobial photodynamic inactivation (aPDI) due to formation of reactive oxygen species (ROS) after light irradiation. However, ROS are partially deactivated during their diffusion through a coating matrix; moreover, coatings should allow oxygen penetration that in contact with the activated PS would generate 1O2, an active specie against bacteria. In the attempt to circumvent such constraints, we report a spray DCS made of micelles loaded with a PS belonging to the BODIPY family (2,6-diiodo-1,3,5,7-tetramethyl-8-(2,6-dichlorophenyl)-4,4′-difluoroboradiazaindacene) that is released in a controlled manner and then activated outside the coating. For this aim, we synthesized several amphiphilic copolymers (mPEG–(PLA)n), which form micelles, and established the most stable supramolecular system in terms of critical micelle concentration (CMC) and ∆Gf values. We found that micelles obtained from mPEG–(PLLA)2 were the most thermodynamically stable and able to release BODIPY in a relatively short period of time (about 80% in 6 h). Interestingly, the BODIPY released showed excellent activity against Staphylococcus aureus even at micromolar concentrations.

Spatial Orientation of Carbon Nanotubes in a Light-Absorbing Coating Matrix

The inability to orient carbon nanotubes perpendicularly to the rays falling on them reduces the amount of light energy that the tubes absorb and convert into heat, which can lead to a decrease in the amount of energy absorbed by the light-absorbing layer. The process of orientation of carbon nanotubes in the coating matrix used in solar panels has been studied in order to obtain maximum absorption of this layer. The paper presents the design of a machine that uses magnetic force to orient carbon nanotubes, and a model that calculates the electric current and the time required to achieve the required orientation of carbon nanotubes.