Evaluation of self-healing properties of inhibitor loaded nanoclay-based anticorrosive coatings on magnesium alloy AZ91D

This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)were loaded with cationic corrosion inhibitors Ce 3+/Zr 4+.These nanocontainers were dispersed in hybrid organic-inorganic sol-gel matrix sol.Coating was applied on magnesium alloy AZ91D using the sols containing modified and unmodified nanocontainers employing the dip coating method and cured at 130℃for 1 h in air.Corrosion resistance of coated/uncoated substrates were analyzed using electrochemical impedance spectroscopy,potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt%NaCl solution for varying time durations between 24 h to 120 h.Self-healing ability of coatings was evaluated by micro-Raman spectroscopy after 120 h exposure to 3.5 wt%NaCl solution.Coatings generated after dispersion of corrosion inhibitor loaded clay in hybrid sol-gel matrix have shown more promising corrosion resistance when compared to just the sol-gel matrix coatings,after prolonged exposure to corrosive environment.

Release rate kinetics of corrosion inhibitor loaded halloysite nanotube-based anticorrosion coatings on magnesium alloy AZ91D

Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby,increase the amount of loading of the corrosion inhibitor.The morphology of as-received and etched halloysite nanotubes was ob-served using TEM analysis.The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis.Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which,they were dispersed into a hybrid sol-gel silica matrix.Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130℃ for 1 h.The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt%NaCl at different pH.The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models.Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt%NaCl solution for 120 h.Coatings generated using Ce^(3+)-Zr^(4+)loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium.

Ultrasound Assisted Synthesis of Starch Nanocrystals and It’s Applications with Polyurethane for Packaging Film

Starch nanocrystals(SNC)were prepared from maize starch using ultrasound assisted acid hydrolysis.The process takes less time for the generation of SNC,which is advantageous over conventional acid hydrolysis.The synthesized SNC were characterized using X-ray diffraction,dynamic light scattering,zeta potential and transmission electron microscopy(TEM).Particle size and TEM data show that the particles were near to 150 nm,with oval morphology.The SNC with higher surface charge are obtained with this innovative approach as compared to conventional acid hydrolysis.Because of high surface charge and oval like morphology,the SNC performed well in reinforcing a polyurethane film.The rise in crystallinity by 16%was observed due to ultrasound cavitation.At the lower concentration of SNC in nanocomposite film,dynamic mechanical analysis demonstrated meaningful increment in mechanical properties of polyurethane nanocomposite film.The decrease in chain slippage over the glass transition temperature was observed because of the SNC reinforcement in polyurethane dispersion.Compared to the conventional acid hydrolysis,the present approach for the synthesis of starch nanocrystals is much faster and easier.

Electrochemical Performance of Starch-Polyaniline Nanocomposites Synthesized By Sonochemical Process Intensification

The present study deals with the intensified synthesis of starch-polyaniline(starch-PANI)nanocomposite using an ultrasound-assisted method.Starch is a key component in this nanocomposite,which acts as a backbone of the nucleation of PANI.The Electrochemical property of the nanocomposite arises due to the addition of PANI.This is one of green approach for the synthesis of bio nanocomposite using ultrasound.The crystallinity of the composite is evaluated using the Scherrer Formula.The starch-PANI nanocomposite was characterized by XRD,FT-IR,Raman,XPS and TEM.The composite nanoparticles show spherical morphology.The elemental composition of starch-PANI showed O 1s peak at 546 eV,N 1s peak at 416 eV,C 1s peak at 286 eV and S 1s peak at 176 eV.The electrochemical studies of the starch-PANI electrodes are evaluated by cyclic voltammetry(CV),galvanostatic charge/discharge(GCD),and electrochemical impedance spectroscopy(EIS).Starch-PANI electrode has shown the maximum specific capacitance of 499.5 F/g at 5 mV/s scan rate.