Polyaniline/polyacrylate core–shell composites: Preparation,morphology and anticorrosive properties

Polyaniline/partially phosphorylated poly(vinyl alcohol)/polyacrylate nanoparticles ((PAn/P-PVA)_x/PAc_y) were synthesized by encapsulation of varying amounts of PAn/P-PVA nanoparticles (x = 0.3, 0.5 or 0.7 g) with PAc (y = 4, 6 or 8 g acrylate monomers) via emulsifier-free emulsion polymerization. A monomer conversion level of 93.9% was achieved for the synthesis of the (PAn/P-PVA)_0.5/PAc₄ nanoparticles. X-ray diffraction analysis revealed that PAc was intercalated between the PAn/P-PVA layers, whilst transmission electron microscopy analysis of the different nanoparticles revealed they were spherical PAn/P-PVA agglomerates coated with PAc. Thermogravimetric analysis revealed that the thermal stability of the (PAn/P-PVA)/PAc nanoparticles decreased with increasing amounts of PAc. Cyclic voltammetry based analysis of the different (PAn/P-PVA)/PAc nanoparticles coated onto carbon fiber electrodes revealed that the PAn/P-PVA nanoparticles were encapsulated sufficiently by the non-conductive PAc and that the peak current decreased with increasing amounts of acrylate. With respect to the corrosion resistance in 1.0 M sulfuric acid, steel coated with the (PAn/P-PVA)_0.7/PAc₈ nanocomposite showed the best corrosion resistance (11.4%), but for the nanocomposites at each PAn/P-PVA loading level, the anticorrosive properties increased with increasing PAc levels, presumably due to the increasing tortuosity of the diffusion pathway through the coating for any corrosion agents.     

The influence of pulse plating parameters on microstructure and properties of Ni-W-Si3N4 nanocomposite coatings

Nanosized silicon nitride (Si₃N₄) particles reinforced Nickel-tungsten composite coatings were deposited on the surface of C45 steel sheet by pulse electrodeposition. The effect of duty cycle, frequency, current pattern and presence of Si₃N₄ nanoparticles on microstructure, phases and corrosion resistance and mechanical properties of the coatings were investigated. The Si₃N₄ phase was incorporated into Ni-W alloy matrix uniformly and the inclusion content of in the coating was analyzed by energy dispersive x-ray spectrometer (EDS). The structure, microhardness and surface roughness of the coatings was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers micro-indenter and atomic force microscopy (AFM). The corrosion protection of steel by the coatings was evaluated by weight loss and electrochemical impedance spectroscopy (EIS). Corrosion rates of the coatings were determined using the Tafel polarization test. The results indicated that the duty cycle of 60%, pulse frequency of 1000 Hz, average current density of 5 A/dm⁻², and Si₃N₄ nanoparticles concentration of 30 g/L were the optimal plating conditions. The amount of Si₃N₄ particles incorporated into the coating that were produced under the optimum plating conditions was 2.1 wt%, and the microhardness was 1031 Hv as well as the crystallite size of this coating was 27 nm.     

Influence of embedded ZnAlCe-NO3− layered double hydroxides on the anticorrosion properties of sol–gel coatings for aluminum alloy

A protective coating was designed by dispersing Ce-doped ZnAl layered double hydroxides (ZnAlCe-LDHs) nanoparticles in hybrid sol–gel (SiO_x/ZrO_x) layer on aluminum alloy AA2024. The concentration of cerium in synthesized LDHs was varied to ascertain the optimum condition for anticorrosion performance. The LDH nanoparticles were characterized in terms of structure, morphology and chemical composition. It was found that Ce (III) was inserted into the sheets of LDHs and two mixture phases of LDHs and CeO₂ were formed when the atomic ratio of Ce/(Al + Ce) was higher than 0.05. The sol–gel coating embedded with LDHs (Ce/(Al + Ce) = 0.1) exhibited high corrosion resistance, probably due to the synergistic inhibition of ZnAlCe-LDHs and CeO₂ nanoparticles.     

In-situ AFM and EIS study of a solventborne alkyd coating with nanoclay for corrosion protection of carbon steel

A solventborne alkyd composite coating containing modified montmorillonite (MMT) nanoclay was made on carbon steel, and its corrosion protection was investigated by in-situ atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements in 3 wt.% NaCl solution. X-ray diffraction (XRD) analysis indicated intercalation of the MMT sheets in the composite coating. Thermo-gravimetric analysis (TGA) demonstrated improved thermal stability of the composite coating due to the modified nanoclay. Scanning electron microscopy (SEM) and AFM examination revealed dispersion and also some aggregation of the nanoclay particles in the coating. In-situ AFM images show a stable coating surface at nano-scale during relative long time exposure in the NaCl solution, indicating an enhanced stability of the composite coating. The EIS results confirmed that the composite coating provides an enhanced barrier type corrosion protection for carbon steel in the corrosive solution, which could be attributed to the intercalated lamellar MMT sheets in the coating that block the defects and decrease the transport of water and corrosive species.     

Al2O3/Si3N4 nanocomposite coating on aluminum alloy by the anodizing route: Fabrication,characterization, mechanical properties and electrochemical behavior

An Al₂O₃/Si₃N₄ nanocomposite coating was successfully fabricated on commercial aluminum alloy. Hardness measurements, polarization and electrochemical impedance spectroscopy (EIS) were employed to study the mechanical and corrosion behaviors of the coatings. Field-Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) were utilized to characterize the surface morphology and phase composition of the coatings. Also, coatings abrasive wear properties were evaluated with a modified ASTM G105 standard. FE-SEM image, EDS and XRD analysis revealed the presence of Si₃N₄ in the coating. Furthermore, the results showed hardness of the coatings to increase from 380±50 HV for the anodized layer to 712±36 HV for the composite coatings that were formed in an electrolyte containing 6 gr/lit Si₃N₄ nanoparticles. Electrochemical measurements indicated that corrosion resistance of the nanocomposite coating significantly increased compared to the anodized coating. In addition, the effect of Si₃N₄ nanoparticles into the nanocomposite coatings on abrasive wear mechanism and mass loss rate of the coatings was investigated.     

Investigation of corrosion protection properties of an epoxy nanocomposite loaded with polysiloxane surface modified nanosilica particles on the steel substrate

In this study, it has been aimed to investigate the corrosion protection properties of an epoxy/polyamide coating loaded with different concentrations (ranged from 3 to 6% (w/w)) of the polysiloxane surface modified silica nanoparticles (nano-SiO₂). The nanocomposites were applied on the steel substrates. Field emission scanning electron microscope (FE-SEM) and UV–vis techniques were utilized in order to investigate the nanoparticles dispersion in the coating matrix. The effects of addition of nanoparticles on the corrosion resistance of the coating were studied by an electrochemical impedance spectroscopy (EIS) and salt spray test. The coating surface degradation was studied by optical microscope and Fourier transform infrared radiation (FT-IR) spectroscopy. Results obtained from UV–vis and FE-SEM analyses revealed proper and uniform distribution of surface modified nanoparticles in the epoxy coating matrix. It was shown that the coating corrosion protection properties were significantly enhanced in the presence of 5 wt% silica nanoparticles. Less degradation occurred on the surface of the coatings loaded with 5 wt% nanoparticles.     

Investigation of the corrosion protection behavior of natural montmorillonite clay/bitumen nanocomposite coatings

The influence of clay particles on the corrosion properties of bituminous coating was studied. Different percentages of natural montmorillonite clay (Cloisite Na⁺) were added to emulsified bitumen in water to make 2 wt.%, 3 wt.% and 4 wt.% of clay/bitumen nanocomposite coatings. The coatings were applied on steel 37. Optical microscopy and transmission electron microscopy (TEM) were employed to study the structure of nanocomposite. To investigate the anti-corrosion properties of the coated panels, electrochemical impedance spectroscopy (EIS) was used. The findings indicated that the addition of clay nanolayers improved corrosion resistance of the coatings. Moreover, increasing clay loading up to 4 wt.%, increased the corrosion resistance.     

Electrosynthesis of PAni/PPy coatings doped by phosphotungstate on mild steel and their corrosion resistances

Polyaniline/polypyrrole (PAni/PPy), polyaniline-phosphotungstate/polypyrrole (PAni-PW₁₂/PPy) and PAni/PPy-PW₁₂ have been successfully electrodeposited on mild steel (MS) by cyclic voltammetry in aqueous oxalic acid solutions. It was found that the incorporation of PW₁₂ enhanced the corrosion resistance of PAni/PPy coating. Moreover, in comparison to PAni-PW₁₂/PPy, PAni/PPy-PW₁₂ coating exhibited better corrosion resistance for mild steel. After immersion of 36 h in 0.1 M HCl, for instance, the polarization resistance of PAni/PPy-PW₁₂ coating reached 1695 Ω cm², more than those of both PAni/PPy and PAni-PW₁₂/PPy.     

Novel bi-layered nanostructured SiO2/Ag-FHAp coating on biodegradable magnesium alloy for biomedical applications

In this study, a novel bi-layered nanostructured silica (SiO₂)/ silver-doped fluorohydroxyapatite (Ag-FHAp) coating was deposited on biodegradable Mg-1.2Ca-4.5Zn alloy via physical vapor deposition (PVD) combined with electrodeposition (ED). The nano-SiO₂ underlayer had a compact columnar microstructure with thickness of around 1 µm while the Ag-FHAp overlayer presented large plate-like crystals accompanied with small rounded particles with thickness about 10 µm. Potentiodynamic polarization test exhibited that the double layer SiO₂/Ag-FHAp coated Mg alloy has superior corrosion resistance compared to uncoated and single layer SiO₂ coated samples. Contact angle measurement showed that Ag-FHAp coating over nano-SiO₂ layers significantly increased surface wettability which is favorable for the attachment of cells. Cytotoxicity tests indicated that the nanostructured SiO₂/Ag-FHAp coating enabled higher cell viability compared to nano-SiO₂ coating and uncoated samples. In addition, bi-layer and single-layer coatings considerably improved the ability of cell attachment than that of the uncoated samples. The cell viability of coated and uncoated samples increased with increasing incubation time. The double layer SiO₂/Ag-FHAp coated biodegradable Mg alloy possessed high corrosion resistance and cytocompatibility and can be considered as a promising material for implant applications.     

The application of polycarbazole,polycarbazole/nanoclay and polycarbazole/Zn-nanoparticles as a corrosion inhibition for SS304 in saltwater

Polycarbazole (PCz), polycarbazole/nanoclay and polycarbazole/Zn-nanocomposites were chemically and electrochemically synthesized on a stainless steel (SS304) electrode. The modified electrodes were characterized by electrochemical methods (CV and chronoamperometry), Fourier transform infrared spectroscopy (FTIR)-attenuated transmission reflectance (ATR), scanning electron microscopy (SEM)-energy dispersive X-ray analysis (EDX), four point probe, electrochemical impedance spectroscopy (EIS), and equivalent circuit model of R_s(Q_c(R_c(Q_pR_ct))). The electrochemical behavior of the modified films on SS304 was assessed by open circuit potential monitoring, potentiodynamic polarization and EIS measurements to test the corrosion protection efficiency against 3.5% NaCl solution. PCz, PCz/nanoclay and PCz/nanoZn films obtained by chemical method coated on SS304 electrode exhibited better corrosion protection performance compared to the films obtained by the electrochemical method. This result may be attributed to the effective formation of a thin and protective layer. The highest protection efficiency (PE = 99.81%) was obtained for chemically synthesized PCz films.     

Corrosion performance of waterborne epoxy coatings containing polyethylenimine treated mesoporous-TiO2 nanoparticles on mild steel

Waterborne epoxy coatings were modified by adding mesoporous-TiO₂ nanoparticles (meso-TiO₂). In order to achieve proper dispersion of meso-TiO₂ in the epoxy-based coating and make possible chemical interactions between meso-TiO₂ and polymeric coating, meso-TiO₂ was treated with polyethylenimine (PEI) of various molecular weights. Corrosion performance of mild steel coated specimens was investigated employing electrochemical impedance spectroscopy (EIS) and salt spray test. Coatings with meso-TiO₂/PEI (600 molecular weight) possessed the best corrosion performance among the coating specimens. The EIS results showed that the resistance value of coating with meso-TiO₂/PEI (600 molecular weight) was above 9.87 × 10⁷ Ω cm² which was higher than neat epoxy coating. Possible chemical interactions between polymeric matrix and treated nanoparticles caused high barrier properties and high degree of cross-linking.     

Comparison of microstructure,toughness, mechanical properties and work hardening of titanium/TiO2 and titanium/SiC composites manufactured by accumulative roll bonding (ARB) process

In this study, the effects of TiO₂ ceramic nanoparticles and SiC microparticles on the microstructure, mechanical properties and toughness of titanium/TiO₂ nanocomposite and titanium/SiC composite were investigated. To achieve this goal, TiO₂ and SiC ceramic particles were incorporated as the reinforcement in titanium through the ARB (accumulative roll bonding) process. By adding SiC ceramic particles, the mechanical properties of the composite and the nanocomposite were enhanced, while their toughness was decreased, as compared to TiO₂ nanoparticles. After applying 8 cycles of the ARB process, UTS in Ti/5 vol% SiC composite reached to about 1200 (MPa), as compared to that in Ti/0.5 wt% TiO₂ nanocomposite, which was about 1100 (MPa). Furthermore, toughness in the Ti/5 vol% SiC composite and the Ti/0.5 wt% TiO₂ nanocomposite was 60 and 29 J/m³, respectively. Finally, SEM and TEM images showed SiC microparticles clustering in Ti/SiC composite samples and a suitable distribution of TiO₂ nanoparticles in the Ti/TiO₂ nanocomposite. By adding TiO₂ nanoparticles, mechanical properties and work hardening coefficient were found to be increased, as compared to those of the monolithic samples. TiO₂ nanoparticles, after being distributed in the titanium matrix through the ARB process, caused pin dislocations. As clearly shown in TEM images, dislocation tangles around TiO₂ nanoparticles acted as the main mechanism improving the work hardening coefficient.     

Development of nonenzymatic hydrogen peroxide sensor based on catalytic properties of copper nanoparticles/Rutin/MWCNTs/IL/Chit

A new electrochemical sensor based on copper nanoparticles for detection of hydrogen peroxide has been developed. Copper nanoparticles/Rutin/Multiwall Carbon Nanotubes/Ionic liquid/Chitosan modified glassy carbon electrode (CuNPs/Rutin/MWCNTs/IL/Chit/GCE) prepared by consecutive coating of MWCNTs/IL/Chit nanocomposite and rutin on the GCE, followed by the electrodeposition of copper. Surface physical characteristics of modified electrode were studied by scanning electron microscopy (SEM). The electrochemical performance of the sensor for detection of H₂O₂ was investigated by cyclic voltammetry and chronoamperometry techniques. The modified electrode exhibits an enhanced electrocatalytic property, low working potential, high sensitivity, excellent selectivity, good stability, and fast amperometric sensing towards reduction of hydrogen peroxide. The response to H₂O₂ is linear in the range between 0.35 μM to 2500 μM, and the detection limit is 0.11 μM.     

A remarkable promoting effect of water addition on selective hydrogenation of p-chloronitrobenzene in ethanol

Selective hydrogenation of p-chloronitrobenzene to p-chloraniline over ruthenium catalyst was found to be promoted remarkably (Selectivity: from 80.4% to 98.6%; TON: from 0.89 × 10⁻² s⁻¹ to 3.20 × 10⁻² s⁻¹) by simply adding some water into the solvent of ethanol. The optimized volume percent of water in ethanol was 30%. The promoting effect of water was also found over various supported metal catalysts, such as Fe/SiO₂, Co/SiO₂, Ni/SiO₂, Cu/SiO₂, and Ag/SiO₂.     

Dielectric behavior and magnetical response for porous BFO thin films with various thicknesses over Pt/Ti/SiO2/Si substrate

A novel sol–gel method has been developed to deposit multiferroic nanocrystalline bismuth ferrite (BFO) thin films over Pt/Ti/SiO₂/Si substrate by spin-coating technique with various thicknesses. It is found that the deposition parameters significantly influence the quality and the thickness of BiFeO₃ films. The films are all uniform and adherent to Pt/Ti/SiO₂/Si substrate. The spin-coated films are characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Atomic force microscope (AFM), photoluminescence spectroscopy (PL) and Fourier transform infrared spectroscopy (FTIR). Rhombohedral structure of BFO is confirmed from the XRD and FT-IR studies. The SEM image shows a porous structure formation of BFO over Pt/Ti/SiO₂/Si substrate. The surface outgrowth for the films at various thicknesses is measured from root mean square (RMS) and surface roughness through AFM. The step height and the RMS are found to be high for the film at 500 nm in comparison with thickness of 200 nm. The influence of the dielectric properties of the porous BFO at different thicknesses is studied using LCRQ meter. Finally, the magnetic behavior of film is compared with M–H hysteresis loop and Magnetoresistance (MR) studies.     

Preparation of antireflective SiO2 nanometric films

Antireflective nanometric SiO₂ films were formed on glass substrates by dip coating from a colloidal SiO₂ sol having an average particle size of 9 nm. Withdrawal speed of dip coating was varied between 100 and 200 mm/min with 25 mm increments, and baking temperature of the films was altered between 300 and 550 °C with 50 °C increments. Obtained SiO₂ films were in 80–200 nm thickness range. Film thickness was seen to increase with increasing withdrawal speed and to decrease with increasing baking temperature. A maximum light transmittance of 95% was obtained with 4.5% points increase, from the films which were withdrawn at 100 mm/min and baked at 450 or 500 °C. It was seen from SEM observations that the films exhibited full coverage on glass surface and contained no voids or cracks. Size of SiO₂ particles in the film was seen in the AFM analyses to increase with baking temperature. Sintering of SiO₂ particles appeared to accelerate at temperatures over 450 °C.     

Fabrication and characterization of in-situ duplex plasma-treated nanocrystalline Ti/AlTiN coatings

Plasma nitriding and plasma-assisted PVD duplex treatment was adopted to improve the load-bearing capacity, fatigue resistance and adhesion of the AlTiN coating. Ion etch-cleaning was applied for better adhesion before plasma nitriding. After plasma nitriding Ti interlayer was in-situ deposited by high power impulse magnetron sputtering (HIPIMS), followed by the AlTiN coating through in-situ deposition by advanced plasma-assisted arc (APA-Arc). The microstructure and properties of the duplex-treated coating were carefully characterized and analyzed. The results show that the thicknesses of the nitriding zone, the γ′-Fe₄N compound layer, the Ti interlayer and the AlTiN top layer with nanocrystalline microstructures are about 60 μm, 2–3 μm, 100 nm and 6.1 μm, respectively. The nitriding rate is about 30 μm/h and the AlTiN coating deposition rate reaches 6.1 μm/h. The interfacial adhesion of the Ti/AlTiN coating is well enhanced by ion etch-cleaning and a Ti interlayer, and the load-bearing capacity is also improved by duplex treatment. In addition, the instinct hardness of the Ti/AlTiN coating reaches 3368HV_0.05 while the wear rate coefficient of 5.394×10⁻⁸ mm⁻³/Nm is sufficiently low. The Ti/AlTiN coating, which possesses a high corrosion potential (E_corr=−104.6 mV) and a low corrosion current density (i_corr=4.769 μA/cm²), shows highly protective efficiency to the substrate.     

Fabrication of corrosion-resistant Al2O3–CeO2 composite coating on AA7075 via plasma electrolytic oxidation coupled with electrophoretic deposition

Al₂O₃–CeO₂ composite coating was fabricated on AA7075 by combining plasma electrolytic oxidation (PEO) with electrophoretic deposition (EPD). CeO₂ nanoparticles are electrophoretically incorporated into the plasma electrolytic oxidized Al₂O₃ coatings by the synergetic effect of PEO and EPD processes. The passivation behavior of Al₂O₃ and inhibiting nature of CeO₂ have been studied by the electrochemical corrosion analysis in 3.5 wt% NaCl solution and salt spray corrosion test (SSCT) in 5 wt% NaCl as per ASTM standards. The results showed that the Al₂O₃–CeO₂ composite coating via PEO coupled EPD significantly improved the corrosion resistance (~10³ times higher R_p) compared to the plasma electrolytic oxidized Al₂O₃ coating.     

Protective properties of Al2O3 + TiO2 coating produced by the electrostatic spray deposition method

Mechanical resistance of Al₂O₃ + TiO₂ nanocomposite ceramic coating deposited by electrostatic spray deposition method onto X10CrAlSi18 steel to thermal and slurry tests was investigated. The coating was produced from colloidal suspension of TiO₂ nanoparticles dispersed in 3 wt% solution of Al₂(NO₃)₃, as Al₂O₃ precursor, in ethanol. TiO₂ nanoparticles of two sizes, 15 nm and 32 nm, were used in the experiments. After deposition, coatings were annealed at various temperatures, 300, 1000 and 1200 °C, and next exposed to cyclic thermal and slurry tests. Regardless of annealing temperature and the size of TiO₂ nanoparticles, the outer layer of all coatings was porous. The first five thermal cycles caused a rapid increase of aluminum content of the surface layer to 30–37 wt%, but further increase in the number of thermal cycles did not affect the aluminum content. The oxidation rate of coating-substrate system was lower during the thermal tests than during annealing. The oxidation rate was also lower for smaller TiO₂ particles (15 nm) forming the coating than for the larger ones (32 nm). The protective properties of Al₂O₃ + TiO₂ coating against intense oxidation of substrate were lost at 1200 °C. Slurry tests showed that coatings annealed at 1000 °C had the best slurry resistance, but thermal tests had weakened this slurry resistance, mainly due to decreasing adhesion of the coating.     

Preparation and characterization of multilayer anti-reflective coatings via sol-gel process

Single layer and multilayer films consisting of SnO₂, Ta₂O₅, SiO₂, TiO₂, indium tin oxide (ITO) and antimony tin oxide (ATO) have been prepared by sol-gel dip coating technique. All of the multilayer films contained a SiO₂ top layer, which was composed of SiO₂ nanoparticles. The other films had polymeric character. Obtained films were characterized by ellipsometry, XRD, AFM and SEM. Light transmittance values of the films were compared. Films other than SiO₂ and Ta₂O₅ were found to have crystalline structure. Thickness values of the films were in the range of 30–115 nm and roughness values were in 1.2–23 nm range. Single layer porous silica provided 95% light transmittance, whereas ITO-TiO₂-SiO₂ multilayer film provided a light transmittance of 97.2%.