Infrared stealth and anticorrosion performances of organically modified silicate‐NiZn ferrite/polyaniline hybrid coatings

Hybrid coatings based on organically modified silicate‐Ni_0.5Zn_0.5Fe₂O₄/polyaniline were synthesized through a sol–gel technique with different NiZn ferrite/polyaniline weight ratio (1/1, 1/2, 1/5). These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection and to act as infrared stealth coatings. The effects induced by the NiZn ferrite/polyaniline hybrids on the chain dynamic, ferromagnetic behavior, infrared stealth, and anticorrosion performances of the coated samples were investigated. The rotating‐frame spin‐lattice relaxation times and scale of the spin‐diffusion path length indicated that the configuration of the hybrid films was highly cross‐linked and dense. The thermal extinction of the hybrid coatings increased with the increase in the polyaniline content. Potentio‐dynamic and salt‐spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 926–935, 2008     

Synthesis and characterization of polydimethylsiloxane-cured organically modified silicate hybrid coatings

Hybrid coatings based on polydimethylsiloxane-cured organically modified silicate were synthesized through a sol-gel technique. Amino-terminated siloxane, 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the different chain lengths of siloxane on the chain dynamics, thermal stability and corrosion performance of the coated samples were investigated. The rotating-frame spin-lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly crosslinked, dense and adhered to the aluminum alloy substrates. The thermal stability and the apparent activation energy, evaluated by van Krevelen's method, of the hybrid coatings depended on the siloxane chain length. Potentiodynamic analysis revealed that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates.     

Characterization and corrosion resistance of organically modified silicate/MO2 (M = Zr,Ti, or Ce) hybrid coatings on a 6061‐T6 aluminum alloy

Hybrid coatings based on organically modified silicate (Ormosil)/ZrO₂ (0–1.0 wt %) and Ormosil/MO₂ (M = Ti or Ce) were synthesized through a sol–gel technique. Tetraethylenepentamine, 3‐glycidoxypropyltrimethoxysilane, tetraethoxysilane, and MO₂ (M = Zr, Ti, or Ce) metallic particle were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the ZrO₂ content and the metallic particle type on the chain dynamics, thermal stability, and corrosion performance of the coated samples were investigated. The rotating‐frame spin–lattice relaxation times and scale of the spin–diffusion path length indicated that the configuration of the hybrid films was highly crosslinked and dense and adhered to the aluminum alloy substrates. The thermal stability and the apparent activation energy, evaluated by van Krevelen's method, of the hybrid coatings depended on the ZrO₂ content and on the metallic particle type. Potentiodynamic and salt‐spray analysis revealed that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 335–342, 2006     

Corrosion protection of aluminium alloy AA2024 with cerium doped methacrylate-silica coatings

The aim of this work is the synthesis and characterization of hybrid coatings doped with cerium salts for corrosion protection of AA2024. The control of the inorganic and organic polymerization process allows the preparation of coatings with an open structure and a hydrophilic character. These facts facilitate the incorporation and mobility of cerium ions through the structure, enhancing its ability to promote a self-healing mechanism. The thermal treatment of the coatings has been limited to 120 °C to preserve the mechanical properties of the alloy. The electrochemical behaviour of the coatings has been evaluated in 0.3 wt% NaCl solution by means of EIS technique. Electrochemical measurements evidence good barrier properties at initial immersion time, and signals of corrosion inhibition from cerium ions at long immersion times could be assigned to the increasing of the impedance modulus at low frequencies and the presence of cerium oxide/hydroxide precipitates.     

Influence of carbon black on the properties of plasticized poly(lactic acid) composites

Using acetyl tributyl citrate (ATBC) and poly(1,3-butylene adipate) (PBA) as the plasticizer of poly(lactic acid) (PLA) and carbon black (CB) as reinforced filler, high performance composites were prepared in melting blend. Fourier transform infrared spectroscopy revealed that the interaction existed between PLA and CB, and plasticizer could improve this interaction. The rheology showed that plasticizer could obviously improve the fluidity of the composites, but just the reverse for CB. Scanning electron microscopy revealed that the addition of plasticizer facilitated the dispersion of the CB in PLA. With the increasing of CB content, the enforcement effect, storage modulus and glass transition temperature increased. The elongation at break of PLA/PBA (30 wt%) could be above 600%, which was higher than the same weight ATBC plasticized PLA. Moreover, CB could restrain the thermally induced migration of plasticizer in plasticized PLA. Compared with ATBC, PBA was a thermal stable plasticizer for PLA.     

Preparation and characterization of anticorrosion Ormosil sol–gel coatings for aluminum alloy

Organically modified silicate (Ormosil) coatings have been synthesized through the sol–gel method for corrosion protection of aluminum alloy. Silica-based unmodified coatings were also designed to investigate the effect of tetraethoxysilane (TEOS) content on the properties of the coatings. The surface morphology of the coatings was characterized by scanning electron microscopy. The corrosion resistance was evaluated by immersion test, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. In addition, the surface potential differences of the coated samples were determined by scanning Kelvin probe. The results showed that a better corrosion resistance of unmodified coating was prepared by controlling the TEOS/EtOH/H₂O molar ratio of 0.109/1/1.52. Ormosil coatings provided excellent barrier properties and corrosion resistance in comparison with the unmodified sol–gel coatings. The Ormosil coating modified with triethoxyoctylsilane exhibited corrosion resistance properties superior to the other Ormosil coatings after exposure to 3.5 wt% NaCl solution for 10 days.     

Inorganic–organic sol gel hybrid coatings for corrosion protection of metals

Inorganic–organic hybrid coatings by sol–gel process are very suitable for fighting corrosion. Inorganic sols in hybrid coatings not only increase adhesion by forming chemical bonds between metals and hybrid coatings, but also improve comprehensive performances of polymer in the coatings. Different organic polymers or organic functionalities are introduced into gel network to achieve tailored properties, such as hydrophobic properties, increasing cross-linking density, etc. As for corrosion protection of metals organic components of hybrid coatings are selected to repel water and form dense thick films and reduce coating porosity. The factors, such as the ratio of inorganic and organic components, cure temperature, pigments in hybrid coatings, need to be optimized for attaining hybrid films with the maximum corrosion resistance. Electro-deposition technique offers relatively thick homogeneous defect-free hybrid coatings in comparison to dip or spin coating techniques. Green cerium ions and non-ionizable organic inhibitors are more developed in hybrid coatings nowadays than other corrosion inhibitors. Long-term corrosion resistance techniques of inhibitors are discussed. The inhibitors entrapped in the nanocontainers are doped in hybrid films to prolong release of the inhibitors to damaged zones, which is discussed in detail. Among all the nanocontainers of corrosion inhibitors the prospective techniques which show superior corrosion protection are cyclodextrin/organic inhibitor inclusion complexes and layer by layer assembly of organic corrosion inhibitors in nanocontainers. Super-hydrophobic property of hybrid coatings derives from low surface tension and surface roughness of hybrid coatings, which endues the films with excellent corrosion protection for metals, but the durable property of super-hydrophobic coatings needs to be improved for industrial application. An ideal multiple model of hybrid coatings for superior anti-corrosion of metals proposed is a combination of super-hydrophobic hybrid coatings and underlying hybrid coatings doped with sustained release of corrosion inhibitors on metal substrates.     

Corrosion protection of carbon steel using a combination of Zr conversion coating and subsequent zinc-rich silicate coating with a flake ZnAl alloy

To improve the corrosion protection properties of zinc-rich silicate coatings on steel, zirconium pretreatment loaded with (3-aminopropyl)triethoxysilane (APTES) 0.025 % (v/v) and the partial replacement of spherical zinc by flake ZnAl alloy were investigated. DC polarization and electrochemical impedance spectroscopy (EIS) show that the zirconium pre-treated layer containing APTES improves the corrosion protection of the bare steel. Zinc-rich silicate coatings containing flake ZnAl with and without pretreatment were evaluated by EIS, salt spray test and pull-off test. Pretreatment with a zirconium conversion layer reduces corrosion products and adhesion loss (from 16.53% to 12.54%) while the performance of corrosion protection significantly increased from 2003 Ω.cm² to 2640 Ω.cm² in comparison with the non-pretreated samples. The results show that flake ZnAl pigment (5 wt%) significantly improves corrosion resistance and prolongs the duration of cathodic protection of zinc-rich silicate coatings.     

Influence of heat treatment on electromagnetic properties of polyimide/carbon black composites

A kind of absorbing materials was prepared by hot pressing method using polyimide as matrix and carbon black (CB) as filler. The mechanical properties, the electromagnetic properties, and the thermal stability of polyimide/CB composites were studied. The results showed that the complex permittivity increased from 6.82 + 1.38i to 18.69 + 9.47i, whereas the flexural strength decreased from 108 MPa to 77 MPa, respectively, when the CB content increased from 2 wt% to 8 wt%. The reflection loss curves shifted to low frequency with increase of the thickness at the same content. The reflection loss below ?10 dB could be obtained in the X band with 6 wt% CB content and did not display significant difference before and after the heat treatment at 400°C for 5 h. When the content of CB was 8 wt%, the decomposition temperature (at 5% weight loss) increased approximately 42°C compared with pure polyimide matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermogravimetric studies on Polyamide-6,6 modified by electron beam irradiation and by nanofillers

This paper reports the results of thermogravimetric studies on: (a) Polyamide-6,6 (abbreviated henceforth as PA66) specimens which were modified by electron beam radiation in air, (b) organic-inorganic hybrid nanocomposite films of PA66/silica prepared by the sol-gel technique and (c) unmodified multi-walled carbon nanotube (abbreviated henceforth as MWCNT) reinforced PA66 films. The activation energies were determined using the Kissinger and the Flynn-Wall-Ozawa methods, which do not require knowledge of the reaction mechanism. The results showed that PA66 specimens which received an irradiation dose of 200 kGy in air had a higher thermal stability than both the neat PA66 and PA66 specimens which received a radiation dose of 500 kGy in air. The PA66/silica hybrid nanocomposites up to a silica loading of 1.5 wt% also showed higher thermal stability over neat PA66 films. At MWCNT loadings of 0.5-1.0 wt% the composite films exhibited higher activation energies than the neat PA66 film but at higher MWCNT loading the activation energy was lower than that obtained for the neat PA66 film.     

Corrosion studies and interfacial bonding of urea/poly(dimethylsiloxane) sol/gel hydrophobic coatings on AA 2024 aluminum alloy

Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an organic-inorganic hybrid, diluted in either EtOH or a mixture of EtOH-PrOH, was used in thin film form (<200 nm) to inhibit the corrosion of AA 2024 alloy. Potentiodynamic, time-dependent cyclovoltammetric measurements and salt spray tests showed that the corrosion inhibition of the latter was 10 times higher than that of the former films. This was correlated with the higher degree of hydrolysis and the formation of more open polyhedral silsesquioxane species (T2) in the bulk heat-treated PDMSU/EtOH-PrOH xerogels (29Si NMR spectra). The structure of the coatings deposited on AA 2024 Al alloy was deduced from the infrared reflection-absorption (IR RA) spectra, which revealed more extensive urea-urea interactions and more efficient silane-Al interface bonding for the PDMSU/EtOH-PrOH coatings with higher corrosion inhibition. Ex situ IR RA potentiodynamic spectroelectrochemical measurements of PDMSU coatings revealed that their degradation did not proceed via the formation of silanol groups and consequent hydration of the coatings but that they decomposed above E(corr) by forming fragments composed of -CH2- segments in an all-trans conformation.     

Synergistic effect of double percolated co‐supportive MWCNT‐CB conductive network for high‐performance EMI shielding application

The recent development in telecommunication technology has led electromagnetic interference (EMI) to a serious threat to both electronic devices and living beings. In this work, we designed a highly efficient EMI shielding material by taking advantage of both carbonaceous hybrid filler and double percolation phenomenon. Here, a flexible, lightweight microwave absorbing conductive polymer composite was fabricated by employing poly (ethylene‐co‐methyl acrylate) and ethylene octene copolymer (EMA/EOC) binary blend as the matrix and multiwall carbon nanotube carbon black (MWCNT/CB) hybrid filler as the conductive moiety. We investigated the effect of MWCNT content in the hybrid composite on mechanical, thermomechanical, electrical, and shielding efficiency. A total EMI shielding efficiency of ?37.4 dB in the X band region was attained with 20 wt% hybrid filler containing 50 wt% MWCNT along with promising mechanical properties.     

Modeling electrochemical surface responses for PANI bronze corrosion protection

Plackett–Burman experimental design was carried out in order to optimize the experimental conditions of polyaniline (PANI) electrodeposition for Cu10Sn bronze alloy corrosion protection in neutral aerated aqueous 0.5 M chloride medium. Seven factors including scan rate, aniline concentration, hydroxyl ions concentration, cycle number, nature of solvent, starting potential, and final potential for the cyclic voltammetry study were considered. The experimental responses were Ecorr, βa, βc, B, Jcorr, Rp, the percentage of protection efficiency and the coatings porosities. A linear mathematical model was applied to estimate the coefficients related to the different experimental responses. The significance of the different factors was evaluated through Pareto analysis. The optimum conditions for PANI electrodeposition were estimated and discussed. PANI coatings were concluded to offer protection efficiency higher than 90% for Cu10Sn bronze alloy. Copyright © 2016 John Wiley & Sons, Ltd.     

Structure stability of polyaniline/graphene nanocomposites in gamma-ray environment

The poor structure stability of graphene limits its application as radical scavenger under γ-rays environment because of short service life. Hence we applied polyaniline (PANI), a fairly stable material under irradiation, to modify graphene and then obtained the PANI functionalized graphene oxide (PGO). According to TEM and BET data, the structure stability of PGO is much better than GO after 500 kGy irradiation doses. Electron spin spectroscopy data reveal that PGNS_0.10 (PGO/PANI coatings, 0.10 wt%) are not almost affected by adverse influence comes from active radicals. Then PGNS_0.10 exhibits the excellent corrosion protection performance after 500 kGy irradiation doses.     

On the application of electrochemical impedance spectroscopy to study the self-healing properties of protective coatings

Active corrosion protection based on self-healing of defects in coatings is a vital issue for development of new advanced corrosion protection systems. However, there is a significant lack of experimental protocols, which can be routinely used to reveal the self-healing ability and to study the active corrosion protection properties of organic and hybrid coatings.The present work demonstrates the possibility to use EIS (electrochemical impedance spectroscopy) for investigation of the self-healing properties of protective coatings applied on a metal surface. The model EIS experiments supported by SVET (scanning vibrating electrode technique) measurements show that an increase of low frequency impedance during immersion in the corrosive medium is related to the suppression of active corrosion processes and healing of the corroded areas. Thus, EIS can effectively be employed as a routine method to study the self-repair properties of different protective systems. The 2024 aluminium alloy coated with hybrid sol–gel film was used as a model system to study the healing of artificial defects by an organic inhibitor (8-hydroxyquinoline).     

Tensile properties,thermal and morphological analysis of thermoplastic polyurethane films reinforced with multiwalled carbon nanotubes

The paper reports on thermal, tensile and morphological properties of thermoplastic polyurethane (TPU) based films obtained by melt-compounding and chill-roll extrusion. Composite films containing up to 1 wt% of multiwalled carbon nanotubes (MWNTs) are characterized in terms of thermal properties, tensile behavior and morphological issues taking the neat TPU film as the reference material.     

Inhibition effect of cerium in hybrid sol–gel films on aluminium alloy AA2024

Aluminium alloys such as AA2024 are susceptible to severe corrosion attack in aggressive solutions (e.g. chlorides). Conversion coatings, like chromate, or rare earth conversion coatings are usually applied in order to improve corrosion behaviour of aluminium alloys. Methacrylate‐based hybrid films deposited with sol–gel technique might be an alternative to conversion coatings. Barrier properties, paint adhesion and possibly self‐healing ability are important aspects for replacement of chromate‐based pre‐treatments. This work evaluates the behaviour of cerium as corrosion inhibitor in methacrylate silane‐based hybrid films containing SiO₂ nano‐particles on AA2024. Hybrid films were deposited on aluminium alloy AA2024 by means of dip‐coating technique. Two different types of coating were applied: a non‐inhibited film consisting of two layers (non‐inhibited system) and a similar film doped with cerium nitrate in an intermediate layer (inhibited system). The film thickness was 5 µm for the non‐inhibited system and 8 µm for the inhibited system. Film morphology and composition were investigated by means of GDOES (glow discharge optical emission spectroscopy). Moreover, GDOES qualitative composition profiles were recorded in order to investigate Ce content in the hybrid films as a function of immersion time in 0.05 M NaCl solution. The electrochemical behaviour of the hybrid films was studied in the same electrolyte by means of EIS technique (electrochemical impedance spectroscopy). Electrochemical measurements provide evidence that the inhibited system containing cerium displays recovery of electrochemical properties. This behaviour is not observed for the non‐inhibited coating. GDOES measurements provide evidence that the behaviour of inhibited system can be related to migration of Ce species to the substrate/coating interface. Copyright © 2010 John Wiley & Sons, Ltd.     

Composite film coatings based on epoxy-polysiloxane systems of cationic polymerization and their anticorrosion properties

The anticorrosion properties of epoxy-polysiloxane coatings on the surface of the aluminum alloy D-16 were studied by a potentiodynamic method. It was established that the use of the hybrid coating led to an increased corrosion resistance from 0.250 kΩm·cm² for uncoated alloy to 0.396-0.996 kΩm·cm² for the coated aluminum support. The yield of the sol fraction, the micro hardness, and the glass transition temperature of the polymers were determined.     

Novel UV-curable and alkali-soluble resins for light-shielding black matrix application

A carbon black (CB) photo resist, comprising CB, CB dispersant, photo-curable resin, photo-initiator, and solvent, has been developed in order to prepare a light-shielding black matrix (BM) in the liquid crystal display application. In order to prepare a BM with a high opacity property or optical density (OD), the effect of CB such as its particle and concentration on light absorption property was first evaluated, and the results showed that 45 wt% CB with a particle size of about 100 nm in BM could reach an OD value of 4 μm⁻¹. Moreover, six different UV-curable and alkali-soluble resins (A1, A2, and A3; B1, B2, and B3) were synthesized as photo-curable resins. Structures of these resins were characterized by FTIR and GPC, in which concentrations of various functional groups, especially carboxylic acid and double bond, were calculated. Subsequently, their photo-initiated polymerization rate with or without CB were measured. Finally, it was found that through a proper selection of the newly synthesized resins to prepare a carbon black photo resist, a BM with an OD of 4 μm⁻¹ and a good resolution of 10 μm was successfully prepared upon low UV irradiation energy of 50 mJ/cm².     

Fabrication and nanoindentation properties of TiN/NiTi thin films and their applications in electrochemical sensing

Nanocrystalline TiN/NiTi thin films have been grown on silicon substrate by dc magnetron sputtering to improve the corrosion and mechanical properties of NiTi based shape memory alloys without sacrificing the phase transformation effect. Interestingly, the preferential orientation of the TiN films was observed to change from (1 1 1) to (2 0 0) with change in nature of sputtering gas from 70% Ar + 30% N₂ to 100% N₂. In present study the influence of crystallographic orientation of TiN on mechanical and corrosion properties of TiN/NiTi thin films was investigated. TiN (2 0 0)/NiTi films were found to exhibit high hardness, high elastic modulus, and thereby better wear resistance as compared to pure NiTi and TiN (1 1 1)/NiTi films. Electrochemical test revealed that TiN coated NiTi film exhibits better corrosion resistance in 1 M NaCl solution as compared to uncoated NiTi film. The application of TiN/NiTi films in the electrochemical sensing of dopamine, which has a critical physiological importance in Parkinson's disease, has been demonstrated. A comparison of voltammetric response of dopamine at silicon based electrodes modified with different nanocrystalline coatings indicated that these films catalyze the oxidation of dopamine.