Silicate‐based post‐anodic treatment for lithographic application

Sodium silicate solutions are widely used chemicals for a variety of applications. In particular, they are commonly used in pre‐treatments of aluminium alloys as cleaners and corrosion inhibitors. Another application is found in offset printing, where after graining and anodising, a silicate‐based post‐anodic treatment (PAT) is considered to optimise the aluminium plate characteristics. It is, however, not clear what type of interaction takes place between the oxide‐covered aluminium and the silicate solution. In this work, silicate‐based PAT is studied. Different barrier‐type and porous‐type aluminium oxides are silicate‐treated by dipping in a water‐based sodium silicate solution and the effect of time on the deposition is studied. Particular attention is given to the role of rinsing when the alumina surface is washed in water after the silicate treatment. A good understanding of the role of rinsing allows us to obtain information on the characteristics of the silicate layer which is formed after dipping. The surface modifications induced by the silicate treatment on the aluminium oxides were monitored by means of field emission scanning electron microscopy and infrared spectroscopic ellipsometry. Quantitative measurements on the amount of deposited silicate were taken by X‐ray fluorescence, and relative comparisons between different oxides are shown. Auger electron spectroscopy was used to study the in‐depth composition of the silicate deposition. Experiments show a high affinity of the silicate to the anodic oxide film. A thin nanometric chemisorbed (alumino)silicate layer is present on the surface after rinsing, while the physisorbed part of the layer is washed away. Copyright © 2009 John Wiley & Sons, Ltd.     

Transparent Aluminium Oxide Coatings of Polymer Brushes

A novel method for the preparation of transparent Al₂O₃ coatings of polymers is presented. An environmental‐friendly sol–gel method is employed, which implies mild conditions and low costs. A thermoresponsive brush is chosen as a model surface. X‐ray photoelectron spectroscopy is used to characterize the samples during the conversion of the precursor Al(OH)₃ into oxide and to prove the mildness of the protocol. The study evidences a relation between lateral homogeneity of alumina and the wettability of the polymer surface by the precursor solution, while morphology and elasticity are dominated by the polymer properties. The study of the swelling behavior of the underneath brush reveals the absence of water uptake, proving the impermeability of the alumina layer. The broad chemical and structural variety of polymers, combined with the robustness of transparent alumina films, makes these composites promising as biomedical implants, protective sheets and components for electric and optical devices.     

Study of hydrophilicity and stability of chemically modified PDMS surface using piranha and KOH solution

Successful realization of various BioMEMS devices demands effective surface modification techniques of PDMS elastomer. This paper presents a detailed report on a simple and cost effective approach for surface modification of PDMS films involving wet chemical treatment in two‐step processes: primarily involving piranha solution followed by KOH dip to improve hydrophilicity and stability of PDMS surface. Chemical composition of the solution and surface treatment condition have been varied and optimized to significantly increase the surface energy. The effect of surface modification of the elastomer after wet chemical treatment is analyzed using contact angle measurement and FTIR‐ATR study. PDMS surface treated in piranha solution with H₂O₂ and H₂SO₄ in the ratio of 2:3 followed by a dip in KOH solution for 15 min duration each, demonstrated a maximum reduction of contact angle to ～27° as compared to untreated sample having a contact angle of ～110°. The removal of hydrophobic methyl group from elastomer surface and subsequent hydrophilization of surface by wet chemical process was confirmed from FTIR‐ATR spectra. This result is also supported by improved adhesion and electrical continuity of deposited aluminum metal film over the modified PDMS surface. Copyright © 2011 John Wiley & Sons, Ltd.     

An inorganic route to decorate graphene oxide with nanosilica and investigate its effect on anti‐corrosion property of waterborne epoxy

This paper reported an inorganic route that uses potassium silicate, which is one type of alkali silicate as an inorganic modifier, taking advantage of its instability and water condensation to decorate graphene oxide (GO) with nano‐SiO₂. The ingredients of prepared nanocomposites were characterized by Fourier‐transform infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS), and the thermodynamic property was tested by thermal gravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to observe the morphology of SiO₂‐GO nanocomposites. All the analyses above revealed the nano‐SiO₂ (<100 nm) was deposited on the surface of GO by chemical bonds. In the meantime, the dispersion test illustrated that nano‐SiO₂ played an important role in improving the dispersity of GO. The effect of SiO₂‐GO nanocomposites on barrier and corrosion protection performance of SiO₂‐GO nanocomposites was tested by immersion experiment and electrochemical impedance spectroscopy (EIS). The results indicated that GO was helped to block the corrosion of aggressive medium; moreover, SiO₂‐GO nanocomposites had the best anticorrosion performance and the slowest rate of corrosion because of its good dispersity with waterborne epoxy coatings.     

Probing Catalytic Solid‐Liquid Interfaces by Attenuated Total Reflection Infrared Spectroscopy: Adsorption of Carboxylic Acids on Alumina and Titania

The adsorption of carboxylic acids (formic, acetic, and pyruvic acid) from corresponding solutions in CH₂Cl₂ solvent on Al₂O₃ and TiO₂ thin films has been studied by attenuated total reflection infrared spectroscopy. The metal‐oxide films were vapor‐deposited on a Ge internal reflection element, which was mounted into a specially designed flow cell. The system allowed in situ monitoring of the processes occurring at the solid‐liquid interface. The metal‐oxide films were characterized by X‐ray photoelectron spectroscopy, ellipsometry, and atomic force microscopy. Formic acid and acetic acid adsorbed predominantly as bridging species on alumina surfaces. Adsorbed free acids were not observed under a flow of neat solvent. Based on the position of the ν_AS(COO) and of the keto‐group stretching vibration of the pyruvate ion, pyruvic acid is proposed to coordinate to the Al₂O₃ surface in a monodentate fashion, whereas, on TiO₂, a bidentate species is preferred. Comparison of the adsorption behavior on the vapor‐deposited alumina film and on an α‐Al₂O₃ layer deposited from a water suspension of the corresponding metal‐oxide powder indicated that pyruvic acid adsorbs in a similar mode, irrespective of the metal‐oxide deposition technique.     

Surface characteristics of AZ91D alloy anodized with various conditions

Anodic oxidation of an AZ91D magnesium alloy was carried out in an attempt to increase the corrosion resistance. The alloy was placed in an electrolyte containing 0.1 M sodium silicate (Na₂SiO₃), 2.0 M sodium hydroxide (NaOH) and 0.1 M sodium phosphate (Na₃PO₄), and treated with a current density of 100–400 mA/cm² for 1 to 4 min. After the anodic oxidation treatment, the surface characteristics were analyzed by SEM, X‐ray diffraction (XRD) and a surface roughness tester. The corrosion resistance was determined by measuring the corrosion potential and corrosion current density using potentiodynamic polarization in a 3.5 wt% NaCl electrolyte solution. Although the anodic oxidation treatment with the base electrolyte resulted in an arrival voltage ranging from 60 to 70 V, the addition of silicate tended to reduce this arrival voltage by approximately 10–20 V and decrease the critical voltage required for the formation of a porous oxide film. The pore size and film thickness increased with increasing applied current and treatment time. The addition of silicate to the electrolyte resulted in films with a homogeneous pore size and a film thickness increasing with the increasing applied current and treatment time. XRD showed the formation of a new MgO and Mg₂SiO₄ phase. The formation of Mg₂SiO₄ was attributed to the presence of SiO₄^4? in the film. After the addition of silicate, the corrosion potential increased and corrosion current decreased, resulting in improved corrosion resistance. Copyright © 2008 John Wiley & Sons, Ltd.     

Study on the capacity of mesoporous alumina with different pore sizes absorb silane inhibitors

By modifying and optimizing the procedures, which were well described and understood for the synthesis of macroporous alumina, mesoporous alumina–based film has been successfully prepared, In this paper, the orderly mesoporous Al₂O₃ thin film was prepared by electrochemical workstation, and via supported N‐octyltriethoxysilane (NOS) coupling agent, corrosion inhibitors be loaded into the different pore sizes of mesoporous alumina films. The physicochemical properties of this thin inhibitors carrier film were characterized. Corrosion resistance of mesoporous alumina and honeycomb ceramic macroporous alumina were compared; the conclusion shows that mesoporous alumina film can be used as good corrosion inhibitors carrier and bring out a high‐efficiency inhibition result. Simultaneously, by compared with corrosion inhibition of different pore sizes (20‐50 nm) mesoporous alumina who absorbed NOS, and a general relationship between the different mesoporous alumina pore sizes and the adsorption capacity of NOS was obtained.     

Electropolymerization of DBSA‐doped polypyrrole films on PTFE via an electroless copper interlayer

We report on the electroless deposition of thin films of copper on poly(tetrafluoroethylene) (PTFE) and their use as substrates for electropolymerization of polypyrrole. Argon plasma‐treated PTFE films were modified by silanization using N‐[3(trimethoxysilyl)propyl]diethylenetriamine (TMS). The TMS‐modified PTFE films were subsequently activated by PdCl₂ for the electroless deposition of copper. The omission of the commonly used SnCl₂ sensitization step represents a significant process enhancement with environmental and cost benefits. The surface composition of the substrate (before and after surface treatments) and overlayer films was studied using high‐resolution x‐ray photoelectron spectroscopy. A combination of time‐of‐flight secondary ion mass spectrometry and water contact‐angle measurements was also used to study the PTFE surface after argon plasma treatment. The Cu/PTFE films were used as substrates for subsequent pyrrole electropolymerization in aqueous dodecylbenzene sulphonic acid (DBSA) solution. The DBSA‐doped polypyrrole overlayers were successfully deposited on the Cu/PTFE surface using a constant applied potential of 1.5 V. The resulting material exhibited a doping level of 39%, determined using chemical component analysis of the N 1s photoelectron peak. Copyright © 2003 John Wiley & Sons, Ltd.     

Grafting of nanoporous alumina membranes and films with organic acids

In this study, direct surface grafting of nanoporous alumina membranes and glass‐supported alumina films was carried out with three different fluorinated organic acids: trifluoroacetic acid, perfluoropentanoic acid and 2,3,4,5,6‐pentafluorobenzoic acid. Elemental surface composition and chemical environment of alumina were investigated using X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Alumina surfaces grafted with fluoro‐organic acids exhibited increased hydrophobic properties compared to ungrafted surfaces when measured using goniometry and atomic force microscopy (AFM). This work describes the evidence for surface chemical modification of alumina using direct reaction with organic acids. An AFM study of the adsorption of the immunoglobulin G (IgG) molecules on the fluoro‐organic‐acid‐grafted surfaces is reported. The results show that an ordered arrangement of immunoglobulin G structures with in‐filling of pores could be achieved only on the more hydrophobic fluoro‐organic‐acid‐grafted alumina membranes. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydrophilic nature and sorption-diffusion properties of nanocomposite hybrid polysulfone films

Hybrid nanocomposite films containing silica (??11.4 wt.%) or titania (??18.8 wt.%) in the polymer matrix were prepared by the sol-gel method using the hydrolytic polycondensation of tetraethoxysilane and tetrabutoxysilane in a THF solution of aromatic polymer, polysulfone (PSF). The influence of the oxide nature and the film composition on the structure, the interaction of the polymer with oxides, hydrophilicity, and sorption-diffusion properties of the hybrid films were studied by FTIR spectroscopy, atomic force microscopy, dynamic light scattering, and a complex of other physicochemical methods. The absence of chemical or intermolecular hydrogen bonds between the polymer and oxide particles in the PSF films was shown. The average size of the oxides (SiO₂, ??20 nm; TiO₂, ??90 nm) in the films and roughness of their surface (??0.2?C0.8 nm) were determined. The introduction of oxides into the polymer matrix increases the hydrophilic properties and the ability of the PSF films to swell in water; the diffusion coefficients of water and permeability of water vapor in the PSF films also increase. Titania also induces a more considerable change in the structure of the polymer matrix and more strongly affects the sorption-diffusion properties of the hybrid films in aqueous solutions of THF. All prepared nanocomposite films PSF/SiO₂ and PSF/TiO₂ are capable of extracting an organic component from aqueous solutions and can be used as sorbents and membrane films for the removal of organic substances from the aqueous medium.     

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

Several silica‐based solutions with 50 g/l of SiO₂ were prepared from sodium silicate solutions and silica sol; the silicate conversion coatings were obtained by immersing hot‐dip galvanized steel sheets in these solutions. These solutions were characterized using high‐resolution transmission electron microscopy and ²⁹Si nuclear magnetic resonance; the morphology of the coatings was observed by SEM and atomic force microscopy while the corrosion resistance was evaluated by electrochemical measurements as well as neutral salt spray tests. The results show that the coatings obtained from the single silica sol solution had poor adhesion and the coating obtained from the sodium silicate solution with low SiO₂/Na₂O molar ratio was uneven. By adding the silica sol to the silicate solution with low molar ratio, uniform coatings with better protection property were obtained. According to the results of ²⁹Si nuclear magnetic resonance spectra, the effects of the distribution of silicate anions with various polymerization degrees in the silica‐based solutions on the microstructure and corrosion resistance of the silicate coatings are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of thermal annealing on the microstructure,hardness and corrosion behavior of TiAlSiCuN nanocomposite films

Nanocomposite TiAlSiCuN films were deposited on high speed steels by filtered magnetic arc ion plating. Detailed properties of the films annealed at various temperatures are studied. After thermal annealing at different temperatures ranging from 400 to 800 °C, changes in the film micro‐structure, chemical and phase composition, surface morphology, hardness and polarization curve properties were systematically characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, nano‐indenter and electrochemical workstation, respectively. It was found that the TiAlSiCuN films could be fully oxidized at 800 °C, Al and Ti atoms all diffused outwards and formed dense protective Al₂O₃ and TiO₂ layer. Simultaneously, the TiAlN phase gradually disappeared. The films annealed at 400 °C obtained the highest hardness because of the certain grain growth and little generated oxides. Besides, the certain formation of dense protective Al₂O₃ layer made the TiAlSiCuN film annealed at 600 °C present the least corrosion current density and the corrosion voltage. Copyright © 2016 John Wiley & Sons, Ltd.     

A comparative study between inductively and capacitively coupled plasma deposited polystyrene films: chemical and morphological characterizations

Thin polystyrene films were deposited on stainless steel substrates by capacitively and inductively coupled radio frequency glow discharge plasma, in order to compare their chemical and morphological properties. The films were characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐Ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), atomic force microscopy (AFM) and scanning electron microscope (SEM). Wettability properties were also determined by contact angle measurements. Ageing effect was studied by analysing films aged for 15 min and for 1 week. Results from both capacitively and inductively plasma polymerized polystyrene (pPS) films aged for 15 min showed that the chemical structure of the bulk, chemical composition of the surface (depth < 10 nm) and wettability properties were rather similar. Only their microstructures were very different: the pPS_capa film's microstructure showed homogeneous distribution of spherical particles of about 100 nm in diameter but the pPS_ind film's microstructure seemed to be mainly influenced by the surface of the metallic substrate: orientated ‘lamellae‐like layers’ of polymers were observed on each metallic grain. Ageing for 1 week in ambient air induced low oxygen uptake in the surface of both pPS films. The pPS_ind topmost surface (depth < 3 nm) was more oxidized than that of pPS_capa but no modification of the chemical structure of the bulk or of the morphology was noticed after ageing. Copyright © 2006 John Wiley & Sons, Ltd.     

In situ investigations of the interaction of small inorganic acidifying molecules in humidified air with polycrystalline metal surfaces by means of TM‐AFM,IRRAS, and QCM

Initial atmospheric corrosion of copper, silver, and iron induced by humidity and oxidizing agents was studied in situ by three highly surface‐sensitive and complementary techniques: infrared reflection‐absorption spectroscopy (IRRAS), quartz crystal microbalance (QCM), and tapping‐mode atomic force microscopy (TM‐AFM). These techniques deliver information about the change of the topography of the sample surfaces with emphasis on the shape and lateral distribution of the corrosion products grown within the first 1300–2800 min of weathering (TM‐AFM), as well as chemical (IRRAS) and kinetic (QCM) data. A completely different mechanism of the initial stages of atmospheric corrosion of the three investigated metals could be observed. A uniform growth of corrosion products was seen on the copper surface (identified by IRRAS and XPS to be cuprite‐like) during exposure to synthetic air with 80% relative humidity (RH), whereas the iron surface remained unattacked. The investigations of the silver surface exposed to humidity revealed that silver is attacked by humidity and tends to form oxide and hydroxide surface species. While an increased humidity content of the surrounding atmosphere causes higher corrosion rates on copper, on the exposed silver sample only a change in the degradation mechanism could be observed. The addition of SO₂ to the humidified air causes the growth of so‐called ‘second‐order’ features on copper, identified to be CuSO₃ · xH₂O‐like, which reveals the formation of a new chemical species on the investigated surface. These features are placed on top of the homogeneous formed oxide layer and tend to form well‐defined islands. In contrast to copper, on a silver surface exposed to humidity and SO₂ no new chemical species are formed; nevertheless an increased corrosion rate could be observed owing to a change of the chemistry in the physisorbed water layer. Iron exposed to humidity and SO₂ still remains unattacked. An iron surface is attacked only if exposed to humidity and SO₂ and NO₂, which show a synergistic effect by the oxidation of four‐valent sulfur‐oxygen species by NO₂. Such an attack leads to the formation of pitting corrosion, which was observed in situ and time‐resolved. The pits mainly occur on predamaged surface structures, such as scratches caused from the polishing process of the samples, and therefore promote the initiation of the corrosion. The results obtained demonstrate the high potential of the surface‐sensitive methods applied for investigating the early stages of corrosion of different metals and for obtaining a better understanding of the molecular mechanisms during degradation. Copyright © 2007 John Wiley & Sons, Ltd.     

Surface characterization and properties of plasma‐modified cyclic olefin copolymer/layered silicate nanocomposites

In this study, cyclic olefin copolymer (COC)/layered silicate nanocomposites (CLSNs) were prepared by the intercalation of COC polymer into organically‐modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of CLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the COC matrix. The effect of layered silicate on the mechanical and barrier properties of the fabricated nanocomposites shows significant improvements in the storage modulus and water permeability when compared with that of neat COC matrix. Surfaces of COC and CLSN films were modified by a mixture of oxygen (O₂) and nitrogen (N₂) plasmas with various treated times, system pressures, and radio frequency (RF) powers. The surfaces of plasma‐modified COC and CLSN were investigated using scanning probe microscopy and contact‐angle measurements. The exposure of the COC and CLSN film to the plasmas led to the combination of etching reactions of polymer surface initiated by plasma and the following addition reactions of new functional groups onto polymer surfaces to change the topology of COC film surfaces. The surface roughness was closely related to how high and how long the RF power was input into the system. The plasmas also led to changes in the surface properties of the CLSN surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surface decreases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2745–2753, 2005     

Layer‐by‐layer deposition of nitrilotris(methylene)triphosphonic acid and Zr(IV): an XPS,ToF‐SIMS,ellipsometry, and AFM study

Layer‐by‐layer assemblies consisting of alternating layers of nitrilotris(methylene)triphosphonic acid (NTMP), a polyfunctional corrosion inhibitor, and zirconium(IV) were prepared on alumina. In particular, a nine‐layer (NTMP/Zr(IV))₄NTMP stack could be constructed at room temperature, which showed a steady increase in film thickness throughout its growth by spectroscopic ellipsometry up to a final thickness of 1.79 ± 0.04 nm. At higher temperature (70 °C), even a two‐layer NTMP/Zr(IV) assembly could not be prepared because of etching of the alumina substrate by the heated Zr(IV) solution. XPS characterization of the layer‐by‐layer assembly showed a saw tooth pattern in the nitrogen, phosphorus, and zirconium signals, where the modest increases and decreases in these signals corresponded to the expected deposition and perhaps removal of NTMP and Zr(IV). Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) confirmed the attachment of the NTMP molecule to the surface through PO^?, PO₂^?, PO₃^?, and CN^? signals. Increasing attenuation of the Al signal from the substrate after deposition of each layer was observed by both XPS and ToF‐SIMS. Essentially complete etching of the alumina by the heated Zr(IV) solution was confirmed by spectroscopic ellipsometry, XPS, and ToF‐SIMS. Atomic force microscopy revealed that all the films were smooth with R_q roughness values less than 0.5 nm. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and properties of Q‐silicon crosslinked siloxane networks: H3PO4‐catalyzed sol–gel dehydration/crosslinking of α,ω‐bis(hydroxy)oligodimethylsiloxanes with tetrakis(hydroxydimethylsiloxy)silane

Six silicate‐crosslinked oligodimethylsiloxane thin films were prepared by the phosphoric acid (1 mol %) catalyzed condensation of α,ω‐bis(hydroxy)oligodimethylsiloxane (P) and tetrakis(hydroxydimethylsiloxy)silane (Q). Other acid catalysts were evaluated. P and Q were prepared by the Pd‐catalyzed oxidation of the corresponding Si? H compounds with water. The starting materials were characterized by IR and ¹H, ¹³C, and ²⁹Si NMR. A thermal cure was achieved with H₃PO₄ in 24 h and with poly(phosphoric acid) in 3 h at 110–120 °C. Dynamic mechanical analysis was used to determine the glass‐transition temperatures and to evaluate the mechanical properties of the films. Their thermal stabilities (≥300 °C) in air and N₂ were determined by thermogravimetric analysis. Small amounts of non‐crosslinked P were recovered from the films by Soxhlet extractions with CH₂Cl₂ and analyzed by IR, gel permeation chromatography, and ²⁹Si NMR. The crosslink densities were evaluated by the CH₂Cl₂ absorption capacities of the films. The surface properties of the films were determined by static and dynamic contact‐angle measurements. Electrochemical impedance spectroscopy was carried out to evaluate the corrosion‐protective properties of the coatings on mild steel as a function of the exposure time to 0.5 N NaCl. The biofoul‐release properties of the films were evaluated with sporelings from mature Ulva linza plants and barnacles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2237–2247, 2006     

Corrosion resistances of passive films on low‐Cr steel and carbon steel in simulated concrete pore solution

The passive ranges of carbon steel rebar and 3Cr steel rebar in saturated Ca(OH)₂‐simulated concrete pore solution with pH 12.6 were determined by means of cyclic voltammetry and potentiodynamic polarization curves. Chronopotentiometry was used to obtain steady‐state conditions for the formation of passive films on rebar samples at different anodic potentials. Electrochemical impedance spectroscopy, Mott–Schottky and X‐ray photoelectron spectrometer curves were employed to compare the formed passive films at different potentials. Additionally, cyclic polarization curves were used to compare the corrosion resistances of formed passive films on the two rebars in saturated Ca(OH)₂‐simulated concrete pore solution with different concentration of Cl^?. The results show that the passive ranges of the two rebars are all between ?0.15 and +0.6 V, and more stable passive films can be formed on both rebars at the anodic potential of +0.3 V. In the absence of Cl^?, the stability and corrosion resistance of the passive film formed on the 3Cr rebar are better than those of CS rebar. The passive film of 3Cr steel has the relatively better pitting corrosion resistance than carbon steel in saturated Ca(OH)₂‐simulated concrete pore solution that contains different concentration of Cl^?. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface modification and characterization of SEBS films obtained by in situ and ex situ oxidization with potassium permanganate

The surface morphologies and compositions of the asymmetric films of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) prepared by in situ and ex situ oxidization with the KMnO₄ aqueous solution and KMnO₄/H₂SO₄ mixed solution were investigated by using scanning electron microscope, atomic force microscope (AFM), X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR‐FTIR). The effect of the oxidization reagents on morphological changes and the influence of in situ and ex situ preparation methods on surface compositions were discussed. Different from the in situ oxidation by degrading the copolymers to form a gradient film, the ex situ oxidation preferentially degraded the uppermost layer of the film. Although both the KMnO₄ oxidation and the KMnO₄/H₂SO₄ oxidation gave hierarchical structures, distinctive differences were found that large ridges and smaller granules were fabricated in the former film and the latter produced large and deep ravines and fine sponge‐like morphologies. Additionally, the oxygen concentration and the oxo‐species implanted by these oxidation treatments were characterized and evaluated to provide a quantitative comparison. Oxygen, as well as manganese was found to be implanted in the surface layer of the oxidized film, forming predominantly O? C and O? C?O groups, as well as a small fraction of O? H and Mn? O compounds. Changes in contact angle of water on these films and total surface oxygen content are related but not directly. The hystereses of water contact angle at a value of 119 ± 3° due primarily to surface roughness and at a value of 63 ± 3° due primarily to chemical heterogeneity are led by different oxidation degrees and oxidation methods. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Effect of nano-Al2O3 particles and of the Co concentration on the corrosion behavior of electrodeposited Ni–Co alloys

Incorporation of nano-Al₂O₃ particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al₂O₃ composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al₂O₃ deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries.