Mechanical polishing,surface roughness,near‐surface deformation,and electrochemical corrosion of Alloy 690TT

The effects of mechanical grinding/polishing, surface roughness, and near‐surface deformation on the electrochemical corrosion behavior of thermally treated (TT) Alloy 690 were studied in a sodium chloride solution. The X‐ray photoelectron spectroscopy and transmission electron microscopy analyses revealed that mechanical grinding/polishing can change the ratio of the elements at the surface of the as‐received Alloy 690TT specimen by removing its Cr‐rich outer layer and causing deformation at the near‐surface microstructure, something which has a direct impact on the rate of the oxygen reduction reaction (ORR), the pitting potential (E_pit), and the corrosion potential (E_corr) of Alloy 690TT. It was observed that the ratio of Cr in the surface is a significant factor that controls the rate of the ORR and the corrosion parameters such as E_corr. Higher amounts of Cr at the surface accelerate the ORR. The near‐surface deformation shifts the E_pit values towards less positive potentials. It was also found that due to the different near‐surface chemical composition of the as‐received Alloy 690TT specimen compared with the ground and the polished specimens, the surface roughness parameters do not have a regular correlation with the rate of the ORR and the values of the E_corr and the E_pit. Only the passive current density increases when the surface roughness is increased. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of compaction and surface roughness on low‐energy ion scattering signals

Investigation of the surface composition of powders often requires compaction. To study the effect of compaction on surface analysis, samples have been compacted at various pressures ranging from 0 Pa (i.e. no compaction) up to 2000 MPa (2 × 10⁴ kg cm^?2) Low‐energy ion scattering (LEIS) was used to determine the composition of the outermost atomic surface layer. Using scanning electron microscopy, changes in the morphology due to compaction have been detected in the SiO₂ test samples. The LEIS yield of a compacted silica powder is found to be independent of the applied pressure during compaction between 2 MPa and 2000 MPa (2 × 10⁴ kg cm^?2). Analysis of a submonolayer of Ta₂O₅ on a silica support shows that the composition of the outermost atomic layer is not changed after compaction up to a pressure of at least 300 MPa. When compaction is applied, the absolute LEIS yield appears to be independent of the specific surface area of silica supports in the range 50–380 m² g^?1. A minor difference in LEIS signals is observed between compacted silica supports and flat quartz samples. In order to determine the surface roughness factor independently, and to study the material dependence of the surface roughness factor, angle‐dependent LEIS measurements have been carried out on oxidized silicon, gallium and gold surfaces. The results on the oxidized silicon confirm the small influence of surface roughness for silica particles, whereas measurements on the more closely packed metallic gallium and gold surfaces indicate a significant surface roughness effect. Copyright © 2004 John Wiley & Sons, Ltd.     

Fabrication of robust superhydrophobic coatings using PTFE‐MWCNT nanocomposite: Supercritical fluid processing

Fabrication of polymer‐carbon composite nanostructure with good dispersion of each other is critical for the desired application due to the nanostructure flaws, agglomeration, and poor absorption between the 2 materials. Fabrication of superhydrophobic surface coating composites of polytetrafluoroethylene (PTFE) with multiwalled carbon nanotubes (MWCNTs) through supercritical fluid processing was explored in this study. Homogeneity of the composite was characterized by X‐ray diffraction and Raman spectroscopy studies, which reveal that the PTFE and MWCNT are uniform in the composite. Microstructural surface evaluation of field‐emission scanning electron microscope and high‐resolution transmission electron microscope studies display that the coating composite possesses roughness structures and fibrillation of the superhydrophobic surface coating. Superhydrophobic character was evaluated on fiber‐reinforced plastic (FRP) sheets, which showed that the prepared coating composite surface showed self‐cleaning properties with a high water contact angle of 162.7°. The surface wettability was studied by increasing different temperatures (30°C to 300°C) in PTFE‐MWCNT composite, which reveals that the FRP sheets were thermally stable up to 200°C and afterward; they transformed from superhydrophobic to hydrophilic state at 250°C. The superhydrophobic surfaces are thermally stable in extreme environmental conditions, and this technique may be used and extendable for large‐scale applications.     

Study of the near‐surface of hot‐ and cold‐rolled AlMg0.5 aluminium alloy

Rolling is known to alter the surface properties of aluminium alloys and to introduce disturbed near‐surface microcrystalline layers. The near‐surfaces of mostly higher alloyed materials were investigated by various techniques, often combined with a study of their electrochemical behaviour. Cross‐sectional transmission electron microscopy (TEM), after ion milling or ultramicrotomy, indicated the presence of disturbed layers characterized by a refined grain structure, rolled‐in oxide particles and a fine distribution of intermetallics. Those rolled‐in oxide particles reduce the total reflectance of rolled Al alloys. Furthermore, various depth profiling techniques, such as AES, XPS, SIMS and qualitative glow discharge optical emission spectroscopy (GD‐OES) have been used to study the in‐depth behaviour of specific elements of rolled Al alloys. Here, the surface and near‐surface of AlMg0.5 (a commercially pure rolled Al alloy with addition of 0.5 wt.% Mg) after hot and cold rolling, and with and without additional annealing is studied with complementary analytical techniques. Focused ion beam thinning is introduced as a new method for preparing cross‐sectional TEM specimens of Al surfaces. Analytical cross‐sectional TEM is used to investigate the microstructure and composition. Measuring the total reflectance of progressively etched samples is used as an optical depth profiling method to derive the thickness of disturbed near‐surface layers. Quantitative r.f. GD‐OES depth profiling is introduced to study the in‐depth behaviour of alloying elements, as well as the incorporation of impurity elements within the disturbed layer. The GD‐OES depth profiles, total reflectance and cross‐sectional TEM analyses are correlated with SEM/energy‐dispersive x‐ray observations in GD‐OES craters. Copyright © 2005 John Wiley & Sons, Ltd.     

Imine‐linked porous organic polymers showing mesoporous microspheres architectures with tunable surface roughness

Different kinds of porous organic polymers (POPs) bearing 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) fluorophores have been developed to generate singlet oxygen upon light illumination. Herein, four imine‐linked POPs were prepared by copolymerization of amine and aldehyde with different ratios of di‐aldehyde A1 and A2. The POPs were investigated by a combination of techniques such as solid ¹³C NMR, FTIR, and nitrogen absorption–desorption isotherms and electronic microscopy. The results demonstrated that these POPs were prone to form hierarchical porous architectures. Scanning electron microscopy and transmission electron microscopy images revealed that the spherical morphologies showed different roughness, that is, BDP‐POPs with more BDP aldehyde A2 presented rougher surface. Finally, these POPs were used to generate singlet oxygen (¹O₂) monitored by 1,3‐diphenylisobenzofuran and bioimaging in HeLa cells. Our results indicated that the ability to generate ¹O₂ is dependent on the amount of BDP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 319–327     

The influence of substrate surface roughness on microstrip transmission line loss using conventional analyses and length‐scale fractal analysis

Two components of conductor topography can impact conductor loss for signals in the GHz frequency range: conductor–ceramic interface roughness and conductor edge angle. This study is an experimental investigation of the influence of these conductor topographies on conductor loss in microstrip circuits produced by thick‐film technology. The aluminum nitride ceramic substrates have different surface roughnesses due to different surface finish processes. The substrate surfaces were characterized using conventional and length‐scale fractal analysis. The conductor–ceramic interface was measured with a contact profilometer. The conductor edge angle and conductor edge profile were measured optically. It was found that there is a direct correlation between conductor loss and conductor edge angle, whereas there is an inverse correlation between loss and substrate roughness or relative length of the conductor–ceramic interface. This is the opposite result to the conventional expectation of surface roughness effects on conductor loss. There is also a negative correlation between conductor edge angle and surface roughness or relative length. The loss behavior can be explained by the interaction of the conductor paste with the surfaces during processing. The paste tends to spread more on the smoother surfaces, and thus creates an elongated edge of diminishing cross‐section and a small edge angle. This leads to greater conductor loss. Copyright © 2009 John Wiley & Sons, Ltd.     

Surface roughness and hydrophilicity enhancement of polyolefin‐based membranes by three kinds of plasma methods

The introduction of antibacterial property, conductivity, wettability and antithrombogenicity into polyolefin‐based membranes has evoked much attention, which can be achieved by coating hydrophilic polymers. Therefore, it is necessary to modify the roughness and hydrophilicity of polyolefin‐based membranes to enhance the coating ability. In this paper, three kinds of plasma methods, including inductively coupled (ICP) plasma, radio frequency low pressure (RFP) plasma and atmospheric dielectric barrier discharge (DBD) plasma, were used to modify the surface of the polyethylene (PE), polypropylene (PP) and polyester‐polypropylene (PET–PP) membranes. The surface roughness of the plasma‐modified PE, PP and PET–PP films was investigated by scanning electron microscopy (SEM) and atomic force microscope (AFM). The polar functional groups of films were observed by energy dispersive spectrometer (EDX) and X‐ray photoelectron spectroscopy (XPS). Besides, the hydrophilicity of the plasma‐modified PE, PP and PET–PP films was evaluated by water contact angle measurement. It was found that the surface roughness and hydrophilicity of plasma‐modified PE, PP and PET–PP films increased with the generation of oxygen‐containing functional groups (i.e. C―O, and C?O). The PET–PP membranes were treated by RFP plasma at different processing powers and times. These results indicated that plasma is an effective way to modify films, and the treatment time and power of plasma had a certain accumulation effect on the membranes' hydrophilicity. As for the roughness and hydrophilicity, the DBD plasma modifies the PE film, which is the optimum way to get the ideal roughness and hydrophilicity. Copyright © 2015 John Wiley & Sons, Ltd.     

Microstructure and surface roughness of graphite‐like carbon films deposited on silicon substrate by molecular dynamic simulation

Molecular dynamics simulations are performed on the atomic origin of the growth process of graphite‐like carbon film on silicon substrate. The microstructure, mass density, and internal stress of as‐deposited films are investigated systematically. A strong energy dependence of microstructure and stress is revealed by varying the impact energy of the incident atoms (in the range 1–120 eV). As the impact energy is increased, the film internal stress converts from tensile stress to compressive stress, which is in agreement with the experimental results, and the bonding of C‐Si in the film is also increased for more substrate atoms are sputtered into the grown film. At the incident energy 40 eV, a densification of the deposited material is observed and the properties such as density, sp³ fraction, and compressive stress all reach their maximums. In addition, the effect of impact energy on the surface roughness is also studied. The surface morphology of the film exhibits different characteristics with different incident energy. When the energy is low (<40 eV), the surface roughness is reduced with the increasing of incident energy, and it reaches the minimum at 50 eV. Copyright © 2012 John Wiley & Sons, Ltd.     

Capillary electrophoresis in a fused‐silica capillary with surface roughness gradient

The electro‐osmotic flow, a significant factor in capillary electrophoretic separations, is very sensitive to small changes in structure and surface roughness of the inner surface of fused silica capillary. Besides a number of negative effects, the electro‐osmotic flow can also have a positive effect on the separation. An example could be fused silica capillaries with homogenous surface roughness along their entire separation length as produced by etching with supercritical water. Different strains of methicillin‐resistant and methicillin‐susceptible Staphylococcus aureus were separated on that type of capillaries. In the present study, fused‐silica capillaries with a gradient of surface roughness were prepared and their basic behavior was studied in capillary zone electrophoresis with UV‐visible detection. First the influence of the electro‐osmotic flow on the peak shape of a marker of electro‐osmotic flow, thiourea, has been discussed. An antifungal agent, hydrophobic amphotericin B, and a protein marker, albumin, have been used as model analytes. A significant narrowing of the detected zones of the examined analytes was achieved in supercritical‐water‐treated capillaries as compared to the electrophoretic separation in smooth capillaries. Minimum detectable amounts of 5 ng/mL amphotericin B and 5 μg/mL albumin were reached with this method.     

SEM and RBS characterization of a cobalt‐based conversion coating process on AA2024‐T3 and AA7075‐T6

Samples of aluminium alloys AA2024‐T3 and AA7075‐T6 were treated with a chromate‐based deoxidizer, then conversion coated with a commercial cobalt‐based solution and finally sealed with a commercial vanadate‐based product. The alloy specimens were examined using scanning electron microscopy, transmission electron microscopy and Rutherford backscattering spectroscopy. The thickness of the cobalt‐based conversion coating increased rapidly up to 5 min of immersion but more slowly for longer times. Sealing resulted in penetration of vanadium through the oxide and a small increase in thickness due to the deposition of a thin sealing coating within the pores and on the external surface of the cobalt‐containing coating. Copyright © 2004 John Wiley & Sons, Ltd.     

Surface roughness and electrical conductivity of the SnO2 ultra‐thin layers investigated by X‐ray reflectivity

Spray pyrolysis technique was applied to deposit two sets of ultra‐thin layers of tin dioxide (SnO₂). For the first and second sets, 0.01 and 0.05 molar precursor solutions were prepared, respectively. In both sets, utilizing the X‐ray reflectivity (XRR) technique, the effect of precursor concentration (PC) and precursor volume (PV) on the layer structure are investigated. The layer thickness of the samples, in each set, is a PV‐dependent parameter. For the same PV, samples with higher PC have a larger thickness and higher density. The electron density profiles deduced from XRR data analyses establish a link between measured values of sheet resistance and electron densities. The samples with higher PV and PC show less sheet resistance. The quantum size effect was utilized to show that the surface roughness for layers of more than almost 200 Å of samples in set two plays no role in the layer conductivity. Meanwhile, the same effect explains, adequately, the role of the surface roughness in the resistivity of the ultra‐thin layers in Set 1.     

Surface characterization of laser-treated poly(ethylene terephthalate) by optical profilometry and scanning tunneling microscopy

Characteristic changes in the surface topography due to UV laser treatment are of high significance for the determination of material destruction thresholds and surface structure development. E.g. irradiation of poly(ethylene terephthalate) (PET) film with pulsed UV laser light of 248 nm modifies the smoth surface of the polymer into a well oriented structured surface. The development of these structures were studied with scanning tunneling microscopy (STM) and high resolution optical profilometry. Three dimensional data of the surface were taken from the samples after each laser pulse. A change of topographic data was found in relation to fluence and number of pulses applied. © 1993 John Wilcy & Sons, Inc.     

Electron Rutherford back‐scattering case study: oxidation and ion implantation of aluminium foil

Electron Rutherford back scattering (ERBS) is a new spectroscopy for determining the composition of surfaces. In this work the surface sensitivity of ERBS was investigated by changing the entrance and exit angle of the electron beam while keeping the scattering angle constant. It was found that in this way the surface sensitivity of the technique can be varied considerably. We use aluminium as a test case for ERBS, as it is well studied. The technique has been used to investigate the oxide film of aluminium foil as manufactured and the native oxide (Al₂O₃) film formed on a clean aluminium surface exposed to air. We have also used ERBS to investigate the presence of Xe, implanted during the sputter cleaning process, at a variety of depths within an aluminium matrix. Copyright © 2007 John Wiley & Sons, Ltd.     

Morphological change of crystalline polymer films by annealing: substrate‐ and heating/cooling‐rate‐dependent surface roughness

We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X‐ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high‐density and low‐density polyethylene films prepared by the cast method. After annealing at 135 °C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X‐ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films. Copyright © 2017 John Wiley & Sons, Ltd.     

Formation and recovery of a cell sheet by a particle monolayer with the surface roughness

We studied the topographical effect of roughness displayed by a closely packed particle monolayer on formation of a cell monolayer (cell sheet). Particle monolayers were prepared by Langmuir-Blodgett deposition using particles, which were 527nm (SA053) and 1270nm (SA127) in diameter. Human umbilical vein endothelial cells (HUVECs) were seeded at a high density (2.0 x10(5)cells/cm(2)) onto particle monolayers. It was found that cells gradually became into contact with adjacent cells on the SA053 monolayer and the formed cell sheet could be readily detached from the particle monolayer by gentle pipetting. On the other hand, cells adhering onto the tissue culture polystyrene (TCPS) and the SA127 particle monolayer were difficult to peel off. At a low cell seeding density (5.0x10(4)cells/cm(2)), pre-coating with bovine plasma fibronectin (FN) allowed cell growth on an SA053 particle monolayer, and a confluent monolayer was able to be peeled as a cell sheet from the particle monolayer just by pipetting. By immunostaining of human fibronectin, we found that fibronectin was secreted and concentrated onto the substrate side of a cell sheet. The obtained cell sheet adhered and grew on the TCPS again within 20min.     

Synthesis and characterization of electroactive epoxy‐based interpenetrating polymer network gel

Epoxy/poly(N‐isopropylacrylamide) interpenetrating polymer network gels were prepared by varying the excess amine content in the matrix (0.4–0.6 equivalent). All the samples were characterized for mechanical properties and swelling in distilled water. The topography of polymer network was characterized by atomic force microscopy. The 0.5 equiv. excess amine sample exhibited optimum properties. Studies on swelling at different pH and electroactivity in different aqueous solution were performed. The bending angle observed during first 1 min was 1–5° at 3–10 V and a maximum of 25° in 5 min at 20 V for 0.5 equiv. excess amine in NaCl solution. Copyright © 2011 John Wiley & Sons, Ltd.     

Self‐assembly of stearic acid on aluminium: the importance of oxide surface chemistry

The influence of ambient atmospheric exposure on the chemistry of the magnetron‐sputtered aluminium surface has been characterized as hydroxyl incorporation to the oxide surface and concurrent adsorption of airborne carbonaceous contamination. Here, the consequence of these changes in oxide surface chemistry upon the adsorption of stearic acid from solution is investigated. Water contact angle and polarization modulation infrared refection–absorption spectroscopy (PM‐IRRAS) reveal a strong dependence of stearic acid monolayer order upon ambient exposure time prior to assembly. It is proposed that hydroxyl formation in the ambient atmosphere increases the stearic acid adsorption density and thus the self‐assembled monolayer (SAM) order, whereas airborne carbonaceous material blocks these adsorption sites and introduces disorder in the monolayers through a decrease in adsorption density. Monolayer adsorption has been correlated with the aluminium oxide surface chemistry. It is proposed that this phenomenon represents an explanation for the irreproducible results often reported for assembly on metal oxide substrates. Furthermore, it indicates that in this broad class of material surfaces assembly can be used as a means of estimating the reactivity of surfaces with respect to organic overlayers such as paints and adhesives. Removal of adsorbed carbonaceous material from the aluminium surface using an oxygen plasma resulted in a significantly increased order of the stearic acid monolayer, as assessed by water contact angle. This observation is rationalized as the removal of carbonaceous material blocking surface adsorption sites by the plasma, but retention of the underlying hydroxyl functionality. This is predicted to have important implications in the preparation of aluminium for painting and adhesive bonding. Copyright © 2004 John Wiley & Sons, Ltd.     

Humidity‐induced surface modification of boric acid

Previous studies of boric acid powder suggest that the surface undergoes restructuring when exposed to changes in relative humidity of the surrounding air. This present work investigates these surface changes using atomic force microscopy (AFM) to provide quantitative topographic information, supplemented by gravimetric analysis of water sorption. The AFM images clearly show the dissolution of small rounded features and z‐height growth of the larger flatter areas, indicating that Ostwald ripening was the prevailing mechanism in the restructuring. Estimation of radii of curvature of asperities on the surface enabled the approximation of supersaturation ratio in the surface film using the Kelvin equation. The value of 1.007 obtained is much less than the value of 3.2 reported for solution‐grown boric acid. It is this high level of supersaturation that is thought to account for the inherent roughness of boric acid, associated with dendritic growth. Conversely, the low supersaturation ratio estimated for the adsorbed surface layer results in regular crystal growth and a decrease in surface roughness. Gravimetric analysis of boric acid revealed a steady loss in water with increase in relative humidity from 10% to 60%. This is attributed to loss of available surface area through the progressive dissolution of fine surface features. Desorption showed a monotonic decrease in water uptake, confirming that the restructuring is not reversible. Changes in surface area were estimated from the AFM images. The loss of surface area between dry and ambient conditions was greater than that inferred from the loss of mass in the gravimetric analysis. This suggests that water is retained on the surface in capillaries that are not apparent in the AFM surface scans. Statistical monolayer coverage of water is achieved at 10% relative humidity, which corresponds to the onset of surface restructuring indicated by the water sorption isotherm. Copyright © 2004 John Wiley & Sons, Ltd.     

Identification of segregation phase on a batch hot‐dip‐coated Zn/0.1Al/0.2Sb surface

The segregation of antimony in a batch hot‐dipped regular‐spangle galvanized coating from a Zn‐0.1Al‐0.2Sb bath was investigated. The samples were characterized by using SEM/EDS. The nature of the segregation phase was determined by XRD as βSb₃Zn₄. Assisted with Sb? Zn phase diagram, the behavior of antimony during the solidification process of the Zn‐0.1Al‐0.2Sb coating is examined. It is suggested that the coating solidification proceeds in three stages. Owing to the cooling rate of batch hot dip galvanizing process smaller than that of continuous hot dip galvanizing line (CGL), the resulting structure of the segregation phase in current work is βSb₃Zn₄ instead of metastable ζSb₂Zn₃ for CGL. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of polystyrene‐graphite nanocomposites via surface RAFT‐mediated miniemulsion polymerization

Graphite oxide (GO) was prepared and immobilized with dodecyl isobutyric acid trithiocarbonate (DIBTC) reversible addition‐fragmentation chain transfer (RAFT) agent. The hydroxyl groups of GO were attached to the DIBTC RAFT agent through an esterification process. The resultant modified GO was used for the preparation of polystyrene (PS)/graphite nanocomposites in miniemulsion polymerization. The RAFT‐grafted GO (GO‐DIBTC) at various loadings was dispersed in styrene monomer, and the resultant mixtures were sonicated in the presence of a surfactant (sodium dodecylbenzene sulfonate) and a hydrophobe (hexadecane) to form miniemulsions. The stable miniemulsions thus obtained were polymerized using azobisisobutyronitrile as the initiator to yield encapsulated PS‐GO nanocomposites. The molar mass and polydispersity index of PS in the nanocomposites depended on the amount of RAFT‐grafted GO in the system, in accordance with the features of the RAFT polymerization method. The PS‐GO nanocomposites were of exfoliated morphology, as confirmed by X‐ray diffraction and transmission electron microscopy measurements. The thermal stability and mechanical properties of the PS‐GO nanocomposites were better than those of the neat PS polymer. Furthermore, the mechanical properties were dependent on the modified GO content (i.e., the amount of RAFT‐grafted GO). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011