The presented paper deals with the measurement methodologies of the structural properties of porous anodic alumina (PAA) films filled with YAlO3:Tb3+ composite using X-ray diffraction, atomic force microscopy and scanning electron microscopy. It shows that the deposited material does not uniformly fill the porous volume of the anodic alumina film and the part of it forms a thick layer on the PAA surface. The aim of this work is to show the differences in the XRD response obtained at different angles of incidence of the excitation beam for the PAA/YAlO3:Tb3+ system. Furthermore, this simple approach enables separation of the signal from both regions on the surface and inside the PAA pores, providing more accurate data interpretation. It reveals that the crystallization of the material on the PAA surface and within the pores is different.

The spallation behaviour of alumina scales grown on FeCrAlY alloy was investigated. Substrates with different thicknesses were oxidized at 1200 °C for 25 h and cooled at various cooling rates. Generally, the scale formed on a thicker substrate or with a faster cooling rate exhibits a larger compressive stress. However, the failure behaviour of alumina scales is more complicated than expected for a compressed film. Specifically, (i) the extent of the spallation is not proportional to the residual stress in the oxide; (ii) the spallation does not occur immediately after cooling, but requires a period of incubation. This indicates that the residual stress is not the sole reason for the failure of scales. It was found that the carbide forms at the oxide–metal interface after cooling, which acts in conjunction with the residual stress to control the spallation of oxides. In addition, the mechanics analysis suggests that the microscopic roughness at the interface is another important factor.

The effect of immersion of type 304 stainless steel in pyrrolidium-2-one trifluoroacetate ionic liquid on surface composition and structure was studied. A passive film with increased protective properties was formed on the steel surface due to enrichment of chromium in the inner region of the oxide film and enrichment of nickel beneath the oxide film. The presence of fluorine bonded to metal and carbon was revealed on the surface of steel that was attributed to interaction of the steel and anions of the ionic liquid. Newly developed plasma profiling time-of-flight mass spectrometry was successfully employed for semi-quantitative analysis of the elemental depth distributions in the thin passive film with high resolution. (C) 2015 Elsevier B.V. All rights reserved.

Physics, Chemistry and Applications of Nanostructures, pp. 373-376 (2015) No AccessNANOSTRUCTURED BISMUTH STRONTIUM TANTALATE SOL-GEL DERIVED XEROGELM. V. RUDENKO, T. I. OREKHOVSKAJA, I. S. MOLCHAN, and G. E. THOMPSONM. V. RUDENKOBelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarus, T. I. OREKHOVSKAJABelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarus, I. S. MOLCHANCorrosion and Protection Centre, School of Materials, The University of Manchester, Manchester M13 9PL, United Kingdom, and G. E. THOMPSONCorrosion and Protection Centre, School of Materials, The University of Manchester, Manchester M13 9PL, United Kingdomhttps://doi.org/10.1142/9789814696524_0091Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Nanostructured bismuth strontium tantalate xerogels were synthesized using the sol-gel method. Xerogel was deposited by a spin-on technique on monocrystalline silicon and porous anodic alumina generated on monocrystalline silicon substrate. The morphologies and phase compositions of the fabricated structures were investigated. FiguresReferencesRelatedDetails Physics, Chemistry and Applications of NanostructuresMetrics History PDF download

The effect of post-anodizing rinsing on the morphology and composition of anodic films formed on titanium at 20 V in 0.2 M ammonium fluoride solution in glycerol, containing 0 and 5 vol.% water is investigated. The films generated in the electrolyte with added water or those rinsed with water exhibited nanotubular morphologies. In contrast, anodizing in the electrolyte with no added water followed by rinsing with ethanol resulted in a porous film appearance due to the presence of a fluoride-rich matrix surrounding the nanotubes. The films rinsed with water revealed less fluorine, oxygen and titanium compared with those rinsed with ethanol that was attributed to dissolution of the fluoride-rich matrix by water. Addition of water to the electrolyte enables the formation of nanotubular films directly due to dissolution of the matrix during anodizing. (C) 2015 Elsevier Ltd. All rights reserved.

Corrosion and Protection Centre, School of Manchester, M13 9PL, UK. E-mail: igor.mol Division of Physical Chemistry, Institute Processes, Nanotechnology and Microsyst 15310 Aghia Paraskevi Attikis, Athens, Gree Separation Technology Group, Department Eindhoven University of Technology, Den Netherlands IoLiTec, Ionic Liquids Technologies Gmb Germany † Electronic supplementary informa 10.1039/c5ra01097g Cite this: RSC Adv., 2015, 5, 35181

Three 1-alkyl-3-methylimidazolium tricyanomethanide (TCM) ionic liquids (ILs) (alkyl = ethyl, butyl and hexyl) and one butyrolactam cation-based IL with a fluorinated anion were synthesised and tested in contact with mild steel (MS) at temperatures up to 80 °C. The corrosion behaviour was evaluated by monitoring the morphological changes on the steel surface after testing. Exposure of MS to the IL results in two main types of degradation that depend on the IL type. General etching over the macroscopic surface of the alloy was revealed for the IL with the fluorinated anion. The 1-alkyl-3-methylimidazolium TCM ILs promoted dissolution of MnS inclusions present in the steel. In the ILs with a shorter alkyl chain in the cation (alkyl = ethyl, butyl), the dissolution of MnS was accompanied by generation of corrosion products around the inclusion sites, which are mainly identified as magnetite and maghemite ferrites by micro-Raman spectroscopy. The rest of the macroscopic steel surface remains unaffected. Etching resulted in significant weight loss due to removal of material, whereas no significant weight loss was revealed following MnS dissolution. Butyrolactam cation-based IL severely attacks MS with the formation of a plethora of corrosion products including ferrites (mainly hematite), zinc oxide, sulphates and carbonates. Addition of 500 ppm sodium molybdate to the butyrolactam cation-based IL resulted in efficient inhibition of etching at both room temperature and 60 °C due to adsorption of molybdate on the alloy surface. A side effect of MS degradation is that the CO2 absorption capacity of the ILs can be severely reduced through the transfer of metal ions and corrosion products from the metallic surface to the liquid phase. Therefore, gravimetric CO2 absorption capacity and kinetic measurements on the selected 1-alkyl-3-methylimidazolium tricyanomethanide ILs before and after their contact with MS were also conducted with the purpose to unveil and study these side effects. Moreover, CO2 absorption experiments of the butyrolactam cation-based IL before and after contact with MS, as well as in the presence of a sodium molybdate inhibitor, showed that sodium molybdate has the capacity to limit significantly the etching rate without affecting the CO2 capture performance of the IL.

The CO2 capture efficiency of nine newly synthesized ionic liquids (ILs), both in their pure states as well as in binary and ternary systems with water and amines, was investigated. The study encompassed ILs with fluorinated and tricyanomethanide anions as well as ILs that interact chemically with CO2 such as those with amino acid and acetate anions. Compared to amines, some of the novel ILs exhibited a majority of important advantages for CO2 capture such as enhanced chemical and thermal stabilities and negligible vapor pressure; the previous features counterbalance the disadvantages of lower CO2 absorption capacity and rate, making these ILs promising CO2 absorbents that could partially or totally replace amines in industrial scale processes. In addition to their ability to capture CO2, important issues including corrosivity and ecotoxicity were also examined. A thorough investigation of the capture efficiency and corrosion properties of several solvent formulations proved that some of the new ILs encou...

An aerospace grade Ti-6Al-4V alloy, treated by an excimer laser, has been analysed by elemental depth profiling using glow discharge optical emission spectrometry (GDOES). Laser exposure may modify the surface morphology of the alloy due to melting and generation of microcracks. Melting reduces the roughness over an area of 1 × 1 μm, whereas the roughness over an area of 100 × 100 μm increases. The influence of such modification of the surface morphology on changes in the shapes of the GDOES elemental depth profiles is discussed.

Laser cleaning is a promising surface preparation technique for applications in high value manufacturing industries. However, understanding the effects of laser processing parameters on various types of contaminants and substrates, is vital to achieve the required cleaning efficacy and quality. In this paper, a two-dimensional transient numerical simulation was carried out to study the material ablation characteristics and substrate thermal effects in laser cleaning of aerospace alloys. Element birth and death method was employed to track the contaminant removal on the surface of the material. The result shows that contaminant ablation increases with laser power and number of pulses. The finite element method (FEM) model is capable enough to predict the optimum number of pulses and laser power required to remove various contaminants. Based on the simulation results, the mechanism of the excimer laser cleaning is proposed. Thus, the use of numerical simulation can be faster and cheaper method of establishing the optimum laser cleaning window and reducing the number of experimental tests.

The corrosion behaviour of mild steel (MS) was systematically investigated as a function of the alkyl chain length in the cation of 1-alkyl-3-methylimidazolium tricyanomethanide ([C(n)mim]TCM, n = 2, 4, 6 and 8) ionic liquids (ILs) with respect to their potential application as a structural material and solvents for CO2 capture plants respectively. The surface of MS was examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and micro-Raman mapping before and after immersion testing at temperatures of 70 and 80 degrees C for durations varying from 1 hour to 10 days. Corrosion initiates at the sites of MnS inclusions on the surface of MS, resulting in the formation of cavities due to the MnS dissolution, which may be surrounded by corrosion products containing magnetite (Fe3O4) and maghemite (gamma-Fe2O3). The amount of the corrosion products generated around the inclusion sites decreased with the increase of the cation alkyl chain length, following the order [C(2)mim]TCM > [C(4)mim] TCM > [C(6)mim] TCM approximate to [C(8)mim]TCM. This was attributed to the corrosion inhibition effect of the ILs through adsorption on the metal surface and blocking active sites, with the inhibition efficiency increasing with the alkyl chain length. The underlying mechanism was associated with corrosion processes at active sites on the MS surface, such as sulphide inclusions, in the presence of residual water and oxygen in the IL. It was shown that increase of the water content in the ILs to about 50 000 ppm resulted in faster dissolution of the MnS inclusions. Finally, it was demonstrated that removal of oxygen from the IL significantly reduced the corrosion rate.

Terbium doped YAlO3 composites, with terbium concentrations up to 2.11 at%, were fabricated by co-precipitation in porous anodic alumina films grown on silicon. The presence of the cubic YAlO3 phase was confirmed by x-ray diffraction and FT-IR analysis. The fabricated samples demonstrate photoluminescence (PL) within the range 350-640 nm, which is associated with f-f transitions from the D-5(3), (5)G(6) and D-5(4) levels of Tb3+ ion. Additionally, a broad and fast- decaying PL band in the blue range has been observed, which is associated with defect states. Based on PL excitation spectra, the main excitation channel of Tb3+ ions is due to 4f-5d transitions. Excitation bands observed at 235, 270 and 320 nm have been related to the permitted low-spin 5d(2) [LS], 5d(1) [LS] and forbidden high-spin 5d(1) [HS] states, respectively. The PL decay spectra have been measured, with the results analysed using the maximum entropy method; a strong indication of ion-ion interaction has been observed. The distribution of Tb3+ ions in the PAA : YAlO3 structure has been proposed and its influence on optical properties of Tb3+ ions has been discussed.

Photo-, radio-, and pulse cathodoluminescence spectra from sol-gel derived titania, doped with strontium and terbium, deposited on porous anodic alumina (PAA) films are reported. The morphology and qualitative elemental depth distributions have been examined by transmission electron microscopy, scanning electron microscopy, and radio-frequency glow discharge optical emission spectroscopy. PAA films with pore and cell sizes ranging from 170 to 190 and 240 to 270 nm, respectively, have been generated on aluminum and monocrystalline silicon substrates followed by spin-on sol-gel derived coating with the subsequent thermal treatment. The resultant PAA surface is not coated with a continuous xerogel film; the xerogel is mainly distributed near the pore bases, leaving much of the pore volume unfilled. The xerogel/PAA structures reveal terbium-related luminescence under x-ray excitation and cathodoluminescence. The same xerogels generated on monocrystalline silicon revealed no cathode- or under-x-ray luminescence. Thus, PAA enhances strongly the cathode- and under x-ray luminescence from terbium and strontium-doped titania xerogels confined in the porous matrix. The fabricated structures are considered as a type of low-cost, thin-film convertor of x-rays, and cathode ray irradiation into visible light, with an average cell size of the convertor of about 250 nm.

This chapter contains sections titled: Introduction Thin and Thick Layers: A Tentative Definition What Specific Information MS Techniques could Bring to thin and thick Films Analysis Compared to other Techniques? Main MS Techniques Applied to Thin/Thick Films Time of Sputtering/Speed of Acquisition Trade-Off Differences in Sputtering/Ionization Mechanisms between SIMS and GD-MS Pulse Shapes and how to Best Use Temporal Information for Pulsed Glow Discharge Mass Spectrometry Measurement and Data Interpretation in GD-TOFMS Practical Examples Conclusions List of Abbreviations References

The pioneering study of Shimizu et al. (J. Anal. At. Spectrom., 2004, 19, 692) on the examination of adsorbed organic molecules on a copper substrate by radio frequency glow discharge optical emission spectrometry (rf-GDOES) displayed the potential of GDOES for determination of the orientations of molecular monolayers. Here, the study has been extended to the examination of thiourea adsorbed on silver, gold and copper surfaces and metal-centred molecular wires (MCMWs) of 4-6 nm length, with cobalt atoms in the middle of the chain adsorbed on a gold surface. According to established data, these molecules are adsorbed onto a metal surface through a sulphur atom. Depth profiling of thiourea adsorbed on the copper surface confirmed the results of Shimizu at al, with a nitrogen peak followed by a sulphur peak in the depth profile revealed with sputtering time. However, in the case of silver and gold substrates, the positions of the sulphur and nitrogen peaks in the depth profiles were not as predicted from the orientation of the thiourea molecule, i.e. the nitrogen peak followed the sulphur peak with sputtering time or the peaks overlapped. In the depth profiles of the adsorbed MCMWs, the sulphur peak appeared prior to the cobalt peak with sputtering time. Further, the time required for sputtering of thiourea and the wires are comparable, whereas the lengths of thiourea and the wire molecules differ by more than one order of magnitude. Thus, in this case, no correlation between the orientation of the molecules and the peak sequence in the depth profiles has been observed.

FeCrAlY sheets of different thicknesses (0.477-7.608 mm) have been oxidized at 1200 degrees C in air for 25 h to form alumina scales, with cooling to room temperature at rates from 1 degrees C/min to 100 degrees C/min. Spallation of the alumina scale occurs with intermediate cooling rates, e.g. 5, 10 and 30 degrees C/min, whereas no spallation is evident in samples with the highest cooling rate of 100 degrees C/min, suggesting that the residual stress is not the only factor to drive the spallation. For a fixed cooling rate of 30 degrees C/min, the spalling is more pronounced on thicker substrates than on a thin FeCrAlY alloy substrate where the thicker substrate leads to higher residual stresses in the alumina scale. Chemical analysis reveals the Cr-carbide segregation at grain boundaries of the Fecralloy and the alumina/Fecralloy interface. The degree of segregation decreased with increase of the cooling rate, and appears to be similar with change of substrate thickness. Meanwhile, the grain size of Fecralloy decreases with increase in cooling rate. It appears that the combination of residual stresses, grain size change and the Cr-carbide segregation controls the spallation of the alumina scale. Based on the spallation phenomena, the alumina/FeCrAlY alloy interfacial toughness has been determined tending to increase with increase of cooling rate. The result suggested that the interface is degraded by the carbide segregation and change in Fecralloy composition. (C) 2011 Elsevier B.V. All rights reserved.

The depth resolutions achieved by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and glow discharge optical emission spectroscopy (GD-OES) are comparable for the analysis of relatively flat specimens. However, the precision of sputtering-induced depth profiling techniques has been shown to be dramatically influenced by the initial roughness of specimen surface. The effect of the specimen roughness on the depth resolution achieved by both techniques has been examined here using textured aluminium substrates supporting anodic oxide films. As a result of dissimilarities in the sputtering processes, TOF-SIMS and GD-OES show significantly different elemental depth profiles for electrolyte-derived species incorporated into anodic oxide films formed on superpure aluminium substrates of controlled texture. Copyright (C) 2010 John Wiley & Sons, Ltd.

The effect of tungsten species on the incorporation and migration of phosphorus species within anodic alumina is investigated. The study employs barrier anodic films, formed on a sputtering‐deposited Al‐15at.%W alloy in phosphate electrolytes. The films consist of either an outer tungsten‐containing region and an inner tungsten‐free region, or a tungsten‐containing region only. Phosphorus species are shown to migrate inward in the tungsten‐containing alumina more slowly than in the tungsten‐free alumina. In contrast, the outward migration of tungsten species is relatively unaffected by the presence of phosphorus species. The relevance of the results to the use of tungsten tracers for the study of porous film growth is discussed. Copyright © 2010 John Wiley & Sons, Ltd.

The performance of a newly developed pulsed RF glow discharge time-of-flight mass spectrometer (GD TOFMS) in analysis of elemental distributions of impurity species, particularly Cr, B, P, Cl and Cu in anodic film on aluminium and beneath the anodic alumina/aluminium interface and P, B, Cr and H in anodic film on tantalum and beneath the anodic tantala/tantalum interface, with high resolution is presented. The orthogonal TOFMS combined with an appropriate acquisition system enables monitoring of ion signals within the glow discharge period, i.e. during the RF pulse, and within following afterglow, where signals of high intensity, resulting from Penning ionisation, are observed. It was found that GD TOFMS profiling is an extremely powerful and reliable technique for depth profiling analysis that is confirmed from the depth distribution of impurities in the thin, non-conducting, anodic oxide films. The developed configuration allows analysis of layers as thin as 2 nm thickness that are enriched with both positive and negative ions.