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Applied Surface Science

آخرین مقالات مجله Applied Surface Science

  1. Publication date: 1 October 2018
    Source:Applied Surface Science, Volume 454

    Author(s): A.F. Alshater, D.L. Engelberg, C.J. Donohoe, S.B. Lyon, A.H. Sherry

    Micro-scale damage with a topographical contrast has been observed in cold-worked Nb-stabilised 20%Cr-25%Ni stainless steel, following irradiation with 2.2 MeV protons at 400 °C and a dose rate of ∼10−5 dpa/s. After an irradiation dose of 3 and 5 dpa, microstructural changes were found to a depth of 22 μm below the irradiated surface, coincident with the estimated mean range of protons in the material as predicted by the TRIM code. Large variations of intragranular mis-orientations, in combination with a depletion of chromium at grain boundaries, were observed in the proton-irradiated layer. This was accompanied by an increase in nano-hardness, which was linked to a partial transformation of tangled dislocation networks into dislocation loops. Such visible microstructural changes have not been reported before in the absence of post-irradiation annealing treatments.

  2. Publication date: 30 September 2018
    Source:Applied Surface Science, Volume 453

    Author(s): Bright Ankudze, Tuula T. Pakkanen

    A quantitative monitoring of a heterogeneously catalyzed reaction based on surface-enhanced Raman scattering (SERS) requires fabrication of a bifunctional substrate with exposed SERS and catalytic sites. Fabrication of such dual-functional substrates is challenging, owing to the different size limits of metal nanoparticles set by both SERS and catalysis. Larger-sized nanoparticles are suitable for SERS, whereas catalysis requires smaller particles, hence, the integration of both features into a single nanostructured material can be demanding. In this study, we report access to simple fabrication of a bifunctional nanostructure based on gold nanoparticle decorated Au-Ag tubes (Au@Au-AgTs) having both SERS and catalytic features. A facile approach using polymer linkages facilitated the immobilization of catalytically active gold nanoparticles on Au-AgTs. The decoration process involves a simple mixing of polyethylenimine capped gold nanoparticles with Au-Ag alloy tubes, and requires no harsh conditions or complex synthetic procedures. The synergistic effect of gold and silver metals enabled a sensitive SERS performance of Au@Au-AgTs, and the small gold nanoparticles functioned as active catalytic sites. Using the catalytic conversion of 4-nitrothiophenol to 4-aminothiophenol as a model reaction, the Au@Au-AgTs exhibited the ability to function as an active catalytic and SERS-responsive platform in quantifying the reaction kinetics.

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  3. Publication date: 1 August 2018
    Source:Applied Surface Science, Volume 448

    Author(s): Konstantin I. Maslakov, Yury A. Teterin, Aleksej J. Popel, Anton Yu. Teterin, Kirill E. Ivanov, Stepan N. Kalmykov, Vladimir G. Petrov, Peter K. Petrov, Ian Farnan

    This work considers the effect of fission-energy ion irradiation on the electronic structure at the surface of bulk and thin film samples of CeO2 as a simulant for UO2 nuclear fuel. For this purpose, thin films of CeO2 grown on Si substrates and bulk CeO2 samples were irradiated by Xe ions (92 MeV, 4.8 × 1015 ions/cm2) to simulate the fission damage that occurs within nuclear fuels. The irradiated and unirradiated samples were characterized by X-ray photoelectron spectroscopy. A technique of the quantitative evaluation of cerium ionic composition on the surface of the samples has been successfully applied to the obtained XPS spectra. This technique is based on the intensity of only one of the reliably identifiable high-energy peak at 916.6 eV in the Ce 3d XPS spectra. The as-produced samples were found to contain mostly the Ce4+ ions with a small fraction of Ce3+ ions formed on the surface in the air or under X-rays. The core-electron XPS structure of CeO2 was associated with the complex final state with vacancies (holes) resulting from the photoemission of an inner electron. The Xe ion irradiation was found to increase the Ce3+ content in the samples of CeO2, with the thin films being more sensitive than the bulks samples.

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  4. Publication date: 15 May 2018
    Source:Applied Surface Science, Volume 440

    Author(s): Abdul Md. Motin, Thomas Haunold, Andrey V. Bukhtiyarov, Abhijit Bera, Christoph Rameshan, Günther Rupprechter

    Pt nanoparticles supported on carbon are an important technological catalyst. A corresponding model catalyst was prepared by physical vapor deposition (PVD) of Pt on sputtered HOPG (highly oriented pyrolytic graphite). The carbon substrate before and after sputtering as well as the Pt/HOPG system before and after Pt deposition and annealing were examined by XPS and STM. This yielded information on the surface density of defects, which serve as nucleation centres for Pt, and on the size distribution (mean size/height) of the Pt nanoparticles. Two different model catalysts were prepared with mean sizes of 2.0 and 3.6 nm, both turned out to be stable upon UHV-annealing to 300 °C. After transfer into a UHV-compatible flow microreactor and subsequent cleaning in UHV and under mbar pressure, the catalytic activity of the Pt/HOPG model system for ethylene hydrogenation was examined under atmospheric pressure flow conditions. This enabled to determine temperature-dependent conversion rates, turnover frequencies (TOFs) and activation energies. The catalytic results obtained are in line with the characteristics of technological Pt/C, demonstrating the validity of the current surface science based model catalyst approach.

  5. Publication date: 30 March 2018
    Source:Applied Surface Science, Volume 435

    Author(s): W. Koczorowski, T. Grzela, A. Puchalska, M.W. Radny, L. Jurczyszyn, S.R. Schofield, R. Czajka, N.J. Curson

    Structural properties of Ba-induced reconstructions on a Ge(001) surface, based on atomic-resolution ultra high-vacuum scanning tunneling microscopy measurements, are discussed. It is shown that while the Ba - Ge layer, which fully covers the surface, is dominated by a phase with an internal 2 × 3 periodicity, it also includes portions of higher order 2 × 6 and 4 × 3 surface reconstructions, always accompanied by 1D protrusions embedded into the dominating phase. Modelling the observed higher order structures, using the elementary cell of the 2 × 3 phase calculated within the density functional theory, is shown to reproduce the experimental data very well. As such the higher order reconstructions can be treated as local defects of the dominating 2 × 3 phase.

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  6. Publication date: 15 March 2018
    Source:Applied Surface Science, Volume 434

    Author(s): Atif Hussain, Juliana Calabria-Holley, Diane Schorr, Yunhong Jiang, Mike Lawrence, Pierre Blanchet

    This is the first time sol-gel technology is used in the treatment of hemp shiv to develop sustainable thermal insulation building materials. The impact on the hydrophobicity of hemp shiv by depositing functionalised sol-gel coatings using hexadecyltrimethoxysilane (HDTMS) has been investigated. Bio-based materials have tendency to absorb large amounts of water due to their hydrophilic nature and highly porous structure. In this work, the influence of catalysts, solvent dilution and HDTMS loading in the silica sols on the hydrophobicity of hemp shiv surface has been reported. The hydrophobicity of sol-gel coated hemp shiv increased significantly when using acid catalysed sols which provided water contact angles of up to 118° at 1% HDTMS loading. Ethanol diluted sol-gel coatings enhanced the surface roughness of the hemp shiv by 36% as observed under 3D optical profilometer. The XPS results revealed that the surface chemical composition of the hemp shiv was altered by the sol-gel coating, blocking the hydroxyl sites responsible for hydrophilicity.

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  7. Publication date: 15 March 2018
    Source:Applied Surface Science, Volume 434

    Author(s): L. Wallenhorst, L. Gurău, A. Gellerich, H. Militz, G. Ohms, W. Viöl

    In this study, artificial ageing of beech wood coated with Zn/ZnO particles by means of a cold plasma spraying process as well as coating systems including a Zn/ZnO layer and additional conventional sealings were examined. As ascertained by colour measurements, the particle coatings significantly decreased UV light-induced discolouration. Even though no significant colour changes were observed for particle-coated and alkyd-sealed samples, ATR-FTIR measurements revealed photocatalytic degradation of the alkyd matrix. In contrast, the polyurethane sealing appeared to be stabilised by the Zn/ZnO coating. Furthermore, morphologic properties of the pure particle coatings were studied by SEM and roughness measurements. SEM measurements confirmed a melting and solidifying process during deposition.

  8. Publication date: 1 March 2018
    Source:Applied Surface Science, Volume 433

    Author(s): M. Coto, S.C. Troughton, J. Duan, R.V. Kumar, T.W. Clyne

    This paper describes a novel set-up for characterization of the performance of membranes designed for purification of water. It involves a recirculatory system, with continuous monitoring of the concentration in the water of a representative pollutant (Methylene Blue). Pressures, flow rates and temperatures are also measured. Results, in the form of rate constants for reduction in pollutant concentration, are presented for three different types of membrane, all of which incorporate relatively high surface areas of titania and have permeability values in a range making them suitable for this type of processing (∼10−11 m2). These results are rationalized in terms of the surface areas of the membranes, and the likely water flow characteristics within them. It is concluded that all of the titania surfaces within them have similar efficiencies for photo-catalytic oxidation of pollutants, but there are significant differences in the ways that the water is exposed to these surfaces, and hence in the pollutant oxidation rates. These points are relevant to the optimization of membrane design for this purpose.

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  9. Publication date: 1 March 2018
    Source:Applied Surface Science, Volume 433

    Author(s): Konstantin I. Maslakov, Yury A. Teterin, Aleksej J. Popel, Anton Yu. Teterin, Kirill E. Ivanov, Stepan N. Kalmykov, Vladimir G. Petrov, Ross Springell, Thomas B. Scott, Ian Farnan

    A (111) air-exposed surface of UO2 thin film (150nm) on (111) YSZ (yttria-stabilized zirconia) before and after the Ar+ etching and subsequent in situ annealing in the spectrometer analytic chamber was studied by XPS technique. The U 5f, U 4f and O 1s electron peak intensities were employed for determining the oxygen coefficient k O =2+ x of a UO2+x oxide on the surface. It was found that initial surface (severalnm) had k O =2.20. A 20s Ar+ etching led to formation of oxide UO2.12, whose composition does not depend significantly on the etching time (up to 180s). Ar+ etching and subsequent annealing at temperatures 100–380°C in vacuum was established to result in formation of stable well-organized structure UO2.12 reflected in the U 4f XPS spectra as high intensity (∼28% of the basic peak) shake-up satellites 6.9eV away from the basic peaks, and virtually did not change the oxygen coefficient of the sample surface. This agrees with the suggestion that a stable (self-assembling) phase with the oxygen coefficient k O 2.12 forms on the UO2 surface.

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  10. Publication date: 15 January 2018
    Source:Applied Surface Science, Volume 428

    Author(s): Binling Chen, Silvia Berretta, Ken Evans, Kaylie Smith, Oana Ghita

    This paper proposes two methods of preparation of graphene/PEEK powders for Laser Sintering (LS) and investigates their behaviour in relation to their microstructure and their properties. Thin composite films were fabricated in an attempt to replicate the thin layer formation of the powder bed process. Both methods of composite powder preparation (wet and dry) led to enhanced mechanical performance of the composite films at 0.1 and 0.5wt% graphene nano-platelets (GNP) concentrations. The TEM images show that the GNP act as a nucleation point in crystallisation of PEEK, being at the centre of the spherulites. The hot stage microscopy reveals a 20s delay in the onset of GNP/PEEK nanocomposite coalescence in comparison with plain PEEK. This is a very important observation for laser sintering, as it will influence the build strategy and specific parameters (e.g. time between layers deposition, multiple exposures). The excellent electrical conductivity properties of graphene were noticeable in the nanocomposite films at concentrations above 1wt% GNP.

  11. Publication date: 1 January 2018
    Source:Applied Surface Science, Volume 427, Part A

    Author(s): Monika Jenko, Matevž Gorenšek, Matjaž Godec, Maxinne Hodnik, Barbara Šetina Batič, Črtomir Donik, John T. Grant, Drago Dolinar

    The surface chemistry and microstructures of titanium alloys (both new and used) and CoCrMo alloys used for hip and knee endoprostheses were determined using SEM (morphology), EBSD (phase analysis), AES and XPS (surface chemistry). Two new and two used endoprostheses were studied. The SEM SE and BE images showed their microstructures, while the EBSD provided the phases of the materials. During the production of the hip and knee endoprostheses, these materials are subject to severe thermomechanical treatments and physicochemical processes that are decisive for CoCrMo alloys. The AES and XPS results showed that thin oxide films on (a) Ti6Al4V are primarily a mixture of TiO2 with a small amount of Al2O3, while the V is depleted, (b) Ti6Al7Nb is primarily a mixture of TiO2 with a small amount of Al2O3 and Nb2O5, and (c) the CoCrMo alloy is primarily a mixture of Cr2O3 with small amounts of Co and Mo oxides. The thin oxide film on the CoCrMo alloy should prevent intergranular corrosion and improve the biocompatibility. The thin oxide films on the Ti alloys prevent further corrosion, improve the biocompatibility, and affect the osseointegration.

  12. Publication date: 1 January 2018
    Source:Applied Surface Science, Volume 427, Part A

    Author(s): Steven J. Bell, Mark A. Baker, Diana D. Duarte, Andreas Schneider, Paul Seller, Paul J. Sellin, Matthew C. Veale, Matthew D. Wilson

    Cadmium zinc telluride (CdZnTe) is a leading sensor material for spectroscopic X/γ-ray imaging in the fields of homeland security, medical imaging, industrial analysis and astrophysics. The metal-semiconductor interface formed during contact deposition is of fundamental importance to the spectroscopic performance of the detector and is primarily determined by the deposition method. A multi-technique analysis of the metal-semiconductor interface formed by sputter and electroless deposition of gold onto (111) aligned CdZnTe is presented. Focused ion beam (FIB) cross section imaging, X-ray photoelectron spectroscopy (XPS) depth profiling and current-voltage (IV) analysis have been applied to determine the structural, chemical and electronic properties of the gold contacts. In a novel approach, principal component analysis has been employed on the XPS depth profiles to extract detailed chemical state information from different depths within the profile. It was found that electroless deposition forms a complicated, graded interface comprised of tellurium oxide, gold/gold telluride particulates, and cadmium chloride. This compared with a sharp transition from surface gold to bulk CdZnTe observed for the interface formed by sputter deposition. The electronic (IV) response for the detector with electroless deposited contacts was symmetric, but was asymmetric for the detector with sputtered gold contacts. This is due to the electroless deposition degrading the difference between the Cd- and Te-faces of the CdZnTe (111) crystal, whilst these differences are maintained for the sputter deposited gold contacts. This work represents an important step in the optimisation of the metal-semiconductor interface which currently is a limiting factor in the development of high resolution CdZnTe detectors.

  13. Publication date: 1 December 2017
    Source:Applied Surface Science, Volume 424, Part 1

    Author(s): J.M. Iglesias, M.J. Martín, E. Pascual, R. Rengel

    The influence of different substrates on the photocarrier relaxation dynamics in monolayer graphene during the early stages of thermalization and cooling is explored and analyzed by means of ensemble Monte Carlo simulations. In addition, phonon dynamics of both intrinsic and surface polar modes associated to the interface between graphene and the underlying substrate are investigated. Suspended graphene and graphene on four of the most common substrates used for nanoelectronics will be studied, showing that depending on the case, carrier relaxation can be accelerated due to the leading role that the surface polar phonon modes take under such out-of-equilibrium situations. Among the considered cases, graphene on Al2O3 shows the highest relaxation rates, while the results of graphene on h-BN, SiO2 and SiC are quite similar. On its behalf, photocarriers in suspended graphene take longer to thermalize than any of the substrate supported cases.

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  14. Publication date: 30 November 2017
    Source:Applied Surface Science, Volume 423

    Author(s): Jingpei Huo, Zhudong Hu, Guozhang He, Xiaxiao Hong, Zhihao Yang, Shihe Luo, Xiufang Ye, Yanli Li, Yubo Zhang, Min Zhang, Hong Chen, Ting Fan, Yuyuan Zhang, Bangyun Xiong, Zhaoyang Wang, Zhibo Zhu, Dongchu Chen

    Three novel polydiacetylenes (PDAs) are synthesized through the self-assembly followed by the topochemical polymerization via controllable electrophoretic deposition. All the samples could undergo a multi-step thermochromic process, turning purple and red successively over a wide range from room temperature to above 250°C. Resulting PDAs are studied by UV–vis, IR, Raman spectroscopies, and chromoisomerism by naked eye visualization; their stabilities by thermogravimetric method, and emission behavior by fluorescence spectroscopy. To study the mechanism of the thermochromic response, temperature-dependent UV–vis spectra, the results of which successfully highlighted the close relationship between chromatic transitions and the conformational changes.

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  15. Publication date: 1 November 2017
    Source:Applied Surface Science, Volume 421, Part A

    Author(s): G. Di Carlo, C. Giuliani, C. Riccucci, M. Pascucci, E. Messina, G. Fierro, M. Lavorgna, G.M. Ingo

    Naturally grown patinas are typically detected onto the surface of modern copper-based artefacts and strictly affect their surface reactivity and appearance. The production of representative patinas is a key issues in order to obtain model systems which can be used for the development and validation of appropriate conservation materials and methods. In this study, we have prepared different artificial representative patinas by using a quaternary Cu-Sn-Zn-Pb alloy with chemical composition and metallurgical features similar to those of valuable modern works of art. In order to produce degradation products usually observed onto their surface, chloride and sulphate species were used to induce corrosion processes. Different patinas were produced by changing the nature of corrosive species and the set-up for the accelerated degradation. The composition and structural properties of the patinas were investigated by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray diffraction, optical microscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The results allow to identify degradation products and to distinguish copper hydroxychloride polymorphs and copper hydroxysulphates with similar structure. Our findings show that patina composition can be tailored by modifying the degradation procedure and patinas representative of modern artefacts made of quaternary Cu-Sn-Zn-Pb alloy can be obtained.

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  16. Publication date: 1 November 2017
    Source:Applied Surface Science, Volume 421, Part B

    Author(s): Petr Janicek, Kham M. Niang, Jan Mistrik, Karel Palka, Andrew J. Flewitt

    ZnO:Sn thin films were deposited onto thermally oxidized silicon substrates using a remote plasma reactive sputtering. Their optical constants (refractive index n and extinction coefficient k) were determined from ellipsometric data recorded over a wide spectral range (0.05–6eV). Parametrization of ZnO:Sn complex dielectric permittivity consists of a parameterized semiconductor oscillator function describing the short wavelength absorption edge, a Drude oscillator describing free carrier absorption in near-infrared part of spectra and a Lorentz oscillator describing the long wavelength absorption edge and intra-band absorption in the ultra-violet part of the spectra. Using a Mott-Davis model, the increase in local disorder with increasing Sn doping is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, an increase in the centroid distance of the valence and conduction bands with increasing Sn doping is shown and only slight increase in intensity of the inter-band optical transition due to Sn doping occurs. The Drude model applied in the near-infrared part of the spectra revealed the free carrier concentration and mobility of ZnO:Sn. Results show that the range of transparency of prepared ZnO:Sn layers is not dramatically affected by Sn doping whereas electrical conductivity could be controlled by Sn doping. Refractive index in the transparent part is comparable with amorphous Indium Gallium Zinc Oxide allowing utilization of prepared ZnO:Sn layers as an indium-free alternative.

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  17. Publication date: 1 October 2017
    Source:Applied Surface Science, Volume 418, Part B

    Author(s): S.P. Banerjee, Thierry Sarnet, Panayiotis Siozos, Michalis Loulakis, Demetrios Anglos, Marc Sentis

    The potential of laser induced breakdown spectroscopy (LIBS) as a non-contact probe, for characterizing organic photovoltaic devices during selective laser scribing, was investigated. Samples from organic solar cells were studied, which consisted of several layers of materials including a top electrode (Al, Mg or Mo), organic layer, bottom electrode (indium tin oxide), silicon nitride barrier layer and substrate layer situated from the top consecutively. The thickness of individual layers varies from 115 to 250nm. LIBS measurements were performed by use of a 40 femtosecond Ti:Sapphire laser operated at very low pulse energy (<10micro-joule) to ensure a fine depth-profiling of the very thin layers. Probing a fixed spot on the sample with successive laser pulses, produced plasma emission spectra corresponding to individual laser ablation events. This enabled discrimination of the different layers on the basis of characteristic spectral lines reflecting key elemental constituents of each layer in the organic solar cell structure, demonstrating the potential of LIBS for fast, non-contact characterization of organic photovoltaic coatings.

  18. Publication date: 30 September 2017
    Source:Applied Surface Science, Volume 417

    Author(s): Jan Winter, Stephan Rapp, Michael Schmidt, Heinz P. Huber

    In this paper, we present ultrafast measurements of the complex refractive index for copper up to a time delay of 20ps with an accuracy <1% at laser fluences in the vicinity of the ablation threshold. The measured refractive index n and extinction coefficient k are supported by a simulation including the two-temperature model with an accurate description of thermal and optical properties and a thermomechanical model. Comparison of the measured time resolved optical properties with results of the simulation reveals underlying physical mechanisms in three distinct time delay regimes. It is found that in the early stage (−5ps to 0ps) the thermally excited d-band electrons make a major contribution to the laser pulse absorption and create a steep increase in transient optical properties n and k. In the second time regime (0–10ps) the material expansion influences the plasma frequency, which is also reflected in the transient extinction coefficient. In contrast, the refractive index n follows the total collision frequency. Additionally, the electron-ion thermalization time can be attributed to a minimum of the extinction coefficient at ∼10ps. In the third time regime (10–20ps) the transient extinction coefficient k indicates the surface cooling-down process.

  19. Publication date: 15 September 2017
    Source:Applied Surface Science, Volume 416

    Author(s): Zhiyong Xia, Lance Baird, Natasha Zimmerman, Matthew Yeager

    In this study, we developed a cost effective method of using thiol functionalized γ-aluminum oxide hydroxide (γ-AlOOH) filters for removing three key heavy metals from water: mercury, lead, and cadmium under non-concomitant conditions. Compared to non-thiol treated γ-AlOOH filters, the introduction of thiol functional groups greatly improved the heavy metal removal efficiency under both static and dynamic filtration conditions. The adsorption kinetics of thiol functionalized γ-AlOOH were investigated using the Lagergren first order and pseudo-second order kinetics models; whereas the isothermal adsorption behavior of these membranes was revealed through the Langmuir and Freundlich models. Heavy metal concentration was quantified by Inductively Coupled Plasma-Mass Spectroscopy, and the thiol level on γ-AlOOH surface was measured by a colorimetric assay using Ellman's reagent. X-ray photoelectron spectroscopy was used to further address the surface sulfur state on the membranes after heavy metal exposure. Mechanisms for heavy metal adsorption were also discussed.

  20. Publication date: 15 September 2017
    Source:Applied Surface Science, Volume 416

    Author(s): Bryan W. Stuart, Miquel Gimeno-Fabra, Joel Segal, Ifty Ahmed, David M. Grant

    Here we show the deposition of 2.7μm thick phosphate based glass films produced by magnetron sputtering, followed by post heat treatments at 500°C. Variations in degradation properties pre and post heat treatment were attributed to the formation of Hematite crystals within a glass matrix, iron oxidation and the depletion of hydrophilic P-O-P bonds within the surface layer. As deposited and heat treated coatings showed interfacial tensile adhesion in excess of 73.6MPa; which surpassed ISO and FDA requirements for HA coatings. Scratch testing of coatings on polished substrates revealed brittle failure mechanisms, amplified due to heat treatment and interfacial failure occurring from 2.3 to 5.0N. Coatings that were deposited onto sandblasted substrates to mimic commercial implant surfaces, did not suffer from tensile cracking or trackside delamination showing substantial interfacial improvements to between 8.6 and 11.3N. An exponential dissolution rate was observed from 0 to 2h for as deposited coatings, which was eliminated via heat treatment. From 2 to 24h ion release rates ordered P>Na>Mg>Ca>Fe whilst all coatings exhibited linear degradation rates, which reduced by factors of 2.4–3.0 following heat treatments.

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