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Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications. Hereby, we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO 2 and Al 2 O 3 coatings in conditions of accelerated aging by sulfidation. The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate. Accelerated aging was performed in dry and more severe wet conditions. Optical micrographic observations, surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and reflectivity measurements were combined to comparatively study the effects of degradation. The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions. [ABSTRACT FROM AUTHOR]

The control of rare-earth ion doping profiles is a key challenge for several photonic applications and quantum technologies that require spatially localized emitters. In this work, we propose to use atomic layer deposition (ALD) followed by an annealing post-treatment to localize europium emitters close to the surface of a Y2O3film or a Y2SiO5single crystal by exploiting in-diffusion. Indeed, ALD is a conformal method that can provide in-depth nanometer-scale positioning accuracy on a large scale. However, the post-thermal annealing required to achieve higher crystalline quality and activate diffusion needs to be precisely controlled to maximize our ability to localize ions. In this paper, we evaluate europium ion diffusion in an ALD-grown Eu2O3/Y2O3/Si stack using Rutherford backscattering spectroscopy (RBS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). We then extend this approach to investigate diffusion from a Eu2O3ALD film into a single-crystalline substrate of Y2SiO5(YSO), a technologically relevant material system for quantum applications. We determine the Eu3+diffusion coefficients in both cases and show that diffusion starts at 950 °C in the polycrystalline Y2O3ALD submicron film, whereas it becomes significant only above 1200 °C in single-crystal YSO. Finally, spectral hole burning of such in-diffused emitters revealed homogeneous lines as narrow as 2 MHz. This study indicates that appropriate annealing of ALD-grown rare-earth oxide films can be harnessed to create localized dopants that preserve their outstanding optical properties, a prerequisite for their integration into photonic and quantum devices.

In this work, we addressed the local degradation mechanisms limiting the prelaunch environmental durability of thin-layered silver stacks for demanding space mirror applications. Local initiation and propagation of tarnishing were studied by combined surface and interface analysis on model stack samples consisting of thin silver layers supported on lightweight SiC substrates and protected by thin SiO2overcoats, deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H2S. The results show that tarnishing is locally initiated by the formation of Ag2S columns erupting above the stack surface. Ag2S growth is promoted at high aspect ratio defects (surface pores) of the SiC substrate as a result of an imperfect protection by the SiO2overcoat. Channels most likely connect the silver layer to its environment through the protection layer, which enables local H2S entry and Ag2S growth. The silver sulfide columns grow in number and size eventually leading to coalescence with increasing H2S exposure. In more advanced stages, tarnishing slows down owing to saturation of all pre-existing imperfectly protected sites of preferential sulfidation. However, it progresses radially at the basis of the Ag2S columns underneath the protection layer, consuming the metallic silver layer and deteriorating the protecting overcoat.

Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the surface oxide film providing corrosion resistance to 316L stainless steel. The as-prepared surface is covered by a [?]2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have bandgap values of 3.0 and 2.6[?]2.7 eV, respectively, and the oxide film would behave as an insulator. Electrochemical passivation in sulfuric acid solution causes the preferential dissolution of Fe(III) resulting in the thickness decrease of the outer layer and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III) enrichment of the inner layer causes loss of photoactivity and improved corrosion protection with the anodic shift of the corrosion potential and the increase of the polarization resistance by a factor of [?]4. Aging in the passive state promotes the Cr enrichment in the inner barrier layer of the passive film.

To elucidate the role of noble metal impurities on corrosion of Mg, 3D time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging in combination with X-ray photoelectron spectroscopy and optical microscopy measurements were carried out on Mg samples (99.9%) before and after Mg polarization at EOCP+0.5 V in 0.1 M NaCl. A significant segregation of Fe (and of Mn and Al) metallic impurities at grain boundaries (GBs) was observed on the Mg surface by 3D ToF-SIMS. A 3-step mechanism of Mg corrosion was proposed, including a catalytic effect of Fe segregated at the GBs on the hydrogen evolution reaction (HER). In the 1st stage, the initiation of Mg corrosion is accompanied by the HER occurring over Fe impurities segregated at GBs leading to formation of small circular defects, and propagation with occurrence of dark filiform-like pattern corrosion enriched in Cl[?]. In the 2nd stage, segregated Fe metallic particles are released by Mg matrix undermining, and are dissolved into Fe2+ ions and in the 3rd stage a redeposition of Fe in the clear areas of Mg surfaces, corresponding to areas with low concentration of Cl[?], takes place.

The corrosion resistance of stainless steels is determined by the thickness, structure, composition and electronic properties of the oxide layers grown on their surface and isolating the metallic substrate from the environment. In the present work, ex situ XPS (X-Ray Photoelectron Spectroscopy) and ToF-SIMS (Time of Flight Secondary Ions Mass Spectrometry) have been combined to in situ PCS (PhotoCurrent Spectroscopy) in order to perform an integrated physicochemical characterization of surface oxide films grown on bright annealed ferritic stainless steel (AISI 434) as-received and after thermal post-treatment in air. The surface oxide film on as-received samples has a bilayer structure with an inner layer close to pure Cr(III) oxide and an outer layer of mixed Fe(III) and Cr(III) oxide enriched in Cr. After thermal post-treatment in air at 350degC and 550degC, the surface oxide films thicken and the outer layers are enriched in Fe(III). Linear voltammetry and electrochemical impedance spectroscopy analysis evidence a decrease of the polarization resistance in the passive range, a cathodic shift of the corrosion potential and an increased cathodic current after thermal post-treatment. The bilayer structure, composition and electronic properties of these surface oxide films and their modifications are discussed to rationalize their corrosion behavior.

The effects of post-treatment applied on Trivalent Chromium Protection (TCP) coatings deposited on aluminum alloy 2024-T3 was studied by electrochemical and surface analytical techniques: X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The aim of the post-treatment was to improve the corrosion resistance of the TCP coating. To understand the influence of the post-treatment, using a bath containing H2O2 and a lanthanum salt as an inhibitor, our approach was to study the effect of these two components separately. It was found that the improved corrosion protection provided by the post-treated TCP was related to a synergetic effect of the two components. XPS and ToF-SIMS analyses showed that (i) the thickness of the TCP coating is not modified by the post-treatment, (ii) lanthanum is present on the surface and in the bulk of the TCP and (iii) is found in very small amount only on the extreme surface. The total concentration of Cr(VI) (oxide/hydroxide) was estimated to be below 0.1 wt% in the post-treated TCP layer. It was concluded that lanthanum plays a significant role in improving the coating density and homogeneity and has a beneficial effect on the TCP coating cracking as observed by Scanning Electron Microscopy.

The composition and stratification of the passive oxide films formed on three Cr-Fe-Co-Ni(-Mo) multi-principal element alloys by electrochemical anodic passivation in sulfuric acid electrolyte containing 0.2 and 4.7 M NaCl were investigated, combining X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry surface analysis. The passive films show a bilayer structure similar to that formed in Cl−-free electrolyte with an inner layer mostly consisting of Cr oxide and an outer layer containing of Cr hydroxide, Ni hydroxide, Mo oxides, and Fe (hydr)oxide. The Mo-free alloy exhibits a thickening of the inner Cr oxide layer and the thinning of the outer layer in 0.2 M Cl−, whereas the two Mo-containing alloys do not show significant alteration even in 4.7 M Cl−evidencing their higher stability in Cl−-containing solutions. The chloride penetration is limited to the external part of the outer oxide layer, except in the most severe tested conditions where traces reach the inner barrier layer, and the chloride entry into the layer is strongly reduced after pre-passivation in Cl−-free solution. The results allow us to discuss the beneficial effects of pre-passivation in Cl−-free conditions and Mo addition providing these alloys enhanced resistance to passivity breakdown.

In situ electrochemical (by electrochemical impedance spectroscopy, EIS) and ex situ surface (by time-of-flight secondary ions mass spectrometry, ToF-SIMS) analysis were applied to investigate solid-state diffusion coefficient (DLi) into conversion-type α-Fe2O3negative electrode for Li-ion batteries. DLivalues obtained from EIS were in the range of 10–16to 10–15cm2s–1for electrodes partially and fully lithiated, respectively, showing that pulverization of the converted material promotes Li-ion migration. ToF-SIMS ion depth profiling performed after partial lithiation enabled discriminating the surface solid electrolyte interphase (SEI) region, a converted electrode region (Li2O/Fe0matrix) of slow diffusion (DLi= 6 × 10–16cm2s–1) and an unconverted region (intercalated Fe2O3matrix) of faster diffusion (DLi= 2 × 10–13cm2s–1) ahead of the conversion front. Comparison of the ex situ and in situ results indicates that the electrode conversion kinetics is limited by Li-ion diffusion in the converted matrix and suggests a hindering effect of the passivating SEI layer. ToF-SIMS depth profile analysis appears as a most appropriate and direct methodology to measure Li-ion diffusion solely in electrode materials, excluding SEI layer effects.

Corrosion protection by ultra-thin ([?] 50 nm) alumina films deposited by atomic layer deposition (ALD) on copper at 250degC was studied in 0.5 M NaCl aqueous solution by combining electrochemical and surface analytical methods. Time-of-Flight Secondary Ion Mass Spectrometry revealed a homogenous in-depth stoichiometry of the alumina coatings and their residual bulk contamination by organic and water precursor fragments. Trace contamination by a spurious Cu oxide was evidenced at the interface with the Cu substrate despite a reducing pre-treatment. Atomic force microscopy images revealed conformal substrate coverage and a granular-like coating morphology at the nanometer scale. Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) showed no electrochemical activity of the coating and a corrosion decrease reaching 4 orders of magnitude for coated samples in comparison with bare copper. Uncoated surface fraction was quantified by application of three different methods using the LSV and EIS data which led to results in excellent agreement. The uncoated surface fraction for 50 nm Al2O3 layers was [?]0.01%, confirming ALD alumina as an excellent coating for corrosion protection with spectacularly low residual corrosion activity restricted to the bottom of channel defects connecting the substrate to environment through the coating.

Si thin films obtained by plasma enhanced chemical vapor deposition (PECVD) were used to investigate chemical and morphological modifications induced by lithiation potential and cycling. These modifications were thoughtfully analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling, which allows to distinguish the surface and bulk processes related to the formation of the solid electrolyte interphase (SEI) layer, and Li–Si alloying, respectively. The main results are a volume expansion/shrinkage and a dynamic behavior of the SEI layer during the single lithiation/delithiation process and multicycling. Trapping of lithium and other ions corresponding to products of electrolyte decomposition are the major reasons of electrode modifications. It is shown that the SEI layer contributes to 60% of the total volume variation of Si electrodes (100 nm). The apparent diffusion coefficient of lithium (DLi) calculated from the Fick’s second law directly from Li-ion ToF-SIMS profiles is of the order of ∼5.9 × 10–15cm2.s–1. This quite low value can be explained by Li trapping in the bulk of electrode material, at the interfaces, continuous growth of the SEI layer and increase of SiO2quantity. These modifications can result in limitation the ionic transport of Li.

Atomic layer deposition (ALD) is a thin film deposition technique that is based on alternating and saturating surface reactions of two or more gaseous precursors. The excellent conformality of ALD thin films can be exploited for sealing defects in coatings made by other techniques. Here the corrosion protection properties of hard CrN and diamond-like carbon (DLC) coatings on low alloy steel were improved by ALD sealing with 50 nm thick layers consisting of Al2O3and Ta2O5nanolaminates or mixtures. In cross sectional images the ALD layers were found to follow the surface morphology of the CrN coatings uniformly. Furthermore, ALD growth into the pinholes of the CrN coating was verified. In electrochemical measurements the ALD sealing was found to decrease the current density of the CrN coated steel by over 2 orders of magnitude. The neutral salt spray (NSS) durability was also improved: on the best samples the appearance of corrosion spots was delayed from 2 to 168 h. On DLC coatings the adhesion of the ALD sealing layers was weaker, but still clear improvement in NSS durability was achieved indicating sealing of the pinholes.

The effect of lithiation–delithiation rate and of the number of cycles on the properties of Si nanowires (SiNWs) and electrolyte interface is presented in this paper. The surface and bulk modifications of SiNW electrode induced by electrochemical process of lithiation–delithiation were investigated by combined electrochemical tests (galvanostatic cycling), field emission gun scanning electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Low lithiation–delithiation rate improves electrochemical performance due to a better penetration depth of lithium into the SiNW electrode and the formation of a homogeneous solid electrolyte interphase (SEI) layer on the SiNWs after the first cycle. However, after repeated cycling, SiNWs suffered strong mechanical stress leading to a rough or porous SiNW structure covered by a porous SEI layer. This study highlights the SEI modifications caused by the lithiation–delithiation rate and the modifications of the Si electrode upon cycling.

Iron oxide (mostly α-Fe2O3) model thin-film electrodes were prepared by thermal oxidation of pure metal iron substrates at 300 ± 5 °C in air and used for comprehensive investigation of the lithiation/delithiation mechanisms of anode material undergoing an electrochemical conversion reaction with lithium ions. Surface (X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS)) and electrochemical (cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)) analytical techniques were combined. The results show that intercalation of Li in the Fe2O3matrix and solid electrolyte interphase (SEI) layer formation both precede conversion to metallic iron and Li2O upon lithiation. Depth profile analysis evidences stratification of the converted thin-film electrode into fully and partially lithiated outer and inner parts, respectively, due to mass transport limitation. The SEI layer has a stable composition (Li2CO3with minor ROCO2Li) but dynamically increases/decreases in thickness upon lithiation/delithiation. Conversion, proceeding mostly in the outer part of the electrode, causes material swelling accompanied by SEI layer thickening. Upon delithiation, lithium is trapped in the deconverted electrode subjected to shrinking, and the SEI layer mostly decomposes and reduces in thickness after deconversion. The nonreversibility of both conversion and surface passivation mechanisms is demonstrated.

Oxide layers play a crucial role in the corrosion resistance of metals and alloys and the growth kinetics of these films is of major interest. To express the oxide growth kinetics, three main models are available: the Cabrera-Mott model, the Fehlner-Mott model and the Point Defect Model (PDM). These models are reviewed in the first part of the paper. Among these models, the PDM is the only one that takes into account the interfacial potential drops during the oxide growth. However, in this model: (i) no parameters relative to the substrate alloy are taken into account, and (ii) the growth is limited by the flow of oxygen vacancies through the film (transport via both cation interstitial and vacancy positions are not taken into account). Here we present a "generalized model" for the kinetics of oxide growth in which the evolution of the interfacial potential drops during oxide growth is included, as well as the variation of the electric field in the oxide during film growth. This new model allows us to describe the growth of oxide films on alloys under non-steady-state conditions. The link between oxide growth and cation release into the solution is also included.

A number of passive film growth models have been advanced in the past, each founded on different assumptions and providing different rate laws. A new, generalized growth model has been developed and the numerical simulation of the transient behavior of oxide film growth on metals and alloys is reported here. This model is based on the transport of anions and cations (in a Cr2O3 film for stainless alloy). In contrast to most models up to date, it describes the time-variant behavior of film and film/solution potential differences. Because these potential differences are expressed as exponential functions of film thickness, asymptotic behaviors can be studied and it is shown that a square root law results for very thin and very thick films. Growth rate for intermediate films and during transient periods, on the other hand, is determined by numerical integration. Parameters which were introduced by the model and whose values are unknown are conveniently regrouped into only four lumped parameters, which are easily estimated by numerical optimisation. It is shown that experimental oxide film thickness measurements on stainless alloys in high-temperature aqueous environments can be reproduced. It is further shown that the diffusional rate expressions of all the species contributing to growth are analogous, explaining why it is possible to fit growth kinetics with a single type of point defect.

Scanning tunneling spectroscopy has been applied to characterize the electronic properties of the granular and intergranular sites of the passive film grown on Ni(111) single-crystal surfaces in acid solution. The passive film, essentially consisting of NiO, shows p-type grains (valence band edge at 0.54 +- 0.03 eV below Fermi level) with unoccupied Ni 3d surface states at 0.5-1.5 eV above Fermi level in the bandgap. At grain boundaries, the p-type semiconductivity is attenuated as evidenced by a downward shift of 0.12 +- 0.06 eV of the valence band edge, and the density of surface states is markedly reduced, both effects indicating the presence of oxygen vacancies in these sites. The dominant point defect in the film is metallic vacancies but oxygen vacancies attenuate locally the resulting p-type property at the grain boundaries. The implications of these local electronic properties on oxidative and reductive electronic transfer and on the corrosion resistance are discussed. The oxygen vacancies at intergranular boundaries imply local changes of the properties of anionic mass transport through the passive film and enhancement of Cl[?] adsorption and/or penetration, which is consistent with the view of passive film grain boundaries playing a key role in passivity breakdown.

The characterization of electrode processes induced by lithiation/delithiation of Sn−Ni alloy films electroplated on a copper substrate is presented. Galvanostatic discharge/charge measurements were combined with X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS shows the buildup of a solid electrolyte interphase (SEI) layer formed by reductive decomposition of the electrolyte at the surface of the Sn−Ni anode during the first discharge. The SEI layer is constituted of a mixture of Li2CO3, ROCO2Li, Li2C2O4, and/or ROLi whose balance is not markedly modified upon cycling. ToF-SIMS depth profiling evidences an incomplete initial alloying process of lithium ion with Sn and the resulting partition of the Sn−Ni layer alloy into a fully lithiated outer part and a partially lithiated inner layer during the first discharge. After the first cycle, the volume expansion/shrink associated with the alloying/dealloying reaction, also evidenced by ToF-SIMS, irreversibly cracks and divides the Sn−Ni alloy into island-like morphology with gaps filled by the SEI layer. Multicycling (tested up to 9 cycles) amplifies the division of the Sn−Ni alloy layer and the related penetration of the SEI layer as indicated by the increase of trapped lithium and chlorine but with no apparent loss of active material or drop of capacity.

Atomic layer deposited (ALD) aluminum and tantalum oxide (Al2O3 and Ta2O5) and their nanolaminates were applied as corrosion protection coatings on AISI 52100 steel. The aim was to combine the good sealing properties of Al2O3 with the chemical stability of Ta2O5 and to optimize the coating architecture in order to obtain the best possible long-term durability. Coating composition and morphology were studied with time-of-flight elastic recoil detection analysis (ToF-ERDA), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) and energy dispersive x-ray spectrometry (EDS). Electrochemical properties were studied with voltammetry and electrochemical impedance spectroscopy (EIS), and corrosion durability with neutral salt spray (NSS) testing. The coatings were observed to be conformal and uniform over rough surfaces, and contained some carbon and hydrogen as impurities. The electrochemical results showed that the Al2O3 coating had superior sealing properties compared to the Ta2O5 coating, and nanolaminates had properties in between those of Al2O3 and Ta2O5. However, in the NSS test the laminate-coated samples survived the best demonstrating long-term durability. Analysis of the laminate structure showed that for 40 and 80 nm laminates the best protection was achieved with 10 and 20 nm layers, respectively.

The present study examines the influence of surface pretreatment on the evolution of nanotubular (T) and nanoporous (P) oxide film morphologies on titanium foil anodized potentiostatically, at , in fluoride-containing electrolyte. The foil was used in the untreated, mechanically/chembreically polished or preanodized conditions. The preanodization resulted in fluoride-free barrier films. Mainly T regions were produced on polished foil during subsequent anodizing in fluoride-containing electrolyte. In contrast, the P regions dominated on polished foil preanodized to . Both P and T regions resulted with rolled foil preanodized to or polished foil preanodized to . Raman spectroscopy disclosed anatase and rutile at P regions, whereas T regions are mainly amorphous. The P film thickened at a constant rate of , while the T film reached a limiting thickness of due to the relatively high solubility of the amorphous oxide. The presence of P film resulted in increased currents during anodizing. Furthermore, the results suggest that the formation of T film depends upon the access of ions to the titanium/film interface, resulting in the stabilization of a mainly amorphous film structure.

The effects of surface finish by mechanical polishing, vibratory polishing, and high-temperature annealing were studied on 316L stainless steel by combining microscopic and spectroscopic analysis of the surface morphology and composition and electrochemical analysis of the corrosion resistance. Compared to mechanical polishing, vibratory finishing promotes passivity at the active-passive transition in acid solution and enhances resistance to chloride-induced passivity breakdown. Cr and Mo enrichments in the native oxide film increase owing to preferential iron etching. The bilayer structure develops a thicker Cr(III) oxide inner barrier layer and an outer exchange layer further enriched in Cr(III) hydroxide and Mo(IV/VI) oxides. The Fe-rich weak sites of passivity are reinforced. High-temperature annealing in reducing hydrogen environment enables us to fully reconstruct the cold-worked layers left by mechanical or vibratory finishing, thus allowing us to expose the bulk microstructure at the topmost surface. The benefits brought by vibratory finishing are lost upon reducing the initial native oxide. The re-formed native oxide develops a bilayer structure with similar Cr and Mo enrichments as that obtained from mechanical polishing and no beneficial effects on passivity. The results provide comprehensive insight into how the passivity of stainless steel can be enhanced by surface enrichment engineering.

Pure (a-Si:H) and methylated [a-Si0.95(CH3)0.05:H] amorphous silicon thin films were analyzed by time-of-flight secondary ion mass spectrometry after partial lithiation. Depth profiling gives insights into the lithiation mechanism of the material, enabling us to study the detailed biphasic process in the first lithiation process. Lithiation induces swelling and roughening of the active layer. In both a-Si:H and a-Si0.95(CH3)0.05:H, no measurable Li diffusion was observed after stopping current-induced lithiation. After applying the same lithiation charges, distinct Li profiles were observed for these two materials. Unlike a-Si:H, the Li concentration drops slowly from the heavily lithiated region to the non-lithiated region in a-Si0.95(CH3)0.05:H. This apparent progressive transition between the lithiated and lithium-free regions is attributed to the presence of nanovoids inside the material. When their concentration is high enough, these nanovoids constitute favorable quasi-percolating paths for lithium during the first lithiation. A specific model was developed to simulate the Li depth profiles, fully supporting this hypothesis.

X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry were combined to characterize the surface oxides (native oxides and passive films) formed on Ni-based alloys containing chromium and molybdenum. Two alloys were studied, Ni-20Cr and Ni-20Cr-10Mo (in wt.%). For Ni-20Cr, both native oxide and passive films formed in acidic medium present a duplex structure comprising a Ni and Cr outer hydroxide layer and a Cr inner oxide layer. The Ni-20Cr-10Mo alloy presents a similar bilayer structure, but with Mo oxide located at the outer layer/inner layer interface. Cr enrichment is observed after passivation for both alloys. The corrosion resistance in acidic solution containing chlorides is enhanced by Mo, and by electrochemical pre-passivation in Cl free solution.

Kinetics expressions for passivity breakdown have been determined based on a model taking into account the presence of intergranular defective sites in passive films. It is shown that depending on the interface at which the potential drop increase predominates, passivity breakdown can occur by enhanced dissolution (i.e., oxide thinning) at the oxide/electrolyte interface or by accelerated interfacial voiding at the metal/oxide interface. In all cases, the rate of the interfacial processes leading to passivity breakdown is increased at the intergranular defective sites of the passive film.

The present work demonstrates that an amorphous anodic oxide on titanium can be converted to a micrometer thick nanoporous rutile layer upon extended polarization in a fluoride-containing electrolyte, whereas extended polarization in a fluoride-free electrolyte leads to a conversion to anatase. Titanium was preanodized in fluoride-free for , then anodization was either continued for in the presence or absence of fluoride ions and the resulting layers characterized. Scanning electron microscopy, X-ray diffraction, and Raman and photocurrent spectroscopy confirm ion-selective structure conversion and extended layer growth at room temperature.

A combination of electrochemical measurements, H2volume measurements and surface analysis using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) was used to investigate the role of the metallic Fe impurities (60 ppm) in high purity (99.9 wt%) magnesium and the effect of sulfur on the hydrogen evolution. The Mg corrosion was studied in NaCl solutions containing dissolved hydrogen sulfide. At OCP and under anodic polarization the hydrogen evolution reaction and the growth of dark corroded areas were significantly inhibited in the presence of H2Saq. ToF-SIMS and XPS analyses showed the presence of sulfur adsorbed on Mg and on Fe segregated at grain boundaries. The observed inhibition of hydrogen evolution at OCP and above is assigned to a poisoning effect by adsorbed S of the H adsorption sites on segregated iron which, in the absence of sulfur, provides catalytic sites for excess HER. The equilibrium Pourbaix diagram for the Mg-Fe-S system including the adsorbed species predicts that S is adsorbed on Mg and Fe in the E-pH conditions of this work, which confirms the role assigned to adsorbed sulfur in the inhibition of excess hydrogen evolution at OCP and under anodic polarization in the presence of H2Saq.

The structure of the title hybrid salt, (C5H8NS)[SnCl3], is built up from segregated layers of organic cations and Sn polyhedra. [SnCl3]−groups are linked together by weak Sn⋯Cl interactions to form a one‐dimensional polymeric chain of anions.

The present work demonstrates that an amorphous anodic oxide on titanium can be converted to a micrometer thick nanoporous rutile layer upon extended polarization in a fluoride-containing electrolyte, whereas extended polarization in a fluoride-free electrolyte leads to a conversion to anatase. Titanium was preanodized in fluoride-free 1MH3PO4for 10min, then anodization was either continued for 5hin the presence or absence of fluoride ions and the resulting layers characterized. Scanning electron microscopy, X-ray diffraction, and Raman and photocurrent spectroscopy confirm ion-selective structure conversion and extended layer growth at room temperature.