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Absorption spectroscopy is the technique that measures the absorption of radiation as a function of wavelength, due to its interaction with the material. During a research project funded by our home university, we were able to investigate the possibilities of this technique to study ancient glasses. One of our main conclusions is that UV-VIS-NIR absorption spectroscopy is especially suited to characterize colored artifacts in terms of composition and furnace conditions. Moreover, for naturally colored window glasses, we have shown that this technique allows us to classify fragments based on differences in iron impurity levels. It is a semi-quantitative analysis tool that can be applied for a first-line analysis of (large) glass collections. Thanks to the commercial available portable instruments, these measurements can be performed at relative high speed and this in-situ if necessary. To illustrate the possibilities of this technique, we describe in this paper two case-studies. In a first test-case we analyze 63 naturally colored window glasses and demonstrate how groups with different iron concentrations can be identified by calculating the absorption edge position from the measured optical spectrum. In a second case-study 8 modern naturally colored and 31 intentionally colored Roman glass fragments are the point of focus. For these samples we first estimate which samples are potentially fabricated under the same furnace conditions. This is done based on the calculated color values. Finally we identify the type of applied colorants.

Nowadays, there is a considerable scientific interest in bulk ultrafine grained materials, due to their potential for superior mechanical properties. One of the possible formation methods of nano-grained materials is cryogenic rolling. The influence of rolling at cryogenic temperatures has been investigated. Significant differences in the textures and the microstructures can be observed between the cryogenically rolled copper and conventionally cold rolled copper, reduced to the same thickness.

No abstract is provided for this article.

No abstract is provided for this article.

. The remineralisation of sinking particles by prokaryotic heterotrophic activities is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May–June 2014) using the particulate biogenic barium (excess barium; Baxs) proxy. Important mesopelagic (100–1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L−1), which was attributed to an intense bloom averaging 6 mg Chl-a m−3 between January and June 2014 and by an intense 1500 m-deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. In comparison, the temperate province, characterized by the lowest Baxs content (391 pmol L−1), was sampled during the bloom period and phytoplankton appear to be dominated by small and calcifying species, such as coccolithophorids. The Baxs content, related to an oxygen consumption, was converted into a remineralisation flux using an updated relationship, proposed for the first time in the North Atlantic. The estimated fluxes were in the same order of magnitude than other fluxes obtained by independent methods (moored sediment traps, incubations) in the North Atlantic. Interestingly, in the subpolar and subtropical provinces, mesopelagic POC remineralisation fluxes (up to 13 and 4.6 mmol C m−2 d−1, respectively) were equalling and occasionally even exceeding upper ocean POC export fluxes, highlighting the important impact of the mesopelagic remineralisation on the biological carbon pump with a near-zero, deep (> 1000 m) carbon sequestration efficiency in spring 2014.

Nanoscopic characterization of heterogeneous intermetallic particles (IMPs) which microstructurally and compositionally evolve during local corrosion is crucial in unravelling the mechanisms and sequence of initial and local corrosion events. Herein, we study site-specific initiation events focused on microscopic constituent intermetallic compounds and nanoscopic dispersoids in AA2024-T3 at the nanoscale using a combined quasi in-situ and ex-situ analytical TEM approach. Our findings show a dealloying-driven local corrosion initiation at the studied IMPs that have been considered as cathodic phases traditionally. Besides, local degradation which is a result of galvanic interactions between dealloyed regions of IMPs and their adjacent alloy matrix is largely governed by the intrinsic electrochemical instability of intermetallic compounds.

Understanding the early stages of electrochemical nucleation and growth is the cornerstone for nanoscale electrodeposition. Although studied since decades, the process is not yet fully understood. In this paper, we introduce a new modelling approach to study the growth of a single hemispherical nucleus: Multi-Ion Transport and Reaction Model (MITReM). This approach takes into account the transport driven by diffusion and migration of all species in the electrolyte together with the electrochemical reactions at the electrode boundary. A Finite Element Method (FEM) is used to solve the balance equations for the concentration of all the active species and the electrolyte potential. In contrast to analytical models or discrete scale modelling techniques, the strength of this approach is that no assumptions on the diffusional or kinetic limitations have to be made. In addition, this novel platform allows to add further levels of complexity, such as multiple nuclei, adatom surface diffusion, aggregation, particle detachment, etc. The simulation results prove that, the initial growth stage of a 10 nm single hemispherical silver nucleus always starts under kinetic control, regardless of concentration and electrode potential. Later on, a transition from kinetic to diffusion control takes place. The time of transition depends on the imposed concentration and electrode potential. Moreover, the simulations clearly show that the growth rate is strongly affected by the imposed concentration and electrode potential, as it has been proven experimentally in countless occasions. Numerical simulation by MITReM proves to be of great interest to gain knowledge towards unravelling the early stages of electrochemical nucleation and growth processes.

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Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation S. Van Gils, Th. Dimogerontakis, G. Buytaert, E. Stijns, H. Terryn, P. Skeldon, G. E. Thompson, M. R. Alexander; Optical properties of magnetron-sputtered and rolled aluminum. Journal of Applied Physics 15 October 2005; 98 (8): 083505. https://doi.org/10.1063/1.2085315 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioJournal of Applied Physics Search Advanced Search |Citation Search

Protein adsorption and its conformational arrangements on the surface of metallic biomaterials directly influence the biocompatibility and the degradation process during the implant lifetime. However, the presence of various species such as phosphates, calcium and hydrogen peroxide (H2O2) in the human body not only control the electrochemical interactions on the biomaterial surface but could also modify the protein adsorption process and its impact on the metal degradation. To this aim bovine serum albumin (BSA) protein adsorption, morphology, surface potential and its impact on the corrosion resistance of a Ti6Al4V alloy was investigated in different solutions, including a sodium chloride (NaCl), a phosphate-buffered saline (PBS) and Hank's physiological solutions. The results indicated that the alloy in PBS solution was more resistant to corrosion than that in Hanks' or NaCl solutions. Mott–Schottky analysis demonstrated that all solutions containing BSA and H2O2 had the highest donor charge carrier. Scanning electron microscopy (SEM) and surface potential images indicated that by changing the physiological solutions from NaCl to PBS and then to Hanks', the morphology of adsorbed BSA protein changed from a globular or unfolded shape to a large micronetwork and then to a fine micro-nanonetwork, accompanied by a gradual increase in the surface potential. Moreover, it was figured out that the BSA protein/substrate interface and the top surface of the BSA protein were susceptible to corrosion initiation owing to the different surface potentials and thus are preferable sites for the adsorption of corrosive counterions, e.g., Cl−.

By using an optimized characterization approach that combines aberration-corrected transmission electron microscopy, electron tomography, and in situ ultrasmall angle X-ray scattering (USAXS), we show that the early stages of Pt electrochemical growth on carbon substrates may be affected by the aggregation, self-alignment, and partial coalescence of nanoclusters of d ≈ 2 nm. The morphology of the resulting nanostructures depends on the degree of coalescence and recrystallization of nanocluster aggregates, which in turn depends on the electrodeposition potential. At low overpotentials, a self-limiting growth mechanism may block the epitaxial growth of primary nanoclusters and results in loose dendritic aggregates. At more negative potentials, the extent of nanocluster coalescence and recrystallization is larger and further growth by atomic incorporation may be allowed. On one hand, this suggests a revision of the Volmer–Weber island growth mechanism. Whereas this theory has traditionally assumed direct attachment as the only growth mechanism, it is suggested that nanocluster self-limiting growth, aggregation, and coalescence should also be taken into account during the early stages of nanoscale electrodeposition. On the other hand, depending on the deposition potential, ultrahigh porosities can be achieved, turning electrodeposition in an ideal process for highly active electrocatalyst production without the need of using high surface area carbon supports.

This work investigates the effect of Ce(III) and Ce(IV) additives on the structure and anti-corrosion properties of poly(methyl methacrylate) (PMMA)-silica coatings on AA7075 aluminium alloy. The results revealed that intermediate Ce(IV) loadings (500 and 1000 ppm) result in a dense hybrid network with a less defective polymeric phase, extending the service time of AA7075 up to 835 days in 3.5% NaCl. Although both additives provide long-term protection, the self-healing ability was observed only for Ce(IV) addition, favoured by the formation of oxides/hydroxides at pH∼3. These properties make the 4 μm-thick PMMA-silica-Ce(IV) coatings very interesting for chromium-free protection technologies.

No abstract is provided for this article.

No abstract is provided for this article.

The adhesion capabilities of sulfuric acid and tartaric-sulfuric-acid anodic oxide films on cladded AA2024-T3 aluminium substrates have been investigated in a quantitative manner. A relatively simple, versatile and industrially applicable test methodology based on DIN EN ISO 29862 has been used. In addition, the effect of anodising process parameters on the oxide film morphology has been studied and correlated with the adhesion results. The process parameters considered are the chemistry of the acidic pickling pre-treatment step, the addition of tartaric acid to the sulfuric acid electrolyte, the formation voltage, and the electrolyte temperature. The suggested tape peel adhesion test is able to differentiate among pre-treatments and anodising conditions showing a good correlation with the morphological features at the ultimate surface. High peel adhesion strengths are measured when topographies such as pore mouth widening and dissolution-driven roughness take place. These morphologies are typically found in anodic layers formed at elevated electrolyte temperatures. The proposed method can be beneficial for a fast assessment of anodising parameters for good adhesion, which is of special interest for the industrial optimisation of anodising processes.