Papers by Bernhard Elsener
Enargite, Cu 3 AsS 4 , is common in some deposit types, e.g. porphyry systems and high sulphidati... more Enargite, Cu 3 AsS 4 , is common in some deposit types, e.g. porphyry systems and high sulphidation epithermal deposits. It is of environmental concern as a potential source of arsenic. In this communication, we review the current knowledge of enargite oxidation, based on the existing literature and our own original data.
Annali di chimica
A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auge... more A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) has been carried out to characterize the chemical state of arsenic in complex environmental samples. The conventional approach, which relies on the chemical shift of the core levels As3d, provides ambiguous results in determining the chemical environment of arsenic. A more accurate approach, based on the Auger parameter and on the Wagner (Chemical State) plot, which combines AsLMM kinetic energy and As3d binding energy, was adopted. This novel method for determining the chemical state of arsenic was employed to completely characterize arsenic in complex environmental samples.
Materials and Structures, 2009
Earlier on-site investigations and laboratory studies have shown that varying corrosion rates are... more Earlier on-site investigations and laboratory studies have shown that varying corrosion rates are obtained when different commercially available instruments are used. The different confinement techniques, rather than the different electrochemical techniques used in the instruments, are considered to be the main reason for the discrepancies. This paper presents a method for the quantitative assessment of confinement techniques. The assessment is
The Journal of Physical Chemistry C, 2009
The knowledge of the depth concentration profile of thin-layered surfaces a few nanometers thick ... more The knowledge of the depth concentration profile of thin-layered surfaces a few nanometers thick is very important for research and applications in microelectronics, corrosion, wear, and tribology. In-depth profiling methods reported in the literature are either destructive (ion sputtering), based on severe approximations (concentration gradients are not taken into account, and electron inelastic mean free paths (IMFPs) are calculated for electrons traveling throughout pure elemental materials) or limited to relatively simple profiles (less than three components and constant IMFPs). A reconstructed depth profile should be consistent with the angleresolved X-ray photoelectron spectroscopy (ARXPS) data acquired, but transformation of XPS signal intensities vs emission angle into chemical species concentrations vs depth is an ill-posed mathematical problem which requires inversion of a Laplace transform. The main goal of this work was thus to develop a new, iterative protocol based on the maximum entropy method (MEM) that allows obtaining in-depth concentration profiles of layered surfaces from nondestructive ARXPS measurements. Numerical experiments were performed on a large series of computer generated, ideal, and error-containing ARXPS data from model depthprofiles with up to four layers and up to eight components. The new algorithm enabled us to reconstruct these depth profiles with a maximum uncertainty of (20% for layer thickness and of (30% for composition of the individual layers. Moreover, the new protocol involves an iterative procedure for calculating the IMFP values of the different components, taking into account the actual depth concentration profile of the sample surface under investigation. The new protocol proved to be more powerful than any of the existing algorithms since it has been successfully applied for reconstructing depth profiles with up to eight components.
Corrosion Science, 2014
ABSTRACT In this work, a novel method for the determination of instantaneous corrosion rates icor... more ABSTRACT In this work, a novel method for the determination of instantaneous corrosion rates icorr is proposed. It relies on recording the current response in the time domain upon imposing an AC voltage signal, and a computational procedure to remove non-faradaic currents and to analyse the data. The method was applied to steel in stirred, unstirred, and sand-filled 1 M KCl; the resulting icorr compared well with different conventional techniques. The proposed method is robust, non-destructive and fast. In addition to icorr, it provides also an estimate of the capacitance and Tafel slopes (thus, no assumption on constant B is required).
Cement and Concrete Research
An experimental setup was designed to simulate the conditions for chloride-induced macro-cell cor... more An experimental setup was designed to simulate the conditions for chloride-induced macro-cell corrosion, in which small anodes are located in a large network of cathodes. The overall aim of the present study was to assess whether measuring the bulk resistivity of reinforced concrete/mortar can give sufficient information about the resistance between anode and cathode inside a macro-cell. Measurements were executed in mortar specimens with high and low resistivities. Both the resistance in the simulated corrosion cells and the bulk resistivity of the mortar mixtures were determined. A comparison of the results showed no direct correlation. This indicates that the common practice of comparing bulk resistivity with corrosion rate may not be sufficient to characterize the corrosion process of chloride induced macro-cell corrosion.
Materials and Corrosion
This paper sums up the International RILEM Workshop on Present and Future Durability Challenges f... more This paper sums up the International RILEM Workshop on Present and Future Durability Challenges for Reinforced Concrete Structures, held at ETH Zurich in Switzerland on 17–18 April 2012. Major focus is put on the discussions. During the latter it was revealed that one of the key durability challenges lies in predicting the performance of new materials, where the increasing diversity of cement and concrete plays a major role. As most current engineering models are not capable of predicting actual field performance adequately, a knowledge-based approach to durability will become more important than ever. Only a scientific approach on a multi-scale and interdisciplinary level will allow predicting the performance of new materials (where no long-term experience is available for fitting purposes). This will facilitate the use of more performance-based durability design that is urgently needed to promote innovative, long-lasting solutions.
Surface and Interface Analysis
Extruded parts of non-sterilized and β-irradiated (25 and 50 kGy) plasticized poly(vinyl chloride... more Extruded parts of non-sterilized and β-irradiated (25 and 50 kGy) plasticized poly(vinyl chloride) (PVC) used for disposable medical devices have been studied to investigate the effect of sterilization on surface chemical composition. The polymer surfaces were analysed using angle-resolved x-ray photoelectron spectroscopy. The inner surface of the blood tubing lines showed a fairly smooth surface both before and after sterilization, so a laterally homogeneous surface can be assumed for XPS analysis. The XPS survey spectra exhibited no signals besides carbon, chlorine, oxygen and calcium. Detailed analysis of the regions showed the C 1s, Cl 2p and O 1s signals to be multi-component, presenting signals of the PVC, the plasticizer and the other additives. Binding energies remained constant irrespective of β-radiation dosage, but the amount of chlorine component at 198.4 ± 0.1 eV (associated with modified PVC) decreased with sterilization dosage. Angle-resolved XPS revealed that this co...
Surface and Interface Analysis
Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devi... more Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non-sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x-ray energy-dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd.
Corrosion Science, 2015
ABSTRACT Local electrochemical measurements (open circuit potential (OCP), cathodic and anodic po... more ABSTRACT Local electrochemical measurements (open circuit potential (OCP), cathodic and anodic polarization curves, pitting potentials) were performed at random locations on 1 m long ribbed steel bars with different surface conditions. The results show that the local OCP values are statistically distributed. The standard deviation was found to be 45 mV for “as received” surface condition, decreasing to 10 mV only after prolonged immersion in sat. Ca(OH)2. A model based on local variations of the reduction current density could explain the variations in local OCP and allowed predicting the overall global OCP of the long bars when completely immersed in solution.
Corrosion of Reinforcement in Concrete, 2007
Corrosion Rates of Steel in Concrete, 1990
Surface and Coatings Technology, 1993
The corrosion behaviour of titanium nitride (TiN) CVD coatings on AISI 31 6L stainless steel and ... more The corrosion behaviour of titanium nitride (TiN) CVD coatings on AISI 31 6L stainless steel and on inert Si 3N4 in hydrochloric acid is studied with a.c. and d.c. electrochemical methods. The electrochemical behaviour of TiN on stainless steel can be divided into active and passive behaviour according to the state ofthe substrate. The measurements indicate that there is an oxide layer on TiN that is responsible for its noble electrochemical behaviour. A model that describes the formation of the oxide layer on TiN in an electrolyteis proposed.
Annali di chimica
A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auge... more A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) has been carried out to characterize the chemical state of arsenic in complex environmental samples. The conventional approach, which relies on the chemical shift of the core levels As3d, provides ambiguous results in determining the chemical environment of arsenic. A more accurate approach, based on the Auger parameter and on the Wagner (Chemical State) plot, which combines AsLMM kinetic energy and As3d binding energy, was adopted. This novel method for determining the chemical state of arsenic was employed to completely characterize arsenic in complex environmental samples.
STALLFORTH:MAT.MED.ENGIN. O-BK, 2000
ABSTRACT The repassivation process of Titanium cp, Ti6Al4V and CoCrMo alloys was studied using a ... more ABSTRACT The repassivation process of Titanium cp, Ti6Al4V and CoCrMo alloys was studied using a novel microcapillary cell with a ceramic tube rotating inside, simulating a possible mechanical disruption of the protective films in a small electrolyte volume. This work is focused on the effect of sample composition and electrolyte on the repassivation process of the implant materials. The open circuit potential (OCP) was measured over time in the range from milliseconds to hours in order to follow the repassivation process and to determine its repassivation rate.An estimate of the corrosion current during rubbing the metallic implants was made by measuring the current at the potential reached after mechanical disruption of the passive film. It was found that the corrosion current of CoCrMo alloys, after disruption of the passive film in serum bovine or sodium sulfate, is lower than cp Ti and Ti6Al4V. Repassivation of CoCrMo alloys changes as a function of pH and it is faster in serum at pH 7.1 while repassivation of cp Ti and Ti6Al4V is independent of electrolyte and pH.
Surface Science Spectra, 2002
X-ray photoelectron spectroscopy was used for characterizing the enargite surface. Freshly cleave... more X-ray photoelectron spectroscopy was used for characterizing the enargite surface. Freshly cleaved samples were analyzed at liquid nitrogen temperature. Enargite is a copper arsenic sulfide of formula it is used as a minor ore of copper. Enargite is a potential source of ...
Surface and Interface Analysis, 2003
... Chemistry, Universit `a degli Studi di Modena e Reggio Emilia, INSTM UdR of Modena Via Campi ... more ... Chemistry, Universit `a degli Studi di Modena e Reggio Emilia, INSTM UdR of Modena Via Campi 183, I41100 Modena, Italy 3 ... The spectra, after background subtraction according to Shirley and Sherwood,16 were resolved into their components using a product of Gaussian ...
Surface and Interface Analysis, 2000
Chemical inhomogeneities (inclusions) present in the alloy are known to affect the stability of t... more Chemical inhomogeneities (inclusions) present in the alloy are known to affect the stability of the passive film on stainless steels in the presence of chloride ions. In this work, three surface analytical techniques-XPS, AES and time-of-flight SIMS (ToF-SIMS)-have been used to characterize the surface films formed on stainless steels following mechanical polishing and immersion in an aggressive 6% FeCl 3 solution, which is utilized for testing the pitting corrosion resistance of stainless steels. Two 18Cr8Ni stainless steels were investigated: one with a low sulphur content, DIN 1.4301 (0.003% S), and one with a high sulphur content, DIN 1.4305 (0.29% S).
Surface and Interface Analysis, 2008
A surface analysis has been conducted on a series of electrodeposited nickel-phosphorus (Ni-P) al... more A surface analysis has been conducted on a series of electrodeposited nickel-phosphorus (Ni-P) alloys containing from 6 to 29 at.% phosphorus, using X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES). No changes in core-level binding energies, Ni2p3/2 and Ni2p1/2, P2p, P2s, or X-ray excited NiLMM and PKLL Auger lines were observed regardless of phosphorus concentration. The only systematic differences observed concerned: (i) the binding energy of the Ni2p satellite peak, (ii) the fine structure of the NiLMM Auger lines, (iii) the percentage of the satellite in the total Ni2p3/2 spectrum and (iv) the valence band density of states in the Ni3d electrons region, all related to the electronic structure of the Ni-P alloys. For the first time, it has been possible to describe and rationalise the influence of (phosphorus) ligand concentration on the electronic structure of nickel-based alloys, using a screening model proposed in the literature for clarifying the role of substituents on the electronic structure of conductor compounds of nickel. As the phosphorus content increases, the number of non-bonding Ni3d electrons decreases. Thus the d-type core-hole screening is less pronounced and the binding energy of the satellite for the final state with a filled Ni4s shell increases.
Surface and Interface Analysis, 2003
Plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices was studied in the ... more Plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices was studied in the nonsterilized state after different exposure times to soft x-ray irradiation in a commercial photoelectron spectrometer (Al Ka, 15 kV/300 W; Mg Ka, 12 kV/240 W) by XPS surface analysis. The detailed spectra of C 1s, Cl 2p and O 1s have been recorded and processed. Irradiation with soft x-rays induces a clear decrease of the total Cl 2p intensity, an increase of total C 1s intensity and a doubling of the O 1s intensity after 45 min of irradiation with Al Ka (300 W). Irradiation with Mg Ka (240 W) is slightly less damaging. These results can be interpreted with the classical PVC degradation model, e.g. bond cleavage with the formation of HCl gas, although the Cl 2p high-resolution spectra reveal the formation of an additional side-product, probably CaCl 2 . For further studies of plasticized PVC using XPS surface analysis it can be concluded that a complete analysis of a polymer sample should not take >10 min of x-ray exposure in order to avoid notable polymer degradation.
Uploads
Papers by Bernhard Elsener