Christofer Leygraf

Surface characteristics, copper release, and toxicity of nano- and micrometer-sized copper and copper(II) oxide particles: a cross-disciplinary study.

An interdisciplinary and multianalytical research effort is undertaken to assess the toxic aspects of thoroughly characterized nano- and micrometer-sized particles of oxidized metallic copper and copper(II) oxide in contact with cultivated lung cells, as well as copper release in relevant media. All particles, except micrometer-sized Cu, release more copper in serum-containing cell medium (supplemented Dulbeccos minimal essential medium) compared to identical exposures in phosphate-buffered saline. Sonication of particles for dispersion prior to exposure has a large effect on the initial copper release from Cu nanoparticles. A clear size-dependent effect is observed from both a copper release and a toxicity perspective. In agreement with greater released amounts of copper per quantity of particles from the nanometer-sized particles compared to the micrometer-sized particles, the nanometer particles cause a higher degree of DNA damage (single-strand breaks) and cause a significantly higher percentage of cell death compared to cytotoxicity induced by micrometer-sized particles. Cytotoxic effects related to the released copper fraction are found to be significantly lower than the effects related to particles. No DNA damage is induced by the released copper fraction.

Corrosion Mechanisms for Nickel Exposed to the Atmosphere

The physical and chemical phenomena responsible for the atmospheric corrosion of silver are presented. Corrosion layer formation, morphology, and chemical makeup are discussed in the context of silver-containing minerals and other crystalline structures that thermodynamics and kinetics suggest are likely to be present. The constituents that form during the corrosion process are then described, and the formation pathways of acanthite (Ag 2 S) and chlorargyrite (AgCl), the two minerals most often reported to be present in silver corrosion layers, are shown in schematic diagrams. The presence of these species and the essential absence of sulfate, nitrate, carbonate, or organic salts of silver are shown to be a natural consequence of the thin aqueous layer chemistry that obtains on silver in humid environments. The primary atmospheric agents responsible for the degradation are identified as H 2 S, COS, particulate chloride, and possibly HCl, all acting in the presence of moderate to high humidity. Gaseous hydrogen peroxide, which is sometimes present, strongly accelerates silver corrosion. Comprehensive kinetic simulations of the corrosion process are desirable, but await laboratory determinations of the rates of dissolution, and transformation of silver-containing chemical species.

A LEED-AES study of the oxidation of Fe (110) and Fe (100)

Simultaneous LEED and AES observations have been used to study the initial stages of oxidation of the Fe(110) and Fe(100) single crystal surfaces at 300 K and 400 K and of a clean Fe polycrystal at 300 K. Accurate surface lattice spacings of the precursory oxide structures have been measured and attempts have been made to quantitatively evaluate the corresponding surface oxygen density. On the (110) single crystal surface the final structure is FeO-like with a lattice spacing 4% larger than that of bulk FeO. The transition to the FeO-like structure starts with a surface lattice expansion in the [110] direction followed by an expansion in the [001] direction in order to accommodate the (111) face of the FeO-like structure. On the (100) single crystal face the oxygen and iron form an fcc (100) face which initially contracts and then expands with increasing oxygen doses. The structure formed at 300 K is spinel-like but heat treatment causes a transition to FeO(100). The changes of the surface unit cell dimensions are interpreted as the result of an interaction between adsorbate and substrate. This interaction is strongest in a direction parallel to the close packed rows of the substrate, making the corresponding periodicity of the adsorbate more resistant to lattice changes. In the case of the polycrystal a hexagonal structure was observed after oxygen adsorption with no simple relation to the oxide structures observed on the single crystals. The initial sticking coefficients in the interval 0–10−5 torr sec ranged from 0.07 to 0.36 depending on temperature and crystal face observed. The latter dependence is explained in terms of the surface structure.

A laboratory study of copper and zinc runoff during first flush and steady-state conditions

The influence of environmental conditions and corrosion layer characteristics have been investigated on the runoff rate of copper and zinc, used as roofing material. For this purpose, a rain device ...

The influence of minor alloying elements (Nb, Ti and Cu) on the corrosion resistivity of ferritic stainless steel in sulfuric acid solution

Abstract The effect of the minor alloying elements (Nb, Ti and Cu) and of Moon the corrosion resistivity of ferritic stainless steel (Fe-26Cr alloy) was investigated in 1.0 mol dm −3 sulfuric acid solution with or without 0.5 mol sodium chloride, based on potentiodynamic polarization, potential decay and reactivation potential measurements. Surface characterization of the ferritic stainless steel subjected to active dissolution or passivated was performed with simultaneous use of Auger electron spectroscopy and an argon-ion sputter-etching technique. Copper and molybdenum suppressed the anodic dissolution of the steel. Copper and niobium were significantly enriched on the steel surface during active dissolution. A chromium enrichment was always found in the passive film of all the investigated steels. No enrichment of the other alloying elements was observed in the passive film and the substrate. Niobium, titanium and molybdenum stabilized the passive film, whereas copper had a detrimental effect on the passivity. The influence of the alloying elements on the corrosion resistivity of the steel is discussed in relation to the surface analytical results.

Effects of exposure direction and inclination on the runoff rates of zinc and copper roofs

The effect of exposure direction and inclination on the runoff rates of both zinc and copper has been studied by field exposures on model roofs. Runoff rates decrease with higher inclinations from ...

The Role of Intermetallic Particles in Localized Corrosion of an Aluminum Alloy Studied by SKPFM and Integrated AFM/SECM

A multi-analytical approach based on in-situ and ex-situ local probing techniques was employed to investigate localized corrosion mechanisms of some aluminum alloys in chloride containing solutions, focusing on the influence of intermetallic particles (IMPs) in the alloys. In the EN AW-3003 alloy, SEM-EDS analysis revealed constituent and dispersoid IMPs. There are two types of constituent IMPs, with size ranging from 0.5 to several μm, and composition typically Al6(Fe,Mn) or Al12(Mn,Fe)3Si, respectively,having a Mn/Fe ratio of about 1:1. Fine dispersoids of 0.5 μm or less in size normally have the composition Al12Mn3Si1-2. Scanning Kelvin probe force microscopy (SKPFM measurements showed that the constituent IMPs have a higher Volta potential compared to the matrix, and the Volta potential difference increased with particle size, probably related to the composition of the IMPs. The SKPFM results also showed a Volta potential minimum in the boundary region adjacent to some larger IMPs. The open-circuit potential and electrochemical impedance spectroscopy measurements indicated local electrochemical activities occurring on the surface, and active-like dissolution in the acidic solutions, but a passive-like behavior in the near-neutral solutions. Infrared reflection-absorption spectroscopy measurements after exposure and thermodynamic calculations suggested the formation of mixtures of aluminum oxyhydroxide and acetate on the surface in acetic acid solutions. The formation and fraction of dominant species of the corrosion products depend on the pH of the solution, and aluminum chloride compounds may form at very low pH. Moreover, an integrated in-situ atomic force microscopy (AFM) and scanningelectrochemical microscopy (SECM) set-up was used to investigate the localized activities on the surface. With a dual mode probe, acting as both AFM tip and SECM microelectrode, concurrent topography and electrochemical current images were obtained on the same area of the surface. Numerical simulations of the SECM suggested a micrometer lateral resolution under favorable conditions and the ability to resolve μmsized active sites with a separation distance of about 3 μm or larger. The simulations were verified by SECM mapping of the aluminum alloys in the chloride solutions. The AFM/SECM measurements revealed enhanced cathodic activity on some larger IMPs and local anodic dissolution around larger IMPs. In-situ AFM monitoring confirmed preferential dissolution in the boundary region adjacent to some of these IMPs. The results elucidate the micro-galvanic effect and size effect of the IMPs during the initiation of localized corrosion of the Al alloys. Furthermore, differences in corrosion properties between EN AW-3003 and a newly developed Al–Mn–Si–Zr alloy were studied with a similar approach. Compared to EN AW-3003, the new alloy had a smaller number of particles with a large Volta potential difference relative to the matrix. In slightly corrosive solutions extensive localized dissolution and deposition of corrosion products occurred on EN AW-3003, whereas only a small number of corroding sites and “tunnel-like” pits occurred on the Al–Mn–Si–Zr alloy. The lower corrosion activity and the smaller tunnel-like pits resulted in lower material loss of the Al–Mn–Si–Zr alloy, which is beneficial for applications using a thin material.

Surface composition studies of the (100) and (110) faces of monocrystalline Fe0·84Cr0·16

Abstract Surface compositions of the (100) and (110) faces of monocrystalline Fe0.84Cr0.16 have been determined using Auger Electron Spectroscopy (AES) and monocrystalline Cr (100), Fe (100), Cr (110) and Fe (110) surfaces as standards. When subjected to different annealing procedures with and without oxygen gas present, drastic changes in Cr enrichment occurred in the investigated surface region, the thickness of which is of the order of 10 A. Under thermal equilibrium conditions the Cr Fe ratio is mainly influenced by differences between Cr and Fe as to surface free energy and affinity to oxygen whereas far from equilibrium, the difference in diffusion rate between Cr and Fe also plays an important role.

In Situ Investigation of Localized Corrosion of Aluminum Alloys in Chloride Solution Using Integrated EC-AFM/SECM Techniques

Scanning electrochemical microscopy (SECM) has been integrated with electrochemical atomic force microscopy (EC-AFM), and applied for in situ studies of localized corrosion of Al alloys in NaCl sol ...

In Situ Infrared Reflection Absorption Spectroscopy for Studies of Atmospheric Corrosion

A new experimental setup for in situ infrared reflection absorption spectroscopy (IRAS) studies of atmospheric corrosion is described. It consists of units for preparation of corrosive air, an in situ cell where samples are exposed, and an optical system linked with a Fourier transform infrared spectrometer. In situ infrared spectra can be recorded in humid air at ambient pressure and results are presented of the oxide formation on copper in clean air at 90% relative humidity and 25 o C. At these exposure conditions copper(I) oxide is formed, and its growth can be monitored from the initial stages to more fully developed oxide films