Low-energy Electron-induced X-ray Spectroscopy Research Articles

Recent Developments in the Spectroscopic Characterization of Modified Surfaces for Adhesive Bonding or Painting

Abstract Low-Energy Electron-Induced X-ray Spectroscopy (LEEIXS) and X-Ray Fluorescence Spectroscopy (XRFS) have been used to study the near-surface chemistry of metallic substrates submitted to various pre-bonding or pre-painting chemical or electrochemical treatments. Applications given in this paper concern firstly stainless-steel and Ti-6Al-4V adherends and secondly steel and galvanized steel sheets. Experiments provide the information necessary to understand how treatments such as anodization, chemical conversion, rinsing… affect the chemistry and properties of surfaces. So, specific examples are shown, outlining how the chemistry of the adherend surface may be correlated with its bondability, the strength of bonded joints being determined using a three-point flexure test. In addition, it is discussed why the information available through the spectroscopic techniques used are quite complementary to the ones provided by more sophisticated surface analysis instrumentations.

Characterization of anodic oxides on 304L stainless steel surfaces

AbstractThe effects of anodization parameters, such as current density, electrolyte concentration, electrolyte temperature, and anodization time on the thickness and composition of the oxides formed on AISI 304L stainless steel anodized in H2SO4K2Cr2O7 were studied by low energy electron induced x‐ray spectroscopy (LEEIXS), glow discharge optical spectroscopy (GDOS), and inert ion sputter profiling in conjunction with Auger electron spectroscopy. The physical and chemical properties of these films were correlated with the results of mechanical tests performed on adhesively bonded structures of the anodized pieces in order to test the feasibility of anodization as a prebond treatment for stainless steel.Anodization in H2SO4K2Cr2O7 produces a Cr(III) enriched 100 nm thick oxide film. The novel technique of LEEIXS was used to characterize the chemical state of chromium while the hydrogen content of the anodic oxide was determined by GDOS.

Surface and near‐surface chemical characterization by low‐energy electron‐induced X‐ray spectrometry (LEEIXS): A review

AbstractVarious experiments show that low‐energy electron‐induced X‐ray spectrometry (LEEIXS), using a gas discharge tube as an efficient and stable electronic excitation source, represents a powerful new technique in many fields of research related to surface and near‐surface chemical characterization of materials. The instrument is a wavelength‐dispersive X‐ray spectrometer capable of high qualitative or quantitative performances in the soft and ultra‐soft region (λ = 0.3—10 nm). LEEIXS applications given in this paper demonstrate how chemical, electrochemical or physical treatments of various substrates modify the solid surface composition.

Adhesive bonding of aerospace materials — surface characterization of metallic adherends

Adhesively bonded structures are widely used in the aerospace industry. Unfortunately, adhesion is a macroscopic property depending specifically upon numerous sub-microoscopic parameters so that producing a strong and durable bond is a difficult task which needs many fundamental and applied research investigations. In this context, the surface composition of adherends plays an extremely important role in the overall performance of a bonded structure: it is well known that surfaces of ‘as-received’ materials are chemically very different from the bulk composition and are usually unsuitable for adhesive bonding. Consequently, surfaces of such materials hav to be submitted to appropriate chemical or electrochemical prebonding treatments in order to modify both their morphology and chemistry. This paper discusses the surface characterization of aluminium, titanium and their alloys at various prebonding stages. Practical applications of X-ray fluorescence spectroscopy, low-energy electron-induced X-ray spectroscopy and glow discharge optical spectroscopy are described.

Study of iron implanted MgO crystals by low-energy electron induced X-ray spectroscopy

Magnesium oxide crystals implanted with Fe + ions have been studied by means of Low-Energy-Electron-Induced X-ray Spectroscopy. All the implantations were carried out with 100 or 150 keV ion energy, at doses in the range from 10 15 to 10 17 ions cm −2. The structure of the Fe L II, L III X-ray emission bands provides information about the iron chemical state. Fe L II/L III band intensity ratio measurements have been performed with a 3 keV electron excitation in order to investigate the whole implanted layer. In addition, by using a filtered Fourier transform technique on observed spectra, some modifications in the oxygen K emission band can be observed in implanted MgO crystals after thermal annealings in air. The oxygen spectrum fine structure suggests that the MgO matrix, partially destroyed by iron implantation, is restored after high temperature treatments. All the implantation, is restored after high temperature treatments. All the results are discussed on the basis of previous Mössbauer Spectroscopy studies and ion channeling investigations.

Applications of soft X-rays in the surface analysis of conversion or passivation films

Capabilities of low-energy electron-induced X-ray spectroscopy (LEEIXS) for providing detailed qualitative and quantitative information about the first 10 to 1000 Å of a solid surface are described. Trace detection of low Z elements such as B and F in thin films formed on titanium substrates is illustrated. These impurities are incorporated from the electrolytes (H 3BO 3 and H 2SiF 6 solutions respectively) during anodization. The characterization of thin films formed on titanium by chemical conversion in phosphate/fluoride solution is also reported. Chemical bonding information is obtained from the fine structure of the Ti L 2,3 X-ray emission bands. Results prove unambiguously that the main component of the conversion films is not a TiO 2 oxide but rather a TiF 4-like fluoride. In addition LEEIXS has been used for obtaining O and P elemental depth profiles through an anodic film grown on niobium in phosphoric baths. Such an investigation was performed in conjunction with an external step by step chemical etching of the specimen surface. Lastly, the application of LEEIXS to the surface characterization of stainless steels prior and after a passivation treatment is described.

Advances in Low-Energy Electron-Induced X-Ray Spectroscopy (LEEIXS)

AbstractUsing low-energy electron induced X-ray spectroscopy (LEEIXS) with a cold cathode tube as excitation source and appropriate calibrations, quantitative surface composition informations are obtained. The results concern anodic film thicknesses and carbon impurities, In addition, qualitative informations on the chemical state of the film components are deduced from the fine structure of X-ray emission bands. The results concern oxygen K emission spectra from CuO and Cu2O, SnO, SnO2 and anodized Sn. It is also shown the capabilities of LEEIXS for gaining element-depth profiles, One example pertaining to phosphorus impurities in Al2O3 anodic films is given. Finally advantages and disadvantages of LEEIXS over ion-induced X-ray spectroscopy are discussed.

Analyse de films minces et ultra-minces: Perspectives nouvelles en spectrométrie d'émission des rayons X

This paper illustrates the capabilities of “low-energy electron induced X-ray spectrometry” (LEEIXS) for surface and thin, or ultra-thin, film analysis. The work deals with anodic films and shows that it is possible to measure oxide film thicknesses in a range between 0 and a few hundred angströms. In addition, it is demonstrated that this technique provides some information about the distribution of impurities in the interior of the films.