X-ray photoelectron spectroscopy was used to compare several pretreatments of aluminium surfaces used in aerospace and aircraft industry. These anodizing processes, which aim at preparing the metal surface for adhesive bonding or painting, all lead to the formation of an aluminium oxide layer. A set of aluminium samples representing the various steps of the processes was analysed by XPS. After curve fitting of the aluminium peak (A1 2p) and oxygen peak (0 1s) recorded at high energy resolution, and correction of charging effects, residual energy shifts between the spectra can be observed. This could be attributed to differences in the Fermi energy values between the treated aluminium surfaces. A classification based on this parameter of the relative Lewis acid-base character of these treated surfaces is proposed. The evolution of this parameter after exposure of the treated samples to a moist environment was also studied.
Experimental and theoretical analysis of the origin of porosity in electron-beam (EB) welding is detailed. The experiments are run with several surface treatments and reasonable welding parameters. The plate faces are characterized before welding with a number of methods, such as scanning electron microscope observation, X-ray photoemission spectroscopy (XPS) and, more significantly, secondary ion mass spectroscopy (SIMS) analysis, elastic-recoil detection analysis (ERDA) for hydrogen analysis, and surface roughness measurement. After welding, pores are sought with X-ray detection, phased-array ultrasonic (US) detection, and destructive control. An original comparison between ERDA and refined SIMS measurements allows a quantitative evaluation of surface pollution with hydrogen, oxygen, and carbon. The theoretical analysis is based on the literature concept that the cavities are nucleated from the adjacent plate faces in the solid state, just before melting. A less classical development is proposed in term of the evolution of bubbles in the weld pool. Once in the liquid, the cavities become bubbles. Their radius oscillates, according to Rayleigh-Plesset equations of bubbles, due to temperature and pressure driving forces. Solidification freezes them as they are, thus, forming pores. The extreme values of the oscillation give a good idea of the range of the size of pores in the weld joint, as the comparison between experiments and prediction states. A criterion of surface cleanliness is set, relating the surface pollution and the surface roughness. Above the criterion, the bubbles remain small during their oscillation. Below the criterion they tend to grow large. All the degraded-surface treatments are in dirty situation (large pores), and the reference surface treatment lies around the criterion for cleanliness.
This paper presents a study of the interface between Cu and a glass fibre reinforced PAMXD 6 polymer. Substrate surface chemistry was characterised before metallisation by spectroscopic techniques including Fourier transform infrared and X-ray photoelectron spectroscopy (XPS). Chemical bonding of Cu layers (20 nm to 2 11mthick) to the polymer was investigated by XPS (depth profiling, argon ion bombardment) and secondary ion mass spectrometry. The results showed that Cu reacts with the polymer, leading to the formation of a Cu-O-C like interfacial compound, and illustrated the influence of the evaporation pressure and temperature parameters on the interfacial structure and final quality of the film. The adhesion strength of the coating, obtained by z axis tensile tests (studs bonded to the PAMXD 6 with an epoxy glue), confirmed the interpretation of the analyses.
We have developed a software tool for the generation of survey spectra in X-ray photoelectron spectroscopy (GOSSIP) to simulate wide spectra in the range 200-1500 eV from nano-structured surfaces. It is based on linear combination of delta layers spectra with the atomic spectra of the elements or compounds of the surface to be simulated. The set of delta layers to reproduce any model is a 200-file database of thin layers regularly buried up to a depth of 40 nm and has been generated with QUASES . The atomic spectra that constitute a second database have themselves been determined with QUASES from experimental spectra of the elements or compounds in pure form. The principle of GOSSIP is described. Then the generation process is validated by comparison with experimental data for simple rectangular in-depth distribution of elements. The use of peak area ratios for quantification quickly gives a set of atomic percentages, but means that the sample composition is assumed to be constant over the depth probed by XPS. This is rarely true and it is precisely because samples are inhomogeneous on the nanometre depth scale that surface analysis (XPS or AES) finds its value compared with other solid materials analytical techniques such as energy dispersive spectrometry (EDS) or X-ray fluorescence spectrometry (XRF). The assumption that a solid composition is constant in the volume of matter probed by XPS or AES can lead to important errors in quantification of surfaces [1] and misinterpretation of recorded data. Surface quantification cannot be decoupled from in-depth atomic distribution, or surface nanostructure determination. Several methods have been established to account for or to determine this nanostructure for reliable surface quantification: peak intensity attenuation, [2] angular-resolved XPS, [2,3] sputter depth profiling.[4]These methods are only based on peak intensities or variation of these intensities with a parameter (angle or time) and do not exploit the rich information contained in the inelastic background associated with the peaks.In that aim, SESSA, [5,6] a new software tool for quantitative AES and XPS has been recently designed and is released by National Institute of Standards and Technology (NIST). [7] SESSA is a database that contains all physical data required to perform quantitative interpretation of auger-electron or X-ray photoelectron spectrum for a layered specimen. A simulation module, based on a Monte Carlo algorithm, is also included into SESSA: the simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with the measured spectra and adjusted to find maximum consistency.In a similar way, with generation of survey spectra in x-ray photoelectron spectroscopy (GOSSIP), depth distribution and concentrations of species are determined through absolute comparison of the measured data and the simulated XPS survey spectrum of the nano-structured surface model. However, a comparison of both software tools is not timely. GOSSIP aims at simulating wide XPS s...
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