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AZ31 Mg alloy sheet was welded using a gas-tungsten arc (GTA) process over inserts containing 2.3-9.3 wt.% Al. The welded specimens were susceptible to SCC in distilled water, with susceptibility increasing with decreasing weld metal Al (or β particle) concentration. Primary stress corrosion cracks initiated at the weld metal-HAZ interface by stress-assisted localised dissolution and propagated through the weld and base metals by transgranular and intergranular H-assisted fracture (TG-HAF and IG-HAF) respectively. The IG fracture mode may be intrinsic to the texture imparted upon the base metal by rolling. The increase in SCC susceptibility with decreasing weld metal Al concentration is contrary to the purported roles of β particles in promoting localised corrosion and as crack nucleation sites, but corresponds with increases in weld - base metal galvanic current density and weld metal localised corrosion susceptibility.
Self-assembled octadecyltrichlorosilane (CH3(CH2)17SiCl3, OTS) films were deposited on an oxidized silicon wafer. They were carefully exposed to a low-pressure oxygen direct current (dc) plasma and/or Cr vapor. Subsequently, they were characterized by X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and atomic force microscopy. Detailed information on the oxygen functionalization and the molecular conformation of the OTS films was obtained. The main result was that functionalization conditions can be found where the order of the film remains almost unaffected. Similarly, Cr evaporation of pure OTS films revealed only slight effects on the order in the film. Cr evaporation of an ordered but functionalized OTS film immediately changes its state toward a fully isotropic one. In the course of interaction, oxygen sites at the surface of the functionalized OTS film are reduced whereas Cr becomes oxidized. A redox reaction scheme is proposed for this interfacial reaction. Finally, it is concluded that the given study should be of importance for advanced plasma processing of polyolefins.
Overlayers of SiO2 (nominally 4, 6 and 8 nm thick) on silicon, prepared by thermal oxidation, were investigated using x-ray photoelectron spectroscopy (XPS). The thickness of these overlayers was obtained from a measurement of the photoelectron intensities originating from the substrate and the oxide overlayer by applying an appropriate quantitative model. The uncertainty budget of that thickness measurement method is given. The relative combined standard uncertainty of the method was found to be 15%. The effective attenuation lengths or the corresponding electron inelastic mean free paths are of considerable importance for both the estimated values of overlayer thickness and combined standard uncertainties. The XPS results were compared with ellipsometry data.
Die Akkreditierung für Prüfverfahren in der Oberflächenanalytik wird gemeinhin als sehr schwierig angesehen. Durch das unlängst eingeführte flexible Konzept der Akkreditierung, auch Prüfartenakkreditierung genannt, eröffnen sich nunmehr neue Möglichkeiten. Aus dem Bereich des Normenwesens in der Oberflächenanalytik erhalten die Prüflaboratorien zusätzliche Unterstützung. Die Validierung von ESCA-Prüfverfahren und ein wohldokumentiertes Prüfmittelmanagement sind weitere Bausteine auf dem Weg zur erfolgreichen Akkreditierung. Oberflächenanalyseverfahren sind akkreditierfähig.
First results of an inter-laboratory comparison (27 participants in Europe, Japan and USA) of XPS data obtained with non-conducting samples are presented. Binding energies of Al 2s for alumina, N 1s and imide C 1s for Kapton and Sr 3p3/2 for a strontium titanate film on glass were obtained after static charge referencing with the help of 15 nm gold particles deposited at the surface of the test samples. For the alumina sample C 1s static charge referenced data are also presented. Repeat standard deviations (sr), between standard deviations (sb), reproducibility standard deviations (sR) and total means are evaluated from the experimental data. It can be stated that although the repeat standard deviation is as small as 0.05 eV in the best case, the standard deviation characterizing the reproducibility of the method is obviously not better than 0.15 eV in the best case at the present time. The knowledge of these standard deviations is important for metrology, validations of analytical procedures relying on qualitative photoelectron spectroscopy and XPS databanking.
Catalyst characterization
(1998)
Catalyst characterization
(2009)