The effect of hot active plasma (HAP) on phosphated zinc coated steel was studied in detail with x-ray photoelectron (XPS) and scanning Auger electron spectroscopy (AES) combined with electron microscopy. In order to extend the scope of the methods from the surface down to the bulk of the coating, Ar+ ion sputter depth profiling coupled with XPS was utilized. While a mild surface cleaning effect was observed for weak treatments, increased HAP intensity caused significant chemical and structural changes on the coating surface. Initially, a partial decomposition of zinc orthophosphate (Zn3(PO4)2), as the sole surface constituent of the untreated coating, led to a mixed zinc metaphosphate (Zn(PO3)x) and zinc oxide (ZnO) phase, highly localized in randomly distributed micrometer sized spots on the treated surface. Finally, the most intensive HAP treatment, leading to a temperature rise of the treated sample up to 700 degrees C as revealed by in-situ temperature measurements, caused a complete transformation of the zinc phosphate material into a porous and rough ZnO layer. Moreover, the heat contribution of the HAP treatment induced remarkable modifications within the bulk of the coating - mixing of zinc with the underlying steel substrate - an effect mimicking a galvannealing process.

6xxx series6xxx series aluminum alloysAluminum alloys are increasingly used within the automotiveAutomotive industry due to their lightweight potential. For assembling several joining techniques are common. This paper focuses on adhesive bondingAdhesive bonding, which is widely employed but its mechanism is by far not fully understood. The sheet metal process, including hot and cold rollingRolling, solution heat treatmentHeat treatment, pickling and Ti/Zr conversion treatment, contributes heavily to the final bonding performance. Even minor changes in the rollingRolling process may alter the surface near deformation layer or a variation during pickling can lead to unfavorable oxidic conditions. To evaluate these changes X-ray photoelectron spectroscopy (XPS)X-ray Photoelectron spectroscopy (XPS), which is extremely powerful in gathering elemental, chemical and oxidic information from the topmost surface (<10 nm), was performed. Furthermore, transmissionTransmission transmission Kikuchi diffraction (TKD) in combination with a focused ion beam (FIB) preparation was employed to investigate the surface near grain structureGrain structure near grain structure. Additionally, scanning electron microscopy (SEM)Scanning electron microscopy (SEM) provided valuable knowledge concerning the surface topography.

The interior structure and chemistry of single-component (1K) polyester-polyurethane (PU) coil coatings, which find preferred application in the construction industry, was comprehensively investigated by energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy and X-ray electron spectroscopy (XPS). Fabrication of extended tapers in the millimetre-range through a double-layered coating system with a total dry film thickness of 50 mu m was achieved by cryo-ultra-low-angle microtomy (cryo-ULAM). The linearity and surface topography of shallow angle ULAM cuts created at different preparation conditions were examined at mesoscopic and microscopic scale by coherence scanning interferometry, atomic force microscopy (AFM) and scanning electron microscopy (SEM). EDX mappings recorded on the exposed sections enabled to determine the elemental structure and the distribution of embedded fillers at plane-view. Focal plane array (FPA) FTIR spec-troscopy in attenuated total reflection (ATR) mode was used to acquire high-resolution chemical data from the fabricated taper, revealing the clustering of nitrogen-containing groups. Compositional depth profiling of the investigated high-build PU coating system was achieved by performing XPS line scans on the exposed sections. Depth analysis at a chemical level was obtained by means of evaluating the high-resolution carbon C1s spectra, which showed an enhancement of nitrogen and oxygen containing functionalities near the primer/substrate interface. All methods of this correlative work of analysis consistently indicate the presence of chemical gradients related to the cross-linking agent.

A principal investigation on the effect of atmospheric pressure plasma on Zn1.5Mg2.5Al coating was performed by means of X-ray photoelectron- and Auger electron spectroscopy as well as by transmission electron microscopy. The type of the medium used to generate the plasma influenced significantly the impact of the proceeded treatment. Although a mild surface cleaning and oxidation effect was observed for air, N2 or H2O plasma, mixed air + H2O and N2 + H2O plasma types already caused a remarkable altering of the chemical composition, structure and thickness of the coating surface layer, a similar effect to an initial corrosion attack.

The microstructure of a hot-dip Zn-Al-Mg anti-corrosion coating on steel was investigated upon quenching during solidification. As expected, at least two different eutectic microstructures were generated and subsequently characterized using scanning and transmission electron microscopy, elemental analysis, and selected area diffraction. The difference was found in the eutectic intermetallic MgZn phase, which was identified as MgZn2 and Mg2Zn11, respectively. Based on the experimental results, we developed an image processing algorithm for electron micrographs, which automatically detects the altered eutectic microstructure. Furthermore, a 3D focused ion beam tomography was performed for an in-depth analysis of the phase morphologies at the interface between the different eutectic structures.

Room-temperature ozone treatment is a promising technique for functionalization of carbon materials: it is fast, well controllable, and leads to oxygen uptakes of up to 15 at.% on carbon fiber surfaces. We investigated the surface chemistry of untreated and room-temperature ozone-treated polyacrylonitrile-based carbon fibers using X-ray photoelectron spectroscopy (XPS). By identifying two different nitrogen species (graphitic and pyridine-like) we developed a new constraint for fitting the C 1s spectra. This approach ensured high consistency between measured elemental concentrations and elemental concentrations calculated from fitted functional group peaks. It also revealed a different relative ordering of functional group concentrations than previously reported for ozone-treated carbons. The results of this new fitting procedure were cross-checked with chemical derivatization XPS measurements, resulting in a good correlation for hydroxyl and carbonyl groups. Examination of single fiber cross-sections using energy-dispersive X-ray spectroscopy in a transmission electron microscope showed that even after intense treatments oxygen can mainly be found in the topmost 40 nm–50 nm, stressing the importance of surface sensitive techniques such as XPS. Furthermore, XPS results suggested only a minor surface degradation caused by the ozone treatment. This was corroborated by atomic force microscopy results.

A principal investigation of the surface and shallow sub-surface region of corrosion protection coatings based on the ZnMgAl system was performed for three different compositions of Mg and Al, varying from 1.5 wt% up to 3.7 wt%, which are known to behave on a macroscopic scale in an interchangeable manner with respect to properties including corrosion resistance, forming behavior or weldability. Therefore, special attention was paid to the effect of the Mg and Al concentration on the chemical composition, structure and the thickness of the resulting native oxide surface layer as well as on the underlying microstructure of the coating on the nanometer scale. For this purpose the chemical composition of the naturally grown oxide surface layer was analyzed by means of X-ray photoelectron spectroscopy, whereas Auger electron spectroscopy was applied in order to obtain the spatial distribution of the surface constituents. Back-scattered electron micrographs revealed in addition the underlying coating microstructure. The thickness of the oxide surface layers was investigated by transmission electron microscopy. It was found that the resulting surface layers are rather similar, especially in terms of their chemical nature, and highly uniform, despite the high variations of Mg and Al concentrations of more than 100% for the different coatings. Only for the lowest here considered amounts of Mg and Al the thickness and composition of the oxide surface layer starts to reflect the underlying complex microstructure.

The dry adhesion strength of polyester/melamine clear coats varying in their branching degrees were applied on galvanized steel panels and investigated by pull-off and T-bend testing. It was found that pull-off tensile adhesion is mainly dominated by the type of coating and less influenced by the pretreatment of the substrate. In contrast, the critical T-bend strain is mainly affected by the surface treatment of the galvanized layer with higher stiffness but lower ductility compared to the clear coat. Pull-off tensile strength at room temperature is correlating with the glass transition temperature Tg and a strong viscoelastic contribution is ascribed to the work of adhesion. Samples with adhesive as well as cohesive failure modes were further investigated by X-ray photoelectron spectroscopy (XPS) to determine the interfacial chemistry. Angle-resolved XPS data suggest that the nitrogen from the melamine crosslinker plays a decisive role for the adhesion of the coatings. Regarding the melamine distribution a micro- and a nanostructural effect has to be considered: while maximum melamine concentrations over coating depth are usually found in the bulk region of these clear coats, this work proposes that the remaining melamine at the interface segregates towards the metallic substrate.

In this review, we present nonlinear optical methods, based on the second and third order nonlinear polarization, especially in the context of material characterization tasks outside the area of life sciences-for which these techniques are mostly designed. An overview of application studies reported to date is given, together with a discussion on the advantages and limits of the individual methods. Furthermore, new ways of experimentally combining different optical concepts are introduced, and their potential for characterisation and inspection tasks is evaluated in the context of various case studies, including the investigation of semiconductor surfaces, metals and related corrosion products, as well as of organic materials.

Chromium compounds are still used in the context of corrosion protection in industrial products, with Cr containing organic coatings on electrical steel as an example. In order to analyse the content of hazardous Cr(VI) components, X-ray photoelectron spectroscopy (XPS) is often promoted as a non-destructive technique which enables the determination of elemental concentrations and chemical states. However, this technique can affect the oxidation state as we show for CaCrO4. The key point is that pure Cr reference materials behave differently as compared to mixed material systems, which has to be considered for a reliable quantification of Cr(VI) by XPS.

A twinning induced plasticity (TWIP) steel, developed for automotive applications, was characterized down to the nanoscale to investigate the nature of the strengthening mechanisms. Both tensile-deformed and non-deformed materials were studied by light optical microscopy, X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The investigated TWIP steel showed extensive twinning upon deformation. With high-resolution transmission electron microscopy, nano-twins as small as 3 nm in width were observed, and large-angle convergent-beam electron diffraction identified the pole mechanism as one of the twinning mechanisms in this TWIP steel. This study emphasizes that a thoughtful combination of techniques is necessary to fully capture the microstructure of this TWIP steel and explain the origin of superior mechanical properties compared to other TWIP steel grades.

The depth distribution of melamine in polyester-based coatings was investigated by XPS (X-ray photoelectron spectroscopy) as well as Raman analysis on cryo-ultra-low-angle microtome (cryo-ULAN) prepared coatings on hot dip galvanized (HDG) steel panels. Additionally, free standing films were analyzed on the air/coating and the coating/substrate interfaces: for polyester/melamine ratios <= 20 wt.% the melamine concentration was equal on both sides of free films, which is in accordance with literature. This finding could not be confirmed for the coatings applied on HDG steel panels that revealed a higher amount of melamine in the surface-near region. In addition various types of non-linear melamine concentration gradients have been detected over depth by XPS as well as Raman spectroscopy. This behavior was confirmed for all types of coatings irrespective of binder chemistry and curing temperatures in the range of 220-260 degrees C. Whereas previous studies have mainly focused on higher melamine concentration where gradient properties are more pronounced, this work tries to fills the gap towards lower melamine contents, which are of greater relevance for industrial coatings. According to these results, a qualitative model on the melamine distribution has been established, which explains the observed non-linear gradients on the basis of transport phenomena and crosslinking kinetics within the curing process. This model is also in agreement with experimental findings from previous works.

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way. (C) 2017 Elsevier B.V. All rights reserved.

Monoatomic ion sputtering is a common concept for surface sensitive analysis methods to clean surfaces prior investigation or to obtain information from deeper regions. However, severe damage of the materials - linked to preferential sputtering, ion implantation, atomic mixing and in worst case chemical degradation - can affect the validity of the analysis. Hence, the impact of C-60 cluster etching, furthermore, of Ar+ ion bombardment with and without azimuthal sample rotation and also the application of heavy projectiles (Xe+ ions) was investigated to find a concept, which is less destructive or with less critical influence on the chemical nature of the investigated materials. In this work the focus is set on hydrozincite and zinc oxide, two common corrosion products of Zn-based coatings. As a main point, all the obtained results from (i)Ar+ ion, (ii) Ar cluster, and (iii) C-60 cluster etching on the degradation kinetics of hydrozincite were compared with respect to the reached sputter depth. In addition, the sputter rate of all three methods was experimentally determined for ZnO. In total, fully non-destructive conditions could not be found, but valuable knowledge on the type and rate of degradation, which is essential to choose the most suited sputter concept. (C) 2017 Elsevier B.V. All rights reserved.

Hot-dip galvanized (HDG) 2nd generation advanced high strength steel (AHSS), nano-TWIP (twinning induced plasticity) with 15.8 wt.% Mn, 0.79 wt.% C, was analyzed at the interface between steel and zinc by scanning Auger electron microscopy (AES) in order to confirm and improve an existing model of additional pre-oxidation treatment before annealing and immersion into the hot zinc bath. Furthermore these steel samples were fractured in the analysis chamber of the AES and analyzed without breaking vacuum. In these measurements the results of an aluminothermic reduction of the manganese and iron surface oxides on the steel could be confirmed by AES. (C) 2015 Elsevier Ltd. All rights reserved.

Monoatomic ion guns mounted on X-ray photoelectron spectrometers are frequently used for depth profiling to determine the depth distribution of various chemical compounds, or for surface cleaning. Sputtering with single ions may cause severe damage to some materials. Hence, in this study the influence of different sputter parameters on the degradation kinetics was examined. For comparison, the potential of Ar cluster sputtering was tested with the same materials, namely hydrozincite and FeO two representatives of corrosion products that are susceptible to degradation. Chemical damage could only be minimized by cooling or cluster sputtering within a narrow cluster energy window. (C) 2015 Elsevier Ltd. All rights reserved.

•Elastic polyurethane (PU) foils were exposed to the vacuum-UV in reactive atmosphere.•The photomodification resulted in improved cytocompatibilty.•Parallel microgrooves formed on the irradiated PU surfaces after strong elongation.•Cells seeded onto microgrooves aligned their shapes in the direction of the grooves.•Elongation occurred also for cells on PU subjected to cyclic mechanical stretching.

In the current study, the evolution of corrosion products on the surfaces of hot-dip galvanized Zn-Mg-Al and standard Zn coatings during short term exposure to standardized salt spray test was investigated by X-ray photoelectron spectroscopy. The obtained results demonstrated a rapid formation of double layered hydroxides (DLH) covering the surface of the Zn-Mg-Al coatings. The DLH surface layer was found to stabilize the surface pH and hinder further surface alkalization as observed for the Zn coatings and indicated by the occurrence of Na2CO3. As a consequence, the progress of Zn-Mg-Al corrosion was slowed down, but not completely stopped. (C) 2014 Elsevier Ltd. All rights reserved.

We report on the flow characteristics of glass-fiber-reinforced polymers in elongational rheometry. Unlike polymers with geometrically isotropic fillers, glass-fiber-reinforced polymers exhibit flow behavior and rheology that depend heavily on the orientation, the length distribution and the content of the fibers.One of the primary objectives of this study was to determine the effect of fiber orientation, concentration and distribution on the entrance pressure drop by means of optical coherence tomography (OCT), full-field optical coherence microscopy (FF-OCM), and X-ray computed tomography (X-CT). Both pressure drop and melt flow were analyzed using a special elongation die (Thermo Scientific X-Die [3]) for inline measurements. Samples with a variety of fiber volume fractions, fiber lengths and processing temperatures were measured.

•Surface oxides formed on two different kind of advanced high strength steel grades during annealing were investigated.•By adjusting the oxidation potential of the annealing atmosphere surface oxides characteristics can be changed.•The surface oxides were characterized by SEM, TEM and XPS.•It is not only the chemical composition of the oxides influencing their morphology and structure.•The oxidation potential of the annealing atmosphere is found to have a significant impact on crystallinity of surface oxides.