Surface chemical analysis anodized surfaces

The XPS mechanism, which can be used for quantitative and qualitative chemical analysis of surfaces, is based on the photoelectric effect. A monochromatic soft Mg or Al anode X-ray source is used to irradiate the surface. The absorbed X-rays ionize die core shell, and in response, the atom creates a photoelectron that is transported to the surface and escapes. The ionization potential of a photoelectron that must be overcome to escape into vacuum is the binding energy (BE) plus the work function of the material. The emitted photoelectrons have a remaining kinetic energy (KE), which is measured by using an electron analyzer. Individual elements can be identified on the basis of their BE. The resulting XP spectrum is a characteristic set of peaks for a specific element, with BE as the abscissa and counts per unit time as... 

Other techniques utilize various types of radiation for the investigation of polymer surfaces (Fig. 2). X-ray photoelectron spectroscopy (XPS) has been known in surface analysis for approximately 23 years and is widely applied for the analysis of the chemical composition of polymer surfaces. It is more commonly referred to as electron spectroscopy for chemical analysis (ESCA) [22]. It is a very widespread technique for surface analysis since a wide range of information can be obtained. The surface is exposed to monochromatic X-rays from e.g. a rotating anode generator or a synchrotron source and the energy spectrum of electrons emitted... 

The reaction products at the outlet of the anode side of the DEFC were analyzed quantitatively by HPLC, as described previously [24]. Large surface area electrodes (25 cm ) were used in order to have a sufficient amount of products. The current density was kept constant and the voltage of the cell was simultaneously measured as a function of time. The ethanol flow rate was chosen close to 2 mL min in order to perform long-term experiments (for at least 4h) to obtain enough reaction products suitable for chemical analysis. 

Porous anodic alumina is a very promising material for nanoelectronics. The injection of different types of impurities inside an alumina matrix can substantially improve its electrophysical properties. It is very important to study the local environment (chemical bonds, electronic structure, etc.) of injected atoms for understanding physical principles of the electronic elements formation. A number of techniques can be used to determine a chemical state of atoms in near surface layers. The most informative and precise technique is X-ray photoelectron spectroscopy. At the same time, Auger electron spectroscopy (AES) is also used for a chemical analysis [1] and can be even applicable for an analysis of dielectrics. The chemical state analysis of Ti and Cu atoms implanted into anodic aliunina films was carried out in this work by means of AES. 

The elemental compositions of modified PU surfaces were determined by using a Physical Electronic PHI 558 electron spectroscopy for chemical analysis (ESCA) spectrometer. The source was a 10 kV, 30 mA monochromatized X-ray beam from a magnesium anode. Surface charge build-up was corrected by considering the shift of peak at 285 eV. 

One model that involves essentiaUy no diffusion in the bulk or on the surface could be characterized as dissolution and reprecipitation. Dissolution of the entire alloy surface under anodic conditions is followed by reprecipitation of the more noble component. Early in this century, many authors postulated this as the most likely mechanism for dealloying [3,37,102]. Much of the early work was done on brasses and involved chemical analysis of the solutions during dealloying. This analysis showed the presence of both copper and zinc, under most conditions. 

Thus, on the basis of the spectral data alone we cannot draw a conclusion concerning the preferable dissolution order of the above mentioned elements. However, the absence of absorption peaks of MoClg , NiCl4 , TiCls " complex ions indicates that these elements do not transfer to the electrolyte during the anodic dissolution of steel. This was also confirmed by the results of the chemical analysis of melt samples. From the electrochemistry point of view, the fact that electropositive nickel [30] and molybdenum [31] remain in the anode material points to the electrochemical nature of the corrosion process. The results of the spectroscopy measurements and chemical analysis were confirmed by X-ray microanalysis - the electrode surface after 2 h of anodic dissolution was slightly depleted in iron and chromium and was enriched in nickel. 

If the rf source is applied to the analysis of conducting bulk samples its figures of merit are very similar to those of the dc source [4.208]. This is also shown by comparative depth-profile analyses of commercial coatings an steel [4.209, 4.210]. The capability of the rf source is, however, unsurpassed in the analysis of poorly or nonconducting materials, e.g. anodic alumina films [4.211], chemical vapor deposition (CVD)-coated tool steels [4.212], composite materials such as ceramic coated steel [4.213], coated glass surfaces [4.214], and polymer coatings [4.209, 4.215, 4.216]. These coatings are used for automotive body parts and consist of a number of distinct polymer layers on a metallic substrate. The total thickness of the paint layers is typically more than 100 pm. An example of a quantitative depth profile on prepainted metal-coated steel is shown as in Fig. 4.39. 

---