X-Ray Photo-electron Spectroscopy XPS

Instrumental Methods for Bulk Samples. With bulk fiber samples, or samples of materials containing significant amounts of asbestos fibers, a number of other instmmental analytical methods can be used for the identification of asbestos fibers. In principle, any instmmental method that enables the elemental characterization of minerals can be used to identify a particular type of asbestos fiber. Among such methods, x-ray fluorescence (xrf) and x-ray photo-electron spectroscopy (xps) offer convenient identification methods, usually from the ratio of the various metal cations to the siUcon content. The x-ray diffraction technique (xrd) also offers a powerfiil means of identifying the various types of asbestos fibers, as well as the nature of other minerals associated with the fibers (9). 

Lee et al. [30] used in situ X-ray photo electron spectroscopy (XPS) measurement on La0 9Sr0 Mn03 as a function of cathodic polarization. The XPS results showed the peaks of Mn 2p spectra were shifted to the lower binding energy as the applied potential became more cathodic, indicating the reduction of Mn ions. The oxygen reduction and the concomitant formation of Mn2+ ions and oxygen vacancies are proposed as ... 

A first parameter to be studied is the applied potential difference between anode and cathode. This potential is not necessarily equal to the actual potential difference between the electrodes because ohmic drop contributions decrease the tension applied between the electrodes. Examples are anode polarisation, tension failure, IR-drop or ohmic-drop effects of the electrolyte solution and the specific electrical resistance of the fibres and yarns. This means that relatively high potential differences should be applied (a few volts) in order to obtain an optimal potential difference over the anode and cathode. Figure 11.6 shows the evolution of the measured electrical current between anode and cathode as a function of time for several applied potential differences in three electrolyte solutions. It can be seen that for applied potential differences of less than 6V, an increase in the electrical current is detected for potentials great than 6-8 V, first an increase, followed by a decrease, is observed. The increase in current at low applied potentials (<6V) is caused by the electrodeposition of Ni(II) at the fibre surface, resulting in an increase of its conductive properties therefore more electrical current can pass the cable per time unit. After approximately 15 min, it reaches a constant value at that moment, the surface is fully covered (confirmed with X-ray photo/electron spectroscopy (XPS) analysis) with Ni. Further deposition continues but no longer affects the conductive properties of the deposited layer. 

To understand the wear mechanism in valve train wear tests, samples of the worn tappet surface were analyzed for surface elements by electron probe microanalysis (EPMA) and X-ray photo electron spectroscopy (XPS). Results of EPMA analysis of the worn surface in terms of concentration of phosphorus and sulfur atoms for oil with primary ZnDDP without MoDTC, showed an increase of zinc and sulfur intensity after 100 hrs of test time, in spite of decreasing phosphorus intensity. Examination of the worn surface by XPS with primary and secondary ZDDP with addition of MoDTC showed the presence of MoS2 in the tribofilm. Using mixtures of ZDDP and MoDTC, the friction coefficient is reduced, and wear is comparable to that of using ZDDP alone (Kasrai et ah, 1997). 

This method has been used, in combination with X-ray Photo-electron Spectroscopy (XPS), to study the N1O-AI2O3OI2O) interaction with various Ni layer thicknesses and at... 

The use of soft x-rays is known as electron spectroscopy for chemical analysis (ESCA), or x-ray photo-electron spectroscopy (XPS). In addition to ejecting electrons from the valence shell orbits, the x-rays have sufficient energy to eject electrons from some of the inner shells. These are essentially atomic in nature and the spectra produced are characteristic of the atom concerned, rather than the molecule of which it forms a part [178]. 

To determine the chemical composition of the Si02/Ca interface, X-ray photo electron spectroscopy (XPS) measurements were conducted at the Darmstadt Integrated System for Material Science (DAISY-MAT). For these experiments traces of Ca were deposited by PVD onto Si02 substrates, at a chamber base pressure of 5 x 10 ° mbar and a rate of 0.5 A/s. The measure-... 

Abstract Surface analyses have been one of the key technologies for corrosion control and surface finishing. It is very important that the most appropriate apparatus for the purpose of the analyses should be selected from various analytical techniques. In this chapter, surface analytical methods for corrosion control and surface finishing, such as X-ray fluorescence analysis (XRF), X-ray diffraction analysis (XRD), X-ray photo-electron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES), Secondary ion mass spectrometry (SIMS), Rutherford back-scattering spectrometry (RBS), Surface-enhanced Raman spectroscopy (SERS), Fourier-transform infrared spectroscopy (FTIR), and so on, are briefly introduced. 

All chemicals were of the highest available purity. Ultrapure water was prepared by passage through a Bamstead purification system. 11-Hexadecanethiol (95%) and Af-succinimidyl pahnitate (X-ray photo electron spectroscopy XPS reference) were purchased from Fluka (Buchs, Switzerland), silicon wafers... 

Several analytical techniques which can be used to obtain information on the chemical composition of modified surfaces are available (58,59). For example, x-ray photo electron spectroscopy (XPS) can be useful for analysis of thin layers (to depths of 20 A) on substrates. XPS can provide both qualitative and quantitative information on the elements present as well as on their oxidation state, organic structure and bonding information. Auger electron spectroscopy (AES) is a similar technique, but offers only marginal information on the chemical environment of the elements. As for XPS, AES is a highly surface-sensitive technique. It is usually the outermost 2-6 atomic layers which are analysed. These surface-sensitive techniques are very prone to interference from absorbed contaminants. Careful handling of the sample between preparation in the electrochemical cell and the characterization experiment is therefore most important. AES is quantitative only to 50% (60). Electron microprobe analysis (EPMA) provides much more accurate quantitative data. 

---