Quantitative Surface Analysis by XPS (X-Ray Photoelectron Spectroscopy): Application to Hydrotreating Catalysts — XPS is an ideal technique to provide the chemical composition of the extreme surface of solid materials, vastly applied to the study of catalysts. In this article, we will show that a quantitative approach, based upon fundamental expression of the XPS signal, has enabled us to obtain a consistent set of response factors for the elements of the periodic table. In- depth spadework has been necessary to know precisely the transmission function of the spectrometer used at IFP. The set of response factors obtained enables to perform, on a routine basis, a quantitative analysis with approximately 20% relative accuracy, which is quite acceptable for an analysis of such a nature. While using this quantitative approach, we have developed an analytical method specific to hydrotrea - ting catalysts that allows obtaining the sulphiding degree of molybdenum quite reliably and reproduci - bly. The usage of this method is illustrated by two examples for which XPS spectroscopy has provided with information sufficiently accurate and quantitative to help understand the reactivity differences bet - ween certain MoS 2 /Al 2 O 3 or NiMoS/Al 2 O 3 -type hydrotreating catalysts.

XPS is an ideal technique to provide the chemical composition of the extreme surface of solid materials, vastly applied to the study of catalysts. In this article, we will show that a quantitative approach, based upon fundamental expression of the XPS signal, has enabled us to obtain a consistent set of response factors for the elements of the periodic table. In-depth spadework has been necessary to know precisely the transmission function of the spectrometer used at IFP. The set of response factors obtained enables to perform, on a routine basis, a quantitative analysis with approximately 20% relative accuracy, which is quite acceptable for an analysis of such a nature. While using this quantitative approach, we have developed an analytical method specific to hydrotreating catalysts that allows obtaining the sulphiding degree of molybdenum quite reliably and reproducibly. The usage of this method is illustrated by two examples for which XPS spectroscopy has provided with information sufficiently accurate and quantitative to help understand the reactivity differences between certain MoS2/Al2O3 or NiMoS/Al2O3-type hydrotreating catalysts.

A procedure for determination of the reduced thickness of the contamination layer for oxygen-inert samples was implemented. The correction algorithm is valid for the reduced thickness of a contamination layer x greater than or equal to 0.3 (x is expressed as the ratio of the layer thickness to the electron attenuation length in the contamination layer at energy 1 keV). It is shown that the linear background subtraction method traditionally used in XPS generally does not provide correct results. Application of an advanced experimental data treatment method with correction for the presence of a contamination layer to quantitative surface analysis of Al2O3, SiO2, GeO2, Fe2O3, NiO, CuO and NaF resulted in a decrease of the mean error of analysis from 27% using the elemental sensitivity factors approach to 5%.

This study is an investigation of the adhesion between poly (phenylquinoxaline) (PPQ) and gamma-aminopropyltriethoxysilane (gamma-APS)-treated silicon wafers. In order to determine the locus of failure of the PPQ film-coated wafers, when the coating was mechanically removed from the surface, the surface-sensitive techniques of X-ray photoelectron spectroscopy and contact angle measurements were employed. This permitted an analysis of the surface that was exposed when the film was removed from the substrate. In addition, FTIR spectroscopy was used to study the effect of the thermal treatment of the film-coated wafers on the silane layer. Treatment of the coated wafers up to temperatures in excess of 250 degrees C caused a deterioration of the gamma-APS layer, leading to a loss in adhesion of the coating, which was likely a result of the decrease in the density of the PPQ chains, which become anchored in the silane layer as the silanol groups condense during curing. When treatment temperatures are allowed to reach 400 degrees C, the silane layer becomes severely degraded. It was found that the locus of failure remained the same, regardless of whether or not the coated wafer was subjected to aging in boiling water. (C) 1993 John Wiley and Sons, Inc.