Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Chemical state detection of dibutyl phosphate using 31P NMR chemical shift change

Abstract: Chemical shift changes of 31P NMR were investigated for dibutyl phosphate (DBP) in several polar solvents and compared with tributyl phosphate (TBP). The chemical shift differences between DBP and TBP in the same solvents were found to reflect only the intermolecular interaction on P—OH in DBP, a moiety that is not present in TBP. Acid dissociation constants, Ka, in several polar solvents were determined using such chemical shift differences of DBP. The Ka determined in pure water is in good agreement with the literature value. The intermolecular interaction between alkaline ions and DBP was also investigated using a similar method. No interactions with Na+ ion and K+ ion were detected from chemical shift change. However, ion association between the tetramethylammonium ion and the DBP− ion was detected and the complex formation constant was determined as Kc = 0.49 ± 0.02 M−1. Key words: Fourier transform nuclear magnetic resonance spectrometry, dibutyl phosphate, chemical shift, acid dissociation, intermo...

QUANTITATIVE AUGER DEPTH PROFILING OF Ni/C MULTILAYERS BY FACTOR ANALYSIS AND COMPARISON WITH T{DYN SIMULATIONS

Abstract: The paper presents the measured depth distribution of elements and of their chemical states in a Ni/C multilayered structure prepared by pulse laser deposition (PLD), the thicknesses of respective layers being dC = 1.7 nm and dNi = 2.1 nm. By simulating the sputtering process and applying factor analysis to the measured Auger depth profiles we have found that the measured depth distribution is notably affected by the process of sputtering (mainly by atomic mixing and preferential sputtering), and that nickel and most likely also carbon are contained in the multistructure in two basic chemical states, namely as pure elements and as a carbide.

Oxidation of aluminum thin films protected by ultrathin MgF 2 layers measured using spectroscopic ellipsometry and X-ray photoelectron spectroscopy

Abstract: To maintain high, broad-band reflectance, thin transparent fluoride layers, such as MgF2, are used to protect aluminum mirrors against oxidation. In this study, we present, for the first time, combined X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometric (SE) studies of aluminum oxidation as a function of MgF2 overlayer thickness (thickness 0-5 nm). Dynamic SE tracks the extent of oxide growth every ca. 2s over a period of several hours after the evaporated Al + MgF2 bilayer is removed from the deposition chamber. Aluminum oxidation changes under the fluoride layer were quantitatively verified with XPS. Changes in chemical state from Al metal to Al oxide were directly observed. Oxide growth is computed from relative XPS peak areas as corrected for electron attenuation through the MgF2 overlayer. An empirical formula fits time-dependent data for aluminum surfaces protected by MgF2 as a function of MgF2 layer thickness: aluminum-oxide thickness = kSE*log(t)+bSE. The slope depends only on MgF2 thickness, decreasing monotonically with increasing MgF2 thickness. This method of employing SE coupled with XPS can be extendable to the study of other metal/overlayer combinations.

Wetting and Interfaces in Metal-Oxide Systems: Sensitivity to Experimental Conditions

Abstract: Wetting results from a balance of the free energies of two surfaces and an interface meeting at a triple line Metal-oxide systems are in bulk chemical equilibrium if the activities of each of the components are identical in the metal, oxide and vapor phases which constitute the system The data available for wetting of oxides by metallic liquids show significant scatter because two principal parameters are not controlled: the chemical equilibrium of the system, ie the chemical state of the surfaces and the interface, and the physical state of the oxide surface Examples are presented to illustrate the manner in which these parameters can influence wetting measurements, and to facilitate comparisons among wetting data reported for various metal-oxide systems

Chemical State Analysis of Silicon-Oxygen Compounds

Abstract: Chemical states of so-called silicon monoxide, powder and evaporated films, were studied by fluorescent X-ray spectroscopy(FXS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy(AES). Si Kα and Kβ spectra show the existence of small amounts of SiOx(0