N. V. Alov

Total reflection X-ray fluorescence analysis: Physical foundations and analytical application (A review)

The current state of the art in one of the most promising techniques of X-ray spectral analysis, namely, total reflection X-ray fluorescence analysis (TXRF), is summarized. The underlying physical processes, including reflection, refraction, total external reflection (TER) of X-rays, and formation of standing waves by TER, are considered. The construction and crucial components of a modern energy-dispersive TXRF spectrometer, involving X-ray tubes, monochromators, detectors, and reflectors, are described. Examples of analytical application of TXRF are given. High efficiency of this technique for qualitative and quantitative chemical analysis of liquids and solids of various natures is demonstrated. The main research trends in surface analysis and investigation of surface layers of solids by TXRF are discussed.

Ion-beam reduction of the surface of higher oxides of molybdenum and tungsten

The process of reduction of the surface of oxides MoO3 and WO3 under irradiation by Ar+ and O2+ ions with an energy of 3 keV in high vacuum is investigated by X-ray photoelectron spectroscopy. It is shown that upon irradiation by Ar+ ions, lower and intermediate oxides and unoxidized metals are formed in the surface layers of higher oxides. Irradiation by O2+ ions mainly leads to formation of intermediate oxides with an insignificant content of lower oxides. It is found that the process of ion-beam reduction of the surface of oxides MoO3 and WO3 substantially depends on the ion type, irradiation dose, and difference in energy of the metal-oxygen bond in oxides.

Total-reflection X-ray fluorescence study of electrochemical deposition of metals on a glass-ceramic carbon electrode surface☆

Abstract The features of electrochemical deposition and co-deposition of copper, cadmium and lead from aqueous solutions on disc glass-ceramic carbon (GCC) electrode surfaces were studied by total-reflection X-ray fluorescence analysis (TXRF). This method was found to be highly sensitive to the varieties of electrodeposit morphology and depth distribution of elements on the electrode surface. It allows identification of the mechanisms of metal nucleation and growth of thin film electrodeposits. The results of the TXRF study are in good agreement with the recent data of a number of spectroscopic and microscopic methods of solid surface analysis. The polished GCC was shown to be an excellent material for preparation of the sample carriers for TXRF analysis.

Formation of binary and ternary metal deposits on glass–ceramic carbon electrode surfaces: electron-probe X-ray microanalysis, total-reflection X-ray fluorescence analysis, X-ray photoelectron spectroscopy and scanning electron microscopy study

Abstract The features of the formation of binary and ternary alloys during the electrochemical deposition and co-deposition of copper, cadmium and lead from aqueous solutions on disc glass–ceramic carbon electrode surfaces were studied by electron-probe X-ray microanalysis, total-reflection X-ray fluorescence analysis, X-ray photoelectron spectroscopy and scanning electron microscopy. The macroscopic properties of electrodeposits such as morphology, lateral distribution of the elements along the disc electrode surface and depth distribution of the elements in the electrodeposit bulk were established. The mechanisms of metal nucleation and growth of thin films of electrodeposits were discussed.

Influence of the distance between a spectrometer and sample on the intensity of X-ray fluorescence

Expressions for calculating the extreme point coordinates of focal spots of X-ray tubes and a detector’s sensitive area are found. These coordinates are used in calculations of the sample area. The dependence of the X-ray fluorescence intensity on the distance between a spectrometer and an analyzed sample is studied experimentally. The intensities of the FeKα spectral lines in iron-containing materials are calculated at different geometric parameters of a spectrometer. It is found that the distance between a sample and detector at which the maximum of the measured intensity is observed depends on the size and position of the detector and X-ray tube collimators, as well as on the relative position of the X-ray tube and detector. Recommendations on how to achieve the maximum intensity of X-ray fluorescence are proposed. The results of the present work can be used for the development of X-ray fluorescence analysis techniques applicable for free-flowing materials directly in technological processes.

Ion-beam reduction of the surface of tantalum higher oxide

The process of reduction of the surface of higher oxide Ta2O5 under irradiation by inert gas (Ar+) and chemically active gas (O2+) ions with an energy of 3 keV in high vacuum is investigated by X-ray photoelectron spectroscopy at room temperature. It is found that intermediate oxide TaO2, lower oxide TaO, and metallic Ta form in the surface layers of Ta2O5 under Ar+ ion bombardment. An insignificant amount of intermediate oxide TaO2 forms in the surface layers of Ta2O5 under O2+ ion bombardment. Ion-beam-induced reduction of the Ta2O5 surface is shown to depend on the type of ion and irradiation dose.

Method for improving the accuracy of continuous X-ray fluorescence analysis of iron ore mixtures

The dependence of the intensity of X-ray fluorescence on the distance between the spectrometer and the test sample is studied. Changes in the intensity of primary X-radiation, absorption of X-rays by the air, and surface area of the analyzed material are calculated. An efficient method is proposed for improving the accuracy of continuous X-ray fluorescence analysis of iron ore mixtures on the conveyor belt through the exclusion of incorrect results by the dead time of the detection unit. The proposed method is universal and can be used for various loose materials.

Electron probe X-ray microanalysis of glass-ceramic carbon electrode surfaces modified by copper, cadmium and lead electrochemical co-deposition

Glass-ceramic carbon electrode surfaces modified by electrochemical co-deposition of copper, cadmium and lead from aqueous solutions were studied by electron probe X-ray microanalysis in combination with X-ray photoelectron spectroscopy and X-ray fluorescence analysis. The metal distribution on the disc electrode surface was calculated. The dependence of the element composition of the modified disc electrode surface on the absolute and relative metal concentrations in solution, the electrode diameter (cathodic current density accordingly) and the type of intermetallic interaction was established. The results of the spectroscopic investigation were compared with those predicted by theoretical electrochemistry. On the basis of the spectroscopic data, mechanisms of metal co-deposition are proposed.

Ion-beam reduction of the surface of higher niobium oxide

X-ray photoelectron spectroscopy is used to study the process of reduction of the surface of the higher oxide Nb2O5 upon bombardment with inert gas ions (Ar+) and reactive gas ions (O2+) with an energy of 1 and 3 keV in high vacuum at room temperature. It is found that, upon bombardment with Ar+ ions, the lower oxide NbO and the intermediate oxide NbO2 are formed in the surface layers of the oxide Nb2O5. Bombardment with O2+ ions leads to the formation of an extremely insignificant amount of the intermediate oxide NbO2 in the surface layers of the oxide Nb2O5. It is revealed that the process of ion-beam reduction of the surface of the oxide Nb2O5 depends on the ion type, dose, and energy of exposure.

Polymer film deposition in inductively coupled radio-frequency discharge plasma of perfluorocyclobutane mixed with sulfur hexafluoride

The effect of an SF6 admixture on the rate of formation and the composition of a polymer film deposited on a substrate in low-pressure inductively coupled radiofrequency (RF) discharge plasma of C4F8 + SF6 under the ion bombardment of the surface was studied. As found by spectroscopic measurements, the relative concentration of CF2· and C2· radicals increased as the concentration of SF6 (<40%) in the mixture was increased. As demonstrated using X-ray photoelectron spectroscopy, the F/C ratio in the film decreased with the increasing amount of SF6 and RF bias power. The mechanism of the ion-enhanced growth of a fluorocarbon film is discussed.