scholarly journals Sulfur-bearing monazite-(Ce) from the Eureka carbonatite, Namibia: oxidation state, substitution mechanism, and formation conditions

2019 ◽  
Vol 84 (1) ◽  
pp. 35-48 ◽  
Author(s):  
Sam Broom-Fendley ◽  
Martin P Smith ◽  
Marcelo B Andrade ◽  
Santanu Ray ◽  
David A Banks ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Photoelectron Spectra ◽  
Precipitation Mechanism ◽  
X Ray ◽  
Charge Imbalance ◽  
Substitution Mechanism ◽  
Heavy Rare Earth Elements ◽  
Coupled Substitution ◽  
Formation Conditions ◽  
Type Substitution

AbstractSulfur-bearing monazite-(Ce) occurs in silicified carbonatite at Eureka, Namibia, forming rims up to ~0.5 mm thick on earlier-formed monazite-(Ce) megacrysts. We present X-ray photoelectron spectroscopy data demonstrating that sulfur is accommodated predominantly in monazite-(Ce) as sulfate, via a clino-anhydrite-type coupled substitution mechanism. Minor sulfide and sulfite peaks in the X-ray photoelectron spectra, however, also indicate that more complex substitution mechanisms incorporating S2– and S4+ are possible. Incorporation of S6+ through clino-anhydrite-type substitution results in an excess of M2+ cations, which previous workers have suggested is accommodated by auxiliary substitution of OH– for O2–. However, Raman data show no indication of OH–, and instead we suggest charge imbalance is accommodated through F– substituting for O2–. The accommodation of S in the monazite-(Ce) results in considerable structural distortion that may account for relatively high contents of ions with radii beyond those normally found in monazite-(Ce), such as the heavy rare earth elements, Mo, Zr and V. In contrast to S-bearing monazite-(Ce) in other carbonatites, S-bearing monazite-(Ce) at Eureka formed via a dissolution–precipitation mechanism during prolonged weathering, with S derived from an aeolian source. While large S-bearing monazite-(Ce) grains are likely to be rare in the geological record, formation of secondary S-bearing monazite-(Ce) in these conditions may be a feasible mineral for dating palaeo-weathering horizons.

scholarly journals Modification of Wood with Monoethanolamino-borate by The Data of X-Ray Photoelectron Spectroscopy

2018 ◽  
Vol 196 ◽  
pp. 04005
Author(s):  
Irina Stepina ◽  
Irina Kotlyarova
Keyword(s):  
Particle Size ◽  
Photoelectron Spectroscopy ◽  
Model Compound ◽  
Hydrolytic Stability ◽  
Photoelectron Spectra ◽  
Wood Cellulose ◽  
Rapid Loss ◽  
X Ray ◽  
Wood Protection ◽  
Cellulose Materials

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

scholarly journals Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 202
Author(s):  
Miranda Martinez ◽  
Anil R. Chourasia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Interaction ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Increasing Trend ◽  
Substrate Temperatures ◽  
Beam Technique

The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

X-Ray photoelectron spectroscopy of monosubstituted perfluorobenzenes

1977 ◽  
Vol 55 (8) ◽  
pp. 1279-1284 ◽  
Author(s):  
Barry C. Trudell ◽  
S. James W. Price
Keyword(s):  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Binding Energies ◽  
Photoelectron Spectra ◽  
Atomic Charges ◽  
X Ray ◽  
Sophisticated Analysis ◽  
Charge Calculations

The gas phase X-ray photoelectron spectra, XPS, were observed for the series C6F5X (X = F, Cl, I, Br, H). Binding energies were determined from the spectra using the ESCAPLOT Program. Charge calculations were carried out using Equalization of Electronegativity, CNDO/2, and ACHARGE approaches on each molecule. The more sophisticated analysis leads to the following equation correlating the (C 1s) binding energies and the atomic charges qi[Formula: see text]

X-Ray Photoelectron Spectroscopic Studies of Palladium Dispersed on Carbon Surfaces Modified by Ion Beams and Plasmatic Oxidation

1995 ◽  
Vol 60 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Zdeněk Bastl
Keyword(s):  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Surface Coverage ◽  
Spectroscopic Studies ◽  
Core Level ◽  
Graphite Surface ◽  
Photoelectron Spectra ◽  
Surface Layers ◽  
X Ray ◽  
Core Level Binding Energy

The effects of ion bombardment and r.f. plasma oxidation of graphite surfaces on subsequent growth and electronic properties of vacuum deposited palladium clusters have been investigated by methods of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy with X-ray excitation (XAES). Due to the significantly increased density of surface defects on which the nucleation process occurs the bulk value of the Pd 3d core level binding energy is achieved at higher surface coverage by palladium on bombarded surfaces than on ordered graphite. Angle resolved photoelectron spectra of oxidized graphite surfaces reveal significant embedding of oxygen in graphite surface layers. The C 1s and O 1s photoelectron spectra are consistent with presence of two major oxygen species involving C-O and C=O type linkages which are not homogeneously distributed within the graphite surface layers. Two effects were observed on oxidized surfaces: an increase of palladium dispersion and interaction of the metal clusters with surface oxygen groups. Using the simple interpretation of the modified Auger parameter the relaxation and chemical shift contributions to the measured Pd core level shifts are estimated. In the region of low surface coverage by palladium the effect of palladium-oxygen interaction on Pd core level binding energy exceeds the effects of increased dispersity.

Analysis of X-ray Photoelectron Spectra through Their Even Derivatives

1979 ◽  
Vol 33 (5) ◽  
pp. 502-509 ◽  
Author(s):  
Attila E. Pavlath ◽  
Merle M. Millard
Keyword(s):  
Curve Fitting ◽  
Photoelectron Spectroscopy ◽  
Least Square ◽  
Photoelectron Spectra ◽  
Original Position ◽  
Noise Background ◽  
X Ray ◽  
Fitting Procedures ◽  
Higher Derivatives ◽  
Derivatives Of

The analysis of organic and inorganic surfaces can be carried out very effectively with the aid of x-ray photoelectron spectroscopy. In many cases, however, the presently available methods and techniques for data treatment resolutions are not suitable for the qualitative and quantitative identification of the various forms of a given atom on the same surface. The number of components and a good approximation of their original position in the composite curve must be known to use the available curve fitting procedures, otherwise the evaluation can be unreliable. It is suggested that the second and higher even derivatives of the composite could provide these data. The possibility of applying even derivatives of composite curves in combination with a nonlinear least square curve fitting program was investigated. It was found that depending on the noise background of the spectra, the resolution could be improved through this method. The resolution is dependent on the half-width of the component curves, their separation, and ratio. Both Gaussian and Lorentzian curves can be resolved, but the resolution of the latter is easier. The resolution is increasing with higher derivatives; however, increased smoothing must be applied at each step to neutralize the influence of the noise background.

scholarly journals Structural and X-Ray Photoelectron Spectroscopy Study of Al-Doped Zinc-Oxide Thin Films

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Bong Ju Lee ◽  
Ho Jun Song ◽  
Jin Jeong
Keyword(s):  
Thin Films ◽  
Zinc Oxide ◽  
Flow Rate ◽  
Photoelectron Spectroscopy ◽  
Gas Flow ◽  
Rf Magnetron Sputtering ◽  
Photoelectron Spectra ◽  
Gas Flow Rate ◽  
X Ray ◽  
Oxide Component

Al-doped zinc-oxide (AZO) thin films were prepared by RF magnetron sputtering at different oxygen partial pressures and substrate temperatures. The charge-carrier concentrations in the films decreased from 1.69 × 1021to 6.16 × 1017 cm−3with increased gas flow rate from 7 to 21 sccm. The X-ray diffraction (XRD) patterns show that the (002)/(103) peak-intensity ratio decreased as the gas flow rate increased, which was related to the increase of AZO thin film disorder. X-ray photoelectron spectra (XPS) of the O1s were decomposed into metal oxide component (peak A) and the adsorbed molecular oxygen on thin films (peak B). The area ratio of XPS peaks (A/B) was clearly related to the stoichiometry of AZO films; that is, the higher value of A/B showed the higher stoichiometric properties.

scholarly journals On the early stages of localised atmospheric corrosion of magnesium–aluminium alloys

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. Shahabi-Navid ◽  
Y. Cao ◽  
J. E. Svensson ◽  
A. Allanore ◽  
N. Birbilis ◽  
...  
Keyword(s):  
Magnesium Alloys ◽  
Photoelectron Spectroscopy ◽  
Aluminium Alloys ◽  
Atmospheric Corrosion ◽  
Surface Film ◽  
Pure Magnesium ◽  
X Ray Diffraction ◽  
Precipitation Mechanism ◽  
X Ray ◽  
Film Thinning

AbstractThe surface film on pure magnesium and two aluminium-containing magnesium alloys was characterised after 96 h at 95% RH and 22 °C. The concentration of CO2 was carefully controlled to be either 0 or 400 ppm. The exposed samples were investigated using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electron microscopy. The results showed that when the alloys were exposed to the CO2-containing environment, aluminium cations (Al3+) was incorporated into a layered surface film comprising a partially “hydrated” MgO layer followed by Mg(OH)2, and magnesium hydroxy carbonates. The results indicated that aluminium-containing magnesium alloys exhibited considerably less localised corrosion in humid air than pure magnesium. Localised corrosion in the materials under investigation was attributed to film thinning by a dissolution/precipitation mechanism.

Synthesis of Ferromagnetic Germanides in 40Ge/60Mn Films: Magnetic and Structural Properties

2014 ◽  
Vol 215 ◽  
pp. 167-172
Author(s):  
Victor G. Myagkov ◽  
A.A. Matsunin ◽  
Y.L. Mikhlin ◽  
Victor S. Zhigalov ◽  
Liudmila E. Bykova ◽  
...  
Keyword(s):  
Solid State ◽  
Curie Temperature ◽  
Photoelectron Spectroscopy ◽  
Magnetic Measurements ◽  
Atomic Ratio ◽  
Photoelectron Spectra ◽  
Solid State Reactions ◽  
Ferromagnetic Phase ◽  
X Ray Diffraction ◽  
X Ray

Solid-state reactions between Ge and Mn films are systematically examined using X-ray diffraction, photoelectron spectroscopy and magnetic measurements. The films have a nominal atomic ratio Ge:Mn = 40:60 and are investigated at temperatures from 50 to 500 °С. It is established that after annealing at ~120 °С, the ferromagnetic Mn5Ge3 phase is the first phase to form at the 40Ge/60Mn interface. Increasing the annealing temperature to 500 °С leads to the formation of the ferromagnetic phase with a Curie temperature TC ~ 360 K and magnetization MS ~ 140-200 emu/cc at room temperature. Analysis of X-ray diffraction patterns and the photoelectron spectra suggests that the increased Curie temperature and magnetization are related to the migration of C and O atoms into the Mn5Ge3 lattice and the formation of the Nowotny phase Mn5Ge3СxOy. The initiation temperature (~120 °С) of the Mn5Ge3 phase is the same both for solid-state reactions in Ge/Mn films, as well as for phase separation in GexMn1-x diluted semiconductors. We conclude that the synthesis of the Mn5Ge3 phase is the moving force for the spinodal decomposition of the GexMn1-x diluted semiconductors.

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