Arsenopyrite: a spectroscopic investigation of altered surfaces

1989 ◽  
Vol 53 (370) ◽  
pp. 223-229 ◽  
Author(s):  
S. Richardson ◽  
D. J. Vaughan
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ammonium Hydroxide ◽  
Binding Energies ◽  
Spectroscopic Techniques ◽  
Xps Spectra ◽  
Natural Systems ◽  
Surface Alteration ◽  
Core Electrons ◽  
Ph Conditions ◽  
Iron Sulphates

AbstractSurfaces of a natural sample of arsenopyrite (FeAsS) were oxidized by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The oxidants used were air during heating to relatively low temperatures (150°C), steam, ammonium hydroxide, hydrogen peroxide, and sulphuric acid. Electrochemical oxidation in water was also undertaken. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and spectral reflectance measurements, were used to characterize the surface compositions. New data are proposed for the binding energies of core electrons in arsenopyrite based on the fitted XPS spectra: 706.9 eV for the Fe 2p3/2 level, 161.2 eV for the S 2p level, and 40.7eV for the As 3d level. Spectroscopic analyses of the surfaces following oxidation indicated a range of iron oxides and hydroxides (Fe1−xO, Fe3O4, Fe2O3, FeOOH and Fe(OH)3), arsenic oxides (As2O3 and As2O5), sulphur and iron sulphates (FeSO4, Fe2(SO4)3). The relative proportions of the different phases present in the surface layer are related to the strength of the oxidant employed and, where relevant, the Eh/pH conditions prevalent during oxidation. The conclusions regarding the nature of the oxidation of arsenopyrite are discussed in relation to arsenopyrite extraction by flotation and leaching, and the breakdown of arsenopyrite in natural systems.

Surface alteration of pentlandite and spectroscopic evidence for secondary violarite formation

1989 ◽  
Vol 53 (370) ◽  
pp. 213-222 ◽  
Author(s):  
S. Richardson ◽  
D. J. Vaughan
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ammonium Hydroxide ◽  
Binding Energies ◽  
Spectroscopic Techniques ◽  
Xps Spectra ◽  
Surface Alteration ◽  
Core Electrons ◽  
Iron Sulphates ◽  
Reflectance Measurements ◽  
Nickel Enrichment

AbstractSynthetic pentlandite surfaces were subjected to oxidation by a range of inorganic oxidants, and the resultant alteration of the surface studied by a range of surface-sensitive spectroscopic techniques. The oxidants used were air during heating to relatively low temperatures (150°C), steam, ammonium hydroxide, hydrogen peroxide, and sulphuric acid. Electrochemical oxidation was also undertaken. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), conversion electron Mössbauer spectroscopy (CEMS), and spectral reflectance measurements were used to characterize the surface compositions. New data for the binding energies of core electrons in pentlandite and violarite, based on the fitted XPS spectra, are proposed. For pentlandite and violarite respectively, values of 707.3 eV and 708.4 eV for the Fe 2p3/2, 853.0 eV and 853.2 eV for the Ni 2p3/2, and 161.2 eV for the S 2p in both sulphides, were obtained. After oxidation the pentlandite surfaces indicated nickel enrichment in the subsurface, with the formation of violarite. The immediate oxidized surface, of approximately 10Å thickness, indicated a range of iron oxides and hydroxides (Fe3O4, Fe2O3 and FeOOH, with possible Fe1−xO and Fe(OH)3), nickel oxide (NiO), and iron sulphates (FeSO4, Fe2(SO4)3). The proportions of the phases present in the surface layer are inferred to be a consequence of both the strength of the oxidant employed, and the thermodynamic stability of the phases, as can be illustrated using partial pressure and Eh/pH diagrams. A sequence of oxidation is proposed, accounting for the sub-surface enrichment in violarite, and the development of the oxidized surface, which is inferred to have a major affect on the rates of oxidation.

Theoretical core spectroscopy of molecules interacting with ice surfaces 

2021 ◽  
Author(s):  
Richard Asamoah Opoku
Keyword(s):  
Electronic Properties ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Trace Gases ◽  
Binding Energies ◽  
Photoelectron Spectra ◽  
Development Fund ◽  
Xps Spectra ◽  
The Core ◽  
Ice Surfaces

<p><strong>Céline TOUBIN</strong><strong><sup>2</sup></strong><strong> and </strong><strong>André Severo Pereira GOMES</strong><strong><sup> 3</sup></strong></p><p><sup>2,3</sup> Laboratoire de Physique des Lasers, des atomes et des Molécules, Université de Lille, Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France</p><p>E-mail : [email protected]<sup>2</sup> ; [email protected]<sup>3</sup></p><p>Ice plays an essential role as a catalyst for reactions between atmospheric trace gases. The uptake of trace gases to ice has been proposed to have a major impact on geochemical cycles, human health, and ozone depletion in the stratosphere [1]. X-ray photoelectron spectroscopy (XPS) [2], serves as a powerful technique to characterize the elemental composition of such interacting species due to its surface sensitivity. Given the existence of complex physico-chemical processes such as adsorption, desorption, and migration within ice matrix, it is important to establish a theoretical framework to determine the electronic properties of these species under different conditions such as temperature and concentration. The focus of this work is to construct an embedding methodology employing Density Functional (DFT) and Wave Function Theory (WFT) to model and interpret photoelectron spectra of adsorbed halogenated species on ice surfaces at the core level with the highest accuracy possible. </p><p>We make use of an embedding approach utilizing full quantum mechanics to divide the system into subunits that will be treated at different levels of theory [3].</p><p>The goal is to determine core electron binding energies and the associated chemical shifts for the adsorbed halogenated species such as molecular HCl and the dissociated form Cl- at the surface and within the uppermost bulk layer of the ice respectively [4]. The core energy shifts are compared to the data derived from the XPS spectra [4].</p><p>We show that the use of a fully quantum mechanical embedding method, to treat solute-solvent systems is computationally efficient, yet accurate enough to determine the electronic properties of the solute system (halide ion) as well as the long-range effects of the solvent environment (ice).</p><p>We acknowledge support by the French government through the Program “Investissement d'avenir” through the Labex CaPPA (contract ANR-11-LABX-0005-01) and I-SITE ULNE project OVERSEE (contract ANR-16-IDEX-0004), CPER CLIMIBIO (European Regional Development Fund, Hauts de France council, French Ministry of Higher Education and Research) and French national supercomputing facilities (grants DARI x2016081859 and A0050801859).</p><p> </p>

XPS and AES Study of Oxygen Interaction on the Surface of the ZrNi Intermetallic Compound

2012 ◽  
Vol 445 ◽  
pp. 709-713 ◽  
Author(s):  
A. Roustila ◽  
A. Rabehi ◽  
M. Souici ◽  
J. Chene
Keyword(s):  
Intermetallic Compound ◽  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Chemical Properties ◽  
Binding Energies ◽  
Ultra High Vacuum ◽  
Ion Sputtering ◽  
Xps Spectra ◽  
Preferential Sputtering ◽  
Application Fields

ZrNi intermetallic compound is used in several application fields due to its very favorable characteristics for the storage of hydrogen. The hydrogen reactions are important, it is vital to examine the evolution of physico-chemical properties at the surface. X-ray photoelectron spectroscopy, is used to follow the evolution of electronic properties of ZrNi versus the ion sputtering in ultra high vacuum in the range 300-600°C. Morever, the evolution of species concentrations at the surface of ZrNi in the range 100-700°C is followed by means of Auger electron spectroscopy. The present results show that temperature and ion sputtering favor significant changes in surface properties of ZrNi. In situ annealing of ZrNi favors the oxygen decontamination associated with segregation of zirconium metal on the surface. The values of binding energies deduced from the reconstruction of XPS spectra, allowed the identification of species present at the surface. The results indicate that nickel is not contaminated and all the obtained sub-oxides are related to bonding states of oxygen with zirconium (Zr2O, ZrO, ZrO2and Zr2O3). The ion sputtering of the surface of ZrNi causes preferential sputtering phenomenon. The later results from the removal of surface layers and from the appearance of zirconium oxide layers initially present on the surface. The results obtained by AES show the segregation of impurities (oxygen and carbon) and of zirconium on the surface of ZrNi. AES observations of Zr segregation start to be important above 300°C and this is in agreement with XPS analysis showing a Zr enrichment of the surface of ZrNi.

XPS and XRD Studies of Samples from the Natural Fission Reactors in the Oklo Uranium Deposits

1993 ◽  
Vol 333 ◽  
Author(s):  
S. Sunder ◽  
N.H. Miller ◽  
A.M. Duclos
Keyword(s):  
Oxidation State ◽  
Photoelectron Spectroscopy ◽  
Xrd Analysis ◽  
Binding Energies ◽  
Uranium Deposits ◽  
Xps Spectra ◽  
X Ray ◽  
Two Samples ◽  
Reactor Zone ◽  
Fission Reactors

ABSTRACTMineral samples from the natural fission reactors 10 and 13 in the Oklo uranium deposits were studied using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to gain information about the long-term behaviour of UO2 fuel in a geological disposal vault. Two samples from reactor zone 10 (samples # D81N-190292 and D73-88) and one sample from reactor zone 13 (sample # SD37-S2/CD) were analysed. Low-resolution XPS spectra were recorded to determine the major elements present in the ore. High-resolution spectra were recorded to gain information about the chemical state of the elements present in the mineral samples. The samples show low values for the U6+/U4+ ratio. The oxidation state of uranium in these samples is even lower than that in U409. The binding energies of the Pb 4f bands indicate most of the Pb is in the +2 oxidation state in these samples. The C Is band indicates the presence of organic carbon. XRD analysis shows that the main uranium-bearing phase is uraninite and lead is present mainly as galena. The significance of the results for nuclear fuel waste management is discussed.

scholarly journals Deposit of AlN thin films by nitrogen reactive pulsed laser ablation using an Al target

2019 ◽  
Vol 65 (4 Jul-Aug) ◽  
pp. 345 ◽  
Author(s):  
F. Chale-Lara ◽  
M. Zapata-Torres ◽  
F. Caballero-Briones ◽  
W. De la Cruz ◽  
N. Cruz Gonzalez ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Photoelectron Spectroscopy ◽  
Hexagonal Phase ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Nitrogen Pressure ◽  
Binding Energies ◽  
Xps Spectra ◽  
X Ray

We report the synthesis of AlN hexagonal thin films by pulsed laser ablation, using Al target in nitrogen ambient over natively-oxidized Si (111) at 600°C. Composition and chemical state were determined by X-ray photoelectron spectroscopy (XPS); while structural properties were investigated using X-ray diffraction (XRD). High-resolution XPS spectra present a gradual shift to higher binding energies on the Al2ppeak when nitrogen pressure is incremented, indicating the formation of the AlN compound. At 30 mTorr nitrogen pressure, theAl2p peak corresponds to AlN, located at 73.1 eV, and the XRD pattern shows a hexagonal phase of AlN. The successful formation of the AlN compound is corroborated by UV-Vis reflectivity measurements.

scholarly journals Enhancement of Electrical Property of Carbon Nanotube by Silicon Incorporation

2020 ◽  
Vol 10 (1) ◽  
pp. 62-65
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Photoelectron Spectroscopy ◽  
Chemical Vapor ◽  
Binding Energies ◽  
Xps Spectra ◽  
X Ray ◽  
Conductivity Increase ◽  
Vapor Deposition Technique ◽  
Si Content

Silicon incorporated carbon nano tube has been synthesized by radio frequency plasma enhanced chemical vapor deposition technique with acetylene gas. Tetraethyl orthosilicate solution was used for the synthesis of silicon incorporation in the CNT thin films. Energy dispersive X-ray analysis shows that the Si atomic percentage in the CNT thin films varied from 0 % to 3.82 %. The different chemical binding energies of carbon and silicon were analyzed from X-ray photoelectron spectroscopy spectra. In the XPS spectra, the peaks at ~531 eV, ~ 285 eV, ~151 eV and ~100 eV are the contributions from O 1s, C 1s, Si 2s and Si 2p respectively. Nanostructure morphologies of the Si-CNT thin films have been analyzed by field emission scanning electron microscopy. The length of the silicon incorporated carbon nano tubes ~100 nm and corresponding diameter ~20 nm. The increase of atomic percentage of Si in the CNT thin films, room temperature electrical conductivity increases. The electrical conductivity increase from 3.87x103 to 4.49x104 S cm-1 as the silicon atomic percentage in the CNT thin films increases from 0 to 3.82 % respectively. This study showed that the Si-CNTs thin films potentially useful in electrical application of varying its conductivity by changing the Si content independently from other parameters

scholarly journals Enhancing electrical properties of carbon nanotubes thin films by silicon incorporation

2021 ◽  
Vol 1206 (1) ◽  
pp. 012028
Author(s):  
Sk Faruque Ahmed ◽  
Mohibul Khan ◽  
Nillohit Mukherjee
Keyword(s):  
Thin Films ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Binding Energies ◽  
Xps Spectra ◽  
X Ray ◽  
Vapor Deposition Technique

Abstract Silicon incorporated carbon nanotube (Si-CNTs) thin films was prepared by radio frequency plasma enhanced chemical vapor deposition technique. Tetraethyl orthosilicate solution was used for incorporation of silicon in CNTs thin films. Energy dispersive X-ray analysis shows that the silicon atomic percentage was varied from 0 % to 6.1 %. The chemical binding energies of carbon and silicon were analyzed from X-ray photoelectron spectroscopy data. The various peaks at ~531 eV, ~ 285 eV, ~155 eV and ~104 eV was observed in the XPS spectra due to the oxygen, carbon and silicon respectively. Surface morphologies of Si-CNTs thin films have been analyzed by field emission scanning electron microscopy, which revels that the length of the silicon incorporated carbon nanotubes ~500 nm and corresponding diameter ~80 nm. The room temperature electrical conductivity was increased whereas the activation energy was decreased with the increase of atomic percentage of silicon in Si-CNTs thin films. The room temperature electrical conductivity was increased from 4.3 × 103 to 7.1 × 104 S cm−1 as the silicon atomic percentage in Si-CNTs thin films increases from 0 to 6.1 % respectively.

scholarly journals Investigation of Approaches to Control the Compositions of Zn(Se,OH) Buffers Prepared by Chemical Bath Deposition Process for Cu(In,Ga)Se2 (CIGS) Solar Cells

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 343 ◽  
Author(s):  
Chia-Hua Huang ◽  
Yueh-Lin Jan ◽  
Wen-Jie Chuang ◽  
Po-Tsung Lu
Keyword(s):  
Chemical Bath Deposition ◽  
Photoelectron Spectroscopy ◽  
Ammonium Hydroxide ◽  
Soda Lime ◽  
Deposition Process ◽  
Bath Temperature ◽  
Binding Energies ◽  
Soda Lime Glass ◽  
Zinc Hydroxide ◽  
Absorption Data

We deposited zinc-based films with various ammonia (ammonium hydroxide; NH4OH) and selenourea concentrations, at the bath temperature of 80 °C, on soda-lime glass substrates using the chemical bath deposition (CBD) process. We analyzed the results using X-ray photoelectron spectroscopy (XPS), which showed binding energies of zinc, selenium, and oxygen. The as-deposited films, containing zinc selenide, zinc oxide, and zinc hydroxide, were also verified. The films prepared in this investigation can be referred to a zinc compound, characterized as Zn(Se,OH). A conformal coverage of the Zn(Se,OH) films, with the smooth surface morphologies, was obtained by optimizing the ammonia or selenourea concentrations in the deposition solutions. The Zn(Se,OH) films had a preferred (111) orientation, corresponding to a cubic crystal structure. The bandgap energies of the as-deposited Zn(Se,OH) films were determined from the optical absorption data, suggesting a dependence of the bandgap energies on the atomic percentages of ZnSe, Zn(OH)2 and ZnO in the films. The same variation tendency of the compositions and the bandgap energies for the films, deposited with an increment in the ammonia or selenourea concentrations was achieved, attributing to the facilitation of ZnSe formation. These results show that the compositions, and therefore the bandgap energies, can be controlled by the ammonia concentrations, or selenourea concentrations.

STUDY OF Ba CORE LEVEL BINDING ENERGIES IN A YBa2Cu3O~7 THIN FILM

1993 ◽  
Vol 07 (08) ◽  
pp. 555-564 ◽  
Author(s):  
P. SRIVASTAVA ◽  
N. L. SAINI ◽  
B. R. SEKHAR ◽  
S. K. SHARMA ◽  
H. S. CHAUHAN ◽  
...  
Keyword(s):  
Thin Film ◽  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Binding Energies ◽  
Core Level ◽  
Energy Component ◽  
Xps Spectra ◽  
X Ray ◽  
Energy Components

A thin film of superconducting YBa 2 Cu 3 O ~7 (YBCO) system (Tc ~ 89 K ) has been studied by x-ray photoelectron spectroscopy (XPS) to investigate the core level electronic structure. The Ba 3d and 4d core level XPS spectra show three binding energy components with the high binding energy component originating from the non-superconducting surface of the system. The role of oxygen ordering/disordering has been discussed to explain the origin of the other two bulk-dependent components. An attempt has been made to resolve some of the discrepancies in the Ba core level spectra reported earlier.

scholarly journals Optical, XPS and XRD Studies of Semiconducting Copper Sulfide Layers on a Polyamide Film

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Valentina Krylova ◽  
Mindaugas Andrulevičius
Keyword(s):  
Photoelectron Spectroscopy ◽  
Copper Sulfide ◽  
Diffusion Method ◽  
X Ray Diffraction ◽  
Xps Spectra ◽  
X Ray ◽  
Xrd Studies ◽  
Polyamide Film ◽  
Indirect Band Gap ◽  
Xrd Method

Copper sulfide layers were formed on polyamide PA 6 surface using the sorption-diffusion method. Polymer samples were immersed for 4 and 5 h in 0.15 mol⋅  solutions and acidified with HCl (0.1 mol⋅) at . After washing and drying, the samples were treated with Cu(I) salt solution. The samples were studied by UV/VIS, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. All methods confirmed that on the surface of the polyamide film a layer of copper sulfide was formed. The copper sulfide layers are indirect band-gap semiconductors. The values of are 1.25 and 1.3 eV for 4 h and 5 h sulfured PA 6 respectively. Copper XPS spectra analyses showed Cu(I) bonds only in deeper layers of the formed film, while in sulfur XPS S 2p spectra dominating sulfide bonds were found after cleaning the surface with ions. It has been established by the XRD method that, beside , the layer contains as well. For PA 6 initially sulfured 4 h, grain size forchalcocite, , was  nm and fordjurleite, , it was 54.17 nm. The sheet resistance of the obtained layer varies from 6300 to 102 .

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