Synchrotron Radiation-based X-ray Diffraction Research Articles

In situ analysis of the nucleation of O- and Zn-polar ZnO nanowires using synchrotron-based X-ray diffraction.

The selection of the polarity of ZnO nanowires grown by chemical bath deposition offers a great advantage for their integration into a wide variety of engineering devices. However, the nucleation process of ZnO nanowires and its dependence on their polarity is still unknown despite its importance for optimizing their morphology and properties and thus to enhance the related device performances. To tackle this major issue, we combine an in situ analysis of the nucleation process of O- and Zn-polar ZnO nanowires on O- and Zn-polar ZnO single crystals, respectively, using synchrotron radiation-based grazing incidence X-ray diffraction with ex situ transmission and scanning electron microscopy. We show that the formation of ZnO nanowires obeys three successive phases from the induction, through nucleation to growth phases. The characteristics of each phase, including the nucleation temperature, the shape and dimension of nuclei, as well as their radial and axial development are found to depend on the polarity of ZnO nanowires. A comprehensive description reporting the dominant physicochemical processes in each phase and their dependence on the polarity of ZnO nanowires is presented, revisiting their formation process step-by-step. These findings provide a deeper understanding of the phenomena at work during the growth of ZnO nanowires by chemical bath deposition and open the perspective to develop a more accurate control of their properties at each step of the formation process.

The Influence of the Soaking Temperature Rotary Forging and Solution Heat Treatment on the Structural and Mechanical Behavior in Ni-Rich NiTi Alloy.

The structural and thermophysical characteristics of an Ni-rich NiTi alloy rod produced on a laboratory scale was studied. The soak temperature of the solution heat-treatment steps above 850 °C taking advantage of the precipitate dissolution to provide a matrix homogenization, but it takes many hours (24 to 48) when used without thermomechanical steps. Therefore, the suitable reheating to apply between the forging process steps is very important, because the product’s structural characteristics are dependent on the thermomechanical processing history, and the time required to expose the material to high temperatures during the processing is reduced. The structural characteristics were investigated after solution heat treatment at 900 °C and 950 °C for 120 min, and these heat treatments were compared with as-forged sample structural characteristics (one hot deformation step after 800 °C for a 30 min reheat stage). The phase-transformation temperatures were analyzed through differential scanning calorimetry (DSC), and the structural characterization was performed through synchrotron radiation-based X-ray diffraction (SR-XRD) at room temperature. It was observed that the solution heat treatment at 950 °C/120 min presents a lower martensitic reversion finish temperature (Af); the matrix was fully austenitic; and it had a hardness of about 226 HV. Thus, this condition is the most suitable for the reheating stages between the hot forging-process steps to be applied to this alloy to produce materials that can display a superelasticity effect, for applications such as crack sensors or orthodontic archwires.

Reversible proton co-intercalation boosting zinc-ion adsorption and migration abilities in bismuth selenide nanoplates for advanced aqueous batteries

Rechargeable aqueous zinc-ion batteries present low-cost, safe, and environmentally-friendly battery technology but suffer from the limited choice of cathode materials because of the sluggish kinetics of divalent zinc-ion associated with the high adsorption and migration energy barrier. Herein, a reversible zinc/bismuth selenide mild aqueous system was demonstrated for the first time, where bismuth selenide nanoplate cathode delivers a high specific capacity of 263.2 mA h g−1 at 0.1 A g−1 and robust rate capability of 100.6 mA h g−1 even at 10 A g−1 with long-term lifespan (82.3% retention after 1000 cycles). Benefiting from the layered structure and nanoplate morphology of the bismuth selenide cathode, surface-dominated ion storage is verified by a quantitative kinetics analysis, particularly at high current rates. Notably, unlike conventional batteries with only the reversible intercalation of alkali ions into metal chalcogenides, zinc/bismuth selenide aqueous batteries possess a sequential proton and zinc-ion insertion/extraction process, identified by in situ synchrotron radiation-based X-ray diffraction. Density functional theory analysis approves the low adsorption energy and preferential embedding process of protons, and that can further optimize Zn2+ adsorption and migration abilities in bismuth selenide nanoplate, which is mainly responsible for the excellent performance.

Preparation and superconducting behavior of triammonium fulleride

The synthesis of triammonium fulleride (NH4)3C60 by ion exchange of either K3C60 or Rb3C60 with NH4Cl in absolute toluene is reported. According to the Rietveld refinement of a synchrotron radiation-based X-ray diffraction pattern, (NH4)3C60 belongs to the same structure type as both K3C60 and Rb3C60 featuring an fcc lattice with intercalated cations occupying tetrahedral and octahedral cavities of the close-packing formed by fullerene С60 spheres. The ion exchange is incomplete and the final formulation of the product is [(NH4)2.88K0.12]C60. In contrast to earlier suggestions and tabulated ionic radii values, the (NH4)3C60 crystal structure is characterized by a lattice parameter slightly smaller than that of K3C60. A similar reaction between K4C60 and NH4Cl proceeds differently involving the redox step and affords [(NH4)0.48K2.52]C60 again emphasizing the fact that ammonium and potassium in the fulleride phase tend to form substitutional solid solutions. According to low-frequency inductive method, all (NH4)3C60-related phases studied are superconducting with similar temperatures of the superconducting transition around Tc = 16.4 K.

MgO Thin Film Growth on Si(001) by Radio-Frequency Sputtering Method.

Herein, sputtering duration and annealing temperature effects on the structure and local electronic structure of MgO thin films were studied using synchrotron radiation based X-ray diffraction and X-ray absorption spectroscopic investigations. These films were grown at substrate temperature of 350 °C by varying sputtering duration from 25 min to 324 min in radio frequency (RF) sputtering method followed by post-deposition annealing at 400, 600 and 700 °C for 3 h. These films were amorphous upto certain sputtering durations, typically upto 144 min and attains crystallization thereafter. This kind of behavior was observed at all annealing temperature. The textured coefficient of crystalline films envisaged that the orientation was affected by annealing temperature. Coordination of Mg2+ ions was more distorted in amorphous films compared to crystalline films. Moreover, onset of molecular oxygen are absorbed at low annealing temperature on these films.

Enhancement of arsenopyrite bioleaching by different Fe(III) compounds through changing composition and structure of passivation layer

Ferric iron has a significant effect on the bioleaching of arsenopyrite, the most efficient way for pretreatment of arsenopyrite-bearing gold ores. Up to date, the differential effect of Fe(III) compounds on that process was rarely studied. Herein, FeCl3, Fe(NO3)3 and Fe2O3 were addressed to unravel their different promotion effects during arsenopyrite biooxidation by Sulfobacillus thermosulfidooxidans, in which the As/Fe/S speciation transformation were comprehensively analyzed mainly with synchrotron radiation-based X-ray diffraction (SR-XRD) and Fe L- and As/S K-edge X-ray absorption near edge structure (XANES) spectroscopy to detect the elimination of passivation, besides the changes in the morphology and the leaching parameters of the mineral. The results showed that, the bioleaching of arsenopyrite was efficiently promoted under addition of the Fe(III) compounds (0.6 g/L), for instance, the extraction rates of As were increased from 55% to 64–77%, the surface of arsenopyrite suffered more serious corrosion and covered with a loose and porous structure, the intermediates S0, thiosulfate and orpiment significantly decreased, and jarosites and schwertmannite increased, the remaining content of arsenopyrite was decreased from 31.5% to 21.7–5.3%. Those results indicated that, the iron/sulfur oxidation activity was enhanced and the transformation of those intermediates was accelerated by the Fe(III) compounds added. Such change intension accompanied with the promotion effect observes the order FeCl3 > Fe(NO3)3 > Fe2O3. These results reveale that the adding Fe(III) compounds, especially for FeCl3, can efficiently promote the biooxidation through removal of some intermediates from the surface of the arsenopyrite and thus optimize the pretreatment of arsenopyrite-bearing gold ores.

Insight Into the Crystallinity of Chinese Ancient Silk by Synchrotron Radiation-Based and Conventional X-ray Diffraction Methods

This study investigates the crystallinity distribution of ancient silk. Owing to the inherent multi-hierarchical structure of silk protein and the complicated structural changes that occur due to various burial environments, it is challenging but worthwhile to study ancient silk ageing behavior, which is based on the fact that ageing begins with a single fiber and then spreads to a whole fabric. Crystallinity was one of the most effective indicators found to reveal the ageing status of silk. Therefore, a synchrotron radiation-based X-ray diffraction(SR-XRD) method was employed to study the crystallinity distribution of single fibers of ancient silk unearthed from seven archaeological sites in China from historical periods including the warring states, Han dynasty, Song dynasty, and Ming dynasty. In comparison, the conventional X-ray diffraction method, which uses large amounts of samples, was also performed to determine the integral crystallinity of ancient silk. Thermal stability experiments by thermogravimetry(TG) as well as morphology observations by scanning electron microscopy(SEM) and optical microscopy(OM) all confirmed the deterioration of ancient silk. Moreover, the ageing mechanism of ancient silk was proposed with the assistance of an artificial ageing study. The results confirmed the effectiveness of SR-XRD as an ageing indicator, revealing the crystallinity distribution. This research could provide motivation to determine the deterioration status of ancient silk, and would also aid in explaining the fragility of ancient silk due to ageing.

In Situ Formation of Hierarchical Bismuth Nanodots/Graphene Nanoarchitectures for Ultrahigh-Rate and Durable Potassium-Ion Storage.

Metallic bismuth (Bi) has been widely explored as remarkable anode material in alkali-ion batteries due to its high gravimetric/volumetric capacity. However, the huge volume expansion up to ≈406% from Bi to full potassiation phase K3 Bi, inducing the slow kinetics and poor cycling stability, hinders its implementation in potassium-ion batteries (PIBs). Here, facile strategy is developed to synthesize hierarchical bismuth nanodots/graphene (BiND/G) composites with ultrahigh-rate and durable potassium ion storage derived from an in situ spontaneous reduction of sodium bismuthate/graphene composites. The in situ formed ultrafine BiND (≈3 nm) confined in graphene layers can not only effectively accommodate the volume change during the alloying/dealloying process but can also provide high-speed channels for ionic transport to the highly active BiND. The BiND/G electrode provides a superior rate capability of 200 mA h g-1 at 10 A g-1 and an impressive reversible capacity of 213 mA h g-1 at 5 A g-1 after 500 cycles with almost no capacity decay. An operando synchrotron radiation-based X-ray diffraction reveals distinctively sharp multiphase transitions, suggesting its underlying operation mechanisms and superiority in potassium ion storage application.

In Situ Structural Characterization of Functionally Graded Ni–Ti Shape Memory Alloy During Tensile Loading

A functionally graded NiTi shape memory alloy wire was investigated by in situ synchrotron radiation-based X-ray diffraction (SR-XRD) during cyclic tensile deformation. The transformation temperatures were determined by DSC and the thermomechanical behaviour was analysed by three-point bending test. The present study focussed on the localized heat treatment (Joule heat effect, reaching 300 °C, 350 and 400 °C pulses for 10 min) of NiTi wires, using an equipment that allows a large variety of graded conditions. Structural, mechanical and thermomechanical characterization is presented to get a perspective of the different types of graded functionality. A combination of two strategies has been used for the in situ analysis by SR-XRD of the tensile tests: (i) continuously following the structural evolution at one single point (at the center of the heat-treated segment) all long the load/unload cycle and (ii) scanning the full heat-treated segmentat previously defined discrete steps of the stress–strain curve. The combined information from both types of tests provided detailed information about the phase transformations taking place in different regions of the functionally graded segment, at different steps of the tensile load/unload cycle, giving a better understanding of the overall mechanical, namely the evidence of the sequence B2 ↔ R ↔ B19′ for the direct and reverse transformations.

On the Schmid's Law for the electric current-induced deformation: An in situ EBSD study

For metals and alloys, electric currents may induce atomic diffusion and morphological changes, known as the electromigration (EM) effect. Here we report the first direct application of conventional solid mechanics’ theory to predict the electric current-induced deformations based on the in situ electron backscattered diffraction and synchrotron radiation-based X-ray diffraction analyses of Cu strips under current stressing. At a given current density, the electric current-induced elastic, slip, or slip accompanying with twinning deformation in Cu strips was revealed. The Schmid's Law is well elucidating the occurrence of the electric current-induced plastic deformations, namely the slip and twinning ones. The study unveils that the electric current-induced strain and deformation can be described in the same context as for the conventional solid mechanics.

The role of cupric ions in the oxidative dissolution process of marmatite: A dependence on Cu2+ concentration

Cupric ions (Cu2+) play an important role in the oxidative dissolution process of marmatite in an acidic environment. In this work, dissolution experiments and numerous analytical techniques were utilized to investigate the role of Cu2+ in the oxidative dissolution process of marmatite in sulfuric acid. The dissolution experiments showed that the role of Cu2+ is significantly dependent on its concentration. A low Cu2+ concentration (0.25–750 mg/L) can significantly accelerate marmatite dissolution, and a relatively high Cu2+ concentration (above 1000 mg/L) can hinder marmatite dissolution. Element analysis, synchrotron radiation-based X-ray diffraction (SR-XRD) and Raman spectra of the leaching residues proved that no copper containing mineralogical phase was produced by the reactions between Cu2+ and marmatite. The X-ray photoelectron spectroscopy (XPS) analysis indicated that Cu2+ was first adsorbed on the marmatite surface and then produced Cu-S surface species. An electrochemical measurement further indicated that the adsorption of Cu2+ can remarkably enhance the electrochemical reactivity of the marmatite surface, thus catalyzing the oxidative dissolution process. However, a high percentage of Cu2+ adsorption on the marmatite surface can produce a passivation layer when the Cu2+ concentration is high in the solution, which decreases the electrochemical reactivity, thus resulting in the hinderance of the oxidative dissolution process of marmatite.

Mechanistic studies on reversible conversion reaction in Li2MnO3-carbon nanotube composite anode

Li2MnO3 is a popular cathode material in lithium-ion batteries, however in this study Li2MnO3-carbon nanotube composite is utilized as an anode material and its electrochemical reaction mechanism is systematically studied by using electrochemical, synchrotron radiation-based X-ray diffraction and absorption techniques along with the density functional calculations. This material demonstrates a significantly high initial reversible capacity of 1006.4 mAh g−1. Electrochemical characterization suggests that this unique anode material operates by a conversion reaction, involving the formation of Li2O and Mn metal. Diffraction patterns are measured at different state of charge and Pawley fitting of these patterns reveal that during lithiation Li2MnO3 initially converts into Mn3O4 and at the end of discharge, Li2O and Mn phases are formed. During delithiation, Li2MnO3 is not reversibly formed, instead [Li0.5Mn0.5]O-type phase appears after a complete electrochemical cycle. X-ray absorption spectroscopy and density functional calculations are used to confirm the validity of the electrochemical redox reaction mechanism derived from the electrochemical and diffraction measurements.

Bioleaching of chalcopyrite with different crystal phases by Acidianus manzaensis

Abstract Bioleaching of chalcopyrite with different crystal structures (α-phase, β-phase and γ-phase) by Acidianus manzaensis was comparatively studied by synchrotron radiation based X-ray diffraction (SR-XRD) and S K-edge X-ray absorption near edge structure (XANES) spectroscopy. The α-phase, β-phase and γ-phase chalcopyrite was prepared by heating original chalcopyrite at 583, 773 and 848 K, respectively. Bioleaching results showed that [Cu2+] in the leaching solution of α-phase, β-phase, γ-phase and original chalcopyrite after 10 days of bioleaching was 1.27, 1.86, 1.43 and 1.13 g/L, respectively, suggesting that β-phase had a better leaching kinetics than others. SR-XRD and XANES results indicated that jarosite and chalcopyrite were the main components in the leaching residues in all cases, and elemental sulfur formed in the early stage of bioleaching. While for β-phase and γ-phase chalcopyrite during bioleaching, bornite was produced in the initial stage of leaching, and turned into chalcocite on day 6.

Modification of poly(ethylene glycol) on the microstructure and mechanical properties of calcium silicate hydrates

With the aim of creating more sustainable building materials, calcium silicate hydrate (C-S-H), the primary binding phase in modern concrete, was integrated with poly(ethylene glycol) (PEG). At the crystal lattice scale, synchrotron radiation-based high-pressure X-ray diffraction (HP-XRD) reveals that the incorporation of PEG increases the ab-planar stiffness of C-S-H leading to a higher bulk modulus, while molecular simulation results indicate polymers are not likely intercalated into the interlayer region. At a higher length scale, nanoindentation measurements show the introduction of PEG lowers the packing density of C-S-H particles and, thus, decreases the indentation modulus. However, a high creep resistance of the C-S-H/PEG sample is still maintained, which suggests a meso-composite may form to restrict the rapid translation between neighboring calcium silicate sheets. Furthermore, 29Si nuclear magnetic resonance (NMR) shows that the presence of PEG shortens the mean chain length of C-S-H, making dimer the predominant structure.

A balance of redox and ligand-exchange processes in the reaction of H2[OsCl6] with thiourea: Isolation and characterization of a novel osmium complex [(NH2)2CSSC(NH2)2]2[OsIVCl6]Cl2·3H2O

A novel complex with the stoichiometry [(NH2)2CSSC(NH2)2]2[OsIVCl6]Cl2·3H2O (1) is isolated as a product of the reaction of H2[OsCl6] with thiourea in concentrated HCl under deliberately optimized conditions favoring a partial thiourea oxidation to α,α′-dithiobisformamidinium dication but preserving hexachloroosmate [OsCl6]2- anions. A bromide analogue [(NH2)2CSSC(NH2)2]2[OsIVBr6]Br2·3H2O 2 is afforded by a similar reaction. A counter synthesis of 1 is accomplished via the direct ion-exchange reaction between H2[OsCl6] and [S2C2(NH2)4]Cl2. Crystal structures of 1 and 2 are unambiguously established by synchrotron radiation-based single-crystal X-ray diffraction at 100 K. The two compounds are isostructural and are crystallized in the orthorhombic space group Cmcm, Z = 4. Unit cell parameters are for 1:a = 11.279(2) Å, b = 13.611(3) Å, c = 16.731(3) Å; for 2: a = 11.695(2) Å, b = 14.005(3) Å, c = 17.015(3) Å. The osmium atoms in [OsX6]2− (X = Cl or Br) anions adopt slightly distorted octahedral coordination. The α,α′-dithiobisformamidinium cations are paired into rings via the NH…Cl− hydrogen bonds. The rings are further linked into a spatial network by H-bonds with water molecules and S…Cl nonvalence interactions.

Synchrotron Radiation Based Study of the Catalytic Mechanism of Ag+ to Chalcopyrite Bioleaching by Mesophilic and Thermophilic Cultures

The catalytic mechanism of Ag+ for chalcopyrite bioleaching by mesophilic culture (at 30 °C) and thermophilic culture (at 48 °C) was investigated using synchrotron radiation-based X-ray diffraction (SR-XRD) and S K-edge and Fe L-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching experiments showed that copper extraction from chalcopyrite bioleaching by both cultures was promoted significantly by Ag+, with more serious corrosion occurring on the minerals surface. SR-XRD and XANES analyses showed that the intermediates S0, jarosite and secondary minerals (bornite, chalcocite and covellite) formed for all bioleaching experiments. For these secondary minerals, the formation of bornite and covellite was promoted significantly in the presence of Ag+ for both cultures, while Ag+ has almost no effect on the formation of chalcocite. These results provided insight into the catalytic mechanisms of Ag+ to chalcopyrite bioleaching by the mesophilic and thermophilic cultures, which are both probably due to the rapid formation of bornite by Ag+ and the conversion of bornite to covellite.

Strain-Reduction Induced Rise in Channel Temperature at Ohmic Contacts of GaN HEMTs

Operating temperature distributions in AlGaN/GaN gateless and gated devices are characterized and analyzed using the InfraScope temperature mapping system. For the first time, a substantial rise of channel temperature at the inner ends of ohmic contacts has been observed. Synchrotron radiation-based high-resolution X-ray diffraction technique combined with drift–diffusion simulations show that strain reduction at the vicinity of ohmic contacts increases electric field at these locations, resulting in the rise of lattice temperature. The thermal coupling of a high conductive tensile region at the contacts to a low conductive channel region is an origin of the temperature rise observed in both short- and long-channel gateless devices.

Macroscopic and microscopic investigation of adsorption and precipitation of Zn on γ-alumina in the absence and presence of As

Contaminants zinc (Zn) and arsenate (As) often coexist in soils. However, little is known concerning the impacts of coexisting As on Zn adsorption and precipitation on soil minerals. In the present study, adsorption and precipitation of Zn on γ-alumina in the absence and presence of arsenate was investigated employing batch experiments and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Results indicated that Zn formed edge-sharing tetrahedral surface complexes at pH 5.5 and Zn-Al LDH-like (layered double hydroxide) precipitates at pH 7.0 on the surface of γ-alumina. The presence of arsenate significantly enhanced Zn sorption densities, and remarkably changed its bonding environment. At pH 5.5, SR-XRD (Synchrotron Radiation-based X-ray Diffraction) and EXAFS showed that koettigite-like precipitate were formed in the cosorption of Zn and As on γ-alumina regardless of the addition sequence of As and Zn. At pH 7.0, when Zn was preequilibrated with γ-alumina prior to the As introduction, mixed Zn-Al LDH-like and amorphous adamite-like precipitates formed. However, when Zn and As were added simultaneously, only amorphous adamite-like precipitate was observed. Zn inner-sphere complexes and surface ternary complexes γ-alumina-As-Zn were the main outcome when As was preequilibrated firstly. Zn-arsenate precipitates could significantly decrease the concentration of Zn in aqueous solution and decrease the bioavailability and mobilization of Zn in soils.

Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate

The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab -planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c -axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach.

Magnetic properties of FeCo alloy nanoparticles synthesized through instant chemical reduction

The chemical synthesis of shape and composition controlled Fe based binary alloys has been challenging due to the highly oxidizing nature of Fe. Here, we report the physical properties of flower-like Fe50Co50 nanoparticles prepared by a unique polyol process based on the addition of precursors at the elevated temperature. The magnetic properties are correlated through synchrotron radiation based X-ray diffraction and 57Fe Mössbauer spectrometry. Transmission electron microscopy analysis exposed the flower-like morphology of the FeCo particles. The FeCo nanoparticles showed a coercivity of 440 Oe, attributed to the shape anisotropy of the flower-like shape. Room temperature Mössbauer investigation revealed hyperfine fields of 34.9 and 36.7 T, suggesting two different Fe environments in the disordered state. Mössbauer analysis also showed the presence of superparamagnetic Fe-oxide with a relative fraction of 17%.