Cation Oxygen Research Articles

Crystal structures of catena-poly[[μ-aqua-di-aqua(μ3-2-methyl-propano-ato-κ4 O:O,O':O')calcium] 2-methyl-propano-ate dihydrate], catena-poly[[μ-aqua-di-aqua-(μ3-2-methyl-propano-ato-κ4 O:O,O':O')strontium] 2-methyl-propano-ate dihydrate] and catena-poly[[μ-aqua-di-aqua-(μ3-2-methyl-propano-ato-κ4 O:O,O':O')(calcium/strontium)] 2-methyl-propano-ate dihydrate

The crystal structures of catena-poly[[μ-aqua-di-aqua-(μ3-2-methyl-propano-ato-κ4 O:O,O':O')calcium] 2-methyl-propano-ate dihydrate], {[Ca(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (I), catena-poly[[μ-aqua-di-aqua-(μ3-2-methyl-propano-ato-κ4 O:O,O':O')strontium] 2-methyl-propano-ate dihydrate], {[Sr(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (II), and catena-poly[[μ-aqua-di-aqua-(μ3-2-methyl-propano-ato-κ4 O:O,O':O')(calcium/strontium)] 2-methyl-propano-ate dihydrate], {[(Ca,Sr)(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (III), are related. (III) can be considered as an Sr-containing solid solution of (I), with Ca2+ and Sr2+ occupationally disordered in the ratio 0.7936 (16):0.2064 (16). (I)/(III) and (II) are homeotypic with different space groups of Pbca and Cmce, respectively. All the title crystal structures are composed of hydro-philic sheets containing the cations, carboxyl-ate groups as well as water mol-ecules. The hydro-phobic layers, which consist of 2-methyl-propano-ate chains, surround the hydro-philic sheets from both sides, thus forming a sandwich-like structure extending parallel to (001). The cohesion forces within these sheets are the cation-oxygen bonds and O-H⋯O hydrogen bonds of moderate strength. Stacking of these sandwiches along [001] is consolidated by van der Waals forces. The structures contain columns defined by the cation-oxygen inter-actions in which just one symmetry-independent 2-methyl-propano-ate anion is included, together with three water mol-ecules. These mol-ecules participate in an irregular coordination polyhedron composed of eight O atoms around the cation. Additional water mol-ecules as well as the second 2-methyl-propano-ate anion are not part of the coordination sphere. These mol-ecules are connected to the above-mentioned columns by O-H⋯O hydrogen bonds of moderate strength. In (II), the Sr2+ cation, two of the coordinating water mol-ecules and both anions are situated on a mirror plane with a concomitant positional disorder of the 2-methyl-propyl groups; the non-coordinating water mol-ecule also shows positional disorder of its hydrogen atom.

Crystal structure of poly[μ-aqua-bis(μ3-2-methylpropanoato-κ4 O:O,O':O')dipotassium

The structure of the title compound, [K2(C4H7O2)2(H2O)] n , is composed of stacked sandwiches, which are formed by cation-oxygen bilayers surrounded by methyl-ethyl hydro-phobic chains. These sandwiches are held together by van der Waals inter-actions between the methyl-ethyl groups. The methyl-ethyl groups are disordered over two positions with occupancies 0.801 (3):0.199 (3). The potassium cations are coordinated by seven O atoms, which form an irregular polyhedron. There is a water mol-ecule, the oxygen atom of which is situated in a special position on a twofold axis (Wyckoff position 4e). The water H atoms are involved in Owater-H⋯Ocarbox-yl hydrogen bonds of moderate strength. These hydrogen bonds are situated within the cation-oxygen, i.e. hydro-philic, bilayer.

Fluorine-Doped LiNi0.8Mn0.1Co0.1O2 Cathode for High-Performance Lithium-Ion Batteries

For advanced lithium-ion batteries, LiNixCoyMnzO2 (x + y + z = 1) (NCM) cathode materials containing a high nickel content have been attractive because of their high capacity. However, to solve severe problems such as cation mixing, oxygen evolution, and transition metal dissolution in LiNi0.8Co0.1Mn0.1O2 cathodes, in this study, F-doped LiNi0.8Co0.1Mn0.1O2 (NCMF) was synthesized by solid-state reaction of a NCM and ammonium fluoride, followed by heating process. From X-ray diffraction analysis and X-ray photoelectron spectroscopy, the oxygen in NCM can be replaced by F− ions to produce the F-doped NCM structure. The substitution of oxygen with F− ions may produce relatively strong bonds between the transition metal and F and increase the c lattice parameter of the structure. The NCMF cathode exhibits better electrochemical performance and stability in half- and full-cell tests compared to the NCM cathode.

Directions of zero thermal expansion and the peritectic transformation in HfTiO4

The anisotropic infinitesimal coefficients of thermal expansion (CTE) and the peritectic transformation of orthorhombic-HfTiO4 (space group: pbcn, #60) to tetragonal-HfO2 (space group: P42/nmc, #137) plus liquid at 1980 °C (O-HfTiO4⇄T-HfO2+L(Hf,Ti,O)) have been studied by in-situ X-ray powder diffraction from room temperature to complete melting (~2300 °C) in air, using a Quadrupole Lamp Furnace (QLF) and a Conical Nozzle Levitator (CNL) equipped with a 400 W CO2laser. Directions of zero thermal expansion were identified in the temperature range ~25 – 580 ˚C and visualized in 3D using distorted cones and 2D stereographic projections. The directions of zero thermal expansion change as a function of temperature. The (021) pole of orthorhombic HfTiO4 was identified as having the lowest root mean squared (rms) thermal expansion, ~12 times lower than the highest rms thermal expansion direction [100] over the temperature range: 25 – 580 ˚C. The topotactic, peritectic transformation has been fully described by extracting the lattice correspondence, lattice variant deformation and a structural motif (grouping of cations) that relates the two structures at the transformation temperature. Symmetry decomposition was performed to show that the orthorhombic-HfTiO4 and tetragonal-HfO2 structures are simply related by polyhedral rotations and cation oxygen coordination changes, in addition to a slight adjustment in cation positions.

Experimental and computational studies on the solubility of carbon dioxide in protic ammonium-based ionic liquids

The solubility data of carbon dioxide (CO2) in the new synthesized protic ionic liquids (PILs), diisopropylethylammonium propanoate [DIPEA][C2COO] and diisopropylethylammonium butanoate [DIPEA][C3COO] have been measured at temperatures range from 303.2 K to 348.2 K and pressures up to 7.04 MPa with a synthetic method. The solubility of CO2 in [DIPEA][C2COO] are found to be much higher than that of [DIPEA][C3COO], about three folds, under the same temperature and pressure. The solubility data of CO2 + [DIPEA][C2COO] were correlated by using the Peng-Robinson equation of state with the temperature-dependent two-parameter van der Waals one-fluid mixing rules. Moreover, the interactions among CO2 and the PIL ions were explored by molecular dynamics (MD) simulation at ambient conditions. The effect of the dissolved CO2 in the PILs on the intermolecular hydrogen bonds between the ammonium hydrogen of the PIL cation and carboxylate oxygen of the anion was also investigated.

Cation Distribution and Magnetic Properties of Gd+3-Substituted Ni-Zn Nano-ferrites

A series of Gd+3-substituted nanocrystalline Ni-Zn ferrites Ni1-xZnxGd0.1Fe1.9O4 (0 ≤ x ≤ 1) are prepared using a low-temperature citrate auto-combustion method. The cation distribution obtained using powder x-ray diffraction demonstrates an increase in hopping length between magnetic and Zn+2 ions. Cation–oxygen vibrations are identified by FTIR spectra. Effect of Zn+2 ion on the magnetic properties at room temperature is determined from the magnetic moment measured through a vibrating sample magnetometer. The magnetic moment and saturation magnetization obey Yafet–Kittel type magnetization with the highest saturation magnetization for x = 0.2 (≈ 54 emu/g). The low squareness ratio of the samples (0.25–0.12) confirms the uniaxial anisotropy.

High-Voltage Cycling Induced Thermal Vulnerability in LiCoO2 Cathode: Cation Loss and Oxygen Release Driven by Oxygen Vacancy Migration.

The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally attributed to the phase transitions from the layered structure to spinel and rocksalt structures that contain less lattice oxygen. Here, a different degradation pathway in LiCoO2 is found, through oxygen vacancy facilitated cation migration and reduction. This process leaves undercoordinated oxygen that gives rise to oxygen release while the structure integrity of the defect-free region is mostly preserved. This oxygen release mechanism can be called surface degradation due to the kinetic control of the cation migration but has a slow surface to bulk propagation with continuous loss of the surface cation ions. It is also strongly correlated with the high-voltage cycling defects that end up with a significant local oxygen release at low temperatures. This work unveils the thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach.

The influence of cation ordering and oxygen nonstoichiometry on magnetic properties of Sr2FeMoO6–x around Curie temperature

The influence of cation ordering and oxygen nonstoichiometry on magnetic properties of Sr2FeMoO6–x around Curie temperature

The influence of cation ordering and oxygen nonstoichiometry on magnetic properties of Sr2FeMoO6–x around Curie temperature

Sr2FeMoO6–x polycrystalline samples with different oxygen content (6−x) and various degrees of superstructural ordering of Fe/Mo cations (P) were obtained by the solid-phase method from the SrFeO2.52 and SrMoO4 precursors. From the investigation on the influence of oxygen non-stoichiometry and the P parameter on the magnetic properties of Sr2FeMoO6–x, it was found that with an increase in P and a decrease in the (6−x) value from 5.99 to 5.94, an increase in the magnetization values is observed in the temperature range 77–600 K. For all the Sr2FeMoO6–x samples there is a tendency that P value rises with increasing x, where, accordingly, the volume fraction of regions in which there are no anti-structural defects increases as well. This is also indicated by Mössbauer spectroscopy data, confirming an increase in the area of the S1 sextet corresponding to Fe ions in highly ordered regions and a decrease in the area of the S2 sextet associated with disordered regions. Using the temperature scanning method, the temperatures of the onset and completion of the transition from the paramagnetic to the ferrimagnetic state and, correspondingly, the blurring width of the transition have been estimated. It turned out that with decreasing P, the blurring of the transition increases, which is associated with an increase in the concentration of anti-structural defects.

Oxygen Radical Absorbance Capacity (ORAC) and In Vitro Anti-Inflammatory Activity of Fruits of Different Plants

Nine well-known fruits of plants (Amla; Bael fruit; Guava white; Grapes green; Mango raw; Papaya; Pomegranate; Tamarind pulp and Tomato ripe) were assessed for phytoconstitutents, total phenolic content (TPC) and total flavonoid content (TFC)), total antioxidant capacity (FRAP) based on the scavenging ability of the cation radical DPPH RSA, ABTS RSA and oxygen radical absorbance capacity (ORAC)) and in vitro anti-inflammatory activity (protein denaturation inhibition (PDI)). The TPC and TFC ranged from 2535.51±10.88 to 26.99±0.58 mg GAE/100 g and 659.61±1.14 to 10.10±1.30 mg RE/100 g, respectively. The higher TPC, TFC and total antioxidant capacity (ORAC, FRAP, DPPH RSA and ABTS RSA) was observed in methanolic extract of amla among all the extracts. The in vitro anti-inflammatory activity could be ranked based on the IC50, as Amla>Grapes>Tomato>Pomegranate>Mango>Tamarind>Papaya>Bael> Guava. Additionally, a significant correlation existed between TPC and antioxidant activity. In general, the results indicate that majority of the fresh fruits of plants studied were rich in phenolic antioxidants with potent ORAC imply their importance to human health.

Control of transition metal–oxygen bond strength boosts the redox ex-solution in a perovskite oxide surface

Tuning of the cation–oxygen bond strength effectively promotes B-site ex-solution in a perovskite, thereby boosting the catalytic activity of CO oxidation.

Emergent magnetic phase transitions in Fe-doped SrTiO3−δ

In defect engineering, both cation doping and oxygen vacancies play key roles in deciding the properties of oxide, and the utilization of their cooperation has attracted much interest in recent years. Here, we report an emergent magnetic phase transition near 18 K in Fe-doped SrTiO3−δ by utilizing the magnetic interactions between the doped Fe cations and oxygen vacancies. The effects of Fe dopants and oxygen vacancies on the structural and magnetic properties were characterized by a high-resolution X-ray diffraction, Raman spectroscopy, and superconducting quantum interference device. In particular, as the temperature rises across the magnetic phase transition, the coercivity of Fe-SrTiO3−δ decreases from ∼7700 Oe at 2 K to ∼104 Oe at 19 K. Our results of creating emergent magnetic phases with the coeffects of both cation dopants and oxygen vacancies could pave a way to inducing novel quantum states in epitaxial films on Fe-SrTiO3−δ single crystal substrates with the magnetic proximity effect.

Effects of temperature and pH on the electrochemical behaviour of alloy 600 in simulated pressurized water reactor primary water

The effects of temperature and pH on the electrochemical properties of Alloy 600 were studied in oxygenated borate buffer solutions by the measurements of open circuit potential (OCP), anodic potentiostatic polarization, Mott-Schottky analysis (MSA), and electrochemical impedance spectroscopy (EIS). At each temperature and pH, the stabilized anodic passive current density was independent of the formation potential, and the slope of the M − S plot for the passive film formed at +0.3 VOCP (OCP + 0.3 V) is positive, indicating that the passive films formed on Alloy 600 have n-type semiconductor character. With increasing temperature (in each solution), the OCP and the impedance modulus decreased, while the passive current density and the defect density calculated from MSA increased, indicating a significant reduction in corrosion resistance. With the increase in pH value, the passive current density decreased, the absolute value of impedance increased slightly, revealing a slight increase in corrosion resistance. According to the optimization of Mixed Potential Model (MPM) on the experimentally measured EIS data for Alloy 600 at OCP and +0.3 VOCP, a series of fundamental parameters related to the micro-characteristic of passive film were extracted. In the barrier layer of the passive film, the concentration of cation interstitials is much higher than that of anion vacancies, indicating that the former was a dominant defect. With increasing temperature, the linear increase in the defect density and film thickness resulted in a linear increase of the anodic current density. However, with increasing pH, the decrease of defect density and the slight increase of film thickness caused a linear reduction in anodic current density. Elevated temperature has a more significant deterioration effect on the corrosion resistance of Alloy 600 than the increased pH value. Additionally, all the kinetics parameters describing the generation of cation interstitials and oxygen vacancies at the substrate/film were obtained.

Antioxidant capacity of germinated quinoa-based yoghurt and concomitant effect of sprouting on its functional properties

In this study, functional yoghurt was produced from germinated and ungerminated quinoa seeds of two different cultivars (Mengli 1 and Mengli 2) obtained from Inner Mongolia Province, China. The effect of germination on the physicochemical, antioxidant compounds, and antioxidant capacity was determined. In the results obtained, germination influenced the nutritional qualities of quinoa yoghurt to a large extent. Total phenolic content (TPC) and Total flavonoid content (TFC) were the highest in germinated quinoa yoghurt of both cultivars. Germinated quinoa yoghurt also recorded high antioxidant capacities with 2,21, diphenyl-1 picrylhydrazyl scavenging activity (DPPH), ferric reducing antioxidant capacity (FRAP), radical cation (ABTS*+) scavenging assay and oxygen radical absorption capacity (ORAC) assays. Thus, it was concluded that yoghurt produced from germinated quinoa could serve as functional yoghurt beneficial for human health.

Laminated microwave absorbers of A-site cation deficiency perovskite La0.8FeO3 doped at hybrid RGO carbon

Laminated hybrid carbon of amorphous carbon and RGO (reduced graphene oxide) perovskite composite, La0.8FeO3/C/RGO-BD, was fabricated by a simple method in one pot. The amorphous carbon was carbonized from d-glucose which also played a role as reducing agent. RGO provided a great condition for the formation of conductive loops. While A-site cation deficiency perovskite La0.8FeO3 doped at carbon nanosheets was induced to adjust the comprehensive microwave absorption properties. The phase and composition characteristics were studied by X-ray diffraction patterns (XRD), Raman and FT-IR spectrums and X-ray photoelectron spectroscopy (XPS), especially the confirmation of the existence of A-site cation deficiency and Oxygen vacancy. The morphology and microstructure of samples were visualized by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The electromagnetic microwave absorption properties were further studied, as the reflection loss of La0.8FeO3/C/RGO-BD reached −42.69 dB at 8.08 GHz with an effective band 2.72 GHz at 3.15 mm. And the excellent microwave absorption properties were confirmed by impedance matching, one quarter-wavelength theory, Debye relaxation polarization theory and eddy current loss.

Stability and Compressibility of Cation-Doped High-Entropy Oxide MgCoNiCuZnO5

High-entropy oxides (HEOx) are multicomponent (≥5) complex oxides that possess material properties and functions unexpected from their constituent simple oxides. Previous studies demonstrated that a cation-doped HEOx, MgCoNiCuZnO5, shows good catalytic activity, excellent ionic conductivity, and high energy storage. The structural and mechanical stabilities of materials are pivotal to their applications. However, how temperature and pressure influence the structural stability of cation-doped HEOx and how doping affects the mechanical properties are yet to be understood. In this work, we investigated the structural stabilities of undoped and Li/Mn-doped MgCoNiCuZnO5 in heating or under compression using in situ synchrotron X-ray diffraction (XRD), and determined their elastic moduli using high-pressure XRD. Our results show that the HEOx compounds are structurally stable at temperatures up to ∼450 °C or at pressures up to ∼50 GPa, and that Li/Mn doping makes the HEOx more compressible. Our molecular static (MS) calculations predicted that the formation reaction of a HEOx is endothermic, consistent with the fact that a single-phase HEOx can only be produced at high temperatures. The MS calculations also revealed that the observed doping-induced elastic softening stems from the introduction of the Li–O/Mn–O ionic bonds in the HEOx compound, which are weaker than other cation–oxygen ionic bonds in the undoped HEOx. These findings will be indispensable to engineer HEOx materials for use in ion batteries, catalysis, and other fields.

Quantum Chemical Modeling of the Structure and H Bonding in Triethanolammonium-Based Protic Ionic Liquids with Sulfonic Acids.

The results of electronic structure calculations based on density functional theory (DFT) for protic ionic liquids (PILs) consisting of triethanolammonium cation paired with anion of different sulfonic acids are reported. The influence of the anion nature on the structure and interactions in the ion pairs that are formed in these PILs is discussed in detail. Multiple H-bonding interactions exist between the protons in the NH/OH groups of the cation and different oxygen atoms of the acid anion in the ion pairs. The quantum theory of "atoms in molecules" has been used to estimate the individual contributions of each hydrogen bond to the stability of the ion pair. The hydrogen-bonding interactions in the ion pairs vary in their strength ranging from weak to moderately strong. In addition to these hydrogen bonds, there are other dispersion and electrostatic-dominant interactions that play an important role in the overall stability of PILs and their physicochemical properties. Aided by results from our previous DFT studies of triethanolammonium class of PILs with inorganic anions, these new data allow us to gain an improved understanding of the structure-property relationships in the studied ionic liquids. Close to linear correlation, in particular, has been found between the melting points and the binding energies of the cation and anion in the ion pairs.

Passivity breakdown of 13Cr stainless steel under high chloride and CO2 environment

Herein, the effect of high chloride ion (Cl−) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO2 environment was demonstrated. The Cl− concentration was varied from 30 to 150 g/L and cyclic potentiodynamic polarization was conducted to investigate the influence of the Cl− concentration on the corrosion potential (Ecorr), passive breakdown potential (Epit), and repassivation potential (Erep). The results of the polarization curves revealed that 13Cr stainless steel is susceptible to pitting under high Cl− concentration. The passive breakdown potential and repassivation potential decreased with the increase of Cl− concentration. The semiconducting behavior of the passive film was investigated by Mott-Schottky analysis and the point defect model (PDM). It was observed that the iron cation vacancies and oxygen vacancies were continuously generated by autocatalytic reactions and the higher Cl− concentration resulted in higher vacancies in the passive film. Once the excess vacancies condensed at the metal/film interface, the passive film became locally detached from the metal, which led to the breakdown of the passive film.

Effect of oxygen content on structural, magnetic and magnetocaloric properties of (La0.7Pr0.3)0.8Sr0.2Mn0.9Co0.1O3±δ

Abstract The present study reports the effect of oxygen content on the structural, magnetic and magnetocaloric properties in the (La0.7Pr0.3)0.8Sr0.2Mn0.9Co0.1O3±δ (δ = +0.02, +0.01, −0.03) in the temperature range of 5–723 К. It has been found that the temperatures of structural phase transitions vary significantly depending on the oxygen index value, δ. In oxygen-deficient samples (δ = −0.03), two structural phase transitions are observed: O′ → O and O → R (O′ – Orbitally ordered orthorhombic phase, O – Orbitally disordered orthorhombic phase, R – Rhombohedral phase). In excess oxygen samples (δ = +0.02, +0.01), the O′-phase is not formed. The O → R transition temperature increases with decreasing δ from TO→R = 353 K (δ = +0.02) to TO→R = 623 K (δ = −0.03). Magnetic measurements show that all our compounds exhibit a paramagnetic-ferromagnetic transition at TC ∼ 205 K. The Arrott plots reveal the occurrence of a second order phase transition. It was found that the transition temperature TC depends on the magnitude of the applied magnetic field, which rarely happens for materials with phase transitions of the second order. It has been shown from evaluation of the Temperature averaged Entropy Change (TEC) that a wide temperature range of MCE does not satisfies the requirements of using the compounds studied as an effective magnetocaloric material for magnetic refrigeration. The substitutions in cation sublattices and oxygen non-stoichiometry have negligible effect on TC and magnetocaloric effect (MCE). To investigate the magnetic interactions responsible for the magnetic transitions, the analysis was done by using the modified Arrott plot (MAP) method. The obtained values of the critical exponents matched well with those predicted for the isotropic short range 3D-Heisenberg model.

Structural features of ISG borosilicate nuclear waste glasses revealed from high-energy X-ray diffraction and molecular dynamics simulations

Vitrification is a widely accepted method to immobilize nuclear waste. Detailed structural information is critical to understand the physical and chemical behaviors, including the long-term chemical durability of these glasses that are to be stored in geological storage sites. High-energy X-ray diffraction studies are used to obtain accurate structural information of the International Simple Glass (ISG), a six-component borosilicate model nuclear waste glass with a composition (mol%) of 60.2SiO2-16.0B2O3-12.6Na2O-3.8Al2O3-5.7CaO-1.7ZrO2. Classical molecular dynamics (MD) simulations with recently developed effective potentials are utilized to generate structural models of the ISG glasses to provide interpretation of the high-energy X-ray structural data and additional short and medium range structural details. The atomic structure model generated from MD simulations shows an excellent agreement with high-energy X-ray diffraction, measured for the first time for ISG, with an Rx value of 5.5%. Systematic investigations of the medium-range structural features of ISG are performed, built upon recent study of the short-range structure. In particular, the glass former cation oxygen polyhedral analysis show that [SiO4]-[SiO4] and [BO4]-[SiO4] connections are the most abundant while [ZrO6] octohedra having higher probability to connect to another [SiO4], [BO4] and [BO3]. Moreover, we have studied the ISG surface structure using MD simulations. Noticeable differences in terms of both chemical compositions and structural features between the bulk and surface are observed. There exist increased small-sized rings, under coordinated Si species, high 3-coordinated boron content (86.5%) on the surface. Very importantly, sodium ions are found to be enriched on the glass surface, consistent with recent experimental results. Both bulk and surface structural information are discussed in terms of the dissolution and corrosion mechanisms of ISG and related nuclear waste glasses.