Rearrangement Of Ions Research Articles

The spoke origin based on the coupling-induced wave model in high-power impulse magnetron sputtering plasma

Spokes, identified as the source of anomalous across-B field transport during the high-power impulse magnetron sputtering (HiPIMS) discharge, have been considered as a result of plasma instability. This paper investigates the evolution of the coupling between two azimuthal waves in HiPIMS plasma by revisiting the dispersion relation. A coupling-induced wave model is proposed for the origin of the spoke. The ion sound wave can be strongly coupled with a Doppler-shifted electron Bernstein wave, inducing a long-scale (cm size) electric field oscillation waving at the frequency difference. The spoke appears to be a collective behavior of ion rearrangement guided by the difference frequency wave along the azimuthal direction. The direct comparison of spoke characteristics, such as rotating velocity, frequency and dynamic features, given by this model with experimental and simulation results from the literature shows a good qualitative agreement. Moreover, the evolution of spoke behavior following on from the model are presented, including rotating velocity and mode number along the racetrack. Their variation tendency matches well with experimental findings, from the literature.

Preparation of high strength double physically cross-linked hydrogels by immersion method—How to avoid uneven soaking

As a fascinating soft material, hydrogel has attracted tremendous attention due to its potential for applications in smart structures and biomedical engineering. However, common hydrogels with low mechanical properties cannot be suitable for rough environments with strong external loads. This study reports a general and facile strategy to fabricate tough and high energy dissipation double cross-linked (DC) hydrogels which contain two kinds of physical interactions - hydrophobic association and metal ions coordination. The double physically cross-linked gels were prepared by a simple, three-step method: synthesis, immersion, and rearrangement. During the immersion procedure, we were surprised to find the core-shell like structure which was caused by the Fe3+ uneven diffusion. The four typical kinds of the core-shell structure were further investigated, and a comprehensive hypothesis mechanism about the soaking and rearrangement was suggested. Consequently, based on the results of above homogeneous double physically cross-linked gels with high strength (9.8–12.4 MPa) and good energy dissipation (21.3–24.07 MJ/m3) were obtained by finding suitable reagent concentration and ion rearrangement processes. This fabrication process enhances our ability to guide the design of next-generation tough hydrogels.

Isolation and Identification of Six Difunctional Ethyl Esters from Bio-oil and Their Special Mass Spectral Fragmentation Pathways

Three difunctional ethyl esters (DFEEs), including ethyl 16-hydroxyhexadecanoate, ethyl (Z)-18-hydroxyoctadec-9-enoate, and diethyl (Z)-octadec-9-ene-1,18-dioate, were isolated as nearly pure compounds from sawdust-derived bio-oil. Their structures were tentatively identified by gas chromatography/mass spectrometry (GC/MS) and high-resolution mass spectrometry (HR-MS). Combination transesterification reaction of DFEEs to difunctional methyl esters (DFMEs) and determination of the GC/MS retention time differences of DFEEs and corresponding DFMEs is a simple method to determine the ester group number of unknown DFEEs. GC/MS results indicate that the fragment ions at mass-to-charge ratios (m/z) of 88 and 98 are typical ions for these DFEEs. The former ion is formed via well-known McLafferty rearrangement, whereas the formation pathway of the ion at m/z 98 is unreported before. HR-MS results show that the fragment ion at m/z 98 should be a cyclohexanone radical ion, which is possibly formed via a novel rearrangement initiated by remote hydrogen rearrangement. Besides long-chain DFEEs, long-chain difunctional carboxylic acids (including dicarboxylic acids, ω-hydroxy acids, diacid monomethyl ester, and diacid monoethyl ester) and DFMEs (including diacid dimethyl ester and ω-hydroxy methyl ester) are also typical of the fragment ion at m/z 98. Hence, it is a common characteristic to form the rearrangement ion at m/z 98 for long-chain difunctional carboxylic acids, DFEEs, and DFMEs, and this special mass spectral rearrangement could facilitate the identification of these classes of compounds. Using this rearrangement rule of DFEEs, three ω-hydroxy ethyl esters, including ethyl 22-hydroxydocosanoate, ethyl 24-hydroxytetracosanoate, and ethyl 26-hydroxyhexacosanoate, were tentatively identified by GC/MS.

Doping Effects and Charge‐Transfer Dynamics at Hybrid Perovskite/Graphene Interfaces

AbstractIn this work doping effects and charge transfer processes at the perovskite/graphene interface in the dark and under illumination are investigated. Hall effect, field effect, and surface photovoltage measurements suggest that hybrid perovskite layers induce strong n‐type doping of graphene after annealing at low temperature (330 K) in vacuum. It is found that the observed photoinduced changes in the electronic properties of graphene, functionalized by a hybrid organic–inorganic perovskite layer, are caused by two independent mechanisms with different time scales: (i) a fast collection of photogenerated holes by graphene from the perovskite layer and (ii) a slow ion rearrangement in the perovskite lattice at the perovskite/graphene interface. The observed annealing‐induced n‐type and photoinduced p‐type doping effects allow to reversibly switch the type of conduction of the perovskite/graphene system.

Optimizing the Structural Evolution of Li-Rich Oxide Cathode Materials via Microwave-Assisted Pre-Activation

Preactivation can play a promising role in suppressing oxygen loss during the first charging process in Li-rich oxide cathode materials, relieving a series of problems such as large initial irreversible capacity loss, structure transformation due to ion rearrangement, and oxidation/decomposition of the electrolyte. However, the strategies previous adopted are mainly chemical delithiation, which has violent effect on the crystal structure and deteriorates the cycle performance. Here, we report a facile and effective microwave-assisted treatment method to preactivate Li-rich layered oxides without structural distortion. The microwave-treated sample shows a high discharge capacity of about 281 mAh g–1 with a Coulombic efficiency of 87% at 0.1 C and exhibits unnormal continuous increase of discharge capacity from 203 mAh g–1 to 218 mAh g–1 during 110 cycles at 1 C as well as presents distinctly improved cycling stability. EIS, GITT and XRD studies reveal that the kinetics of electrochemical reaction on electr...

Transition-Metal-Free Multicomponent Approach to Stereoenriched Cyclopentyl-isoxazoles through C-C Bond Cleavage.

An efficient multicomponent reaction for the synthesis of stereoenriched cyclopentyl-isoxazoles from camphor-derived α-oximes, alkynes, and MeOH is reported. Our method involved a series of cascade transformations, including the in situ generation of an IIII catalyst, which catalyzed the addition of MeOH to a sterically hindered ketone. Oxidation of the oxime, and rearrangement of the α-hydroxyiminium ion generated a nitrile oxide in situ, which, upon [3+2] cycloaddition reaction with an alkyne, delivered the regioselective product. This reaction was very selective for the syn-oxime. This multicomponent approach was also extended to the synthesis of a new glycoconjugate, camphoric ester-isoxazole C-galactoside.

GaN light-emitting device based on ionic liquid electrolyte

Ionic liquids (ILs) are attractive materials for fabricating unique hybrid devices based on electronics and electrochemistry; thus, IL-gated transistors and organic light-emitting devices of light-emitting electrochemical cells (LECs) are investigated for future low-voltage and high-performance devices. In LECs, voltage application induces the formation of electrochemically doped p–n homojunctions owing to ion rearrangements in composites of semiconductors and electrolytes, and achieves electron–hole recombination for light emission at the homojunctions. In this work, we applied this concept of IL-induced electrochemical doping to the fabrication of GaN-based light-emitting devices. We found that voltage application to the layered IL/GaN structure accumulated electrons on the GaN surface owing to ion rearrangements and improved the conductivity of GaN. The ion rearrangement also enabled holes to be injected by the strong electric field of electric double layers on hole injection contacts. This simultaneous injection of holes and electrons into GaN mediated by ions achieves light emission at a low voltage of around 3.4 V. The light emission from the simple IL/GaN structure indicates the usefulness of an electrochemical technique in generating light emission with great ease of fabrication.

Toward low friction in water for Mo2N/Ag coatings by tailoring the wettability

Increasing demands for robust surfaces in harsh conditions, such as erosion, abrasion and sea-water, has stimulated the development of self-lubricated protective coatings. Meanwhile, due to the oil crisis, research in water lubrication again attracts much attention from both academics and practical engineers. Here, a higher hydrophilicity accompanying with a remarkable drop of friction coefficient in water environment was achieved successfully in Mo2N/Ag coatings by increasing Ag content. To do these, the Mo2N/Ag coatings with different Ag content were deposited by co-sputtering, which exhibit a nanocomposite structure consisting of precipitate Ag embedded in the Mo2N matrix. The high hydrophilicity can be ascribed to the combined contributions of the partial oxidation of Mo2N and high polarity of Ag precipitates. The decrease of friction coefficient is illustrated by the colloidal friction products and a mode with electric double layer. In which, enhanced hydrophilicity will result in forming a thin “water film” layer between the interface of counterpart and the coatings. And the MoOx/Ag2Mo4O13 derived from the hydrolysis action of Mo2N/Ag sliding in water could function as lubricant phase. Meanwhile, these negative charged MoOx/Ag2Mo4O13 colloidal particles induce the rearrangement of positive ions in the “water film” and form an electric double layer, which also contributes to the decrease of friction coefficient.

An atomic-level look at the structure-property relationship of cerium-doped glasses using classical molecular dynamics

Ce-containing bioactive glasses are of great interest in biomedical field since they exert antioxidant properties associated with low toxicity and a broad spectrum of bacteriostatic activities. The results obtained by classical molecular dynamics simulations allow the elucidation of the correlations between the effect of the inclusion of cerium doping ions into the structure of phosphosilicate and silicate bioactive glasses and their properties. The addition of small quantities of Ce to the silicate bioglass favours the depolymerisation of the silicate network with a positive effect on the ability to dissolve in body fluid. Moreover, the under coordination of both the Ce3+ and Ce4+ species in these glasses enhances their catalytic activity towards hydrogen peroxide. Conversely, the formation of cerium phosphate domains in the phosphosilicate glasses leads to detrimental effects for both the solubility and the catalytic activity of the glasses. Finally, a new quantitative view of the structure-activity relationships governing the macroscopic properties of these glasses has been obtained by means of structural descriptor that takes into account the fragmentation of the Si network and the consequent rearrangement of the modifier ions and the network destruction per cerium unit descriptor.

Ion Conduction, Dielectric and Mechanical Properties of Epoxy-Based Solid Polymer Electrolytes Containing Succinonitrile

We use impedance spectroscopy to investigate ionic conduction and dielectric response and mechanical tests to study mechanical properties of cross-linked epoxy-based solid polymer electrolytes (SPEs) containing a mixture of succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with different ratio of mechanically robust epoxy and ionic conducting SN/LiTFSI mixture content. Increasing SN/LiTFSI mixture content results in a proportional increase in ionic conductivity σ DC , and its maximum conductivity approaches σ DC ∼10-4 S/cm at room temperature. This is consistent with accelerating the observed relaxation processes such as ion rearrangement and segmental motion, upon adding further SN/LiTFSI content. The combination of epoxy and SN/LiTFSI also leads to a large increase in static dielectric constant e s ∼75, which is higher than the prediction from the Landau and Lifshitz mixing rule, compared to the host epoxy (e s ∼4) and pure SN/LiTFSI mixture (e s ∼53). On the other hand, the addition of SN/LiTFSI decreases Young’s modulus (E), compared to the neat epoxy, and approaches E∼10 MPa at room temperature, reflecting a trade-off relationship between E and σ DC .

Gas chromatographic-mass spectrometric investigation of n-alkanes and carboxylic acids in bottom sediments of the northern Caspian Sea

Abstract Prior to the start of experimental oil production in the Kashagan field (northern part of the Caspian Sea), n-alkanes and carboxylic acids contained in samples obtained from bottom sediments in the area of artificial island “D” were investigated by gas chromatography–mass spectrometry. Concentrations of 10 n-alkanes (composed of C10-C13, C15-C20) and 11 carboxylic acids (composed of C6-C12, C14-C16) were identified and measured. Concentrations of individual alkanes and carboxylic acids in bottom sediments of the various samples varied between 0.001 ÷ 0.88 μg/g and 0.001 ÷ 1.94 μg/g, respectively. Mass spectra, in particular the M+ molecular ion peak and the most intense peaks of fragment ions, are given. The present study illustrates the stability of molecular ions to electronic ionisation and the main fragment ions to the total ion current and shows that the initial fragmentation of alkanes implies radical cleavage of C2H5 rather than CH3. All aliphatic monocarboxylic acids studied were characterised by McLafferty rearrangement leading to the formation of F4 cation-radical with m/z 60 and F3 cation-radical with m/z 88 in the case of ethylhexanoic acid. The formation of oxonium ions presents another important aspect of acid fragmentation. Using mass numbers of oxonium ions and rearrangement ions allows determination of the substitution character in α- and β- C atoms. The essence of our approach is to estimate the infiltration of hydrocarbon fluids from the enclosing formation into sea water, comprising an analysis of derivatives of organic compounds in bottom sediments. Thus, concentrations of derived organic molecules can serve as a basis for estimates of the depth at which hydrocarbon fluids leak, i.e., to serve as an auxiliary technique in the search for hydrocarbon deposits and to repair well leaks.

Effect of secondary thermal treatment on crystallinity of spinel-type Co(Cr,Al)2O4 pigments synthesized by solution combustion route

The effect of a post-synthesis thermal treatment on CoCr2−2ΨAl2ΨO4 (0.0 ≤ Ψ ≤ 1.0) ceramic pigments synthesized by Solution Combustion Synthesis (SCS) has been studied. As-synthesized SCS pigments were treated at two different calcination temperatures (800 °C and 1000 °C) to study changes in mineralogy, microstructure and thermal behaviour, as well as their effect over the colouring power.Spinel-type Fd-3m crystalline structure was developed in all cases. Nevertheless, crystallinity parameters were highly affected by both analysed processing parameters: composition (Ψ) and post-synthesis calcination temperature (Tc). A Cr(III) enrichment along with Tc increase favoured ion rearrangement to promote sample crystallization and crystallite growth. Fast kinetics of SCS makes Al-rich spinels with transition metals difficult to be synthesized. The application of a secondary thermal treatment resulted in a favourable evolution towards a well-crystallized structure. Lattice parameter did not seem to be affected by Tc, although it evolved indeed with composition. From a microstructural point of view, as-synthesized pigments were foamy, with a very low bulk density and nanometric grain size. After the thermal treatment, larger grain sizes were obtained, especially for the samples richer in Al and treated at higher Tc.All pigments developed intense colours in a transparent glaze without showing heterogeneities, indicating a stable behaviour against glazing process. Glaze colour evolved from green to perfectly blue shades, indicating an important dependence on composition. Nevertheless, colouring power seemed to be rather affected by calcination process.

Solubility and ion-irradiation effects of uranium in Nd2Zr2O7 pyrochlore

Nd2Zr2O7 pyrochlore with higher physicochemical and radiation stability has been considered as a host matrix for actinide immobilization of high level radioactive wastes. Uranium is a constituent and the decay-daughter product of high level radioactive wastes. It is necessary to study the solubility and ion-irradiation effect of uranium in Nd2Zr2O7 pyrochlore. The solubility of U is studied by the A site substitution in the pyrochlore structure. A series of uranium-doped zirconate pyrochlore compositions is prepared by the sol-gel-spray pyrolysis-high temperature sintering method. The structures of immobilization are studied by using X-ray diffraction (XRD) and Raman spectroscopy. The XRD and Raman spectroscopy studies reveal that the solubility limit of uranium in Nd2Zr2O7 is estimated at 10 at%. The lattice parameter of pyrochlore decreases with U content increasing, which is due to lower ionic radius of U. The immobilization structure changes from order pyrochlore to disorder structure. Further addition of U content leads to the separation of U3O8 phase in the immobilization. The U ions with high valance may be substituted at A or B site in Nd2Zr2O7 pyrochlore, which results in the A–O and B–O bond destruction. In order to keep the balance of charge, extra O ions should enter into the vacancy site, the structure of pyrochlore maybe transforms into a disorder structure. The radiation resistance of immobilization is investigated by ion-beam irradiation with 2 MeV Kr15+ ions at room temperature. The Nd2Zr2O7 and Nd1.9U0.1Zr2O7 are irradiated at doses of 1 dpa and 3 dpa, respectively. Analyses of the XRD and Raman spectroscopy data show that the Nd2Zr2O7 pyrochlore remains full pyrochlore structure even at a higher irradiation dose, which suggests that the Nd2Zr2O7 exhibits higher radiation resistance as potential immobilization. In contrast, the Nd1.9U0.1Zr2O7 immobilization shows the weaker radiation resistance, the pyrochlore structure completely transforms into a disorder fluorite structure. The A–O and B–O bonds of Nd1.9U0.1Zr2O7 pyrochlore structure are easy to destroy under ion irradiation conditions due to the disorder of pyrochlore. At the same time, the excess O ions are rearranged in U-rich pyrochlore after irradiation. Bond destruction and ion rearrangement of pyrochlore structure result in the full disorder fluorite structure. The actinides-doped pyrochlore structure is modified due to the change in physicochemical propertyof actinide, which results in the reductionof the solubility limit and radiation resistance.

Rutile nanopowders for pigment production: Formation mechanism and particle size prediction

Formation mechanism and particle size prediction of rutile nanoparticles for pigment production were investigated. Anatase nanoparticles were observed by oriented attachment with parallel lattice fringe spaces of 0.2419 nm. Upon increasing the calcination temperature, the (1 1 0) plane of rutile was gradually observed, suggesting that the anatase (1 0 3) planes undergo internal structural rearrangement of oxygen and titanium ions into rutile phase due to ionic diffusion. Backpropagation neural network was used to predict particle size of rutile nanopowders, the prediction errors were all smaller than 2%, providing an efficient method to control particle size in pigment production.

In-situ structure reconstitution of NiCo2Px for enhanced electrochemical water oxidation

Gaining insight into the structure evolution of transition-metal phosphides during anodic oxidation is significant to understand their oxygen evolution reaction (OER) mechanism, and then design high-efficiency transition metal-based catalysts. Herein, NiCo2Px nanowires (NWs) vertically grown on Ni foam were adopted as the target to explore the in-situ morphology and chemical component reconstitution during the anodic oxidation. The major factors causing the transformation from NiCo2Px into the hierarchical NiCo2Px@CoNi(OOH)x NWs are two competing reactions: the dissolution of NiCo2Px NWs and the oxidative re-deposition of dissolved Co2+ and Ni2+ ions, which is based primarily on the anodic bias applied on NiCo2Px NWs. The well balance of above competing reactions, and local pH on the surface of NiCo2Px NW modulated by the anodic oxidation can serve to control the anodic electrodeposition and rearrangement of metal ions on the surface of NiCo2Px NWs, and the immediate conversion into CoNi(OOH)x. Consequently, the regular hexagonal CoNi(OOH)x nanosheets grew around NiCo2Px NWs. Benefiting from the active catalytic sites on the surface and the sufficient conductivity, the resultant NiCo2Px@CoNi(OOH)x arrays also display good OER activity, in terms of the fast kinetics process, the high energy conversion efficiency, especially the excellent durability. The strategy of in-situ structure reconstitution by electrochemical reaction described here offers a reliable and valid way to construct the highly active systems for various electrocatalytic applications.

The Role of Solvating 12-Crown-4 Plasticizer on Dielectric Constant and Ion Conduction of Poly(ethylene oxide) Single-Ion Conductors

The role of solvating plasticizer on lithium ion conduction is investigated for a poly(ethylene oxide)-based single-ion conductor, plasticized with 12 wt % 12-crown-4 (12C4). The addition of 12C4 not only increases the static dielectric constant (es) but also accelerates the ion rearrangement (α2) and segmental motion (α) compared to the host ionomer. A physical model of electrode polarization is used to estimate number density of simultaneously conducting ions and their mobility. The complex of 12C4 with lithium cation lowers the activation energy of simultaneously conducting ions, increasing the simultaneously conducting ion content by >3×. This is consistent with an initial large increase in es, which is higher than the prediction from the Landau and Lifshitz mixing rule, reflecting that ion aggregates observed in the host ionomer are solvated by 12 wt % 12C4. Furthermore, the dissolution of the aggregates promotes ion mobility owing to an increase in polymer chain flexibility, with a reduction in glas...

Solution combustion synthesis of (Co,Ni)Cr2O4 pigments: Influence of initial solution concentration

Abstract Initial solution concentration effect was studied on the synthesis of mixed spinels Co 1-Ψ Ni Ψ Cr 2 O 4 (0≤Ψ≤1) obtained by Solution Combustion Synthesis. Fd-3m spinel structure was developed in all range of compositions analysed, regardless of the concentration. However, structural characteristics such as ion rearrangement and crystal size showed a noticeable dependence on the initial concentration, being the spinel network more ordered and with higher crystallite size as the concentration increased. Cell parameter, however, presented dependence on composition but not on initial solution concentration. All as-synthesized pigments showed a significant colouring power in ceramic glazes without any significant influence of initial solution concentration. Therefore, a second thermal treatment was not needed. The coloured glazes covered a broad range of tones in the green section of colour space, which evolved as a function of composition.

Fuel effect on solution combustion synthesis of Co(Cr,Al)2O4 pigments

The fuel effect on the synthesis of a ceramic pigment with a composition CoCr2−2ΨAl2ΨO4 (0≤Ψ≤1) by means of solution combustion synthesis process (SCS) has been studied. Three different fuels were selected to carry out the synthesis (urea, glycine and hexamethylentetramine (HMT)). Highly foamy pigments with very low density were obtained. Fd-3m spinel-type structure was obtained in all the experiments. Nevertheless, crystallinity and crystallite size of the spinels show significant differences with composition and fuel. The use of glycine along with the chromium-richest composition favours ion rearrangement to obtain the most ordered structure. Lattice parameter does not seem to be affected by fuel, although it evolves with Ψ according to Vegard's law.Colouring power in a transparent glaze shows important variations with composition. On the other hand, fuel effect presents a rather low influence since practically the same shades are obtained. However, it exerts certain effect on luminosity (L*).

Rearrangement of potassium ions and Kv1.1/Kv1.2 potassium channels in regenerating axons following end-to-end neurorrhaphy: ionic images from TOF-SIMS.

The voltage-gated potassium channels Kv1.1 and Kv1.2 that cluster at juxtaparanodal (JXP) regions are essential in the regulation of nerve excitability and play a critical role in axonal conduction. When demyelination occurs, Kv1.1/Kv1.2 activity increases, suppressing the membrane potential nearly to the equilibrium potential of K+, which results in an axonal conduction blockade. The recovery of K+-dependent communication signals and proper clustering of Kv1.1/Kv1.2 channels at JXP regions may directly reflect nerve regeneration following peripheral nerve injury. However, little is known about potassium channel expression and its relationship with the dynamic potassium ion distribution at the node of Ranvier during the regenerative process of peripheral nerve injury (PNI). In the present study, end-to-end neurorrhaphy (EEN) was performed using an in vivo model of PNI. The distribution of K+ at regenerating axons following EEN was detected by time-of-flight secondary-ion mass spectrometry. The specific localization and expression of Kv1.1/Kv1.2 channels were examined by confocal microscopy and western blotting. Our data showed that the re-establishment of K+ distribution and intensity was correlated with the functional recovery of compound muscle action potential morphology in EEN rats. Furthermore, the re-clustering of Kv1.1/1.2 channels 1 and 3months after EEN at the nodal region of the regenerating nerve corresponded to changes in the K+ distribution. This study provided direct evidence of K+ distribution in regenerating axons for the first time. We proposed that the Kv1.1/Kv1.2 channels re-clustered at the JXP regions of regenerating axons are essential for modulating the proper patterns of K+ distribution in axons for maintaining membrane potential stability after EEN.

Xylose Migration During Tandem Mass Spectrometry of N-Linked Glycans.

Understanding the rearrangement of gas-phase ions via tandem mass spectrometry is critical to improving manual and automated interpretation of complex datasets. N-glycan analysis may be carried out under collision induced (CID) or higher energy collision dissociation (HCD), which favors cleavage at the glycosidic bond. However, fucose migration has been observed in tandem MS, leading to the formation of new bonds over four saccharide units away. In the following work, we report the second instance of saccharide migration ever to occur for N-glycans. Using horseradish peroxidase as a standard, the beta-1,2 xylose was observed to migrate from a hexose to a glucosamine residue on the (Xyl)Man3GlcNac2 glycan. This investigation was followed up in a complex N-linked glycan mixture derived from stem differentiating xylem tissue, and the rearranged product ion was observed for 75% of the glycans. Rearrangement was not favored in isomeric glycans with a core or antennae fucose and unobserved in glycans predicted to have a permanent core-fucose modification. As the first empirical observation of this rearrangement, this work warrants dissemination so it may be searched in de novo sequencing glycan workflows. Graphical Abstract ᅟ.