Metal Ion Layers Research Articles

Effect of Processing Route and Dopant on Capacity/Fading of Layered Oxide Cathode

Although several crystal structures have been demonstrated and shown reversible capabilities during lithiation/delithiation processes in cathode of Li ion batteries; oxides with layered structure still remain the ones that provide higher capacities. However, higher charging capacity means the creation of more ionic/electronic defects in both cation and/or anion sublattices of layered structure. Higher defect concentration in either cation or anion sublattices tend to destabilize its crystal structure. As a result, the phase change is frequently observed in repeatedly cycled cathode. Furthermore, the phase-changing layered cathode tends to show the capacity fading after cycling tests. Based on defect consideration, the stability of highly defective materials may be enhanced by using dopant and/or better processing control. In this study, the electrical/electrochemical/structural properties of NMC 811 and LiNi0.8Co0.15Al0.05 will be investigated. Since Ni content is fixed at 80% in the transition metal ion layers in these cathode materials, the variation in electrochemical properties will be caused by the minor elements/dopants such as Mn and Al. First, the electrical measurement of NMC 811 and LiNi0.8Co0.15Al0.05 are conducted using sintered disc. Assembled cells using above-mentioned cathode and Li anode with desired liquid electrolyte will be tested and cycled. XPS, SEM and XRD analyses will be conducted on as-assembled as well as cycled cells. The analyzing results will be illustrated based on the chemical characteristics of doping ions and the accompanying defects created.

Structural evolution in metallomicroemulsions - the effect of increasing alcohol hydrophobicity.

Small-angle neutron scattering and contrast variation has been employed to quantify how a series of alcohols with increasing hydrophobicity exert different abilities to structure a model toluene based metallomicroemulsion - a microemulsion system stabilised with a metallosurfactant. Classical microemulsion phase evolution and droplet structure are observed, leading to an oil rich core stabilised by a surfactant film containing a highly concentrated, hydrated metal ion layer.

Unique, non‐Earthlike, meteoritic ion behavior in upper atmosphere of Mars

AbstractInterplanetary dust particles have long been expected to produce permanent ionospheric metal ion layers at Mars, as on Earth, but the two environments are so different that uncertainty existed as to whether terrestrial‐established understanding would apply to Mars. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission made the first in situ detection of the continuous presence of Na+, Mg+, and Fe+ at Mars and indeed revealed non‐Earthlike features/processes. There is no separation of the light Mg+ and the heavy Fe+ with increasing altitude as expected for gravity control. The metal ions are well‐mixed with the neutral atmosphere at altitudes where no mixing process is expected. Isolated metal ion layers mimicking Earth's sporadic E layers occur despite the lack of a strong magnetic field as required at Earth. Further, the metal ion distributions are coherent enough to always show atmospheric gravity wave signatures. All features and processes are unique to Mars.

Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells.

We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La0.6Sr0.4CoO3−δ (LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions.

Designable Architectures on Nanoparticle Surfaces: Zirconium Phosphate Nanoplatelets as a Platform for Tetravalent Metal and Phosphonic Acid Assemblies

Surface-functionalized zirconium phosphate (ZrP) nanoparticles were synthesized using a combination of ion exchange and self-assembly techniques. The surface of ZrP was used as a platform to deposit tetravalent metal ions by direct ion exchange with the protons of the surface phosphate groups. Subsequently, phosphonic acids were attached to the metal ion layer, effectively functionalizing the ZrP nanoparticles. Use of axially oriented bisphosphonic acids led to the ability to build layer-by-layer assemblies from the nanoparticle surface. Varying the metal ion and ligand used allowed designable architectures to be synthesized on the nanoparticle surface. X-ray powder diffraction, XPS, electron microprobe, solid-state NMR, FTIR, and TGA were used to characterize the synthesized materials.

Synthesis, Structure, and Magnetic Properties of Some Layered Compounds Based on Long‐Chain Sulfonium Cations and Complex Cobalt and Copper Anions

AbstractTwo new materials of the composition ({CH3(CH2)15(CH3)2S}+)2[CoBr4]2– (1) and ({CH3(CH2)15(CH3)2S}+)2[CuBr4]2– (2 and 3), of which the latter exists in two polymorphs, were synthesized. The materials display the synthetically targeted structures, comprising of layers of complex metal ions and layers of long‐chain sulfonium cations. The crystal structures of the materials were determined. The interlayer distances are around 24 Å, with metal–metal distances about 8 Å. The magnetic properties of 1 were investigated, and the material is paramagnetic. ({CH3(CH2)15(CH3)2S}+)2[CuBr4]2 is polymorphic. Both polymorphs crystallize with triclinic symmetry.

Meteoric ion layers in the ionospheres of venus and mars: Early observations and consideration of the role of meteor showers

Layers of metal ions produced by meteoroid ablation have been known in Earth’s ionosphere for decades, but have only recently been discovered at Venus and Mars. Here we report the results of a search for meteoric layers in earlier datasets from Venus and Mars. We find 13 candidates at Venus in Mariner 10, Venera 9/10, and Pioneer Venus Orbiter data that augment the 18 previously identified in Venus Express data. We find 8 candidates at Mars in Mariner 7 and Mariner 9 data that augment the 71 and 10 previously identified in Mars Global Surveyor and Mars Express data, respectively. These new findings extend the ranges of conditions under which meteoric layers have been observed, support studies of the temporal variability of meteoric layers, and (for Venus) independently confirm the existence of meteoric layers. One of the proposed causes of temporal variations in the occurrence rate of meteoric layers is meteor showers. This possibility is controversial, since meteor showers have minimal observed effect on meteoric layers in Earth’s ionosphere. In order to aid progress towards a resolution of this issue, we present a series of tests for this hypothesis.

New Polymorph of the Highly Efficient LED-Phosphor SrSi2O2N2:Eu2+ – Polytypism of a Layered Oxonitridosilicate

SrSi2O2N2:Eu2+ is an outstanding yellow emitting phosphor material with practical relevance for application in high power phosphor-converted light-emitting diodes. The triclinic compound exhibits high thermal and chemical stability and quantum efficiency above 90% and can be excited by GaN-based UV to blue LEDs efficiently. We have now discovered a hitherto unknown monoclinic polymorph of SrSi2O2N2, synthesized by solid-state reaction, which is characterized by an alternating stacking sequence of silicate layers made up of condensed SiON3 tetrahedra and metal-ion layers. As proven by single-crystal X-ray diffraction, the arrangement of the silicate layers is significantly different from the triclinic polymorph. The translation period along the stacking direction is doubled in the monoclinic modification (P21, Z = 8, a = 7.1036(14), b = 14.078(3), c = 7.2833(15) Å, β = 95.23(3)°, V = 725.3(3) Å3). TEM investigations in combination with HRTEM-image simulations confirm the structure model. The powder X-ray diffraction pattern shows that the volume fractions of the monoclinic and triclinic modifications are approximately equal in the corresponding powder sample. The emission wavelength of 532 nm (fwhm ∼2600 cm–1) as determined by single-crystal luminescence measurements of the monoclinic phase exhibits a shift to smaller wavelengths by ∼5 nm compared to the triclinic polymorph. Differences of the luminescence properties between the monoclinic and triclinic phase are interpreted with respect to the differing coordination of Eu2+ in both phases. The new monoclinic SrSi2O2N2:Eu2+ polymorph is a very attractive phosphor material for the enhancement of color rendition of white-light pc-LEDs.

The New Carbodiimide Li2Gd2Sr(CN2)5 Having a Crystal Structure Related to That of Gd2(CN2)3

AbstractThe new carbodiimide compounds Li2RE2Sr(CN2)5 (RE = Sm, Gd, Eu, Tb) were prepared by a straight forward solid state metathesis reaction of REF3, SrF2, and Li2(CN2) at around 600 °C. The crystal structure of Li2Gd2Sr(CN2)5 was solved based on X‐ray single‐crystal diffraction data. Corresponding Li2RE2Sr(CN2)5 compounds were analyzed by isotypic indexing of their powder patterns. The crystal structure of Li2Gd2Sr(CN2)5 can be well related to that of Gd2(CN2)3, because both structures are based on layered structures composed of close packed layers of [N=C=N]2– sticks, alternating with layers of metal ions. The crystal structure of Li2Gd2Sr(CN2)5 can be considered to contain an ABC layer sequence of [N = C=N]2– layers with the interlayer voids being occupied by (three) distinct types of cations.

ChemInform Abstract: Cosmic Dust in the Earth′s Atmosphere

AbstractReview: 100 refs.

How do meteoroids affect Venus's and Mars's ionospheres?

Recent discoveries in the ionospheres of Venus and Mars of layers of metal ions that have been known to exist on Earth for decades have opened a new area for observationally constrained comparative planetology. These new observations raise four questions, amenable to study with current data and models, whose solutions will collectively answer the titular question of this article.

Cosmic dust in the earth's atmosphere

This review discusses the magnitude of the cosmic dust input into the earth's atmosphere, and the resulting impacts from around 100 km to the earth's surface. Zodiacal cloud observations and measurements made with a spaceborne dust detector indicate a daily mass input of interplanetary dust particles ranging from 100 to 300 tonnes, which is in agreement with the accumulation rates of cosmic-enriched elements (Ir, Pt, Os and super-paramagnetic Fe) in polar ice cores and deep-sea sediments. In contrast, measurements in the middle atmosphere - by radar, lidar, high-flying aircraft and satellite remote sensing - indicate that the input is between 5 and 50 tonnes per day. There are two reasons why this huge discrepancy matters. First, if the upper range of estimates is correct, then vertical transport in the middle atmosphere must be considerably faster than generally believed; whereas if the lower range is correct, then our understanding of dust evolution in the solar system, and transport from the middle atmosphere to the surface, will need substantial revision. Second, cosmic dust particles enter the atmosphere at high speeds and undergo significant ablation. The resulting metals injected into the atmosphere are involved in a diverse range of phenomena, including: the formation of layers of metal atoms and ions; the nucleation of noctilucent clouds, which are a sensitive marker of climate change; impacts on stratospheric aerosols and O(3) chemistry, which need to be considered against the background of a cooling stratosphere and geo-engineering plans to increase sulphate aerosol; and fertilization of the ocean with bio-available Fe, which has potential climate feedbacks.

Sporadic metal atom and ion layers and their connection to chemistry and thermal structure in the mesopause region at Arecibo

We present an analysis of two separate and distinct sporadic layer events in the mesosphere and lower thermosphere region above the Arecibo Observatory. These layers were observed in both neutral K and ionic Ca + with lidars, and in electron density with incoherent scatter radar. Temperature profiles were determined from the K lidar. One sporadic event was a high altitude layer, in which both atomic and ion sporadic layers were positioned above 100 km altitude. This represents a relatively common sporadic layer visible in both ions and neutrals at Arecibo. The other observation was less typical, with a lower altitude and more diffuse sporadic E layer, extending from below 90 km to above 95 km, which dissipated coincident with growth of a sporadic neutral K layer. We analyze these separate events using a temperature-dependent chemical model, which employs commonly accepted chemical processes. We find that the model successfully reproduces the high altitude layer of June 12–13, 2002. The result shows a temperature dependence related to the chemical lifetimes of the metallic constituents, and that the neutral layer would not have formed had the temperature profile matched that of the MSIS-90 model. Second, the temperature dependent chemistry model also reproduced K + in close agreement with electron densities on June 14–15, 2002. However, the modeled neutrals do not agree well with the observation above 90 km, and it likely requires inclusion of dynamical forcing and advection. We speculate that model and observational deficiencies, primarily exclusion of dynamics such as advection and wave interactions, are the likely shortcomings in the failure to reproduce the observations.

Reflecting on Mica

Geochemistry![Figure][1] CREDIT: GC MINERALS/ALAMY Trace metals in soils and sediment predominantly exist as either tiny mineral grains or mobile aqueous ions in pore water. In both cases, adsorption and desorption reactions at the surface of mineral grains control their fate and transport through the subsurface. Because the size of ions and strength of the surrounding hydration shell are highly variable, predicting the way in which metals are distributed even at one specific mineral/water interface is challenging. To systematically address this question, Lee et al. measured—using an X-ray reflectivity technique sensitive enough to determine the thickness of a single layer of water—the manner in which divalent metal ions adsorbed on a hydrated muscovite surface. As expected, metal ions with weak hydration shells lost water and bound tightly to muscovite within just 2.5 A; stronger hydration shells remained intact, pushing other metal ions further out (3.5 to 4.5 A from the surface). The reflectivity profiles also revealed, surprisingly, an unexpected additional broad layer of metal ions 5 to 10 A away from the mineral surface. Computational models of similar interfaces may need to be adjusted to account for this extended layer. Langmuir 26 , 16647 (2010). [1]: pending:yes

First simultaneous lidar observations of sodium layers and VHF radar observations of E-region field-aligned irregularities at the low-latitude station Gadanki

Abstract. Simultaneous observations of atmospheric sodium (Na) made by a resonance lidar and E-region field-aligned-irregularities (FAI) made by the Indian MST radar, both located at Gadanki (13.5° N, 79.2° E) and horizontal winds acquired by a SKiYMET meteor radar at Trivandrum (8.5° N, 77° E) are used to investigate the relationship among sodium layer, FAI and neutral winds in the mesosphere and lower thermosphere region. The altitudes and descent rates of higher altitude (~95 km) Na layer and FAI agree quite well. The descending structures of the higher altitude Na layer and FAI are found to be closely related to the diurnal tidal phase structure in zonal winds observed over Trivandrum. At lower altitudes, the descent rate of FAI is larger than that of Na layer and zonal tidal phase. These observations support the hypothesis that the metallic ion layers are formed by the zonal wind shear associated with tidal winds and subsequently get neutralized to manifest in the form of descending Na layers. The descending FAI echoing layers are manifestation of the instabilities setting in on the ionization layer. In the present observations, the altitudes of occurrence of Na layer and FAI echoes being low, we surmise that it is quite possible that the FAI echoes are due to the descent of already formed irregularities at higher altitudes.

Solar eclipse‐induced E‐region plasma irregularities observed by the Gadanki radar

We investigate the generation of low latitude E‐region plasma density irregularities that were triggered during a solar eclipse on 11 August 1999. The observations were made using the Gadanki radar. The present study shows that a solar eclipse can provide night‐like ionospheric conditions which allow the excitation of plasma instabilities and the generation of irregularities in the E‐region at multiple height regions, as happens routinely during post‐sunset hours. We surmise that the echo layers were associated with long‐lived metallic ion layers that were made manifest when the more abundant ordinary molecular ions disappeared through recombination in the absence of photoionization. We propose that the layers turned unstable via the gradient‐drift instability mechanism. This is the first time that a solar eclipse has been conclusively shown to generate E‐region plasma irregularities.

First observation of micrometeoroid differential ablation in the atmosphere

Every day, billions of microgram‐sized‐extraterrestrial particles enter and ablate in the upper layers of the Earth's atmosphere, depositing their mass in the mesosphere and lower thermosphere (MLT). This evaporated meteoric mass is the source of global layers of neutral metal atoms, sporadic E layers of metal ions, and meteoric smoke particles. Because their kinetic energy is insufficient to produce detectable optical emissions, these particles can only be observed using sensitive radars, which detect the plasma (i.e., electrons) either immediately surrounding the meteoroid (head‐echo), or left behind along its path (trail‐echo). Here we show that observed short‐scale temporal features in the radar returned signal from the meteor head‐echo are explained by differential ablation of the chemical constituents. These results represent the first observation of this mass‐loss process, indicating that this is the main mechanism through which the meteoric mass of micron‐sized particles is deposited in the MLT.

Stacking Design of Inverse Perovskites: The Systems (Sr3-xBaxN)E, E = Bi, Sb

The first representatives of 4H (BaMnO3-type structure, P63/mmc, Z = 4) and 9R (BaMnO3-type structure, Rm, Z = 9) inverse Perovskite phases are presented. The phases are obtained within the solid solutions (Sr3-xBaxN)E with E = Bi, Sb. The crystal structures and homogeneity ranges were studied by combined X-ray and neutron diffraction as well as chemical analyses. The cubic Perovskite phase with Bi (Sb) is stable in the range of 0.00 < or = x < or = 0.90(5) (0.00 < or = x < or = 1.30(5)), the 4H variant is stable for 1.55(5) < or = x < or = 2.10(5) (1.85(5) < or = x < or = 2.45(5)), the 9R structure is stable for 2.50(2) < or = x < or = 2.55(2) (2.56(2) < or = x < or = 2.60(2)), and the 2H phase is stable for 2.75(5) < or = x < or = 3.00 (2.80(5) < or = x < or = 3.00). Ba occupies preferable sites in the hexagonal stacking of close packed layers of alkaline earth metal ions and E3-; Sr is mainly located in cubic stacked layers. The phase order upon going from cubic (Sr3N)E to 2H-type (Ba3N)E concomitant to the pronounced Sr/Ba partial order can, in general, be rationalized considering the Coulomb repulsion of nitride ions, as well as the size and charge density of the alkaline earth metal ions.

Self-Assembled Multilayers of Transition-Metal−Terpyridinyl Complexes; Formation, and Characterization

Layer-by-layer (LBL) growth of terpyridinyl ligands with a range of metal ions is reported. Monolayers of mercaptophenyl terpyridine on gold were used to initiate LBL assembly by complexing the first layer of metal ions. Tetra-2-pyridinylpyrazine was used as a linking ligand between subsequent metal ion layers. The assembly of the terpyridines with 21 different metals was evaluated using UV absorbance spectroscopy, variable-angle spectroscopic ellipsometry, and atomic force microscopy. Successful LBL growth appears to depend on the ionic radius of the metal ion. Metals that formed multilayered LBL structures were primarily limited to a small range of effective ionic radii between 66 and 73 pm. Metal ions with smaller ionic radii usually formed initial layers but seldom exhibited consistent LBL growth, while ions with radii larger than 73 nm generally did not demonstrate any evidence of LBL growth.

Comparison of the electronic structures of two non-cuprate layered transition metal oxide superconductors

Comparison is made of the electronic structure of the little-studied layered transition metal oxide LiNbO 2 with that of Na x CoO 2 , which has attracted tremendous interest since superconductivity was discovered in its hydrate. Although the active transition metal d states are quite different due to different crystal fields and band filling, both systems show a strong change of electronic structure with changes in the distance between the transition metal ion layer and the oxygen layers. The niobate is unusual in having a large second-neighbor hopping amplitude, and a nearest-neighbor hopping amplitude that is sensitive to the Nb–O separation. Li x NbO 2 also presents the attractive simplicity of a single band triangular lattice system with variable carrier concentration that is superconducting.