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Modern lithium-ion batteries using layered R-3m intercalation positive electrodes have insufficient practical capacity and energy density to meet the future demands of portable electronics, and electric vehicles. If the complete, reversible, theoretical capacity upon full delithiation of these materials could be accessed while retaining high voltages and a narrow voltage swing, a significant advancement in energy density could be achieved. Although, full delithiation of most layered compounds has been known for decades, the failure modes that prevent practical cycle life are still in question. This paper focuses on a model R-3m layered compound of Li[Ni0.8Co0.15Al0.05]O2 (NCA) and explores the failure modes at the surface and subsurface utilizing a unique combination of operando microcalorimetry / electrochemical impedance spectroscopy , high resolution transmission electron microscopy, electron energy loss spectroscopy, x-ray photo electron microscopy, x-ray absorption spectroscopy, hard x-ray photoelectron spectroscopy, and x-ray diffraction. The development of operando microcalorimetry (isothermal and DSC mode) enables simultaneous measurement of the heat flux, current, and impedance, while controlling the environmental temperature and the electrochemical testing parameters. Although surface changes are known in NCA, we explore the evolution of the surface and subsurface at extreme levels of delithiation and take efforts to isolate the failure modes induced by cycling vs. static transitions. The progression of the surface and subsurface structure and chemistry is found to be much more complex than previously identified and has direct implications to impedance development throughout the electrochemical cell. Specific attention was given to surface catalyzed triggers of the surface and subsurface failure modes, evolution of surface and subsurface phase transformations, and comments on the broad applicability of our findings to other layered compounds.

The pronounced capacity fade in Ni-rich layered oxide lithium ion battery cathodes observed when cycling above 4.1 V (versus Li/Li+) is associated with a rise in impedance, which is thought to be due to either bulk structural fatigue or surface reactions with the electrolyte (or combination of both). Here, we examine the surface reactions at electrochemically stressed Li1–xNi0.8Co0.15Al0.05O2 binder-free powder electrodes with a combination of electrochemical impedance spectroscopy, spatially resolving electron microscopy, and spatially averaging X-ray spectroscopy techniques. We circumvent issues associated with cycling by holding our electrodes at high states of charge (4.1 V, 4.5 V, and 4.75 V) for extended periods and correlate charge-transfer impedance rises observed at high voltages with surface modifications retained in the discharged state (2.7 V). The surface modifications involve significant cation migration (and disorder) along with Ni and Co reduction, and can occur even in the absence of sign...

We report the fabrication of a rare-earth-free permanent-magnet material Co3Si in the form of nanoparticles and investigate its magnetic properties by experiments and density-functional theory (DFT). The DFT calculations show that bulk Co3Si has an easy-plane anisotropy with a high K1 ≈ −64 Merg/cm3 (−6.4 MJ/m3) and magnetic polarization of 9.2 kG (0.92 T). In spite of having a negative anisotropy that generally leads to negligibly low coercivities in bulk crystals, Co3Si nanoparticles exhibit high coercivities (17.4 kOe at 10 K and 4.3 kOe at 300 K). This result is a consequence of the unique nanostructure made possible by an effective easy-axis alignment in the cluster-deposition method and explained using micromagnetic analysis as a nanoscale phenomenon involving quantum-mechanical exchange interactions.

High switching frequency in power electronic converters reduces the size and weight of passive elements used in the converter but increases the switching losses of the power electronic devices. Remedy for high switching losses is the use of soft switching techniques which reduce switching losses and inturn increases efficiency. Zero voltage switching (ZVS) is one type of soft switching technique. In this paper a ZVS strategy based buck converter is presented operated at 50kHz. Performance analysis and simulation of the converter has been done by using SequelGUI2 software. Finally, a small laboratory phototype of rating 50W, 50kHz has been designed, fabricated and tested. The experimental results and simulated performance are found to be in good agreement.

Coaxial probe fed rectangular microstrip antenna is a popular type of patch antenna having applications in communication and radar systems. Particle Swarm Optimization (PSO) is a popular optimization algorithm and recently it is being used for design optimization of microstrip patch antennas. In this paper PSO has been used for optimization of resonant frequency of coaxial probe fed rectangular microstrip antenna. Investigation is made at different microwave frequencies and ranging between 3 GHz and 18 GHz. The optimization problem has three variables namely, patch length, patch width and position of the feed. Results encourage the use of PSO for optimal design.

Aperture coupled microstrip antenna is gathering a lot of interest in communication and radar systems. Particle swarm optimization (PSO) has been introduced to the electromagnetic community recently for design optimization of microstrip patch antenna .In this paper PSO has been used for accurate determination of resonant frequency of rectangular aperture-coupled microstrip antenna. The investigation is made at different microwave frequency ranges and it extends up to Ku band. The procedure is repeated for different dielectric constant of antenna and feed substrate. The optimization problem has three variables namely, aperture length, aperture width and stub length respectively. Accuracy of the results encourages the use of PSO.

The limitation and degradation of the ionic and electronic transport across the positive electrode/electrolyte interface can potentially reduce the achievable capacity of Li-ion batteries. This is evident for the layered oxides such as those based on nickel that operate outside the stability of today’s organic electrolytes. The rise in impedance and capacity fade with cycling has been identified as a result of loss of electrical contact originating from the instability of electrode surface and decomposition of the electrolyte. In this talk, we will discuss the surface and subsurface properties of LiNi0.8Co0.15Al0.05O2 (NCA). NCA provides a model system for correlating capacity fade with the formation and evolution of the cathode electrolyte interface with cycling. Our studies directly compare x-ray spectroscopy, electron spectromicroscopy, and high-resolution electrochemical characterization of the same NCA electrodes as a function of both initial charging and extended cycling. This research is supported by the Northeast Center for Chemical Energy Storage (NECCESS), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001294.

We show how atomic-scale exchange phenomena can be controlled and exploited in nanoscale itinerant magnets to substantially improve magnetic properties. Cluster-deposition experiments, first-principle simulations, and analytical calculations are used to demonstrate the effect in Co2Si nanoclusters, which have average sizes varying from about 0.6 to 29.5 nm. The cluster-deposited nanoparticles exhibit average magnetic moments of up to 0.70 μB/Co at 10 K and 0.49 μB/Co at 300 K with appreciable magnetocrystalline anisotropies, in sharp contrast to the nearly vanishing bulk magnetization. The underlying spin correlations and associated cluster-size dependence of the magnetization are explained by a surface induced ferromagnetic spin polarization with a decay length of the order of 1 nm, much larger than the nearest-neighbor interatomic distance in the alloy.

Nanoscale magnets with characteristic dimensions in the range of 1–100 nm are important in several areas of nanoscience and technology. First, this length scale spans the typical important dimensions of exchange lengths and domain-wall widths, which means that significant control of magnetic properties can be obtained by varying grain or particle dimensions. Second, the nonequilibrium synthetic processes used for clusters, particles, and films, often lead to new real-space crystal structures with completely novel spin structures and magnetic properties. Third, a basic-science challenge in this class of matter involves the spin-polarized quantum mechanics of many-electron systems containing 10–10 000 atoms. Finally, the materials under study may have important future applications in high-density data storage, ultra-small spintronic devices, or high-energy magnetic materials. In this article, we discuss our recent work on novel Fe-Au nanoclusters, MnAu-Mn coreshell structures, and complex high-anisotropy Co-rich intermetallic compound clusters. We also present new results on Fe-based alloys including the magnetic properties of semiconducting FeSi2 nanoclusters and spin correlations in FeGe nanocluster films. V C 2015 AIP Publishing LLC.

TO THE EDITOR: Hemolytic uremic syndrome (HUS) is characterized by a triad of non-immune hemolytic micro-angiopathic anemia, thrombocytopenia, and acute renal failure [1]. The majority of cases are "typical HUS," caused by an enteric infection of Shiga toxin-producing Escherichia coli. Rarely, however, HUS is caused by dysregulation of the alternative pathway of the complement system and is known as atypical HUS (aHUS). One rare subtype is caused by anti-complement factor H (CFH) antibodies. Such patients are commonly treated by nephrologists; however, they will usually present to a hematologist for variable cytopenias. We report here one such patient who presented to us primarily for cytopenias.

Co(Zr) nanoclusters having a small fraction of Zr (≤7.8 at. %) were produced using a cluster-deposition method and aligned using a magnetic field of about 5 kOe prior to deposition. This study shows that Zr addition to Co nanoclusters improves the fraction of hexagonal close-packed structure, magnetic anisotropy, and easy-axis alignment process. Co(Zr) nanoclusters having 7.8 at. % of Zr exhibit a considerably enhanced magnetic anisotropy constant K1 ≈ 6.7 Mergs/cm3 and coercivity Hc ≈ 700 Oe at 300 K as compared to those of Co nanoclusters (K1 ≈ 2.9 Mergs/cm3 and Hc ≈180 Oe).

An ordered L10 structure has been formed in near-stoichiometric Fe-Au alloy nanoparticles. The L10 structure with a = 0.367 nm and c = 0.360 nm was observed in nanoclusters with diameters below 10 nm after slow cooling from 600 °C. The stable L10 structure formed from a parent fcc solid solution phase observed in the as-formed clusters. The fcc phase has a lattice parameter of 0.417 nm, significantly expanded compared to both Au and γ-Fe. The saturation magnetization and coercivity of both fcc and L10 structures were much lower than expected considering Fe dilution effects suggesting competing ferromagnetic and anti-ferromagnetic ordering.