Montmorillonite-based ceramic membranes as novel lithium-ion battery separators

Novel montmorillonite-based ceramic membrane (CM) has been prepared with poly(vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP) copolymer as binder. Physical properties such as surface morphology, porosity, liquid electrolyte uptake and thermal stability were analysed. The ceramic membrane was activated by soaking it in a non-aqueous liquid electrolyte (1.0 M LiPF₆ solution in 1/1 v/v ethylene carbonate/diethyl carbonate mixture) for 10 min. The compatibility of the membrane with lithium metal anode as a function of storage time was analysed by assembling a Li/CM/Li symmetric cell. Finally, a lab-scale cell composed of Li/CM/LiFePO₄ is assembled and its cycling performance analysed at different C-rates. Although the ceramic membrane is not flexible, it shows high thermal stability and stable interfacial properties when in contact with the lithium metal anode. A stable cycling behaviour is demonstrated even at 1C-rate with limited fade in capacity.     

K-line X-ray fluorescence from highly charged iron ions under dense astrophysical plasma conditions

In the present work, we report an investigation of plasma environment effects on the atomic parameters associated with the K-vacancy states in highly charged iron ions within the astrophysical context of accretion disks around black holes. More particularly, the sensitivity of K-line X-ray fluorescence parameters (wavelengths, radiative transition probabilities, and Auger rates) in Fe XVII–Fe XXV ions has been estimated for plasma conditions characterized by an electron temperature ranging from 10⁵ to 10⁷ K and an electron density ranging from 10¹⁸ to 10²² cm⁻³. In order to do this, relativistic multiconfiguration Dirac-Fock atomic structure calculations have been carried out by considering a time averaged Debye-Hückel potential for both the electron–nucleus and electron–electron interactions.     

The photon-ion merged-beams experiment PIPE at PETRA III—The first five years

The Photon-Ion Spectrometer at PETRA III—in short, PIPE—is a permanently installed user facility at the "Variable Polarization XUV Beamline" P04 of the synchrotron light source PETRA III operated by DESY in Hamburg, Germany. The careful design of the PIPE ion-optics in combination with the record-high photon flux at P04 has lead to a breakthrough in experimental studies of photon interactions with ionized small quantum systems. This short review provides an overview over the published scientific results from photon-ion merged-beams experiments at PIPE that were obtained since the start of P04 operations in 2013. The topics covered comprise photoionization of ions of astrophysical relevance, quantitative studies of multi-electron processes upon inner-shell photoexcitation and photoionization of negative and positive atomic ions, precision spectroscopy of photoionization resonances, photoionization and photofragmentation of molecular ions, and of endohedral fullerene ions.     

Order sequencing on a unidirectional cyclical picking line

A real life order-picking configuration that requires multiple pickers to cyclically move around fixed locations in a single direction is considered. This configuration is not the same, but shows similarities to, unidirectional carousel systems described in literature. The problem of minimising the pickers’ travel distance to pick all orders on this system is a variant of the clustered travelling salesman problem. An integer programming (IP) formulation of this problem cannot be solved in a realistic time frame for real life instances of the problem. A relaxation of this IP formulation is proposed that can be used to determine a lower bound on an optimal solution. It is shown that the solution obtained from this relaxation can always be transformed to a feasible solution for the IP formulation that is, at most, within one pick cycle of the lower bound. The computational results and performance of the proposed methods as well as adapted order sequencing approaches for bidirectional carousel systems from literature are compared to one another by means of real life historical data instances obtained from a retail distribution centre.     

Modeling and numerical approximations for bubbles in liquid metal

In simulations of liquid metals, various model approximations, each of which justified by experimental results lead to a simplified two-phase flow problem. This paper discusses numerical justifications for these approaches and provides quantitative results for a single rising bubble as a benchmark. Representing a bubble as a rigid object is shown to be valid for low Eötvös numbers in contaminated systems. Qualitative differences can be observed for larger Eötvös numbers. Further simulations are undertaken with different ratios of inner and outer viscosity. The benchmark problem considered may also be interesting for more general applications.     

Development of a Miniaturized Energy Converter Without Moving Parts

New developments in portable electrical and mechanical devices have created demand for increasing amounts of energy and thus new ways of supplying energy. The high energy density of hydrocarbon fuels are a possible way to solve this issue. This paper deals with the development of an adapted thermodynamic concept for a micro energy converter based on the thermoelectric effect. Developing a PowerMEMS device that does not contain any moving parts is the main design feature. In the proposed concept liquid hydrocarbon fuel, such as methanol, is evaporated in a micro evaporator, mixed with air, and combusted in a micro combustion chamber. The combustion process is assisted by catalytically coated microfibers. Electrical power can be generated by a thermoelectric generator, which is located between the hot combustion zone and the cold micro evaporator. This arrangement leads to large temperature differences between hot and cold junctions, which is necessary for efficient thermoelectric energy conversion and hence power generation. For a more detailed investigation of thermal boundary conditions and interior thermal management, in-situ temperature measurements of the combustor walls are performed using thermographic phosphors.