Nanostructuring polymeric materials by templating strategies

This contribution summarizes efforts in designing, assembling/synthesizing, and structurally and functionally characterizing nanostructured materials using anodized aluminum oxide (AAO) as a thin-film template. Optical waveguide spectroscopy, using a nanoporous template as the guiding structure, is a particularly powerful analytical tool. The layer-by-layer approach for the fabrication of multilayer assemblies is shown to allow the fabrication of nanotube arrays. In addition to using dendrimers as building blocks, semiconducting nanomaterial (e.g., quantum dot) hybrid architectures with very interesting photophysical properties can be assembled. These can be employed, for example, in biosensing applications. Other strategies for using the AAO layers as templates include the growth of polymeric nanorod arrays from different functional monomers, which, after the dissolution of the template, are still able to guide light. This opens up novel concepts for integrated optics platforms with nanostructured materials.     

Efficient numerical methods for the large‐scale,parallel solution of elastoplastic contact problems

Quasi‐static elastoplastic contact problems are ubiquitous in many industrial processes and other contexts, and their numerical simulation is consequently of great interest in accurately describing and optimizing production processes. The key component in these simulations is the solution of a single load step of a time iteration. From a mathematical perspective, the problems to be solved in each time step are characterized by the difficulties of variational inequalities for both the plastic behavior and the contact problem. Computationally, they also often lead to very large problems. In this paper, we present and evaluate a complete set of methods that are (1) designed to work well together and (2) allow for the efficient solution of such problems. In particular, we use adaptive finite element meshes with linear and quadratic elements, a Newton linearization of the plasticity, active set methods for the contact problem, and multigrid‐preconditioned linear solvers. Through a sequence of numerical experiments, we show the performance of these methods. This includes highly accurate solutions of a three‐dimensional benchmark problem and scaling our methods in parallel to 1024 cores and more than a billion unknowns. Copyright © 2015 John Wiley & Sons, Ltd.     

Event driven algorithms applied to a high energy ball mill simulation

In the physics community, event driven molecular dynamics simulations have been successfully applied to typical physical topics, such as granular gases. In contrast, in the engineering sciences, event driven algorithms have not become as popular, even though they can be far more efficient for special systems. In this paper, we present an event driven simulation of a high energy ball mill, where the motion and energy transfer of the grinding balls during operation are simulated. Stable numerical algorithms for collision detection and collision response are developed and several possible pitfalls are discussed. Furthermore, an improved event list handling technique and a specialized space subdivision method is presented. The performance of the partitioning is demonstrated by experiments. It is shown that the scaling rules usually applied are oversimplified. A new way of scaling the process parameters to obtain a higher production yield using iso-impact diagrams is presented.     

Photoluminescent lead(II) coordination polymers stabilised by bifunctional organoarsonate ligands

Four lead(II) coordination polymers were isolated under hydro(solvo)thermal conditions. The applied synthetic methodology takes advantage of the coordination behaviour of a new bifunctional organoarsonate ligand, 4-(1, 2, 4-triazol-4-yl)phenylarsonic acid (H₂TPAA) and involves the variation of lead(II) reactants, metal/ligand mole ratios, and solvents. The constitutional composition of the four lead(II) coordination polymers can be formulated as [Pb₂(TPAA)(HTPAA)(NO₃)]·6H₂O (1), [Pb₂(TPAA)(HTPAA)₂]·DMF·0.5H₂O (DMF = N, N-Dimethylformamide) (2), [Pb₂Cl₂(TPAA)H₂O] (3), and [Pb₃Cl(TPAA)(HTPAA)₂H₂O]Cl (4). The compounds were characterized by single-crystal and powder x-ray diffraction techniques, thermogravimetric analyses, infra-red spectroscopy, and elemental analyses. Single-crystal x-ray diffraction reveals that 1 and 2 represent two-dimensional (2D) layered structures whilst 3 and 4 form three-dimensional (3D) frameworks. The structures of 1, 2, and 4 contain one-dimensional (1D) {Pb^II/AsO₃} substructures, while 3 is composed of 2D {Pb^II/AsO₃} arrays. Besides their interesting topologies, 1–4 all exhibit photoluminescence properties in the solid state at room temperature.     

Nafion/polypyrrole and Nafion/DMSO Organic Coatings for Magnesium Protection

Nafion/polypyrrole and Nafion/Dimethysulfoxid （DMSO） organic coatings were prepared on the surface of pure magnesium by simple immersion and heat treatment. The morphologies and corrosion resistance of the organic coatings were investigated by using optical microscopy and electrochemical corrosion testing, respectively. It is shown that Nafion/polypyrrole organic coatings resulted in the corrosion resistance of magnesium decreasing; while Nafion/DMSO organic coatings can effectively improve the corrosion resistance of magnesium. Also, the corrosion resistance increased with the thickness of the Nafion/DMSO organic coating increased.