Electroactive Polymers: Developments of and Perspectives for Dielectric Elastomers

We present the development and applications of dielectric elastomers. For the last 10 years the significance of this class of polymers has risen as more applications seem possible and first products have been commercialized.     

The First Catalytic Synthesis of an Acrylate from CO2 and an Alkene—A Rational Approach

For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C₁ building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO₂, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal.     

Electronic transport in graphene nanostructures on SiO2

We report two experiments on graphene nanostructures. The first was performed on a graphene nanoribbon, where the nature of electronic transport was investigated in detail. Electrons or holes are found to localize in pockets of the potential along the ribbon. Transport is governed by the joint action of localization and Coulomb interaction. The temperature-dependence of the conductance shows activated behavior at temperatures above a few Kelvin. The activation energy retraces the edges of Coulomb blockade diamonds found in nonlinear transport. In the second experiment the metallic tip of a low-temperature scanning force microscope was scanned above a graphene quantum dot. In addition to the familiar Coulomb blockade fringes, localized states are detected forming in the constrictions connecting the dot to source and drain.     

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.     

Physical fabrication of colloidal ZnO nanoparticles combining wet-grinding and laser fragmentation

Combination of wet-grinding and laser fragmentation is a promising approach to advance both methods: Laser fragmentation will be more efficient when combined with mechanical treatment and wet-grinding may take advance of the abrasion-free laser process to achieve fabrication of smaller particles. By mechanical pre-treatment of zinc oxide microparticles in a stirred-media mill, the starting material is activated by generation of crystallographic defects, which strongly enhance the efficiency of subsequent laser fragmentation. Picosecond-laser irradiation of mechanically treated and untreated microparticles suspended in water yielded in colloidal zinc oxide nanoparticles. Furthermore, nanoparticle productivity and properties can be controlled by variation of anionic surfactant concentration.