Mechanical and electrical failure of transparent nanowire Electrodes

Flexible transparent electrodes have to withstand large mechanical strains without sacrificing electrical performance. For such applications, silver nanowire (Ag NW) networks are highly promising as they combine mechanical flexibility with low sheet resistance and high optical transmittance. In order to improve the performance of such nanowire electrodes a microscopic understanding of the interplay between mechanical and electrical failure is required. This can be achieved by a combination of in situ (or interrupted) tensile tests in a scanning electron microscope (SEM) with 4-probe electrical measurements of the sheet resistence. Please click Additional Files below to see the full abstract

In situ ultrafine force measurement with nanowire based cantilevers in SEM

In nanomechanics the measurement of ultrafine forces becomes increasingly important for unravelling subtle details of elastic and plastic deformation processes. In particular, achieving high force resolution in combination with in situ imaging is a major challenge which is becoming exceedingly difficult with conventional methods. In this work, we introduce a novel systematic method to measure ultrafine forces using well-defined nanowires as cantilever beams in situ in the Scanning Electron Microscope (SEM). Forces can be measured variably in the range from micro-newtons (mN) down to femto-newtons (fN), depending on the chosen reference nanowire. The reference wires are picked with a manipulator tip without the use of FIB (see Figure 1 a). Please click Additional Files below to see the full abstract

Intrinsic nano-diffusion-couple for studying high temperature diffusion in multi-component superalloys

We present a new approach for the quantitative study of high-temperature diffusion in compositionally complex superalloys on the nano-scale. As key element, the approach utilizes the γ/γ\u27-microstructure itself as intrinsic nano-diffusion-couple (NDC). By establishing equilibrium at one temperature followed by annealing at a different temperature, well-defined transient states are generated which are studied using STEM-EDXS. We demonstrate this approach for a multi-component superalloy of CMSX-4 type. The temporal evolution of element concentrations is consistently revealed for γ- and γ\u27-forming elements and is compared to diffusion simulations based on DICTRA. Excellent agreement is obtained for Ni, Co, and Cr whereas diffusion of Al and, in particular, Re lacks behind in experiment. Finally, it is demonstrated that transient states can also be captured by in situ TEM using chip-based heating devices. The NDC approach offers great opportunities for diffusion studies in compositionally complex superalloys and might be extended to other two-phase multi-component systems

Combined 3D characterization of porous zeolites by STEM and FIB tomography

German Research Foundation Priority Program 1570German Research Foundation Cluster of Excellence EXC 315 “Engineering of Advanced Materials

Compressed sensing electron tomography of needle-shaped biological specimens--Potential for improved reconstruction fidelity with reduced dose.

Electron tomography is an invaluable method for 3D cellular imaging. The technique is, however, limited by the specimen geometry, with a loss of resolution due to a restricted tilt range, an increase in specimen thickness with tilt, and a resultant need for subjective and time-consuming manual segmentation. Here we show that 3D reconstructions of needle-shaped biological samples exhibit isotropic resolution, facilitating improved automated segmentation and feature detection. By using scanning transmission electron tomography, with small probe convergence angles, high spatial resolution is maintained over large depths of field and across the tilt range. Moreover, the application of compressed sensing methods to the needle data demonstrates how high fidelity reconstructions may be achieved with far fewer images (and thus greatly reduced dose) than needed by conventional methods. These findings open the door to high fidelity electron tomography over critically relevant length-scales, filling an important gap between existing 3D cellular imaging techniques.The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative–I3), as well as from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC grant agreement 291522 - 3DIMAGE. B.W. and E.S. acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG) within the framework of the SPP 1570 as well as through the Cluster of Excellence “Engineering of Advanced Materials” at the Friedrich-Alexander-Universität ErlangenNürnberg. G.D. and C.D. acknowledge funding from the ERC under grant number 259619 PHOTO EM. B.W. acknowledges the Research Training Group “Disperse Systems for Electronic Applications” (DFG GEPRIS GRK 1161). R.L. acknowledges a Junior Research Fellowship from Clare College.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.ultramic.2015.10.02

Surface functionalisation of sol-gel-based bioactive glass scaffolds for drug delivery

ITN FP-7 project “GlaCERCo

Effect of size and shape on the elastic modulus of metal nanowires

Abstract Size effects decisively influence the properties of materials at small length scales. In the context of mechanical properties, the trend of ‘smaller is stronger’ has been well established. This statement refers to an almost universal trend of increased strength with decreasing size. A strong influence of size on the elastic properties has also been widely reported, albeit without a clear trend. However, the influence of nanostructure shape on the mechanical properties has been critically neglected. Here, we demonstrate a profound influence of shape and size on the elastic properties of materials on the example of gold nanowires. The elastic properties are determined using in-situ mechanical testing in scanning and transmission electron microscopy by means of resonance excitation and uniaxial tension. The combination of bending and tensile load types allows for an independent and correlative calculation of the Young's modulus. We find both cases of softening as well as stiffening, depending critically on the interplay between size and shape of the wires. Graphic abstrac