Deformation of Silica Aerogel During Fluid Adsorption

Aerogels are very compliant materials - even small stresses can lead to large deformations. In this paper we present measurements of the linear deformation of high porosity aerogels during adsorption of low surface tension fluids, performed using a Linear Variable Differential Transformer (LVDT). We show that the degree of deformation of the aerogel during capillary condensation scales with the surface tension, and extract the bulk modulus of the gel from the data. Furthermore we suggest limits on safe temperatures for filling and emptying low density aerogels with helium.Comment: 8 pages, 5 figures, submitted to PR

Thermal assessment of ambient pressure dried silica aerogel composite boards at laboratory and field scale

In the context of increasing energy costs and the need for global reduction of CO2 emissions, the development of superinsulation materials for the construction sector allows the design of low-energy buildings. Since still being in an experimental or at early-commercial stage, R&D of these materials focused on its final application is required, to accelerate access to the market for renovation of the building stock where space is a critical metric. In this paper, the experimental assessment of the thermal performance of a novel ambient pressure dried silica aerogel based composite is presented. In order to provide assessments at both, material and system levels, stress-strain tests, hot plate measurements, as well as full scale tests under realistic boundary conditions were conducted. The overall results are that this material provides good insulation properties (thermal conductivity in the range of 0.015–0.018 W/mK), along with sufficient mechanical properties, and allows for the creation of superinsulating assemblies even at small wall thickness.European Commission's FP

Influence of Elastic Strains on the Adsorption Process in Porous Materials. An Experimental Approach

The experimental results presented in this paper show the influence of the elastic deformation of porous solids on the adsorption process. With p+-type porous silicon formed on highly boron doped (100) Si single crystal, we can make identical porous layers, either supported by or detached from the substrate. The pores are perpendicular to the substrate. The adsorption isotherms corresponding to these two layers are distinct. In the region preceding capillary condensation, the adsorbed amount is lower for the membrane than for the supported layer and the hysteresis loop is observed at higher pressure. We attribute this phenomenon to different elastic strains undergone by the two layers during the adsorption process. For the supported layer, the planes perpendicular to the substrate are constrained to have the same interatomic spacing as that of the substrate so that the elastic deformation is unilateral, at an atomic scale, and along the pore axis. When the substrate is removed, tridimensional deformations occur and the porous system can find a new configuration for the solid atoms which decreases the free energy of the system adsorbate-solid. This results in a decrease of the adsorbed amount and in an increase of the condensation pressure. The isotherms for the supported porous layers shift toward that of the membrane when the layer thickness is increased from 30 to 100 microns. This is due to the relaxation of the stress exerted by the substrate as a result of the breaking of Si-Si bonds at the interface between the substrate and the porous layer. The membrane is the relaxed state of the supported layer.Comment: Accepted in Langmui

Machine Learning in the development of Si-based anodes using Small-Angle X-ray Scattering for structural property analysis

Material development processes are highly iterative and driven by the experience and intuition of the researcher. This can lead to time consuming procedures. Data-driven approaches such as Machine Learning can support decision processes with trained and validated models to predict certain output parameter. In a multifaceted process chain of material synthesis of electrochemical materials and their characterization, Machine Learning has a huge potential to shorten development processes. Based on this, the contribution presents a novel approach to utilize data derived from Small-Angle X-ray Scattering (SAXS) of SiO_2 matrix materials for battery anodes with Neural Networks. Here, we use SAXS as an intermediate, high-throughput method to characterize sol–gel based porous materials. A multi-step-method is presented where a Feed Forward Net is connected to a pretrained autoencoder to reliably map parameters of the material synthesis to the SAXS curve of the resulting material. In addition, a direct comparison shows that the prediction error of Neural Networks can be greatly reduced by training each output variable with a separate independent Neural Network

Fünf Fagottkonzerte: in Dresdner Überlieferung: Partitur

Der vorliegende Band vereint fünf Fagottkonzerte, die in der Sächsischen Landesbibliothek – Staats- und Universitätsbibliothek Dresden überliefert sind und die hier erstmals, nahezu drei Jahrhunderte nach ihrer Entstehung, der musikalischen Öffentlichkeit in einer neuen Ausgabe vorgelegt werden. Bei vier der insgesamt sieben Quellen – darunter auch zwei Autographe – handelt es sich um Abschriften Dresdner Hofnotisten. Sie wurden im sog. »Schranck No: II.« in der Katholischen Hofkirche aufbewahrt, was sie als Repertoire der Kammermusik der Dresdner Hofkapelle der ersten Hälfte des 18. Jahrhunderts ausweist. Die außerordentliche Beliebtheit von Solo- und Gruppenkonzerten innerhalb der Dresdner Hofmusik im Augusteischen Zeitalter wird heute durch einen viele hunderte Kompositionen zählenden Werkbestand verdeutlicht

Fünf Fagottkonzerte

Der vorliegende Band vereint fünf Fagottkonzerte, die in der Sächsischen Landesbibliothek – Staats- und Universitätsbibliothek Dresden überliefert sind und die hier erstmals, nahezu drei Jahrhunderte nach ihrer Entstehung, der musikalischen Öffentlichkeit in einer neuen Ausgabe vorgelegt werden. Bei vier der insgesamt sieben Quellen – darunter auch zwei Autographe – handelt es sich um Abschriften Dresdner Hofnotisten. Sie wurden im sog. »Schranck No: II.« in der Katholischen Hofkirche aufbewahrt, was sie als Repertoire der Kammermusik der Dresdner Hofkapelle der ersten Hälfte des 18. Jahrhunderts ausweist. Die außerordentliche Beliebtheit von Solo- und Gruppenkonzerten innerhalb der Dresdner Hofmusik im Augusteischen Zeitalter wird heute durch einen viele hunderte Kompositionen zählenden Werkbestand verdeutlicht