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

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

How do the micropores of carbon xerogels influence their electrochemical behavior as anodes for lithium-ion batteries?

This work aims at shedding light on how the microporous texture of porous carbons influences their electrochemical behavior when used as anodes for Li-ion batteries. To this aim, a synthetic hard carbon (carbon xerogel, CX), prepared from a resorcinol-formaldehyde precursor gel, underwent several post-synthesis treatments in order to modulate its micropore to total pore volume ratio. The micropore volume was either expanded by physical activation or decreased using chemical vapor deposition (CVD) of a carbon layer. Several variables other than the micropore texture of the obtained carbons, which could influence their behavior as anode active materials for Li-ion batteries, such as the particle size or the electrode characteristics, were carefully controlled. The thickness of electrode coatings and the pore texture of the active material-binder composite were analyzed. It was shown that CX-binder composites resulting from water-based slurries preserve the microporosity of the starting materials. Detailed electrochemical characterization of the electrodes prepared with carbon xerogels displaying various defined micropore textures was performed. A clear linear dependency could be evidenced between the Li+ insertion and de-insertion in half-cell configuration with the increase of the volume of supermicropores (0.7 – 2 nm), demonstrating the effect of micropore enlargement by activation on the storage capacity, provided the maximum charge potential value is set at 3.0 V vs. Li+/Li

Hydrocarbon degradation, plant colonization and gene expression of alkane degradation genes by endophytic Enterobacter ludwigii strains

The genus Enterobacter comprises a range of beneficial plant-associated bacteria 2 showing plant growth-promotion. Enterobacter ludwigii belongs to the Enterobacter 3 cloacae complex and has been reported to include human pathogens but also plant-4 associated strains with plant beneficial capacities. To assess the role of Enterobacter 5 endophytes in hydrocarbon degradation, plant colonization, abundance and expression of 6 CYP153 genes in different plant compartments, three plant species (Italian ryegrass, 7 birdsfoot trefoil and alfalfa) were grown in sterile soil spiked with 1% diesel and 8 inoculated with three endophytic Enterobacter ludwigii strains. Results showed that all 9 strains were capable of hydrocarbon degradation and efficiently colonized the 10 rhizosphere and plant interior. Two strains, ISI10-3 and BRI10-9, showed highest 11 degradation rates of diesel fuel up to 68% and performed best in combination with Italian 12 ryegrass and alfalfa. All strains expressed the CYP153 gene in all plant compartments, 13 indicating an active role in degradation of diesel in association with plants.Higher Education Commission of Pakistanhttp://www.sciencedirect.com/science/journal/0269749