Springback effect and structural features during the drying of silica aerogels tracked by in-situ synchrotron X-ray scattering

The springback effect during ambient pressure drying of aerogels is an interesting structural phenomenon, consisting of a severe shrinkage followed by almost complete re-expansion. The drying of gels causes shrinkage, whereas re-expansion is believed to be linked to repelling forces on the nanoscale. A multi-scale structural characterization of this significant volume change is key in controlling aerogel processing and properties. In this work, hydrophobic, monolithic silica aerogels with high specific surface areas were synthesized by modification with trimethylchlorosilane and ambient pressure drying. Here, we report a multi-method approach focusing on in-situ X-ray scattering to observe alterations of the nanostructured material during the drying of surface-modified and unmodified silica gels. Both show a porous fractal nanostructure, which partially collapses during drying and only recovers in surface-modified samples during the springback effect. Distinct changes of the X-ray scattering data were reproducibly associated with the shrinkage, re-expansion and drying of the gel network. Our findings may contribute to tailor aerogels with specific functionality, as the springback effect has a direct influence on properties (e.g., porosity, pore size distribution), which is directly affected by the degree of re-expansion

Fabrication and characterization of porous mullite ceramics derived from fluoride assisted Metakaolin Al OH 3 annealing for filtration applications

In this work, polycrystalline mullite whiskers are synthesized by fluoride assisted method from metakaolin and several aluminum containing compounds such as amp; 947; Al OH 3, AlF3 3H2O, and amp; 945; Al2O3 corundum . The mullite formation and crystallization are assessed both in ex situ and in situ synchrotron X ray diffraction experiments under synthesis conditions. Polycrystalline mullite starts to form from metakaolin, Al OH 3, and AlF3 3H2O reactants at 680 C, whereas mullite does not form even at 1000 C when corundum is used. Porous mullite ceracmics are fabricated at sintering temperatures between 1000 and 1700 C and tested for water permeance. Scanning Electron Microscopy SEM and synchrotron X ray tomography amp; 956;CT reveal that ceramics are comprised of pore channels with an interlocked network of mullite whiskers. With competitive porosity up to 63 , compressive strength up to 20 MPa , and pure water flux up to 579 L m2 h at 1 bar , fabricated mullite ceramics are promising candidates for water filtration and purificatio

Extrusion based additive manufacturing of fungal based composite materials using the tinder fungus Fomes fomentarius

Background Recent efforts in fungal biotechnology aim to develop new concepts and technologies that convert renewable plant biomass into innovative biomaterials. Hereby, plant substrates become metabolized by filamentous fungi to transform them into new fungal based materials. Current research is thus focused on both understanding and optimizing the biology and genetics underlying filamentous fungal growth and on the development of new technologies to produce customized fungal based materials. Results This manuscript reports the production of stable pastes, composed of Fomes fomentarius mycelium, alginate and water with 71 wt. mycelium in the solid content, for additive manufacturing of fungal based composite materials. After printing complex shapes, such as hollow stars with up to 39 mm in height, a combination of freeze drying and calcium crosslinking processes allowed the printed shapes to remain stable even in the presence of water. The printed objects show low bulk densities of 0.12 amp; 8201; amp; 8201;0.01 g cm3 with interconnected macropores. Conclusions This work reports for the first time the application of mycelium obtained from the tinder fungus F. fomentarius for an extrusion based additive manufacturing approach to fabricate customized light weight 3D objects. The process holds great promise for developing light weight, stable, and porous fungal based materials that could replace expanded polystyrene produced from fossil resource

Silicon oxycarbonitride ceramic containing nickel nanoparticles from design to catalytic application

Nickel containing silicon oxycarbonitride ceramic nanocomposites are synthesized from hydrous nickel acetate and poly vinyl silazane Durazane 1800 or perhydropolysilazane NN120 20 A PHPS . A room temperature chemical reaction results in Ni containing polysilazane precursors which are transformed into ceramic nanocomposites with nickel nanoparticles 2 4 nm upon pyrolysis at elevated temperatures 700 1100 C under an argon atmosphere. The ceramic nanocomposites derived from the Durazane 1800 Ni precursor by the thermolysis process at 700 and 900 C manifest a microporous structure with a BET specific surface area of amp; 8764;361 and amp; 8764;232 m2 g amp; 8722;1, respectively. In contrast, all pyrolyzed samples derived from the PHPS Ni precursor exhibit a nonporous structure. The Ni SiOCN ceramic nanocomposites tested in a plug flow fixed bed reactor display significant catalytic activity in dry methane reforming to syngas. The highest CH4 reaction rate of 0.18 mol min amp; 8722;1 gNi amp; 8722;1 is observed at 800 C for the sample derived from the PHPS Ni precursor by pyrolysis at 900 C. All these make the materials developed in this work, i.e. nickel nanoparticles in situ formed in the SiOCN ceramic matrix, as promising candidates for heterogeneous catalysi

Pbca-Type In2O3: the high-pressure post-corundum phase at room temperature

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp5061599High-pressure powder X-ray diffraction and Raman scattering measurements in cubic bixbyite-type indium oxide (c-In2O3) have been performed at room temperature. On increasing pressure c-In2O3 undergoes a transition to the Rh2O3-II structure but on decreasing pressure Rh2O3-II-type In2O3 undergoes a transition to a previously unknown phase with Pbca space group which is isostructural to Rh2O3-III. On further decrease of pressure, we observed a phase transition to the metastable corundum-type In2O3 near room conditions. Recompression of the metastable corundum-type In2O3 at room temperature leads to a transition to the Rh2O3-III phase, thus showing that the Rh2O3-III phase is the post-corundum phase at room temperature. Our results are supported by theoretical ab initio calculations. Furthermore, they show that the Rh2O3-III phase could be present in other sesquioxides, thus prompting to a revision of the pressure-temperature phase diagrams of sesquioxidesFinancial support by the Spanish MEC under Grant No. MAT2010-21270-C04-01/03/04, MAT2013-46649-C4-1/2/3-P, by MALTA Consolider Ingenio 2010 project (CSD2007-00045) and by Generalitat Valenciana (GVA-ACOMP-2013-012). Red Espanola de Supercomputacion (RES) and ALBA Synchrotron Light Source are also acknowledged. B.G.-D. and J.A.S. acknowledge financial support through the FPI program and Juan de la Cierva fellowship, respectively. We also thank J. L. Jorda for fruitful discussions. A.L.J.P. acknowledges financial support through Brazilian CNPq. A.S. expresses thanks to FEDER Grant UNLV10-3E-1253 for financial support.García-Domene, B.; Sans Tresserras, JÁ.; Gomis, O.; Manjón Herrera, FJ.; Ortiz, HM.; Errandonea, D.; Santamaría Pérez, D.... (2014). Pbca-Type In2O3: the high-pressure post-corundum phase at room temperature. Journal of Physical Chemistry C. 118(35):20545-20552. https://doi.org/10.1021/jp5061599S20545205521183

Synergistic NGF/B27 Gradients Position Synapses Heterogeneously in 3D Micropatterned Neural Cultures

Native functional brain circuits show different numbers of synapses (synaptic densities) in the cerebral cortex. Until now, different synaptic densities could not be studied in vitro using current cell culture methods for primary neurons. Herein, we present a novel microfluidic based cell culture method that combines 3D micropatterning of hydrogel layers with linear chemical gradient formation. Micropatterned hydrogels were used to encapsulate dissociated cortical neurons in laminar cell layers and neurotrophic factors NGF and B27 were added to influence the formation of synapses. Neurotrophic gradients allowed for the positioning of distinguishable synaptic densities throughout a 3D micropatterned neural culture. NGF and B27 gradients were maintained in the microfluidic device for over two weeks without perfusion pumps by utilizing a refilling procedure. Spatial distribution of synapses was examined with a pre-synaptic marker to determine synaptic densities. From our experiments, we observed that (1) cortical neurons responded only to synergistic NGF/B27 gradients, (2) synaptic density increased proportionally to synergistic NGF/B27 gradients; (3) homogeneous distribution of B27 disturbed cortical neurons in sensing NGF gradients and (4) the cell layer position significantly impacted spatial distribution of synapses

Effect of Complexation of Thiocyanate Ion with Co2+ on the Adsorption of Tetraethylammonium Iodide from Aqueous Solutions Containing NH4SCN

94-9

AC conductivity and dielectric properties of In

Stoichiometric In2S3 films were prepared by thermal evaporation technique onto clean glass substrates. According to X-ray investigations, the as-deposited films were in amorphous state. Both the ac conductivity and dielectric constants were measured in the frequency range 100 Hz−100 kHz at different temperatures. Different parameters such as the frequency exponent parameter s, the density of states near the Fermi level $N(E_{\rm F})$, the activation energy $(\Delta E)$ and the optical band gap Eg of In2S3 amorphous thin films were estimated. The hopping conduction was recognized as the conduction mechanism for the investigated films

Polarization Resistance Study on Copper Corrosion in Aqueous Potassium Hydrogen Phthalate Solution

The effect of temperature on corrosion of copper in 0.1 M aqueous solution of potassium hydrogen phthalate (KHPh) has been investigated using polarization resistance technique. it was found that that the corrosion rate in the range 25�65�C obyes Vant Hoff's and Arrhenius Laws. The results indicate that corrosion of copper in KHPh is mainly cathodically controlled process. The polarization resistance decreases with rising the temperature in accordance with Stern-Geary equation