Auto-combustion synthesis of perovskite-type oxides SrTi1−xFexO3−δ

A versatile one-pot auto-combustion method for the synthesis of powders of iron-doped strontium titanate, SrTi1−xFexO3−δ, has been developed. The synthesis is optimized by the combined use of EDTA and citric acid as chelating agents, and an appropriate balance between fuel and oxidizing elements in the reaction mixture. The method produces immediately an almost phase-pure perovskite oxide powder, with an ultra-fine crystallite size of 20–40 nm, and with a low level of organic residues. Highly sinter-active powders are obtained after calcination and ball-milling of the powders

Rapid densification of sol–gel derived yttria-stabilized zirconia thin films

A method based on X-ray reflectivity was used to study the densification behavior of 8 mol% yttria-stabilized zirconia for use in solid oxide fuel cells. Sol–gel derived thin electrolyte films were prepared via spin coating. Subsequent microwave-assisted rapid thermal annealing at 650–1000 °C resulted in crack-free 70 nm thin films. A maximum density of approximately 95% was achieved within 5 min at 1000 °C. X-ray photoelectron spectroscopy depth analysis on the thin films showed that the shorter annealing times, as opposed to conventional heating, resulted in lower Si concentrations at the top surface and at the substrate interfac

Een tweede archeologisch inventariserend veldonderzoek (IVO) door middel van proefsleuven op bestemmingsterrein Achter 't Holthuis te Twello, gemeente Voorst (Gld.)

ARC-projectcode: 2007/02

Micro- and nanopatterning of functional materials on flexible plastic substrates via site-selective surface modification using oxygen plasma

A simple and cost effective methodology for large area micro and nanopatterning of a wide range of functional materials on flexible substrates is presented. A hydrophobic-hydrophilic chemical contrast was patterned on surfaces of various flexible plastic substrates using molds and shadow masks with which selected areas of the substrate surface were shielded from exposure to oxygen plasma. The exposed areas became hydrophilic and were used as templates for site-selective adsorption, electroless deposition and solution phase deposition of functional materials like ZnO, Ag thin films, Au nanoparticles, conducting polymers, titania and ZnO nanowires. The patterned surfaces and functional materials were characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy

Op zoek naar de noordelijke grens van de Bronstijd/ IJzertijdnederzetting bij Borger : een archeologisch inventariserend veldonderzoek (IVO) door middel van proefsleuven op bestemmingsterrein 'Natuurtransferium' langs de Koesteeg/Rolderstraat te Borger, gemeente Borger-Odoorn (Dr.)

Lit.opg

Rapid Glucocorticoid Receptor-Mediated Inhibition of Hypothalamic-Pituitary-Adrenal Ultradian Activity in Healthy Males

Contains fulltext : 84121.pdf (publisher's version ) (Open Access)10 p

Archeologie rond de middenstip : een archeologisch inventariserend veldonderzoek (IVO) door middel van proefsleuven op plangebied Achter 't Holthuis te Twello, gemeente Voorst (Gld.)

ARC-Projectcode 2003-010

Numerical Investigation of Propeller–Flap Interaction in Inclined Over-the-Wing Distributed-Propulsion Systems

In this study, unsteady RANS simulations are performed to investigate the effect of over-the-wing (OTW) propeller inclination on the aerodynamic interaction with a wing featuring a plain flap. A comparison to experimental data shows that the numerical approach is capable of modeling the wing and propeller separately and can capture the effect of the wing on the propeller in the OTW configuration, but under-predicts propeller-induced flow separation over the flap. The results show that, if the propeller is installed over the flap hinge and aligned with the freestream velocity (baseline configuration), the slipstream and blade tip-vortices generate additional adverse pressure gradients on the wing surface, leading to a local increase in flow separation downstream. However, if the propeller is tilted and aligned with the flap surface (inclined configuration), the slipstream increases the momentum in the boundary layer and the flow remains attached. The propeller alters the pressure distribution of the wing such that higher lift is generated in the baseline case, while a larger drag reduction is achieved in the inclined case. However, combined with the thrust vector of the propeller, the baseline configuration is found to have the largest combined axial force in thrust direction, while the inclined configuration presents the highest effective lift. These results indicate that inclining the propeller can enhance the low-speed performance of OTW distributed-propulsion systems.Virtual/online event due to COVID-19Flight Performance and Propulsio

Nanostructure Development in Alkoxide-Carboxylate-Derived Precursor Films of Barium Titanate

The structural evolution in wet alkoxide-carboxylate sol–gel precursor films of barium titanate upon drying was investigated by time-resolved small-angle X-ray scattering (SAXS). The morphology of as-dried amorphous precursor thin films was investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Sols were prepared from titanium(IV) iso-propoxide in 2-methoxyethanol and barium acetate in acetic acid. The structures that were visible with SAXS could be divided into oligomeric structures with fractal-like scattering characteristics, and randomly packed agglomerates of nanoparticles of similar size. The fractal-like morphologies disappeared during film drying, probably because they were not stable in the absence of a solvent matrix. Only the ordered agglomerate-like structures remained in the as-dried films. EELS on as-dried films showed that spatial separation between barium and titanium-rich domains occurred during the drying of the thin films on a length scale of nanometers, depending on hydrolysis ratio. This demonstrates that as-dried films are not necessarily uniform on the mesoscopic level