Search results for "Etre"
showing 10 items of 350 documents
Comparative Acoustic and Contact Studies of Elasticity of Ferroelectric LixNa1 - xTa0.1Nb0.9O3Solid Solutions at Nanometer Spatial Resolution
2009
Comparative acoustic and contact studies of elastic properties of the Li x Na 1−x Ta 0.1 Nb 0.9 O 3 (x = 0.015–0.135) ferroelectric solid solution ceramics are reported. A good agreement is obtained between the values of elastic modules determined by acoustic and contact methods at nano-scale spatial resolution.
Evidence for the verwey transition in highly nonstoichiometric nanometric fe-based ferrites
2001
The nanometric scale allows an investigation of the Verwey transition: the impact of varying degree of oxidation of Fe cations on this transition was studied by means of zero-field-cooled superconducting quantum interference device measurements in nanometric highly nonstoichiometric particles of pure and Ti-substituted magnetite synthesized using soft chemistry route. It is clearly shown that (i) there is a shift of the transition towards higher temperatures for nanometer scaled compounds and (ii) the amplitude, the temperature, and the order of the transition are only depending on the number of ${\mathrm{Fe}}^{2+}{/\mathrm{F}\mathrm{e}}^{3+}$ pairs in octahedral coordination.
Synthesis of Multifunctional Inorganic Materials
2018
Abstract Both, novel and older widely and routinely used methods of chemical synthesis fornew multifunctional inorganic (nano) materials with different sizes and morphologies are reviewed and summarized in this chapter. Illustrative examples of micro- and nanoparticle preparations are provided regarding different applications: renewable and sustainable energy harvesting, water splitting and hydrogen generation, fuel and solar cell devices, luminescent materials for white light–emitting diodes and clean environment. We give our perspective on the current status of the topic: methods of colloidal chemistry, coprecipitation, reverse-micelle technique, sol–gel, spray pyrolysis, microwave-assist…
Microactuators: Control of the Properties of Micrometer Sized Actuators from Liquid Crystalline Elastomers Prepared in a Microfluidic Setup (Adv. Fun…
2010
In this article new results on the preparation of monodisperse particles from a liquid crystalline elastomer in a microfluidic setup are presnted. For this, droplets from a liquid crystalline monomer are prepared in a microfluidic device and polymerized while they are flowing inside a microtube. The particles obtained by this method possess an internal orientation, which gives them actuating properties. When they are heated into the isotropic phase of the liquid crystalline material they show a reversible change in shape whereby they change their length in one direction by almost 100%. It is shown how the variation of experimental parameters during their synthesis impacts the properties of…
Exfoliation of Alpha-Germanium: A Covalent Diamond-Like Structure
2021
2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow-bandgap semiconductor presenting a 3D diamond-like structure with strong covalent bonds. Pure α-germanium is exfoliated following a simple one-step procedure assisted by wet ball-milling, allowing gram-scale fabrication of high-quality layers with large lateral dimensions and nanometer thicknesses.…
Microfluidic synthesis of micrometer-sized photoresponsive actuators based on liquid crystalline elastomers
2016
The fabrication of photoresponsive micrometer-sized liquid crystalline elastomer (LCE) particles has been described in this article for the first time. The preparation of the LCE particles using a microfluidic device by a continuous “on the fly” technique allows their fast processing with an irradiation time of less than 2 seconds. In order to accelerate the polymerization and to make the preparation of samples with thicknesses of several hundred microns possible, we modified a NIR-photoinitiation system by adding a bleaching agent. In addition to the photoinitiator, a side-chain liquid crystalline monomer containing an azo-group and a LC-crosslinker were used in the polymerization mixture.…
Smart composite films of nanometric thickness based on copper-iodine coordination polymers. Toward sensors.
2018
One-pot reactions between CuI and methyl or methyl 2-amino-isonicotinate give rise to the formation of two coordination polymers (CPs) based on double zig-zag Cu2I2 chains. The presence of a NH2 group in the isonicotinate ligand produces different supramolecular interactions affecting the Cu-Cu distances and symmetry of the Cu2I2 chains. These structural variations significantly modulate their physical properties. Thus, both CPs are semiconductors and also show reversible thermo/mechanoluminescence. X-ray diffraction studies carried out under different temperature and pressure conditions in combination with theoretical calculations have been used to rationalize the multi-stimuli-responsive …
Plastic Deformation of Single Nanometer-Sized Crystals
2008
We report in situ electron microscopy observations of the plastic deformation of individual nanometer-sized Au, Pt, W, and Mo crystals. Specifically designed graphitic cages that contract under electron irradiation are used as nanoscopic deformation cells. The correlation with atomistic simulations shows that the observed slow plastic deformation is due to dislocation activity. Our results also provide evidence that the vacancy concentration in a nanoscale system can be smaller than in the bulk material, an effect which has not been studied experimentally before.
Alginate gel beads filled with halloysite nanotubes
2013
Abstract Novel hybrid gel beads with a well defined and controlled size formed by alginate biopolymer and halloysite (Hal) nanotubes were designed, prepared and characterized from the physico-chemical viewpoint. The thermogravimetry made it possible to determine the water content, the total as well as the local compositions of Hal into the gel beads. Dielectric spectroscopy evidenced that Hal reduced the fluctuation of ions. The SEM micrographs showed that the dried beads exhibit a rough surface, with pores in the micrometer range. In addition, the concentration of nanotubes was higher into the bead core at a higher overall loading. The performance of these materials was verified with the s…
Organometal Halide Perovskites: Bulk Low-Dimension Materials and Nanoparticles
2015
Organometal halide perovskites (hybrid perovskites) contain an anionic metal–halogen-semiconducting framework and charge-compensating organic cations. As hybrid materials, they combine useful properties of both organic and inorganic materials, such as plastic mechanical properties and good electronic mobility related to organic and inorganic material, respectively. They are prepared from abundant and low cost starting compounds. The perovskite stoichiometry is associated with the dimensionality of its inorganic framework, which can vary from three to zero, 3D consisting of corner-sharing MX6 octahedra, and 0D consisting of isolated octahedra. Small-sized organic cations can fit into the MX6…