Search results for "Metre"
showing 10 items of 150 documents
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…
Dense nanostructured materials obtained by spark plasma sintering and field activated pressure assisted synthesis starting from mechanically activate…
2004
The preparation of highly dense bulk materials with a grain size in the range of a few to a few hundreds nanometers is currently the objective of numerous studies. In our research we have achieved a measure of success in this regard by using the methods of mechanically-activated, field-activated, pressure-assisted synthesis, MAFAPAS, which has been patented, and mechanically-activated spark plasma sintering, MASPS. Both methods, which consist of the combination of a mechanical activation step followed by a consolidation step under the simultaneous influence of an electric field and mechanical pressure, have led to the formation of dense nanostructured ceramics, intermetallics, and composite…
Precursor-based synthetic pathways to nanometer NdNiO3−x particles
1993
Abstract The oxygen deficient neodymium nickel perovskite, NdNiO3−x, has been obtained by different low temperature-low oxygen pressure synthetic procedures. Besides a solid-matrix based route, both ordered and disordered chemical-precursors have been used as starting products. X-ray powder diffraction shows that the structure of this defective perovskite is orthorhombic. The study of the grain morphology of the products as resulting from the different synthetic procedures indicates that the main parameter determining the average particle size, which is in the nanometer range, is the maximum temperature achieved in the synthesis. Resistivity and DSC measurements show the existence of a meta…
Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness
2014
The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-…
Nonlinear Transport in Hybrid Polypyrrole–Gold Nanostructures
2010
We have studied charge transport in nanometer scale films of polypyrrole (PPy) that were grown electrochemically onto discontinuous ultrathin films of gold. The gold films consisted of 100 nm size islands, separated from each other by nanometer-size gaps. The thickness of PPy can be varied from 30 to 200 nm. The I-V characteristics of these hybrid PPy-Au nanostructures show strong non-linearity at low temperatures, and in particular for the more insulating samples. The hopping transport is further verified from the log / versus V-1/4 plots. Furthermore, the I-V data follow an empirical relation dlog//dV(1/4) similar to T-1/2.
Mechanical properties of the nanometer scale pre-crystalline order of a poly (ethylene terepthalate) / poly (ethylene naphthalene) blend
2006
A previous study carried out on PET has shown that this polymer undergoes a continuous structural modification over a wide cooling rate interval when solidified from the melt[1] assuming a semi-crystalline structure below 2 K s 1 and a completely amorphous one above 100 K s 1. Most important was the existence of a state of intermediate order between the above cooling rates which was evidenced by the absence of crystalline reflections in the WAXS patterns and the occurrence of SAXS maxima[2] and exothermic peak areas (DSC) in the cooling rate range above 2 K s 1. Microhardness (MH) measurements revealed that this phase affects the mechanical properties[3] plausible if one thinks of crystalli…
Micrometer-resolution reconstruction and analysis of whole mouse brain vasculature by synchrotron-based phase-contrast tomographic microscopy
2021
AbstractNervous tissue metabolism is mainly supported by the dense thread of blood vessels which mainly provides fast supplies of oxygen and glucose. Recently, the supplying role of the brain vascular system has been examined in major neurological conditions such as the Alzheimer’s and Parkinson’s diseases. However, to date, fast and reliable methods for the fine level microstructural extraction of whole brain vascular systems are still unavailable. We present a methodological framework suitable for reconstruction of the whole mouse brain cerebral microvasculature by X-ray tomography with the unprecedented pixel size of 0.65 μm. Our measurements suggest that the resolving power of the techn…
Scattering perspectives on nanostructural inhomogeneity in polymer network gels
2017
Abstract Scattering methods based on spatial and temporal contrast fluctuations in polymer-network gels, which originate from polymer-segmental density fluctuations, reveal rich insight into different types and levels of nanostructural inhomogeneity in these soft materials. Complementary contrasting as provided by light, neutron, and X-ray scattering allows such information to be obtained on nano- to micrometer length scales. On top of that, complementary use of static and dynamic scattering methods allows the interplay and effect of these inhomogeneities to be unraveled. This article interrelates a multitude of studies on the application of scattering techniques for analytical assessment o…