1,721,105 research outputs found
Investigation of bio-related minerals by electron-diffraction tomography: Vaterite, dental hydroxyapatite, and crystalline nanorods in sponge primmorphs
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Single nano crystal analysis using automated electron diffraction tomography
No full textMost of hitherto unknown natural phases and many new synthetic compounds can grow only in the form of nanocrystals. X-ray powder diffraction is the most widespread technique for the structural characterization of nanomaterials, but its use is limited by two main restrictions: structural information is projected in one dimension and data come from the whole sample and not from a specific single crystallite. On the other hand, crystallographic methods based on the scattering of accelerated electrons are able to obtain 3-D structural data from single volumes of few tens of nanometers. Automated diffraction tomography is a recently developed method able to record more kinematical and complete electron diffraction data. This method consists in the acquisition of a series of electron diffraction patterns while the sample is rotated around an arbitrary tilt axis by sequential mechanical steps, within the full tilt range of the microscope goniometer. Data collection can be performed on highly beam sensitive materials, as no time is required for orienting the crystal along specific crystallographic orientations and mild illumination conditions are used. In the last years many nanocrystalline materials belonging to different material classes have been characterized by automated diffraction tomography. This review describes the different experimental and analytical approaches used for the determination of inorganic and organic phases and points out the advantages offered by automated diffraction tomography for the characterization of minor phases available only in polyphasic nanomixtures and for the description of domain arrangement in polycrystalline nanocomposites
Automated electron Diffraction Tomography (ADT) – a new technique for routine structure solution of nano-crystalline zeolites and porous materials
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“Ab-initio” structure solution of nano-crystalline minerals and synthetis materials by automated electron tomography
No full textAutomated electron Diffraction Tomography (ADT) for solving structures of beam sensitive nanoporous materials
No full textStructure characterization of nanocrystalline porous materials by tomographic electron diffraction
No full textSeveral porous phases have been characterized in the last years by tomographic electron diffraction. This paper provides an overview of the analyzed phases, pointing out the difficulties associated with different classes of materials or specific sample characteristics. The two methods for tomographic electron diffraction acquisition, automated diffraction tomography and rotation electron diffraction, are described in detail, as well as data reduction algorithms. Attainments and limits of different structure determination and refinement algorithms are discussed for inorganic, organic and hybrid organic-inorganic materials. Finally, it is shown how tomographic electron diffraction and X-ray powder diffraction data can be combined for a comprehensive characterization of porous materials
Single-crystal analysis of nanodomains by electron diffraction tomography: Mineralogy at the order-disorder borderline
No full textElectron diffraction tomography is a powerful emerging method for the structure characterization of materials available only as sub-micrometric grains. This technique can in fact deliver complete 3D information from a single crystal of few hundreds or few tens of nanometers, allowing the analysis of polyphasic or polytypic mixtures that generally cannot be fully addressed by X-ray methods. In this paper, we report and discuss three mineralogy-related study cases where electron diffraction tomography was the only way for achieving a proper description of the sample, by the identification and the structure determination of all the phases or all the polytypes within. We also show how electron diffraction tomography and dynamical refinement can be combined for finding accurate atomic positions and localizing hydrogen atoms at room conditions. Finally, we stress the future potential of this method in the fields of mineralogy and experimental petrology, where till now many samples cannot be properly described because nanocrystalline, polyphasic or disordered. Electron diffraction tomography can be used for detecting unexpected or unknown phases in high-pressure synthetic yields or for the characterization of fine rocks formed under extreme conditions, like impactites or meteorites. Eventually, this method allows the structure characterization of single domains that are ordered only at the scale of few cell repetitions, and therefore it makes possible investigating those materials at the borderline between crystalline and amorphous matter and delivers crucial and unique elements for the understanding of the first stages of solid matter organization
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