71 research outputs found
Particle anisotropy and crystalline phase transition in one-pot synthesis of nano-zirconia: A causal relationship
No full textCrystalline phase evolution and morphological changes are strictly correlated phenomena during the growth of zirconia nanoparticles. In this work, the effects of synthetic variables, reaction time (up to 24 hours) and precursor concentration (0.16 and 0.5 M), of a one-step non-hydrolytic sol-gel route to zirconia are investigated. Zirconium tetrachloride (ZrCl4) is chosen as a zirconium oxide precursor to react in benzyl alcohol. At a low precursor concentration and a short reaction time, pseudo-spherical particles of size 2 nm with a narrow size distribution are observed by transmission electron microscopy (TEM). At this stage, mainly the tetragonal phase is detected. By increasing both the zirconium precursor concentration and reaction time, a broadening of size distribution is observed resulting from the growth of anisotropic particles. Concurrently, an increasing amount of the monoclinic is detected by X-ray diffraction and Raman spectroscopy. As a novelty, Rietveld investigations on electron diffraction ring patterns obtained by transmission electron microscopy are performed. This procedure allows the collection of comprehensive information about nanostructured particles in one-step analysis. The results derived from this analysis, together with the high resolution transmission electron microscopy (HR-TEM) data, consistently support the structural transition from pseudo-spherical tetragonal particles to rice-shaped monoclinic particles
Full-profile search–match by the Rietveld method
No full textA new search–match procedure has been developed and tested which, in contrast to previously existing methods, does not use a set of lines identified from a diffraction pattern, but an optimized Rietveld fitting on the raw data. Modern computers with multicore processors allow the routine to be fast enough to perform the entire search in a reasonable time using quite large databases of crystal structures. The search–match is done using the crystal structures for all phases and the instrumental geometry, and as such can be applied to every kind of diffraction experiment, including X-rays, thermal/time-of-flight neutrons and electrons. The methodology can also be applied to nanocrystalline samples for which peak identification may be a problem. A web interface has been developed to permit easy testing and evaluation of the procedure. The quality of the results mainly depends on the availability of the sought phase in the structure database. The method permits not only phase identification but also a rapid quantification of the phases and their gross microstructural features, provided the instrumental function is known. © 2019 Luca Lutterotti et al. Journal of Applied Crystallography published by IUCr Journals
Structural and morphological phase control by supersonic beams on titanyl phthalocyanine: An investigation on the growth
No full textTitanyl Phthalocyanine (TiOPc) is a cyclic oligomer widely used in organic electronics for its good stability, optical properties and charge mobility. Several polymorphs of TiOPc are known, showing different physical properties and consequently, in particular in the growth of thin films, the full control over the crystal phase formation is critical to effectively tune the conductive properties of the material. As a consequence, the availability of growth techniques allowing a precise control of both the morphology and crystal phase of the obtained films is crucial for the production of devices. In this work the structural properties and polymorphism of titanyl phthalocyanine thin films, grown on silicon substrates, have been systematically studied by synchrotron radiation grazing incidence X-rays diffraction and atomic force microscopy. Films obtained by the use of hyperthermal seeded supersonic beams technique allowed to unveil the key role played by the kinetic energy of the molecules in stabilizing specific polymorphs of TiOPc. The different growth conditions lead to grain dimensions in a range from the nanometric to the micrometric scale, depending on the substrate temperature and on the kinetic energy of the beam, while a high degree of fiber-like crystallographic order is observed in all the analyzed samples. The excellent control over phase selection, grain size and shape together with the production of well oriented high quality crystals makes of the hyperthermal seeded supersonic beams technique a promising tool for the realization of TiOPc thin films with structural and morphologic properties suitable for electronic application
Effect of Processing and Orientation on Structural and Mechanical Properties of Polypropylene Products
No full text32-Channel silicon strip detection module for combined X-ray fluorescence spectroscopy and X-ray diffractometry analysis
No full textA compact detection module for the simultaneous measurement of XRF and XRD in portable analytical applications, in particular in the mining sector, is presented. The detector head is based on 32 silicon strip detectors, fabricated with a low-leakage technology by FBK and readout by two 16-channel low noise CUBE charge-sensitive amplifiers. The design of the module and its characterization are reported. Multiple configurations are experimentally compared in terms of strip length, spacing, collimation and charge sharing
effects. The optimal configuration for a strip length of 6mm and pitch 0.2mm is thus identified. It offers an energy resolution of better than 200 eV at 5.9 keV with moderate cooling (−10°C) and peaking time of 14 μs
Method for the simultaneous determination of anisotropic residual stresses and texture by x-ray diffraction
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Rietveld texture analysis from synchrotron diffraction images. I. Calibration and basic analysis
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