This work presents the results of a simulation by the Monte Carlo method, performed through the GEANT4 code, of the irradiation and energy deposition by high flux X-rays on the piezoelectric ceramic Bismuth-Sodium Titanate doped with Barium. X-rays energies were around the Ti-K absorption edge emulating a transmission experiment, and the irradiation with 5300 eV X-rays for a fluorescence experiment. The method consists of introducing the data that describes a characteristic R3c structure of the polarized ceramic, reported in the literature. The absorption coefficients for the energies of interest, as well as the energy deposited in the form of radiation doses, are calculated. Intensity changes for specific energy lines in the micro-fluorescence spectra, which suggest the presence of vacancies in the crystal structure, are verified via simulation. The vacancy density produced by a typical photon flux of a fourth-generation synchrotron beam is calculated through the threshold displacement energy for vacancy production. Consequently, the simulation is carried out for a structure with appropriate Bi and O vacancies, and the ability to detect the radiation damage is verified by comparison with micro-XRF and XAFS experimental results. The simulation predicts a maximum dose of 1.21-1.27x105 Gy irradiating 107 photons for the given energy and a maximum vacancy density of 1.10x108 / micron3 for oxygen atoms and 6.90x107 /micron3 for bismuth atoms.
Preparation of concentrated silver nanoparticles in water remains a challenge today. The intrinsic reactivity of silver, as well as the high surface energy of nanoparticles, make it difficult to handle them without altering their pristine properties. Herein, we report the preparation of concentrated silver nanoparticles (AgNPs) dispersion (2 mM; 1.5⋅10 15 NPs/mL) by reducing Ag + in-situ of a β-cyclodextrin-epichlorohydrin polymer (βCDP) as a capping agent. The prepared nanoparticles (AgNPs@βCDP) with a Surface Plasmon Resonance band at 396 nm, and a hydrodynamic diameter of 21.4 � 1.8 nm, retained both features after being precipitated and redispersed in water. The AgNPs core had a spherical morphology, with a 12.7 � 1.5 nm diameter in size, as determined by TEM. The AgNPs@βCDP showed outstanding bactericidal properties against Escherichia coli (MIC = 0.37 nM), one of the lowest ever achieved for silver nanoparticles. We suggest that the polymer acts as a Trojan horse with AgNPs as payload.
Research on lead-free piezoceramics is a trending topic [1]. A significant component of this search is the characterization of the effect of texture on the properties of polycrystalline electroceramics. The present contribution describes an integrated methodology, systematized in a software package, to solve the following tasks: (a) interpretation by numerical simulation of XRD patterns produced by textured samples; (b) forecast of the effective elasto-electrical properties of piezoceramics, starting from the knowledge of the corresponding single-crystal tensors and the texture determined in (a).
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