Publications

Bulk high density MgB2 and a composite material made of a PLA matrix and MgB2 powder inclusions were in vivo tested as candidates for biodegradable materials for orthopedic implants. A rat model was used. Implants were introduced into femoral bone, in transversal and longitudinal directions. Assessment of the implant-tissue interaction was performed by X-ray imaging, X-ray computer tomography, electron microscopy, cytology, and histopathology on samples at 40 and 90 days after surgery. Both materials are biocompatible, bone and adjacent soft tissue showing good tolerance of implants. Biodegradation of MgB2 is faster than for PLA-MgB2 composite, but in both cases, it is accompanied by bone regeneration. Results suggest that use of MgB2-containing composites can promote space and time control of degradation and promotes MgB2 as a promising material for fracture repair. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

NiTi cylindrical materials were obtained by spark plasma sintering at 850??C or 900??C from high purity Ni and Ti powders. These mixtures were previously processed by mechanical alloying for 8 and 15 hours. In order to increase the alloy homogeneity, the NiTi materials were subjected to post aging treatment in protective atmosphere at constant temperature 400??C and cooling in water with ice. All samples were characterized by optical microscopy, differential calorimetry (DSC), X-ray measurements (XRD) and micro/nanoindentation measurements. The results demonstrate that the NiTi materials obtained by this preparation route have good mechanical properties and can serve as a quantitative reference for the microstructure design of shape memory materials for various applications, such as the biomedical ones.

The dielectric and electric properties of a core-shell SrFe12O19 - BNT-BT nanocomposite were explored in this study. The desired composition and the existence of the magnetoplumbite SrFe12O19 and perovskite BNT-BT structures were verified by X-ray diffraction. The dielectric constant values approached the case of BNT-BT due to the small amount of hexaferrite content. The electric properties were also derived.

A consistent quantitative description of radiation-induced degradation on p-type Silicon detectors is conducted within CERN RD50 collaboration. The present contribution summarizes the first obtained results for epitaxial 50 mu m thin pad diodes irradiated with protons, neutrons and gamma rays. Microscopic and Macroscopic damage-driven effects are analyzed.

Recent progress in "Green" Nanotechnology is trying to fight against many diseases, a special interest being given to silver-based nanoparticles biogenerated from plants. In this study, phytogenic silver chloride nanoparticles (m-AgClNPs) were "green" synthesized by using an aqueous extract of Mentha piperita L. leaves, and then examined against urease activity. Urease, a nickel-containing enzyme, has been reported to contribute to the pathogenesis of many diseases (hepatic coma, encephalopathy, gastritis, gastric ulcer, and others). The obtained m-AgClNPs presented good physical stability (checked by zeta potential measurements) and high antioxidant activity (evaluated by chemiluminescence technique). Their size was estimated by Dynamic Light Scattering (DLS) measurements. UV-Vis absorption and fluorescence emission spectroscopy were used to study the impact of bio-AgNPs on urease. Our bio-developed m-AgClNPs exhibited good urease inhibitory activity and no destabilization of urease structure against thermal denaturation. These findings could be exploited in the development of novel inhibitors of urease for agronomic and biomedical applications.

Carbon-Titanium multilayer and composite thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisted by a carbon base layer and seven alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. By changing of substrate temperature, and on the other hand the bias potential up to ???700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Grazing Incidence X-ray Diffraction (GIXRD) and Electron Microscopy technique (TEM). The measurements show that increase of the substrate temperature reveal the changes in TixCy lattice parameters. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively and a Bruker Hystrion TI 980 TriboIndenter. Was found that the coefficient of friction depends on the synthesis temperature, bias voltage and also by the C content, Ti content and amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedeman-Frantz law was obtained the thermal conductivity.

Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO samples were sintered at 450, 550 and 630 degrees C, in ambient air. The thermal treatment did not influence the crystal phase composition, preserving in all cases the anatase single phase. As expected, the crystalline anatase quality improved with the annealing temperature. Nevertheless, slight differences in nanotubular morphology, such as the appearance of grains inside the walls, were observed in the case of the sample sintered at 630 degrees C. Chemical analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the substrate to TiO2. For the substrate was used FTO glass whose top layer consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and Time-of-Flight Elastic Recoil Detection Analysis were carried out to study the elemental depth profile of the films. It was found that the temperature of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse towards the TiO2 NTs surface for the samples annealed at 450 and 550 degrees C. The diffusion is however hindered in the case of the heat treatment at 630 degrees C. Besides, the Ti diffusion into the SnO2 underlayer was observed, together with the formation of TiO2/SnO2 interfaces. One then expected but not a great difference in absorption between samples, since all contained anatase phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of Sn was however detected for the sample annealed at 550 degrees C, which accounts for a slight red absorption shift. The importance of controlling the annealing parameters of the anodized TiO2/FTO structures was highlighted through the formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can play an essential role in increasing the photoperformances of TiO2 NTs/FTO based structures of photovoltaic cells.

Europium doped (0.1% and 1%) chlomborate BaO-B2O3-BaCl2 glass and glass-ceramic with embedded BaCl2 nanocrystals have been synthesised, investigated, and compared with the corresponding nanocrystalline powder. The structural analysis of the glass evidenced ionic bonds characteristic to the glass host structure and compositional changes during the melting. X-ray diffraction and transmission electron microscopy revealed the formation of orthorhombic BaCl2 nanocrystals of about tens on nm in size and a smaller amount of BaB2O4 nanocrystals. Structural analysis of the Eu2+-doped BaCl2 nanocrystals has shown a distortion of the crystalline cell assigned to the growth process, affected by defects and ionic impurities. Photoluminescence spectra of the glass-ceramic revealed Eu3+ and Eu2+ luminescent ion species, but only Eu2+ is incorporated within the BaCl2 nanocrystalline phase. Electron paramagnetic resonance measurements in X-band sustain the presence of Eu2+ ions. The EPR parameters (g values and hyperfine constants) resulting from the Q-band EPR spectra simulations recorded on glass-ceramic are similar to those in Eu2+-doped BaCl2 and confirmed the partial incorporation of Eu2+ ions within the BaCl2:Eu2+ nanocrystals in the glass-ceramics.

The local crystal/magnetic structures of the SrFe12-xInxO19 solid solutions (x = 0.1; 0.3; 0.6 and 1.2) were investigated using neutron powder diffraction. The measurements of the electric polarization for all investigated samples were carried out as a function of the external electric field. The presence of the ferroelectric and ferromagnetic ordering (dual ferroic ordering) in the SrFe12-xInxO19 hexaferrites at 300 K was found. This appearance contradicts to the conventional opinion describing their crystal structure (centrosymmetric space group P6(3)/mmc (No. 194)). The reason for the existence of a spontaneous polarization (nonzero dipole moment) in the SrFe12-xInxO19 hexaferrites continues controversial. The crystal structure of the hexaferrites was considered both the centrosymmetric P6(3)/mmc and non-centrosymmetric P6(3)mc space groups. This fact made it possible to find a connection between the emerging dipole moment and not equal distortions of the neighbor oxygen polyhedral. The nature description of the nonzero dipole moment formation in a quasi-centrosymmetrical system of the In-substituted SrFe12-xInxO19 hexaferrites was presented based on the neutron diffraction data. (C) 2021 Elsevier B.V. All rights reserved.

Piezoelectric hard/soft effects of multivalence co-dopants (Sb and Mn) in correlation with their location in the lattice, were investigated in PZT ceramics, prepared by conventional ceramic technology, with the following compositions: Pb0.98Sr0.02 ((Ti0.49Zr0.51)(1-0.015-x)Mn0.015Sbx)O-3 with x = 0, 0.005, 0.01, 0.02, 0.03, where antimony was initially assumed to substitute for Ti/Zr ions. The antimony valence state was found to be +3 in all samples by X-ray Photoelectron Spectroscopy investigations. The Electron Paramagnetic Resonance spectra evidenced a steep enhancement of the Mn2+ concentration upon increasing antimony doping level, explained by a charge compensation mechanism, between the Sb3+ ions substituting Pb2+ at the A-sites and the Mn2+ ions, localized at the B-sites. The incorporation of Sb3+ at the A-site of the PZT lattice is also supported by the variation of the lattice parameters, determined by X-ray Diffraction, with the increasing Sb concentration. The investigation of the dielectric, electromechanical and ferroelectric properties evidenced a hard piezoelectric behavior, mainly attributed to the presence of large sized Mn2+ ions, localized at B-sites. Our results prove that the piezoelectric hard/soft response is decisively influenced by the interplay between multiple valence states and locations of the co-dopants, on one hand, and the charge compensation mechanisms, on the other hand. This provides indirect information about the location of some co-dopants which can substitute for both cationic sites in the PZT based ceramics.