51 research outputs found
Preparation and magnetic properties of the (1-x)BiFeO3 – xBaTiO3 solid solutions
No full text(1-x)BiFeO3 – xBaTiO3 (0 ≤ x ≤ 0.30) ceramics were prepared by the solid state reaction method. After sintering at 800°C/1h and slow cooling, single phase compositions were obtained for both presintered and sintered samples, including the composition x=0, which was rarely reported. The gradual attenuation of the rhombohedral distortion with the increase of BaTiO3 content was pointed out. The BaTiO3 admixture acts also as inhibitor for the grain growth process, contributing to the decrease of the average grain size. The compositions corresponding to x=0.30 exhibits multiferroic behavior at room temperature, having both antiferromagnetic and ferroelectric order and low losses (< 3%). The Raman activity proved the existence of the local non-centrosymmetry and of some grain boundary characteristics at room temperature. The magnetic data indicates a composition-dependent antiferromagnetic character
Multiferroic (Nd,Fe)-doped PbTiO3 ceramics with coexistent ferroelectricity and magnetism at room temperature
No full textWe report the structural, dielectric, elastic, ferroelectric and ferromagnetic properties of multiferroic (Nd, Fe)-doped PbTiO3 perovskite ceramics with composition (Pb 0.88 Nd 0.08 )(Ti 0.94 Fe 0.04 Mn 0.02 )O 3 , prepared by different solid state reaction methods: the first one based on a single-stage calcination (Method I) and the second based on a double-stage calcination (Method II). Structural, dielectric and anelastic measurements evidenced a double phase transition for samples prepared by Method I, which has been attributed to phase separation. This phase separation has been confirmed also by TEM and HRTEM investigations. Samples prepared by Method II showed a single phase transition from paraelectric to ferroelectric phase. We found coexistent ferroelectric and ferromagnetic properties, also at room-temperature, but only for ceramics prepared by Method II. The crucial role of calcination process for avoiding phase separation and obtaining homogeneous structures with ferroelectric and ferromagnetic order is underlined
Recent advances in synthesis, characterization of hydroxyapatite/polyurethane composites and study of their biocompatible properties
No full textDesign, fabrication, and characterization of new materials based on zirconia doped with mixed rare earth oxides: Review and first experimental results
No full textMonazite is one of the most valuable natural resources for rare earth oxides (REOs) used as dopants with high added value in ceramic materials for extreme environments applications. The complexity of the separation process in individual REOs, due to their similar electronic configuration and physical–chemical properties, is reflected in products with high price and high environmental footprint. During last years, there was an increasing interest for using different mixtures of REOs as dopants for high temperature ceramics, in particular for ZrO2‐based thermal barrier coatings (TBCs) used in aeronautics and energy co‐generation. The use of mixed REOs may increase the working temperature of the TBCs due to the formation of tetragonal and cubic solid solutions with higher melting temperatures, avoiding grain size coarsening due to interface segregation, enhancing its ionic conductivity and sinterability. The thermal stability of the coatings may be further improved by using rare earth zirconates with perovskite or pyrochlore structures having no phase transitions before melting. Within this research framework, firstly we present a review analysis about results reported in the literature so far about the use of ZrO2 ceramics doped with mixed REOs for high temperature applications. Then, preliminary results about TBCs fabricated by electron beam evaporation starting from mixed REOs simulating the real composition as occurring in monazite source minerals are reported. This novel recipe for ZrO2‐based TBCs, if optimized, may lead to better materials with lower costs and lower environmental impact, as a result of the elimination of REOs extraction and separation in individual lanthanides. Preliminary results on the compositional, microstructure, morphological, and thermal properties of the tested materials are reported
Structural and characterisation analysis of zinc-substituted hydroxyapatite with wet chemical precipitation method
No full textHydroxyapatite (HAp) is a biocompatible, bioactive and biodegradable biomaterial widely used in the biomedical area. In this work, the synthesis of zinc substituted hydroxyapatite (Zn-HAp) is described. Zn-Hap nano-powders with 0.5, 2, 5, 10 and 25 wt.% zinc were produced by wet chemical synthesis method. The samples were analysed by XRD for determine crystallite size and phase composition of each sample, SEM and HR-TEM for determine the size and shape of the nanoparticles while FTIR was used to identify the chemical changes of the samples. According to the XRD data, the crystallite size decreased when the increase of the zinc concentration. Therefore, HAp structure was observed in all samples except the sample with 25 wt.% Zn where mostly monetite and parascholzite were obtained instead of HAp. Its structure was deformed and also agglomerated by high zinc-content. Copyright © 2016 Inderscience Enterprises Ltd
Physical-chemical characterization and biological assessment of simple and lithium-doped biological-derived hydroxyapatite thin films for a new generation of metallic implants
No full textWe report on the synthesis by PLD of simple and lithium-doped biological-origin hydroxyapatite (HA) films. The role of doping reagents (Li2CO3, Li3PO4) on the morphology, structure, chemical composition, bonding strength and cytocompatibility of the films was investigated. SEM investigations of the films evidenced a surface morphology consisting of particles with mean diameters of (5-7) mu m. GIXRD analyses demonstrated that the synthesized structures consisted of HA phase only, with different degrees of crystallinity, mainly influenced by the doping reagent type. After only three days of immersion in simulated body fluid, FTIR spectra showed a remarkable growth of a biomimetic apatitic film, indicative of a high biomineralization capacity of the coatings. EDS analyses revealed a quasi-stoichiometric target-to-substrate transfer, the values inferred for the Ca/P ratio corresponding to a biological apatite. All synthesized structures displayed a hydrophilic behavior, suitable for attachment of osteoblast cells. In vitro cell viability tests showed that the presence of Li2CO3 and Li3PO4 as doping reagents promoted the hMSC growth on film surfaces. Taking into consideration these enhanced characteristics, corroborated with a low fabrication cost generated by sustainable resources, one should consider the lithium-doped biological-derived materials as promising prospective solutions for a next generation of coated implants with rapid osteointegration. (C) 2018 Elsevier B.V. All rights reserved
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