The Luminescent Properties of Yttrium Oxyapatite Doped with Eu3+ ions

The structural and luminescent properties of Ca2Y8(SiO4)(6)O-2 (CYS) silicate based oxyapatite doped with Eu3+ ions have been reported in this paper. The sample was synthesized using reflux method assisted by urea subsequent degradation. Very specific, shell- and and rope-like morphologies were observed by SEM. The powder X-ray diffraction study revealed that the Eu3+ : CYS system crystallized in a hexagonal lattice structure (space group P63/m) characteristic of oxyapatite. In the host oxyapatite structure, a partial replacement of Ca2+ and Y3+ ions by luminescent active Eu3+ ions have been done, and its photoluminescent spectra were analyzed. The performed analysis indicate the presence of Eu3+ ions in both, nine-fold coordinated 4f, and seven-fold coordinated 6h sites, showing a slight shift towards the blue area in comparison to a typical spectra of other yttrium-silicate phases as hosts

Creating of Highly Active Calcium-Silicate Phases for Application in Endodontics

The synthesis of active silicate phases by combined sol gel and high-temperature self-propagating wave method, is described in this paper. They show a significant decrease of setting time and good mechanical properties, which are very important for its potential application in endodontic practice. Particularly, process of hydration of calcium silicate phases is carefully analyzed, from the aspect of phase changes during their soaking in water for 1, 3, 7 and 28 days. XRD and FTIR methods were used for phase analysis of all samples, while morphological characteristics and chemical composition of the given phases were investigated by SEM and EDS

Ex situ integration of iron oxide nanoparticles onto exfoliated expanded graphite flakes in aqueous suspension

Hybrid structures composed of exfoliated expanded graphite (EG) and iron oxide nanocrystals were produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA), or poly(acrylic acid) (PAA) were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under the support of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinnimide (NHS). EG flakes both naked and functionalized with branched polyethylenimine (PEI) were employed. Complete integration of the two constituents was achieved and stability was maintained for more than 12 months. No preferential spatial distribution of anchoring sites for attachment of iron oxide nanoparticles was observed, regardless of whether the EG flakes were used naked or functionalized with PEI molecules. The structural and physicochemical characteristics of the exfoliated expanded graphite and its hybrid nano-structures were investigated by SEM, TEM, FTIR and Raman techniques

Sol-gel as a Method to Tailor the Magnetic Properties of Co1+yAl2-yO4

The magnetic properties of mesoscopic materials are modified by size and surface effects. We present a sol-gel method used to tailor these effects, and illustrate it on Co1+yAl2-yO4 spinel. Nanocomposites made of spinel oxide Co1+yAl2-yO4 particles dispersed in an amorphous SiO2 matrix were synthesized. Samples with various mass fractions -x of Co1+yAl2-yO4 in composite, ranging from predominantly SiO2 (x = 10 wt%) to predominantly spinel (x = 95 wt%), and with various Co concentrations in spinel y were studied. The spinel grain sizes were below 100 nm with a large size distribution, for samples with predominant spinel phase. Those samples showed Curie-Weiss paramagnetic behavior with antiferromagnetically interacting Co ions (theta approximate to -100 K). The grain sizes of spinel stays confined in 100 nm range even in the spinel samples diluted with as low as 5 wt% concentration of amorphous SiO2. For the samples with predominant SiO2 the crystalline nanoparticles are well separated and of size of around 100 nm, but with presence of much smaller spinel nanoparticles of about 10 nm. The magnetic properties of the samples with predominant silica phase showed complex behavior, spin-glass magnetic freezing at the lowest temperatures and lower absolute value of theta and consequently lower exchange constant

Magnetic Properties of Lithium Ferrite Nanoparticles with a Core/Shell Structure

We present a magnetic study of lithium ferrite nanoparticles of composition Li0.5Fe2.5O4, synthesized by a citrate gel decomposition method. The as prepared sample was composed of nearly spherical nanoparticles with an average particle size LT d GT (TEM)similar to 12 nm. Further annealing at 573 K and 673 K for 4 hours did not increase particle size noticeably, while annealing at 973 K led to morphology changes and significant increase in size ranging from 40 to above 200 nm. The magnetic properties of samples have been studied using Mossbauer specroscopy, and static magnetic measurements. The hyperfine parameters obtained from Mossbauer data at T = 10 K are in agreement to the bulk lithium ferrite phase. Annealed samples showed an evolution from monodomain structure to polycrystalline behaviour, what is evident from TEM imagines, as well as the evolution of the coercive filed, H-C, and the saturation magnetization, M-S, with particle size increase. The exchange interactions have been observed in the single-domain nanoparticles, which probably originate from their core-shell structure. At low temperatures and in high enough magnetic fields, the cubic magnetic anisotropy stays preserved and the magnetic moments in the particle core are aligned along LT 111 GT directions of the spinel structure

Biomimetic deposition of hydroxyapatite on the surface of silica thin film covered steel tape

The biomimetic deposition of hydroxyapatite (HA) on the surface of SiO2 thin film coated metal substrates was developed and investigated. The structural investigations of HA were made by XRD and FTIR-ATR, while morphological and chemical changes during HA biomimetic deposition on the surfaces of silica thin films were investigated by SEM with EDS. The HA film thicknesses were estimated from the mass changes of samples including the corresponding correction of the pore volume inside of them, which was calculated by the Lecloux and Pirard method based on the Dollimore-Heal method. (c) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved

The crystal structure refinement and magnetic susceptibility study of La2-xErxO3

The X-ray powder diffraction patterns of La2-xEr2O3 (X = 0,2, 0.3, 1, 1.8, 2) samples were refined by the Rietveld full profile method. The magnetic susceptibility was measured in the temperature range 4-300 K, and the magnetic behavior of trivalent erbium ion is discussed in connection with the different local symmetry sites. (C) 2003 Elsevier Science B.V. All rights reserved

Influence of the cation distribution on the physical properties of the diluted magnetics Li1.33Ti1.67O4/Co2TiO4

Spinel samples of Li1.33xCo2-2xTi1+0.67xO4 crystallize in two space groups: Fd 3 m for 0less than or equal tox:less than or equal to0.40 and x=1, and P4(3)32 for 0.50less than or equal toxless than or equal to0.875. In S.G. P4(3)32 magnetic Co2+ ions occupy 8c sites (for x=0.75 and 0.875), or 8c, 4b and 12d sites (for x=0.50). In x=0.25 and 0.40 samples Co2+ occupy both 8a and 16d cation sites of the S.G. Fd 3 m [1]. Observed differences in magnetic 2+ behaviour of the samples are induced by crystallographic distribution of Co2+. Possible paths for exchange interactions in S.G. P(4)332 were analysed. It was found that the superexchange is the dominant exchange mechanism where Co2+(8c)-O(24e)-CO2+(12d) path was the most important one. On the basis of the results on crystallographic distribution we suggest x=0.50 sample as potential electrode material in Li ion rechargeable batteries.8th European Powder Diffraction Conference, May 23-26, 2002, Uppsala, Swede

Spin glass formation in Li-substituted Co2TiO4 spinel

DC magnetization and AC susceptibility measurements point to the formation of a spin glass state in the ternary spinel-type compounds Li1.33xCo2-2xTi1+0.67xO4. The dynamics of spin freezing was analysed with both the critical slowing down and the thermally activated dynamics models. The parameter values obtained, as well as the behaviour of the zero- field-cooled and field-cooled magnetization as a function of temperature, indicate the existence of a cluster glass state in disordered spinel samples with x = 0.25 and 0.40, and probably also in the ordered spinel with x = 0.50. Ordered spinel samples with x = 0.75 and 0.875 were found to be paramagnetic down to the temperature of 1.7 K with a random distribution of Co2+ ions

Influence of size distribution and field amplitude on specific loss power

Herein we present the results of specific loss power (SLP) analysis of polydisperse water based ferrofluids, Fe3O4/PEG200 and Fe3O4/PEG6000, with average Fe3O4 particle size of 9 nm and 11 nm, respectively. Specific loss power was measured in alternating magnetic field of various amplitudes and at fixed frequency of 580.5 kHz. Maximum SLP values acquired were 195 W/g for Fe3O4/PEG200 and 60 W/g for Fe3O4/PEG6000 samples. The samples were labeled as superparamagnetic by magnetization measurements, but SLP field dependence showed deviation from the behavior predicted by the commonly employed linear response theory. The scope of this theory for both samples with wide particle size distribution is discussed. Deviation from the expected behavior is explained by referring to polydisperse nature of the samples and field dependent relaxation rates. (C) 2015 AIP Publishing LLC