A study of the electronic structure and structural stability of Gd2Ti2O7 based glass-ceramic composites

NSERCGlass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. Borosilicate- and Fe–Al–borosilicate glass-ceramic composites containing pyrochlore-type Gd2Ti2O7 crystallites were synthesized at different annealing temperatures and investigated by multiple techniques. Backscattered electron (BSE) images were collected to investigate the interaction of the pyrochlore crystallites with the glass matrix. Examination of the X-ray absorption near edge spectroscopy (XANES) spectra from the composite materials has shown how the glass composition, pyrochlore loading, and annealing temperature affects the chemical environment around the metal centers. These investigations have shown that the Gd2Ti2O7 crystallites can dissolve in the glass matrix depending on the glass composition and annealing temperature. The borosilicate glass composite materials were implanted with high-energy Au ions to mimic radiation induced structural damage. Surface sensitive glancing angle XANES spectra collected from the implanted composite materials have shown that structural damage of Gd2Ti2O7 occurs as a result of implantation, and that these materials show a similar response to ion implantation as Gd2Ti2O7 alone

Microwave-assisted synthesis of highly crystalline, multifunctional iron oxide nanocomposites for imaging applications

We report a reproducible single-step, microwave-assisted approach for the preparation of multifunctional magnetic nanocomposites comprising superparamagnetic iron oxide (Fe3O4) cores, a polyelectrolyte stabilizer and an organic dye with no requirement for post-processing. The stabilisers poly(sodium 4-styrenesulfonate) (PSSS) and sodium polyphosphate (SPP) have been thoroughly investigated and from analysis using electron microscopy, dynamic light scattering measurements, magnetic hysteresis and magnetic resonance (MR) imaging, we show that the higher degree of Fe3O4 nanoparticle crystallinity achieved with the PSSS stabiliser leads to enhanced magnetic behaviour and thus better contrast agent relaxivity compared to the less crystalline, poorly defined particles obtained when SPP is employed as a stabiliser. We also demonstrate the potential for obtaining a multifunctional magnetic-fluorescent nanocomposite using our microwave-assisted synthesis. In this manner, we demonstrate the intimate link between synthetic methodology (microwave heating with a polyelectrolyte stabilizer) and the resulting properties (particle size, shape, and magnetism) and how this underpins the functionality of the resulting nanocomposites as agents for biomedical imaging

Investigation of the Structural Stability of Ion-Implanted Gd₂Ti_2–<i>x</i>Sn_<i>x</i>O₇ Pyrochlore-Type Oxides by Glancing Angle X‑ray Absorption Spectroscopy

Rare-earth titanate and stannate pyrochlore-type oxides have been investigated in the past for the sequestration of nuclear waste elements because of their resistance to radiation-induced structural damage. In order to enhance this property, it is necessary to understand the effect of radioactive decay of the incorporated actinide elements on the local chemical environment. In this study, Gd₂Ti_2–<i>x</i>Sn_<i>x</i>O₇ materials have been implanted with Au^– ions to simulate radiation-induced structural damage. Glancing angle X-ray absorption near-edge spectroscopy (GA-XANES), glancing angle X-ray absorption fine structure (GA-EXAFS) analysis, and powder X-ray diffraction have been used to investigate changes in the local coordination environment of the metal atoms in the damaged surface layer. Examination of GA-XANES/EXAFS spectra from the implanted Gd₂Ti_2–<i>x</i>Sn_<i>x</i>O₇ materials collected at various glancing angles allowed for an investigation of how the local coordination environment around the absorbing atoms changed at different depths in the damaged surface layer. This study has shown the usefulness of GA-XANES to the examination of ion-implanted materials and has suggested that Gd₂Ti_2–<i>x</i>Sn_<i>x</i>O₇ becomes more susceptible to ion-beam-induced structural damage with increasing Sn concentration

Location and characterization of heterogeneous phases within Mary Rose wood

Preserving the Mary Rose oak hull for future generations is a major challenge due to the highly heterogeneous nature of waterlogged wooden artifacts, which contain polycrystalline, amorphous, and nanostructured materials that test traditional characterization methods. Effective conservation requires detailed knowledge of the distribution and chemical nature of these species to develop strategies for preventing multiple chemo-mechanical degradation pathways. Here, we apply synchrotron-based computed tomography total scattering methods to the Mary Rose keelson wood that provides valuable position-resolved structural information on multiple embedded species of different length and concentration scales. We identify 5 nm zinc sulfide nanoparticles in the wood, presumably deposits from bacteria operating on the sulfur energy cycle under the anaerobic conditions on the seabed. These are identified as precursors to acid attack on the wood upon removal to an aerobic environment. These insights inform not only next-generation conservation strategies, but also the efficacy and unforeseen issues of previous treatments

Graphene oxide modulates inter-particle interactions in 3D printable soft nanocomposite hydrogels restoring magnetic hyperthermia responses

Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications.Science Foundation IrelandŁukasiewicz Research Network - Institute of Electronic Materials Technology satutory gran