Browsing by Author "Scales, N"

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    Anisotropy in the thermal expansion of uranium silicide measured by neutron diffraction
    (Elsevier, 2018-09) Obbard, EG; Johnson, KD; Burr, PA; Lopes, DA; Liss, KD; Griffiths, GJ; Scales, N; Middleburgh, SC
    In-situ neutron diffraction patterns were collected for a sample of as-cast U3Si2 during heating to 1600 °C. Anomalous changes were observed above 1000 °C, including the formation of a new diffraction peak not belonging to P4/mbm U3Si2, unequal changes in the peak intensities and onset of anisotropic lattice expansion. The large data-set enabled derivation of a function-fitted isotropic thermal expansion coefficient to high precision, in close agreement with previous dilatometry results but reducing linearly with temperature over the studied interval. Anisotropy in the instantaneous lattice thermal expansion corresponded to anomalies reported by White et al. (2015) at a similar temperature. © Elsevier B.V
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    Aqueous chemical synthesis of Ln2Sn2O7 pyrochlore-structured ceramics
    (John Wiley and Sons, 2013-06-03) Kong, L; Karatchevtseva, I; Blackford, MG; Scales, N; Triani, G
    Pyrochlore-structured lanthanide stannate ceramic (Ln2Sn2O7) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics. © 2013, The American Ceramic Society.
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    Dose enhancement effects to the nucleus and mitochondria from gold nanoparticles in the cytosol
    (IOP Publishing, 2016-07-20) McNamara, AL; Kam, WWY; Scales, N; McMahon, SJ; Bennett, JW; Byrne, HL; Schuemann, J; Paganetti, H; Banati, RB; Kuncic, Z
    Gold nanoparticles (GNPs) have shown potential as dose enhancers for radiation therapy. Since damage to the genome affects the viability of a cell, it is generally assumed that GNPs have to localise within the cell nucleus. In practice, however, GNPs tend to localise in the cytoplasm yet still appear to have a dose enhancing effect on the cell. Whether this effect can be attributed to stress-induced biological mechanisms or to physical damage to extra-nuclear cellular targets is still unclear. There is however growing evidence to suggest that the cellular response to radiation can also be influenced by indirect processes induced when the nucleus is not directly targeted by radiation. The mitochondrion in particular may be an effective extra-nuclear radiation target given its many important functional roles in the cell. To more accurately predict the physical effect of radiation within different cell organelles, we measured the full chemical composition of a whole human lymphocytic JURKAT cell as well as two separate organelles; the cell nucleus and the mitochondrion. The experimental measurements found that all three biological materials had similar ionisation energies  ~70 eV, substantially lower than that of liquid water  ~78 eV. Monte Carlo simulations for 10–50 keV incident photons showed higher energy deposition and ionisation numbers in the cell and organelle materials compared to liquid water. Adding a 1% mass fraction of gold to each material increased the energy deposition by a factor of  ~1.8 when averaged over all incident photon energies. Simulations of a realistic compartmentalised cell show that the presence of gold in the cytosol increases the energy deposition in the mitochondrial volume more than within the nuclear volume. We find this is due to sub-micron delocalisation of energy by photoelectrons, making the mitochondria a potentially viable indirect radiation target for GNPs that localise to the cytosol. © 2016 Institute of Physics and Engineering in Medicine
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    Dysprosium complexes with mono-/di-carboxylate ligands—from simple dimers to 2D and 3D frameworks
    (Elsevier, 2014-11-01) Zhang, YJ; Bhadbhade, MM; Scales, N; Karatchevtseva, I; Price, JR; Lu, KT; Lumpkin, GR
    Four dysprosium (Dy) single carboxylates, a formate, a propionate, a butyrate and an oxalate have been synthesized and structurally characterized. The structure of Dy(HCO2)3 (1) contains nine-fold coordinated Dy polyhedra in perfect tricapped trigonal prisms. They are linked through trigonal O atoms forming 1D pillars which are further linked together through tricapped O atoms into a 3D pillared metal organic framework. The network structure is stable up to 360 °C. The structure of [Dy2(C2O4)3(H2O)6]·2.5H2O (2) contains nine-fold coordinated Dy polyhedra linking together through μ2-bridging oxalate anions into a 2D hexagonal layered structure. Both [Dy2(Pr)6(H2O)4]·(HPr)0.5 (3) [Pr=(C2H5CO2)−1] and [Dy2(Bu)6(H2O)4] (4) [Bu=(C3H7CO2)−1] have similar di-nuclear structures. The Raman vibration modes of the complexes have been investigated. © 2016 Elsevier B.V.
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    Hierarchically porous carbon–zirconium carbide spheres as potentially reusable transmutation targets
    (Elsevier, 2015-08-01) Scales, N; Chen, J; Hanley, TL; Riley, DP; Lumpkin, GR; Luca, V
    The preparation of hierarchically porous phase-pure carbon–zirconium carbide spheres with surface areas upwards of 70 m2/g and diameters in the 1–2 mm range has been achieved. The zirconium carbide beads were prepared through carbothermal reduction of polyacrylonitrile-zirconium composites prepared via three different routes including infiltration of a zirconium precursor into preformed polyacrylonitrile (PAN) beads and two one-pot co-precipitation methods. Depending on the route used to prepare the composites, relatively high surface area phase-pure zirconium carbides with the radial macroporous internal structure of the PAN template could be prepared. The adsorption of the elements U, Mo, Cs and Sr by the zirconium carbide beads was studied as a function of pH in the range 1–13 and target element concentrations of 0.025 mmol/L. The as-prepared hierarchical zirconium carbide beads demonstrated almost quantitative uptake of Mo below pH 4 with uptake decreasing to close to zero and above pH 10.5. On the other hand, U uptake was negligible below pH 4 and became quantitative in the range 4–12. Cesium was not extracted to any significant extent in the pH range studied and Sr only to a limited extent above pH 10. The engineered hierarchical porosities, neutron transparency, thermal stability and anticipated chemical stability of the present zirconium carbide spheres makes them promising candidates as reusable transmutation targets for Minor Actinide incineration. © 2015 Elsevier Inc.
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    Hybrid inorganic-organic adsorbents, Part 1: synthesis and characterization of mesoporous zirconium titanate frameworks containing coordinating organic functionalities
    (American Chemical Society, 2010-12-22) Griffith, CS; Reyes, MDL; Scales, N; Hanna, JV; Luca, V
    A series of functional hybrid inorganic−organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1 × 104 in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd < 100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and that of the other hybrid phases suggests that the surface-bound ATMP ligand functions as a chelating ligand toward 153Gd3+ under these acidic conditions. © 2010, American Chemical Society
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    Hydrolytic stability of mesoporous zirconium titanate frameworks containing coordinating organic functionalities
    (American Chemical Society, 2013-04-12) de los Reyes, M; Majewski, PJ; Scales, N; Luca, V
    The hydrolytic stability of lanthanide and actinide selective mono- and polyphosphonate-functionalized mesoporous zirconium titanium oxide adsorbents has been investigated in nitric acid solutions. Hydrolytic degradation of the surfaces, as measured through the fractional loss of phosphorus and elements of the oxide framework, increased by more than an order of magnitude as the nitric acid concentration was increased from 0 to 2 mol/L. The unfunctionalized parent oxide suffered considerable dissolution in 2 mol/L acid over a period of 72 h. Under identical conditions, the fractional Zr and Ti release was reduced to 1 × 10–2 for monophosphonate functionalized hybrids and reached as low as 1 × 10–6 for trisphosphonate functionalized variants. The bisphosphonates showed intermediate values. The leaching of P, Zr and Ti was found to be incongruent with the Zr leaching to a lesser extent implying enhanced stability of the Zr–O–P bond. Quantitative analysis of the dissolution kinetics indicated a parabolic dissolution model with a rate constant in the range of 0.5–1.5 mg g–1 min–1/2 for the elemental leaching of P, Ti, and Zr. The leaching of Zr from the mesoporous matrix was relatively more complex than for the other elements with evidence of a leaching mechanism involving two processes. ToF-SIMS and DRIFT analysis demonstrated that after leaching in 2 M HNO3 for 24 h, a significant proportion of grafted ligands remained on the surface. The oxide functionalized with amino trismethylenephosphonic acid, which had previously shown excellent 153Gd3+ selectivity, was demonstrated to have outstanding stability, with low fractional elemental losses and preservation of mesoporous texture even after leaching for 24 h in 2 M HNO3. This suggests this particular hybrid to be worthy of additional study. © 2013, American Chemical Society.
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    Hydrothermal synthesis, structures and properties of two uranyl oxide hydroxyl hydrate phases with Co(II) or Ni(II) ions
    (Royal Society of Chemistry., 2016-04-11) Zhang, YJ; Čejka, J; Lumpkin, GR; Tran, TT; Aharonovich, I; Karatchevtseva, I; Price, JR; Scales, N; Lu, KT
    Two new iso-structured uranyl oxide hydroxyl hydrate (UOH) phases with the incorporation of cobalt(II) or nickel(II) ions have been synthesised under hydrothermal conditions and structurally characterised. Both K4Co(OH)3(H2O)9[(UO2)12(O)7(OH)13] (1) and K4Ni(OH)3(H2O)9[(UO2)12(O)7(OH)13] (2) have two-dimensional (2D) polymeric uranyl oxohydroxyl layers with either potassium and hydroxyl cobalt(II) (1) or potassium and hydroxyl nickel(II) (2) ions between layers via uranyl–cation interactions. This work highlights the feasibility of making new UOH phases via a hydrothermal route at relatively higher solution pHs. It also demonstrates that other transition metal ions which are readily available in the environment may also be incorporated into such UOH phases during the natural weathering of uraninite as well as during the storage and disposal of spent nuclear fuels. © 2016 The Royal Society of Chemistry
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    In-situ neutron characterization of advanced nuclear ruels - the road to a new neutron irradiation testing capability
    (The Minerals, Metals & Materials Society, 2020-02-23) Obbard, EG; Gasparrini, C; Burr, PA; Johnson, KD; Lopes, DA; Anghel, C; Middleburgh, SC; Gregg, DJ; Liss, KD; Griffiths, GJ; Scales, N; Thorogood, GJ; Lumprin, GR
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    Nanofiltration applications of tough MWNT buckypaper membranes containing biopolymers
    (Elsevier, 2017-05-01) Rashid, MHO; Triani, G; Scales, N; in het Panhuis, M; Nghiem, D; Ralph, SF
    The ability of biopolymers (bovine serum albumin, lysozyme, chitosan, gellan gum and DNA) to facilitate formation of aqueous dispersions of MWNTs was investigated using a combination of absorption spectrophotometry and optical microscopy. Subsequently, self-supporting carbon nanotube membranes, known as buckypapers (BPs), were prepared by vacuum filtration of the dispersions. Microanalytical data obtained from the BPs confirmed the retention of biopolymers within their structures. Tensile test measurements performed on the BPs showed that incorporation of the biopolymers resulted in significant improvements in mechanical properties, compared to analogous BPs containing MWNTs and the low molecular mass dispersant Triton X-100. For example, MWNT/CHT BPs (CHT=chitosan) exhibited values for tensile strength, ductility, Young's modulus and toughness of 28±2MPa, 5.3±2.7%, 0.9±0.3GPa and 1.7±0.3J g−1, respectively. Each of these values are significantly greater than those obtained for MWNT/Trix BPs, prepared using a low molecular weight dispersant (6±3MPa, 1.3±0.2%, 0.6±0.3GPa and 0.10±0.06J g−1, respectively). This significant improvement in mechanical properties is attributed to the ability of the long biopolymer molecules to act as flexible bridges between the short CNTs. All BPs possessed hydrophilic surfaces, with contact angles ranging from 29±2° to 57±5°. Nitrogen gas porosimetry showed that the BPs have highly porous internal structures, while scanning electron microscopy (SEM) showed their surface morphologies have numerous pore openings. The permeability of the BPs towards water, inorganic salts, and dissolved trace organic contaminants (TrOCs), such as pharmaceuticals, personal care products, and pesticides, was investigated through filtration experiments. Of the twelve TrOCs investigated in this study, nine were rejected by more than 95% by BPs composed of MWNTs and chitosan. The latter BPs also demonstrated good rejection of both NaCl (30–55%) and MgSO4 (40–70%). © 2017 Elsevier B.V.
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    Neodymium coordination polymers with propionate, succinate and mixed succinate–oxalate ligands: synthesis, structures and spectroscopic characterization
    (Elsevier, 2015-12-14) Scales, N; Zhang, YJ; Bhadbhade, MM; Karatchevtseva, I; Kong, L; Lumpkin, GR; Li, F
    Three neodymium (Nd) coordination polymers with propionate, succinate and mixed succinate–oxalate ligands have been synthesized and structurally characterized. Nd2(C3H5O2)6(H2O)3·3H2O (1) has a 1D polymeric structure built with both ninefold and ten-fold coordinated neodymium polyhedra linked through μ2-bridging propionate ligands. Nd2(C4H4O4)3(H2O)2 (2) has a 3D polymeric structure constructed with two distinct ninefold coordinated neodymium polyhedra linked through three types of succinate ligands, two in μ4- and one in μ3-coordination modes. Nd2(C4H4O4)2(C2O4)(H2O)4·3H2O (3) is built with two types of ten-fold coordinated neodymium polyhedra linked through μ4-succinate ligands into 2D undulating layers which are further connected through μ2-oxalate ligands forming a 3D network with channels. Their vibrational modes and thermal stabilities have been further investigated. Crown Copyright © 2015 Published by Elsevier Ltd.
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    One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands
    (Elsevier B.V., 2016-07-27) Shepherd, ND; Zhang, YJ; Karatchevtseva, I; Price, JR; Kong, L; Scales, N; Lumpkin, GR
    A method to produce picolinate ligand in situ under hydrothermal conditions has been used to synthesize four uranyl hydroxyl, oxo- and oxohydroxyl picolinato complexes. (UO2)(OH)(Pic) (1) (HPic = picolinic acid) contains 7-fold coordinated uranyl hydroxyl dimers linked through μ2-bridging Pic ligands forming a one-dimensional (1D) polymer. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) consists of 7-fold coordinated uranyl oxohydroxyl trinuclear units linked through both μ2- and μ3-Pic ligands forming a 1D polymer. (NH4)[(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked through oxo- and μ3-Pic ligands forming a 1D polymer. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]·H2O (4) (HINT = isonicotinic acid) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands forming a 1D polymer. All four polymers are thermal robust to 350 °C. Raman spectroscopy confirmed the presence of uranyl ion and Pic ligand. In addition, red enhanced fluorescence emissions have been observed for both 1 and 4. The synthesis method, with the advantage of controlling uranyl hydrolysis and generating ligand in situ, provides a more reliable way to make new coordination polymers of carboxylate ligands with various uranyl hydrolysis species. © 2016 Elsevier Ltd.
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    One-pot preparation and uranyl adsorption properties of hierarchically porous zirconium titanium oxide beads using phase separation processes to vary macropore morphology
    (American Chemical Society, 2010-11-16) Drisko, GL; Kimling, MC; Scales, N; Ide, A; Sizgek, E; Caruso, RA; Luca, V
    A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H2O beads) or liquid nitrogen (LN2 beads). The inorganic beads obtained after calcination (550°C in air) had surface areas of 140 and 128 m2 g−1, respectively, and had varied pore architectures. The H2O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN2-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network. © 2010, American Chemical Society
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    Removal of aluminium from aqueous solutions using PAN-based adsorbents: characterisation, kinetics, equilibrium and thermodynamic studies
    (Springer, 2014-12-04) Aly, Z; Graulet, A; Scales, N; Hanley, TL
    Economic adsorbents in bead form were fabricated and utilised for the adsorption of Al(3+) from aqueous solutions. Polyacrylonitrile (PAN) beads, PAN powder and the thermally treated PAN beads (250 °C/48 h/Ar and 600 °C/48 h/Ar-H2) were characterised using different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, specific surface analysis (Brunauer-Emmett-Teller), thermogravimetric analysis as well as scanning electron microscopy. Effects of pH, contact time, kinetics and adsorption isotherms at different temperatures were investigated in batch mode experiments. Aluminium kinetic data best fit the Lagergren pseudo-second-order adsorption model indicating a one-step, surface-only, adsorption process with chemisorption being the rate limiting step. Equilibrium adsorption data followed a Langmuir adsorption model with fairly low monolayer adsorption capacities suitable for freshwater clean-up only. Various constants including thermodynamic constants were evaluated from the experimental results obtained at 20, 40 and 60 °C. Positive values of ΔH° indicated that the adsorption of Al(3+) onto all three adsorbents was endothermic with less energy input required for PAN powder compared to PAN beads and low-temperature thermally treated PAN. Negative ΔG° values indicated that the aluminium adsorption process was spontaneous for all adsorbents examined. © 2020 Springer Nature
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    Template synthesis and adsorption properties of hierarchically porous zirconium titanium oxides
    (American Chemical Society, 2009-05-05) Drisko, GL; Luca, V; Sizgek, E; Scales, N; Caruso, RA
    Hierarchical morphologies in metal oxides are advantageous for many applications, including controlled drug release, photocatalysis, catalysis, synthetic biomaterials, and adsorption and separation technologies. In this study, agarose gel has been used as a template to prepare zirconium titanium mixed oxide pellets with bimodal porosity. Sol−gel chemistry conducted within the agarose gel produced "coral-like" interconnected networks of oxide nanoparticles with controllable quantities of zirconium and titanium. The materials were characterized using N2 sorption, extended X-ray absorption fine structure, X-ray diffraction, TEM, SEM, zeta potential, and thermogravimetric analysis (to measure surface hydroxyl group density). The oxides were then tested for the adsorption of vanadyl and vanadate to determine which Zr mole fraction exhibited the highest capacity and fastest kinetics. The material containing 25 mol % Zr exhibited the highest surface area (322 ± 8 m2/g) of the compositions investigated and also displayed a superior adsorption rate and capacity. Vanadate adsorption occurred with faster kinetics than did vanadyl adsorption. A comparative study demonstrated that the macro/meso pore structure had improved transport properties over a monomodal mesopore structure of similar Zr/Ti composition. The faster vanadate adsorption kinetics is attributed to enhanced surface accessibility in a hierarchical material. © 2009, American Chemical Society
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    Uranium(VI) hybrid materials with [(UO2)3(µ3‐O)(µ2‐OH)3]+ as the sub–building unit via uranyl–cation interactions
    (John Wiley and Sons, 2016-01-14) Zhang, YJ; Clegg, JK; Lu, KT; Lumpkin, GR; Tran, TT; Aharonovich, I; Scales, N; Li, F
    The hydrothermal reaction of uranyl nitrate with 1,4-benzenedicarboxylic acid (H2bdc) in the presence of strontium or potassium hydroxides and nitrates afford the formation of two new uranyl hybrid materials featuring extensive uranyl-strontium or uranyl-potassium interactions with [(UO2)3(µ3-O)(µ2-OH)3]+ as the sub-building unit. Sr1.5[(UO2)12(O)3(OH)13(bdc)4]⋅6H2O (1) contains one-dimensional (1D) uranyl oxohydroxyl ribbons made of trinuclear pentagonal bipyramidal uranyl units. The ribbons are linked together via uranyl-strontium interactions to form 2D inorganic domains which are further connected through µ4-bdc anions forming a 3D hybrid structure. This is the first reported uranyl-strontium interaction in extended hybrid solid with the shortest Sr-O−yl bond length of 2.596 (8) Å. K3[(UO2)12(O)3(OH)13(bdc)4]⋅8H2O (2) has a similar 3D hybrid structure built up through extensive K-O−yl interactions with the shortest K-O−yl bond length of 2.620 (6) Å. Raman spectroscopy has confirmed the presence of oxo-bridging (U−O−U) vibrations. Thermal stabilities and photoluminescent properties are reported. © 2016 Wiley‐VCH Verlag GmbH & Co.