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The geopolymer catalyst supports utilized in the nuclear waste containers for the Fukushima Daiichi Nuclear Power Station will be required to have high porosity and durability. This work presents the synthesis of a potassium and metakaolin‐based geopolymer and its performance upon dehydration. During water content measurements of the samples, it was seen that in the demolded samples, the water content quickly decreased to less than 30% within 7 days, while the samples that had the cap removed from the container retained more than 50% of the water after 28 days. The pore size distribution of the samples that were post‐cured at different temperatures up to 28 days did not vary greatly with respect to the average pore size. We can infer that structurally stable pores were formed in the first 4 days and were not affected by the post‐curing rate, which may be related to rheological properties and the drainage path of water or hydrogen gas during post‐curing.

Nanoporous zirconium phosphonate materials are considered promising candidates for practical applications such as catalysis and separations, in particular due to their excellent stability resulting...

The thermal expansion of NH4TcO4 and NH4ReO4 between 97 and 500 K has been established using variable temperature synchrotron X-ray diffraction. Both oxides display a tetragonal scheelite-type structure over the temperature range. The observed anomalous thermal expansion is associated with disorder in the orientation of the NH4 groups and the presence of anisotropic, equatorial and axial, interactions between the H atoms and the BO4 tetrahedra. The importance of the hydrogen interactions was verified by a study of the isostructural compound NaReO4 over a similar temperature range. The differences in the details of the Negative Thermal Expansion (NTE) behaviour of NH4TcO4 and NH4ReO4 is a consequence of differences in the H BO4 interactions due to changes in the B O bond lengths within the BO4 groups. Both ammonium salts decompose when heated above ∼500 K.

Current fission-based methods of

In order to reproduce the irradiation environment of Europa, NaCl-0-2mol%KCl crystals were grown and irradiated with pulsed intense relativistic electron beams at RT and 77 K in the optical absorbance spectra. The peak wavelength of the F-center was shortened by decreasing the measurement temperature and the KCl content. This phenomenon can be explained by the changes of the lattice constant and utilized to determine temperature and KCl content in the sea of Europa.

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO2 in two materials, and as a mixture of UO2, U3O8 and an intermediate species U3O7 in the third material. Electronic supplementary material The online version of this article (10.1007/s10967-017-5666-3) contains supplementary material, which is available to authorized users.

Current fission-based methods of 99Mo production require single use uranium targets which leads to spent uranium waste. This waste could be reduced if a target is developed that does not require dissolution so that it can be reused for multiple production runs. MCNP6.2 was used to model reusable targets of 20% and 1% enrichment for activity produced, target efficiency and burnup. The 1% enriched target was found to be much more efficient but had a lower activity produced compared to the 20% enriched target. The ideal target design for 99Mo production that optimises efficiency and reusability and reduces the self-shielding effect of UO2 was found to be a target that is made from 1% enriched UO2 with density as high as allowable for sufficient yields, efficient 99Mo extraction and having an irradiation time of 5 days, with the target able to be re-irradiated and re-processed 2–4 times.

The structure of TcO2 between 25 and 1000 °C has been determined in-situ using powder diffraction methods and is found to remain monoclinic in space group P21/c. The thermal expansion in TcO2 is highly anisotropic with negative thermal ex-pansion of the b-axis observed above 700 °C. This is the result of an anomalous expansion along the a-axis that is a consequence of weakening of the Tc-Tc bonds. Australian Synchrotron Australian Research Council

In order to obtain insight into the hardening mechanism of Cr(N,O) thin films with respect to increase in oxygen content, the microstructure of Cr(N,O) grains in thin films was studied. High resolution transmission electron microscopy provided evidence that the grains in Cr(N,O) thin films prepared by pulsed laser deposition, which have an oxygen content of > 27 mol%, contained stacking faults. Phase identification via electron diffraction, indicated that the grains consisted of two phases, which had a NaCl-type and corundum-type structure and these phases had the same orientation as that of the Cr 0.67 O thin film. The estimated stacking fault energy of Cr(N,O) with an oxygen content of 34 mol% was 20 mJ/m 2 . Our results revealed the Cr(N,O) grains had the same nano-lamellar morphology as that of the Cr 0.67 O thin film which supports the possibility that the nano-lamellar morphology was formed by the introduction of extended dislocations. It is also possible that the hardening of Cr(N,O) was caused by dislocation pinning at the boundaries of the nano-lamellar morphology.

A new class of materials, which rely on the dispersion strengthening of SiC particles in addition to precipitation strengthening by nano-precipitates is being developed for the application in molten salt nuclear reactors. A battery of dispersion and precipitation strengthened (DPS) NiMo-based alloys containing varying amount of SiC (0.5–2.5 wt.%) was prepared via a mechanical alloying (MA) route followed by spark plasma sintering (SPS), rapid cooling, high-temperature annealing and water quenching. Lab X-ray Diffraction (XRD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the microstructural characterization of this new type of alloys. It is shown that the NiMo matrix of these alloys is effectively reinforced by dispersion of SiC from the initial powder mixture and nano-Ni3Si precipitates, which precipitated during the sintering/annealing process. Furthermore, the matrix is strengthened by solid-solution of Mo in Ni. As a result, these newly developed NiMo alloys take advantage of dispersion, precipitation and solid solution strengthening, which leads to their superior mechanical properties. Keywords: Powder metallurgy, DPS strengthening, Spark plasma sintering, Transmission electron microscopy, Electron backscatter diffraction, Molten salt reactor

International audience; We demonstrate that the Swift-Hohenberg functional as used to describe patterning observed in out of equilibrium systems such as diblock copolymers, Rayleigh-Benard convection and thin film magnetic garnets, can be applied to radiation-induced patterns that occur in non-miscible alloys. By comparing ground states obtained from the minimization of this functional and a 2D numerical simulation performed on an irradiated AgCu material which is the archetype of a non-miscible alloy we show that the Swift-Hohenberg functional provides all possible patterns generated under irradiation and the solubility limits of radiation-induced precipitates in these patterns. To rationalize the formation of these radiation-induced patterns, we propose a generic "pseudo phase diagram" that relies not only on the irradiation flux and temperature but also the overall composition of the alloy. Tuning this overall composition offers the opportunity to tailor new materials with various micro-structures overcoming the limitation of the equilibrium phase diagram.

A combination of S-XRD and NPD demonstrate the structure of Ba 2 Y 0.879 UO 6+x to be monoclinic in space group I 2/ m . That the U is hexavalent is evident from the U L 2 -edge XANES measurements. This appears to be a rare example of a double perovskite containing vacancies at the octahedral B -sites and interstitial oxygen defects, which combine to stabilise hexavalent U and appears to be a consequence of the preparation of the sample in air. The Y vacancies, coupled with anion disorder, results in a distortion of the B O 6 octahedra.

The grain size refinement, enhancement of mechanical properties, and static recrystallization behavior of metallic nickel-silicon carbide nano-particle (Ni-3wt.%SiCNP) composites, milled for times ranging from 8 to 48 h have been examined. One set of Ni-SiCNP composite samples were annealed at 300 °C for 250 h, while the other set of samples were maintained at room temperature for control purposes (reference). The electron backscatter diffraction results indicate that the grain size of the annealed Ni-SiCNP composite was refined due to grain restructuring during static recrystallization. The x-ray diffraction results indicate that low-temperature annealing effectively reduced the density of dislocations; this can be explained by the dislocation pile-up model. Additionally, the tensile tests indicated that the annealed Ni-SiCNP composite had a significant increase in strength due to an increase of the Hall–Petch strengthening effect with a slight increase in the total elongation. The decrease of dislocation pile-up in the grain interiors and the increase in grain boundary sliding are assumed to be the main mechanisms at play. The relationship between the microstructural evolution and the variation of tensile properties is examined in this study.

Excavations at Akchakhan-kala in Uzbekistan, a region known in antiquity as Chorasmia, recovered a large, elaborately carved and heavily burned cylinder of some very solid material. Its poor condition made identification of the raw material difficult. Here we used neutron tomography to examine the internal structure in a non-destructive way, and X-ray Diffraction to determine the main chemical composition of the material which confirmed it as ivory. This was followed by preparation for stable isotope and radiocarbon analysis. The stable isotope analysis suggests a tropical or subtropical grassland source for the ivory, which is unlikely to be from Uzbekistan. The dating shows the ivory to be much earlier than the context in which it was found. Whatever its origin, the ivory travelled far to reach Chorasmia, perhaps in its raw state, and perhaps also for some time in its carved form.

Silicon carbide nanoparticle-reinforced nickel metal (Ni-SiCNP composite) samples were bombarded by helium ions with fluences of 1 x 10(16) and 3 x 10(16) ions/cm(2) at two different fluxes. The microstructural and mechanical changes were characterized via TEM and nanoindentation. Nano-scaled helium bubbles in the shape of spheres were observed in the samples irradiated at high flux and polygons at low flux. The number of helium bubbles increased with the fluence, whereas their mean size remained unaffected. In addition, the nanohardness of the damage layer also increased as the fluence increased. In addition this study suggests that a higher flux results in a higher number of smaller helium bubbles, while showing no obvious effect on the irradiation-induced hardening of the materials. (C) 2015 Elsevier B.V. All rights reserved.

The structure and magnetic properties of the mixed technetium-ruthenium perovskites SrTcxRu1-xO3 (x ​= ​0.25 and 0.5) have been investigated using variable temperature synchrotron X-ray diffraction, magnetic susceptibility measurements, and DFT calculations. Both oxides are isostructural with SrRuO3 and SrTcO3, and there is no evidence of long-range cation order. Magnetostriction is observed along the c-axis for both oxides. The inverse susceptibility and DFT calculations suggest a cation-disordered ferrimagnetic ground state for SrTc0.5Ru0.5O3.

In this study, in-situ micro-tensile testing technique was used to investigate the mechanical properties of ultrafine grained Ni-3wt% SiC composite the size effect on the mechanical properties of the ultrafine grained Ni-3wt% SiC composite, and to further reveal the reasons for the low ductility of the bulk Ni-3wt%SiC composite. Dog-bone micro-tensile samples were manufactured using a Focused Ion Beam (FIB) milling machine to 15 μm length with a cross sectional area of 5 μm by 5 μm. The micro-tensile samples are pulled in tension at a quasi-static strain rate of 0.000087/s (LSR) and a relatively faster strain rate of 0.011/s (HSR). Analysis of experimental stress-strain plots for the LSR tests measured yield stress, ultimate tensile stress and modulus values that approach values previously reported for bulk/macro-level tensile tests. However, the elongation and fracture energy at the micro-level is approximately half that at the bulk scale. This discrepancy is attributed to the presence of unwanted carbon and silicon oxide impurities ∼1.5 μm in diameter which act as stress concentrators especially given their large size relative to the width of the tensile specimens. The composition of these impurities was validated by transmission electron microscopy, and they seem to be the most likely cause of low ductility of the Ni-3wt% SiC composite. In all, the study undertaken here was able to replicate mechanical properties observed at the macro scale as well as reproduce a strain rate effect. Furthermore, the failure mode of Ni-3wt% SiC composite was identified and analysed in detail.

99Mo is an essential medical isotope that comprises of at least 70% of radioactive procedures globally. Currently an essential component of 99Mo manufacturing is the uranium target from which 99Mo is produced by fission. As the world moves towards low enriched uranium (LEU) targets due to non-proliferation concerns it is becoming of interest to find methods to increase the efficiency of the LEU targets in order to reduce the ever increasing nuclear waste levels of which a long term solution for disposal or treatment has yet to be satisfactorily found. Advantages and disadvantages of various target designs are investigated and discussed along current disposal and reprocessing methods. The idea of a reusable target is introduced as a way forward in reducing the nuclear waste burden for future generations.

The crystal structures of seven samples of orthorhombic ( Pnma ) Ln 2 TiO 5 compounds with Ln =La, Pr, Nd, Sm, Gd, Tb and Dy were refined by Rietveld analysis of synchrotron X-ray powder diffraction (S-XRD) data. With increasing size of the lanthanide cation, the lattice parameters increase systematically: c by only ~1.5% whereas both a and b by ~6% from Dy 2 TiO 5 to La 2 TiO 5 . The mean Ti–O bond length only increases by ~1% with increasing radius of the Ln cation from Gd to La, primarily due to expansion of the pair of Ti–O 3 bonds to opposite corners of the Ti–O 5 square based pyramid polyhedra. For Dy 2 TiO 5 and Tb 2 TiO 5 , a significant variation in Ti–O 1 and Ti–O 4 bond lengths results in an increased deformation of the Ti–O 5 base. The particular configuration consists of large rhombic shaped tunnels and smaller triangular tunnels along the b axis, which have implications for defect formation and migration caused by radiation damage or the ionic conductivity.

The high temperature structural behaviour of the uranium perovskites Ba2CaUO6 and BaSrCaUO6 has been investigated using a combination of synchrotron X-ray and neutron powder diffraction. Ba2CaUO6 undergoes a complex sequence of structures associated with the progressive loss of cooperative octahedral tilting: P21/n → I2/m → I2/m → I4/m → Fm3[combining macron]m. The observation of the intermediate tetragonal structure, I4/m, in this, contrasts with the previously reported rhombohedral R3[combining macron] intermediate formed by the Ba2SrUO6 oxide. The importance of π-bonding in determining the structural sequence is discussed.

The structure of TcO

Intuitively scientists accept that order can emerge from disorder and a significant amount of effort has been devoted over many years to demonstrate this. In metallic alloys and oxides, disorder at the atomic scale is the result of occupation at equivalent atomic positions by different atoms which leads to the material exhibiting a fully random or modulated scattering pattern. This arrangement has a substantial influence on the material’s properties, for example ionic conductivity. However it is generally accepted that oxides, such as defect fluorite as used for nuclear waste immobilization matrices and fuel cells, are the result of disorder at the atomic scale. To investigate how order at the atomic scale induces disorder at a larger scale length, we have applied different techniques to study the atomic composition of a homogeneous La2Zr2O7 pyrochlore, a textbook example of such a structure. Here we demonstrate that a pyrochlore, which is considered to be defect fluorite, is the result of intricate disorder due to a random distribution of fully ordered nano-domains. Our investigation provides new insight into the order disorder transformations in complex materials with regards to domain formation, resulting in a concord of chemistry with crystallography illustrating that order can induce disorder.

A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process.

Copper-doped nanosized zeolite A crystals were synthesized by an in situ templating approach using [Cu(EDTA)]2−-complex. The structural properties of the copper containing zeolite crystals were characterized by a suite of different techniques including SEM–EDX, ESR, mid-IR and Far-IR, Raman, in situ XRD and non-ambient neutron powder diffraction. The SEM investigations on the morphology show spheroidal zeolite A crystals with average size ∼200 nm. The asymmetric ESR spectrum shows that the Cu2+ ion is in a tetragonal-distorted octahedral crystal field. FT-IR and Raman spectroscopies provide information on coordination environment of the copper ion. The band due to stretching vibration of C–N bond, where N is coordinated to the copper ion (C–N–Cu), was observed at 1109 cm−1 in the mid-infrared region. The Raman band due to the Cu–O bond is present at 630 cm−1 indicating the coordination of the Cu2+-cation to COO−-group of the EDTA-ion. The XRD data shows an enlarged d-spacing between the adjacent zeolite lattice planes due to the presence of the [Cu(EDTA)]2−-complex in comparison to template-free LTA zeolite structure. LeBail fitting approach on temperature-dependent in situ X-ray and neutron diffraction profiles have demonstrated the expansion of the zeolite cell during the thermal treatment followed by subsequent contraction with the decomposition of the organic template.

The β-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au7Cu5Al4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 A, b = 5.8996 A, c = 17.8130 A); however, when this composition is cooled to only ∼260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P21/m, a = 4.4742 A, b = 5.9265 A, c = 13.3370 A, β = 91.425°). In contrast, a sample with decreased Al content (Au7Cu5.7Al3.3) transforms fully to monoclinic phase if cooled to ∼260 K.

The incorporation of uranium into gadolinium zirconate (Gd2Zr2O7) is investigated by synchrotron X-ray powder diffraction and X-ray absorption near-edge structure (XANES) spectroscopy. The results suggest that the uranium cation is largely located on the pyrochlore B-site instead of the targeted A-site. Cation disorder in Gd2Zr2O7 and U-doped Gd2Zr2O7 is investigated by positron annihilation lifetime spectroscopy (PALS) which demonstrates the absence of cation vacancies in these systems. This work provides direct evidence for cation antisite (A- and B-site mixing) disorder in U-doped and off-stoichiometric Gd2Zr2O7 pyrochlore.

Ceramics with the sodium zirconium phosphate or NZP type structure have potential as nuclear waste form and inert matrix materials. For both applications the material will be subjected to self-radiation damage from α-decay of the incorporated actinides. In this study, ion-beam irradiation using Au- and He-ions has been used to simulate the consequences of α-decay and the effects of irradiation on the structural and macroscopic properties (density and hardness) have been investigated. Irradiation by Au-ions resulted in a significant volume contraction of ∼7%, a reduction in hardness of ∼30% and a loss in long-range order at fluences above 1014 Au-ions/cm2. In contrast, little effect on the material properties was noted for samples irradiated with He-ions up to a fluence of 1017 ions/cm2. Thermal annealing was investigated for the highest fluence Au-ion irradiated sample and significant decomposition was observed.

To simulate the burst irradiation environment of Europa, single crystals of NaCl were irradiated by pulsed intense relativistic electron beams (PIREBs) with a peak energy of 6 MeV, a current of −800 A, and a pulse width of 70 ns. After irradiation, the optical absorption of the samples was measured, and results indicated that the irradiation induced F- and F2-centers. The density of F-centers was estimated to be 8.9 × 1016 cm−3 from 1 shot of PIREB irradiation with 6 MeV. The absorbed energy to form F-centers by PIREB was comparable but slightly higher than those induced by conventional direct current accelerators. The effect of pulsed heating, which should be taken into account for the detection of NaCl on Europa, is discussed.

CrUO4 and (Cr, Al)UO4 have been fabricated by a sol–gel method, studied using diffraction techniques and modelled using empirical pair potentials. Cr2O3 was predicted to preferentially form CrUO4 over entering solution into hyper-stoichiometric UO2+x by atomic scale simulation. Further, it was predicted that the formation of CrUO4 can proceed by removing excess oxygen from the UO2 lattice. Attempts to synthesise AlUO4 failed, instead forming U3O8 and Al2O3. X-ray diffraction confirmed the structure of CrUO4 and identifies the existence of a (Cr, Al)UO4 phase for the first time (with a maximum Al to Cr mole ratio of 1:3). Simulation was subsequently used to predict the partition energies for the removal of fission products or fuel additives from hyper-stoichiometric UO2+x and their incorporation into the secondary phase. The partition energies are consistent only with smaller cations (e.g. Zr4+, Mo4+ and Fe3+) residing in CrUO4, while all divalent cations are predicted to remain in UO2+x. Additions of Al had little effect on partition behaviour. The reduction of UO2+x due to the formation of CrUO4 has important implications for the solution limits of other fission products as many species are less soluble in UO2 than UO2+x.

The incorporation of TcO 2 into the rutile phase of TiO 2 has been theoretically examined to understand the potential of the system for use as a wasteform. The effects of defect clustering and the transmutation of Tc into Ru were considered. Results suggest that as a single defective species, Tc has a temperature-dependent, moderate solubility into rutile TiO 2 , which increases when clustering is considered. The {2Tc Ti } cluster that preferentially forms was found to have a Tc–Tc bond length similar to the cation distance in TcO 2 . The transmutation of Tc to Ru has two effects: first, the preferred binary cluster morphology changes from that of first nearest neighbour for {2Tc Ti } to that of second nearest neighbour for {2Ru Ti }. Second, the defect solubility is lower for single Ru Ti defects and Ru-containing defect clusters. This will likely result in the formation of a secondary phase as transmutation proceeds, if Tc is added to rutile TiO 2 to its solution limit. The varying solubility of RuO 2 in TiO 2 with temperature was compared with previously published experimental data with encouraging results. The use of two different DFT codes (one plane-wave and one local-orbital) was used to find the correct magnetic ordering in the defective lattices, which increased the confidence in the methods and therefore the results.

The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy) to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave manufacturing process equipped to generate rapid heating rates and mechanical vibration. The results suggested that the quaternary ammonium surfactant on C30B clay reacted with the epoxy during cure, while the primary ammonium surfactant (I.30E) catalysed the polymerisation reaction. These effects led to important differences in nanocomposite clay morphologies. The use of mechanical vibration at 4 Hz prior to matrix gelation was found to facilitate clay dispersion and to reduce the area fraction of I.30E clay agglomerates in addition to increasing flexural strength by over 40%.

The structure of one of the oxides proposed to be present in the grey phase of irradiated mixed oxide fuel, the double perovskite Ba 2 SrUO 6 has been investigated from room temperature to 1300 K using synchrotron X-ray powder diffraction methods. The divalent strontium and hexavalent uranium are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygen atoms. At room temperature Ba 2 SrUO 6 adopts a monoclinic structure in space group P 2 1 / n . Heating to above 900 K induces a first order transition to a rhombohedral structure, and further heating to above 1200 K results in a continuous transition to a cubic structure. The sequence of structures is associated with the progressive loss of cooperative tilting of the corner sharing SrO 6 and UO 6 octahedra.

Low temperatures and frequent soil freeze–thaw in polar environments present challenges for the immobilisation of metals. To address these challenges we investigated the chemical forms of Pb, Zn and Cu in an Antarctic landfill, examined in vitro reaction kinetics of these metals and orthophosphate at 2 and 22 °C for up to 185 days, and subjected the products to freeze–thaw. Reaction products at both temperatures were similar, but the rate of production varied, with Cu-PO4 phases forming faster, and the Zn- and Pb-PO4 phases slower at 2 °C. All metal-orthophosphate phases produced were stable during a 2.5 h freeze–thaw cycle to −30 °C. Metal immobilisation using orthophosphate can be successful in polar regions, but treatments will need to consider differing mineral stabilities and reaction rates at low temperatures.

Single-phase samples of Ln 2−x Ca x CoO 4+ δ ( Ln = Pr 3+ − Gd 3+ ) around x ∼1 have been prepared. For the first time, the phase field for these compounds has been defined using powder X-ray diffraction and a very narrow solid solution was observed. Under our synthetic conditions, the K 2 NiF 4 structure was not formed for the large La 3+ ion, or for compositions containing the smaller rare earths ions ( 3+ ) and Y 3+ . Thermogravimetric analysis indicates average cobalt oxidation states ranging between ∼3.2+ and ∼3.3+. Rietveld refinement of structures using synchrotron powder X-ray diffraction data indicates that the larger rare earth ions Ln CaCoO 4+ δ ( Ln = Pr 3+ − Sm 3+ ) form tetragonal ( I4/mmm ) structures at room temperature, while ( Ln = Eu 3+ , Gd 3+ ) crystallised with orthorhombic ( Bmab ) structures. The evolution of structure between the low temperature orthorhombic form and the high temperature tetragonal form was investigated between 80 K and 575 K using high-resolution synchrotron X-ray powder diffraction. Orthorhombic to tetragonal transitions were observed for SmCaCoO 4.17 (T∼230 K), EuCaCoO 4.13 (T∼320 K) and GdCaCoO 4.11 (T∼465 K). Magnetic measurements for Ln CaCoO 4+ δ ( Ln = Pr 3+ − Gd 3+ ) indicate paramagnetic behaviour along with weak antiferromagnetic interactions and Co 3+ in a 6 t 2g low-spin state. PrCaCoO 4.17 was found to order antiferromagnetically below 15 K.

This paper investigates the effect of both the mixing technique and heating rate during cure on the dispersion of montmorillonite (MMT) clay in an epoxy resin. The combination of sonication and using a 10 °C/min heating rate during cure was found to facilitate the dispersion of nanoclay in epoxy resin. These processing conditions provided a synergistic effect, making it possible for polymer chains to penetrate in-between clay galleries and detach platelets from their agglomerates. As the degree of dispersion was enhanced, the flexural modulus and strength properties were found to decrease by 15% and 40%, respectively. This is thought to be due to individual platelets fracturing in the nanocomposite. Complementary techniques including X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX), transmission electron microscopy (TEM) and optical microscopy were essential to fully characterise localised and spatial regions of the clay morphologies.

The structure of the defect pyrochlore NaW 2 O 6+ δ · n H 2− z O after ion exchange with K, Rb, Sr or Cs for Na has been investigated using thermal analysis, solid-state nuclear magnetic resonance, laboratory X-ray and neutron diffraction methods. Neutron diffraction studies show that both the A -type cations (Na + , K + , Rb + , and/or Cs + ) and the water molecules reside within the channels that form in the 111 direction of the W 2 O 6 framework and that these strongly interact. The analytical results suggest that the water and A -type cations compete for space in the tunnels within the W 2 O 6 pyrochlore framework, with the total number of water molecules and cations being approximately constant in the six samples investigated. The interplay between the cations and water explains the non-linear dependence of the a lattice parameter on the choice of cation. It appears that the ion-exchange capacity of the material will be controlled by the amount of water initially present in the sample.

The β-phase of Au 7 Cu 5 Al 4 undergoes a reversible shape-memory phase transformation, however there has been some uncertainty regarding the crystal structure or structures of the parent phase. Here we show that, under equilibrium conditions, the parent phase possesses the L2 1 structure between its A p (about 79 °C) and ∼630 °C, and the B2 primitive cubic structure between ∼630 °C and its melting point. It melts directly from B2 into the liquid state and hence never achieves the random bcc A2 structure that has been previously mooted. Splat-cast samples of the alloy are martensitic, proving that development of equilibrium order and defect concentration are not pre-requisites for the A → M transformation to occur.

Synchrotron X-ray diffraction and neutron diffraction have been used to investigate the phase changes that the titanosilicate mineral sitinakite undergoes when dehydrated. Refinements of the powder diffraction data of the material before and after heating to 573K indicate a phase change from space group P42/mcm to P42/mbc. Upon exposure to normal atmospheric conditions for an extended period the material transforms back to P42/mcm with a reduced lattice parameter. If the material is heated in a sealed capillary, it is possible to get the two phases coexisting. The coexistence of these two phases in sealed system suggests that it is only the loss of H2O that is driving the reversible phase transformation.

Ceramics based on Ln TiTaO 6 ( Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using scanning electron microscopy, synchrotron X-ray powder diffraction and neutron diffraction techniques. The unit cell volume of the ceramics decreased with a decrease in ionic radius of the rare-earth ions until a phase change was seen at Ho where the space group changed from Pnma to Pbcn . The results confirmed that the boundary of the aeschynite to euxenite phase change that lies between DyTiTaO 6 and HoTiTaO 6 and demonstrate that this is a result of distortion of the channels in the aeschynite structure.

Boron carbide (B4C) added manganese dioxide (MnO2) used as a cathode material for a Zn–MnO2 battery using aqueous lithium hydroxide (LiOH) as the electrolyte is known to have higher discharge capacity but with a lower average discharge voltage than pure MnO2 (additive free). The performance is reversed when using potassium hydroxide (KOH) as the electrolyte. Herein, the MnO2 was mixed with 0, 5, 7 and 10 wt.% of boron carbide during the electrode preparation. The discharge performance of the Zn|LiOH|MnO2 battery was improved by the addition of 5–7 wt.% boron carbide in MnO2 cathode as compared with the pure MnO2. However, increasing the additive to 10 wt.% causes a decrease in the discharge capacity. The performance of the Zn|KOH|MnO2 battery was retarded by the boron carbide additive. Transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy analysis (EDS) results show evidence of crystalline MnO2 particles during discharging in LiOH electrolyte, whereas, manganese oxide particles with different oxygen and manganese counts leading to mixture of phases is observed for KOH electrolyte which is in agreement with X-ray diffraction (XRD) data. The enhanced discharge capacity indicates that boron atoms promote lithium intercalation during the electrochemical process and improved the performance of the Zn|LiOH|MnO2 battery. This observed improvement may be a consequence of B4C suppressing the formation of undesirable Mn(III) phases, which in turn leads to enhanced lithium intercalation. Too much boron carbide hinders the charge carrier which inhibits the discharge capacity.

The structures of the defect pyrochlores A Al 0.33 W 1.67 O 6 where A =K, Rb or Cs have been investigated using X-ray and neutron powder diffraction methods as well as the ab initio modelling program VASP. The three cubic pyrochlores exhibit a non-linear increase in lattice parameter with respect to ionic radius of the A cation as a consequence of displacive disorder of the A -type cations. Solid state 27 Al MAS NMR studies of this pyrochlore system reveal shifts in the δ ∼21–22 ppm range that are indicative of pseudo-5 coordinate Al environments and emanate from distorted Al octahedral with one abnormally long Al–O bond. Solid state 39 K, 85 Rb, 87 Rb and 133 Cs MAS and static NMR studies reflect the local cation disorder demonstrated in the structural studies.

This article reports on the in situ analysis of nickel silicide (NiSi) thin films formed by thermal processing of nickel thin films deposited on silicon substrates. The in situ techniques employed for this study include micro-Raman spectroscopy (microRS) and X-ray diffraction (XRD); in both cases the variations for temperatures up to 350 degrees C has been studied. Nickel silicide thin films formed by vacuum annealing of nickel on silicon were used as a reference for these measurements. In situ analysis was carried out on nickel thin films on silicon, while the samples were heated from room temperature to 350 degrees C. Data was gathered at regular temperature intervals and other specific points of interest (such as 250 degrees C, where the reaction between nickel and silicon to form Ni(2)Si is expected). The transformations from the metallic state, through the intermediate reaction states, until the desired metal-silicon reaction product is attained, are discussed. The evolution of nickel silicide from the nickel film can be observed from both the microRS and XRD in situ studies. Variations in the evolution of silicide from metal for different silicon substrates are discussed, and these include (100) n-type, (100) p-type, and (110) p-type silicon substrates.