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The first multiband photometric solutions of the short-period V Gru eclipsing binary from the southern hemisphere is presented in this study. Light curves of the system were observed through BVI filters at the Congarinni Observatory in Australia for 15 nights. In addition to the new ground-based data, we also used the TESS observations in two sectors. We analyzed the light curves of the system using the PHysics Of Eclipsing BinariEs (PHOEBE) 2.4.7 version code to achieve the best accordance with the photometric observations. The solutions suggest that V Gru is a near-contact binary system with q=1.302(81) mass ratio, f1=0.010(23), f2=-0.0.009(21), and i=73.45(38). We considered the two hot spots on the hotter and cooler components for the light curve analysis. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach. Using our new light curves, TESS, and additional literature minima, we computed the ephemeris of V Gru. The system's eclipse timing variation trend was determined using the MCMC method. This system is a good and challenging case for future studies., Comment: Accepted by the Research in Astronomy and Astrophysics (RAA) journal

New spectrometric (HERCULES) and ground-based multi-colour photometric data on the multiple star V410 Puppis are combined with satellite photometry (HIPPARCOS and TESS), as well as historic astrometric observations. Absolute parameters for V410 Pup Aab are derived: $M_{Aa}$ = $3.15 \pm 0.10$, $M_{Ab}$ = $1.83 \pm 0.08$ (M$_{\odot}$); $R_{Aa}$ = $2.12 \pm 0.10$, $R_{Ab}$ = $1.52 \pm 0.08$ (R$_\odot$); $a$ = $6.57 \pm 0.04$ R$_\odot$; $T_{Aa}$ = $12500 \pm 1000$, $T_{Ab}$ = $9070 \pm 800$ (K), and photometric distance $350 \pm 10$ (pc). We report the discovery of a low-amplitude SPB variation in the light curve and also indications of an accretion structure around V410 Pup B as well as emission cores in V410 Pup C. We argue that V410 Pup is probably a young formation connected with the Vela 2 OB Association. The combined evidence allows an age in the range 7-25 Myr from comparisons with standard stellar evolution modelling., 14 pages, 15 figures, 12 tables. MNRAS (accepted)

New CCD photometric observations and their investigation of the W UMa-type binary, V870 Ara, are presented. Light curves of the system were taken through BVI filters from the Congarinni Observatory in Australia. The new ephemeris is calculated based on seven new determined minimum times, together with the TESS data and others compiled from the literature. Photometric solutions determined by the Wilson-Devinney (W-D) code are combined with the Monte Carlo simulation to determine the adjustable parameters' uncertainties. These solutions suggest that V870 Ara is a contact binary system with a mass ratio of 0.082, a fillout factor of 96+-4 percent, and an inclination of 73.60+-0.64 degrees. The absolute parameters of V870 Ara were determined by combining the Gaia EDR3 parallax and photometric elements., Comment: 5 tables, 6 figs, accepted in the Open Astronomy Journal

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R) and $logJ_0-logM$ diagrams. According to a sample, we were able to present relations for the mass-radius (M-R) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M-R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships., Comment: 11 Figures, 9 Tables, Accepted by the PASP Journal

An aqueous solution route was employed to prepare cerium titanate oxide brannerite. Thermal analysis, X-ray diffraction, Raman spectroscopy, transmission and scanning electron spectroscopy, were used to investigate the brannerite structure formation and bulk properties. Mixed metal oxides (TiO2, CeO2 and brannerite CeTi2O6) were formed upon calcination at 800 °C for 12 h. The amount of brannerite phase decreased to form the constituent oxides with increasing calcination temperature and only pure TiO2 and CeO2 were present after 1200 °C calcination. The brannerite CeTi2O6 phase reformed at 1300 °C, and its relative amount was increased with dwell time. After 48 h calcination at 1300 °C, brannerite with only minor metal oxide impurities (

MgO-Nd 2 Zr 2 O 7 composites with ratios of 50–70 vol% MgO were produced via a one-pot combustion synthesis. A suite of characterization techniques, including X-ray diffraction, scanning and transmission electron microscopy were employed to investigate the structural properties while dilatometry, simultaneous thermal analysis and laser flash analysis were used to characterize the thermal properties of the composites. Dense pellets were produced after sintering at 1400 °C with grain sizes between 200 and 500 nm for both phases. The thermal properties of the composites are similar to those produced using standard methods. The composite with 70 vol% MgO was found to have the highest thermal conductivity below 1000 °C, while above this temperature the thermal conductivity was found to be similar and independent of MgO content. This novel synthesis route produces materials which show significant improvements in homogeneity with smaller particle sizes when compared to current standard synthesis techniques without significantly reducing thermal conductivity.

Garnets have been considered as host phases for the safe immobilisation of high-level nuclear waste, as they have been shown to accommodate a wide range of elements across three different cation sites, such as Ca, Y, Mn on the a-site, Fe, Al, U, Zr, and Ti on the b-site, and Si, Fe, Al on the c-site. Garnets, due to their ability to have variable composition, make ideal model materials for the examination of radiation damage and recovery in nuclear materials, including as potential waste forms. Kimzeyite, Ca 3 Zr 2 FeAlSiO 12 , has been shown naturally to contain up to 30 wt% Zr, and has previously been examined to elucidate both the structure and ordering within the lattice. This study examines the effects of radiation damage and recovery using in-situ ion beam irradiation with 1 MeV Kr ions at the IVEM-TANDEM facility, Argonne National Laboratory. The complementary Hf containing system Ca 3 Hf 2 FeAlSiO 12 was also examined, and found to have a different response to irradiation damage. A sample of irradiated Ca 3 Zr 2 FeAlSiO 12 , at 1000 K, was characterised using aberration corrected (S)TEM and found to contain discreet, nano-sized, crystalline Fe rich particles, indicating a competing process during recovery is occurring.

Coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea-level rise due to their low elevation and proximity to the coastline. Intact soil cores from a levee, acid-sulfate soil scald and four backswamp sites on a coastal floodplain in eastern Australia were inundated with artificial seawater treatments (0%, 50% and 100%) for 14 days to examine the short term consequences for surface water and floodplain sediment geochemistry. All sites displayed an initial decrease in surface water pH following inundation with 50% and 100% seawater. In addition, higher concentrations of trace metals (Al, Fe, Mn, Ni and Zn) were observed in most sites inundated with 50% or 100% seawater. This was generally attributed to competitive exchange and desorption of trace metals from sediments due to the higher ionic strength of the seawater solutions and upward diffusive flux of metals from the sediments to surface waters. At one backswamp site, reductive processes had established by day 7, which also resulted in elevated Fe 2 + concentrations in the overlying surface waters. Transmission electron microscopy (TEM) identified the presence of poorly crystalline ferrihydrite and schwertmannite, and goethite and jarosite. These meta-stable Fe(III) minerals can act as a source of metals for desorption and can also be readily reduced and act as a source of Fe 2 + to surface waters. Importantly, inundation with either 50% or 100% seawater resulted in a similar magnitude of acidity and trace metal mobilisation. The data suggest that an inundation event of ~ 0.2 m depth with either 50% or 100% seawater could cause a pulse mobilisation of up to 64.8 and 9.1 kg ha − 1 of Fe and Al, respectively — quantities of similar magnitude to previous estimates of annual drainage fluxes from similar backswamps. This study suggests that the short term inundation of coastal floodplain sediments by either brackish water or seawater will result in rapid declines in surface water quality as a result of increased liberation of acidity and trace metals.

Pyrochlore structured Nd 2 Sn x Zr 2− x O 7 ( x =0–2) ceramics were prepared by a new chemical synthesis route in an aqueous media. Raman spectra and X-ray diffraction patterns confirmed the formation of the pyrochlore structure after sintering at 1400 °C. SEM results showed pelletized materials became dense with increasing Zr/Sn mole ratio and sintering temperature. These candidate materials have characteristic structures for the development of nuclear waste forms or inert matrix nuclear fuels.

Pyrochlore structured Gd2Zr2O7 and Nd2Zr2O7 are produced via complex precipitation processing. A suite of characterization techniques, including FTIR, Raman, X-ray and electron diffraction, TEM, SEM as well as nitrogen sorption are employed to investigate the structural and grain size evolution of the synthesized and calcined powder. Results show that Gd2Zr2O7 with the pyrochlore structure are produced after calcination at 1400 °C for 12 h while Nd2Zr2O7 has already formed the pyrochlore structure at 1200 °C. This method allows the formation of dense materials at relatively low temperature, with bulk densities over 92% of the theoretical values achieved after sintering at 1400 °C for 50 h. This unique aqueous synthetic method provides a simple pathway to produce pyrochlore lanthanide zirconate without using either organic solvent and/or mechanical milling procedures, making the synthesis protocol an attractive potential scale-up production of highly refractory ceramics.

This paper systematically compares the activity of Au/TiO 2 photocatalysts (Au loadings 0–10 wt.%) for H 2 production from ethanol–water mixtures under UV excitation. Degussa P25 TiO 2 was used as the support phase. TEM analyses revealed that the average Au nanoparticle size at all loadings was 5 ± 2 nm, with the Au nanoparticles preferentially located at the interfacial sites between TiO 2 crystallites. XRD, XRF, XPS, and UV–Vis measurements established that metallic Au was the only gold species on the surface of the photocatalysts. The Au/TiO 2 photocatalysts showed an intense absorption maximum centred around 560–570 nm due to the localised surface plasmon resonance (LSPR) of the supported gold nanoparticles. Photoluminescence measurements revealed that gold nanoparticles effectively suppress electron–hole pair recombination in TiO 2 , even at low Au loadings. All of the Au/TiO 2 photocatalysts displayed high activity for H 2 production from ethanol–water mixtures under UV irradiation, with the highest activities observed in the Au loading range 0.5–2 wt.% (H 2 production rate 31–34 mmol g −1 h −1 ). In order to deconvolute the role of the P25 TiO 2 support in promoting H 2 production, anatase and rutile nanoparticles were isolated from P25 TiO 2 by selective chemical dissolution and then functionalised with gold nanoparticles (3 wt.% loading, size 5 ± 2 nm). The H 2 production activity of the resulting Au/anatase and Au/rutile photocatalysts was 22 and 10 mmol g −1 h −1 , respectively, and substantially lower than the corresponding Au/P25 TiO 2 photocatalyst (32 mmol g −1 h −1 ). The data provide strong evidence that synergistic electron transfer between the TiO 2 polymorphs and supported Au nanoparticles is responsible for the high rates of H 2 production observed in the Au/P25 TiO 2 system. The interface between anatase and rutile crystallites, where gold nanoparticles preferentially deposit, is identified as a photocatalytic ‘hot spot’ for H 2 production. High Au loadings reduce the efficiency of such ‘hot spots’.

While Zn vacancies are regarded as the charge compensators in Ti-rich Zn2TiO4, no evidence of cation vacancies in essentially single-phase samples containing up to 13 wt% excess TiO2 was evident from positron annihilation lifetime spectroscopy (PALS). Nor was there strong evidence of cation vacancies in Ta-doped samples targeted to contain either tetrahedral or octahedral vacancies, although there was a small increase in the lifetime as the doping level increased and the structure changed from cubic to tetragonal.

A series of uranium-containing gadolinium zirconate samples have been fabricated at 1450 °C in oxidizing, inert and reducing atmospheres. X-ray diffraction, Raman spectroscopy and transmission electron microscopy have been utilized to confirm adoption of pyrochlore or defect fluorite structures. X-ray diffraction allowed determination of the bulk averaged structure while Raman spectroscopy and transmission electron microscopy were used to determine ordering at the microdomain scale. Diffuse reflectance, X-ray absorption near edge structure and X-ray photoelectron spectroscopies indicated a predominantly U 6+ oxidation state for all the air-sintered samples, even when Ca 2+ or A-site vacancies were incorporated to charge balance for U 4+ , a mixed U 5+ /U 6+ oxidation state was found for samples sintered in argon, while a mixed U 4+ /U 5+ oxidation state occurred for sintering under N 2 –3.5%H 2 . This demonstrates a degree of uranium oxidation state control through sintering conditions, and the potential of using gadolinium zirconates as host materials for uranium in nuclear waste applications.

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.

The Mn valency and the crystallinity of Li 2 MnSiO 4 cathodes ( Pmnb form) were examined with electron energy-loss spectroscopy (EELS) and selected area electron diffraction (SAED) both before and after electrochemical lithium extraction. A decrease in the crystallinity of the delithiated charged cathode particles compared to the as-prepared material was observed. The decrease in crystallinity varied from particle to particle. EELS analysis showed that the non-uniform decrease in crystallinity was due to a non-uniform extraction of lithium from the particles. The observed decrease in discharge capacity of the Pmnb polymorph of Li 2 MnSiO 4 with cycling was attributed to the progressive loss of crystallinity and the structural collapse of Li diffusion pathways.

Davidite (A1−xM21O38) samples from five different geological localities contain approximately 0.2 to 9.5 wt% UO2 (0.02 to 0.65 atoms per formula unit) and

Jarosite (KFe 3 (SO 4 ) 2 (OH) 6 ) is an important host-phase for As in acid mine drainage (AMD) environments and coastal acid sulfate soils (CASS). In AMD and CASS wetlands, jarosite may encounter S(− II) produced by sulfate reducing bacteria. Here, we examine abiotic sulfidization of As(V)-bearing K-jarosite at pH 4.0, 5.0, 6.5 and 8.0. We quantify the mobilization and speciation of As and identify corresponding Fe mineral transformations. Sulfide-promoted dissolution of jarosite caused release of co-precipitated As and the majority of mobilized As was re-partitioned to a readily exchangeable surface complex (As Ex ). In general, maximum As mobilization occurred in the highly sulfidized end-members of all treatments and was greatest at low pH, following the order pH 5.0 ≈ 4.0 > 8.5 > 6.5. X-ray absorption spectroscopy revealed that most solid-phase As remained as oxygen-coordinated As(V) when pH values were > 5.0 — even during latter stages of sulfidization and the presence of ≥ 100 μM dissolved S(− II). In contrast at pH 4.0, As transitioned from oxygen-coordinated As(V) to a sulfur-coordinated orpiment-like phase. This transition coincided with a marked decrease in As Ex , attenuation of As (aq) and TEM-EDX spectra indicate concurrent formation of nano-scale zones variably enriched in As (~ 1–15%). Although discordant with geochemical modeling, the formation of an orpiment-like precipitate appears to be a primary control on As mobility during the late stages of complete jarosite sulfidization under acidic conditions (pH 4.0). Mackinawite was the main Fe-mineral end product in all pH treatments. However, at pH 8.0, jarosite rapidly ( (aq) , the transformation process itself was incongruent with electron transfer to Fe(III). Further investigation is required to determine whether the electron donor triggering this transformation was direct via S(− II), or indirect via surface complexed Fe(II) and hence akin to the widely-known Fe(II)-catalyzed transformation of Fe(III) minerals. The results demonstrate that abiotic sulfidization of As(V)-co-precipitated jarosite can mobilize substantial As and that pH exerts a major control on the subsequent As solid-phase speciation, electron transfer kinetics and Fe mineralization pathways and products. The findings are particularly relevant to heterogeneous sediments in which As-bearing jarosite encounters dissolved sulfide under a range of pH conditions.

Lanthanum zirconate has been prepared via a new chemical synthesis method by combining sol–gel processing and complex precipitation. The synthesis was carried out in aqueous solution under ambient conditions. The synthesized powder possessed the pyrochlore superstructure upon calcination above 1200°C. A suite of characterization techniques, including FTIR, Raman, X-ray and electron diffraction, TEM, SEM, and nitrogen sorption were employed to investigate the microstructural evolution and bulk properties. Dense ceramics (>90% relative density) were obtained after sintering at 1400°C, without need for additional processing (i.e., hot or cold isostatic pressing) or any milling steps. A mechanism has been proposed that elucidates molecular assembly of this chemical synthesis method.

The structural characteristics of olivine-type lithium orthophosphate Li(Mg0.5Ni0.5)PO4 synthesized via solid-state reaction have been studied using X-ray diffraction, ion beam technique, scanning electron microscopy, infrared spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis. The parent LiNiPO4 compound can be synthesized in olivine structure without any evidence of secondary phases as impurities. The structural quality of the parent LiNiPO4 in the absence of secondary component phases resulted in the formation of hexagonal closed packed structure. The olivine analogue compound containing mixed M (M = Mg, Ni) cations, Li(Mg0.5Ni0.5)PO4 contained Li3PO4 as a second phase upon synthesis, however a carbothermal reduction method produced a single-phase compound. The redox behaviour of carbon-coated Li(Mg0.5Ni0.5)PO4 cathode in aqueous lithium hydroxide as the electrolyte showed reversible lithium intercalation.

The ability to decrease the electron/hole recombination rate, and decrease the band gap of titania to allow photoactivity on irradiation with visible light is attracting more and more attention. Here, boron doping of the titania, the deposition of gold nanoparticles, along with a meso-macroporous structure were obtained using a facile agarose gel templating process combined with sol-gel chemistry. The Au/B/TiO(2) nanocomposites were characterized using SEM, TEM, XRD, N(2) gas sorption, diffuse UV-vis, photoluminescence, and SIMS. The photocatalytic activity was assessed by degradation of an organic probe molecule (methylene blue) under visible light (λ420 nm). The resulting materials achieved photocatalytic activities up to 50% greater than the commercial Degussa P25 under visible light. The enhancement in photocatalytic activity was primarily attributed to the decrease in band gap as a result of the boron doping and its influence on the anatase to rutile phase formation: The doped materials were highly crystalline and an optimum anatase to rutile ratio (3:1) was obtained with 0.25 wt % boron in the sample calcined at 650 °C. In addition, the presence of the gold nanoparticles decreased recombination between the photoexcited electrons and holes, which further improved the photocatalytic activity.

Rutile powder was synthesized via sol–gel processing of Tyzor TE precursor in an aqueous solution at 40°C–50°C. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction, were employed to investigate the microstructural evolution. The synthesized powder was phase-pure rutile possessing high surface area (144.7 m2/g), an average pore size of 24.9 nm, and pore volume of 0.66 cm3/g. A reaction mechanism is proposed for the preferential evolution of rutile over other titania polymorphs (i.e. amorphous or anatase).

Pyrochlores based on the general composition Ln2TiO5 (Ln2.67Ti1.33O6.67) and Ln2Ti2O7, where Ln = Y or Yb, have been irradiated through the crystalline–amorphous transition with 1 MeV Kr ions at the IVEM-TANDEM facility, Argonne National Laboratory. The results show that the Tc (critical temperature for amorphization) differs significantly between each series, e.g. for Y2TiO5 it is 589 ± 18 K and for Y2Ti2O7 665 ± 33 K. The difference suggests that recovery from damage is more rapid with increasing Ln content, i.e. a lower Tc for amorphization. These results are discussed in the context of the melting points of each phase, atomic disorder, the pyrochlore–fluorite order–disorder transition and the implications for oxide dispersion-strengthened additives.

Considering the safety, cost and low ohmic resistance issues with respect to the non-aqueous electrolytes that are generally used in rechargeable lithium ion batteries, aqueous electrolytes attract wide interest. A traditional Zn-MnO2 battery in which potassium hydroxide (KOH) has been replaced with a lithium hydroxide (LiOH) electrolyte is discussed. As lithium intercalation materials are of special interest as cathode in rechargeable batteries, the new concept has been extended to use lithium nickel phosphate as cathode for aqueous rechargeable batteries. Here, we show reversible extraction and insertion of lithium from and into olivine LiNiPO4 in aqueous solutions. These cells are found to be cheap, rechargeable and safe. The unique sol-gel synthesis has been used to synthesize LiNiPO4 which has been characterized in order to evaluate a new potential cathode for aqueous rechargeable batteries.

The effect of alkaline-earth oxide additions on aqueous rechargeable battery is investigated using microscopic and spectroscopic techniques. The alkaline-earth oxide additions such as magnesium oxide (MgO) and barium oxide (BaO) were physically mixed to the manganese dioxide (MnO2) cathode of a cell comprising zinc as an anode and aqueous lithium hydroxide as the electrolyte. The results showed that such additions greatly improved the discharge capacity of the battery (from 145 to 195 for MgO and 265 mAh/g for BaO). Capacity fade with subsequent cycling is reduced only for MgO but not for BaO. With an aim to understand the role of these additives and its improvement in cell performance, we have used microscopy, spectroscopy, ion beam analysis and diffraction based techniques to study the process. Transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy analysis (EDS) results showed evidence of crystalline MnO2 particles for MgO as additive, whereas, MnO2 particles with diffused structure leading to mixture of phases is observed for BaO additives which is in agreement with X-ray diffraction (XRD) data. This work relates to improvement in the electrochemical behaviour of the Zn-MnO2 battery while the MgO additive helps to reduce the formation of manganese and zinc such as hetaerolite that hinders the lithium intercalation

A novel 1 V battery composed of Sn-LiCoPO4 using aqueous lithium hydroxide electrolyte is described. Reversible extraction and insertion of lithium from and into the olivine-type LiCoPO4 is reported. The electrochemical behavior of the Sn-LiCoPO4 battery was analyzed using charge/discharge cycling and cyclic voltammetry. Sn-LiCoPO4 battery exhibited charge/discharge voltages of 1.3 V/0.8 V versus Sn with a reversible capacity of 80 mAh/g. The structural and morphological changes of LiCoPO 4 particles before and after electrochemical measurements were investigated by X-ray diffraction (XRD) and transmission electron microscopy. XRD data showed that extraction of lithium proceeds via at least a two-phase mechanism with LiCoPO4 and CoPO4 phases. Upon lithium reinsertion crystalline LiCoPO4 was formed. The cell voltage indicated these batteries were not completely charged, forming single-phase CoPO4 material. Energy-dispersive X-ray analysis coupled with transmission electron microscopy confirmed the chemical quality of the charged and discharged LiCoPO4 in terms of crystallinity and elemental distribution.

Incorporation of TiS2 additive by physical admixture into the LiMnPO4 cathode leads to modification of the electrochemical performance of the cathode, such as an improved delithiation and lithiation mechanism. Cyclic voltammetry suggests that the TiS2 additive suppresses proton deinsertion/insertion mechanism and does not contribute directly to the reduction/oxidation reactions of the LiMnPO4 working electrode.

In this study, the mechanism of precursor dissolution and the influence of kinetics of dissolution on titanate nanotube formation were investigated. This comparative study explored the dissolution kinetics for the case of commercial titania powders, one composed of predominantly anatase (>95%) and the other rutile phase (>93%). These nanoparticle precursors were hydrothermally reacted in 9 mol L−1 NaOH at 160 °C over a range of reaction times of between 2 and 32 h. The high surface area nanotube-form product was confirmed using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscopy. The concentration of nanotubes produced from the different precursors was established using Rietveld analysis with internal and external corundum standardization to calibrate the absolute concentrations of the samples. Interpretation of the dissolution process of the precursor materials indicated that the dissolution of anatase proceeds via a zero-order kinetic process, whereas rutile dissolution is through a second-order process. The TiO2 nanostructure formation process and mechanism of TiO2 precursor dissolution was confirmed by non-invasive dynamic light scattering measurements. Significant observations are that nanotube formation occurred over a broad range of hydrothermal treatment conditions and was strongly influenced by the order of precursor dissolution.

Boron compounds generally produce a battery with high energy density. Since boron is an excellent conductor of electricity a battery with a high power density can also be achieved. With this objective, the electrochemical characteristics of boron carbide (B4C) added manganese dioxide (MnO2) for use as a cathode in alkaline battery were investigated during the discharge–charge process. Results of electrochemical measurements, X-ray diffraction and transmission electron microscopy show that boron aids the formation of lithium intercalated MnO2 (LixMnO2) during discharge with some degree of reversibility, however, capacity fade and a steep voltage profile is observed. The addition of boron nitride (BN) improved the discharge performance and characteristics of the cell are also compared and discussed.

Thin crystals of La 2 O 3 , LaAlO 3 , La 2/3 TiO 3 , La 2 TiO 5 , and La 2 Ti 2 O 7 have been irradiated in situ using 1 MeV Kr 2+ ions at the Intermediate Voltage Electron Microscope-Tandem User Facility (IVEM-Tandem), Argonne National Laboratory (ANL). We observed that La 2 O 3 remained crystalline to a fluence greater than 3.1×10 16 ions cm −2 at a temperature of 50 K. The four binary oxide compounds in the two systems were observed through the crystalline–amorphous transition as a function of ion fluence and temperature. Results from the ion irradiations give critical temperatures for amorphisation ( T c ) of 647 K for LaAlO 3 , 840 K for La 2 Ti 2 O 7 , 865 K for La 2/3 TiO 3 , and 1027 K for La 2 TiO 5 . The T c values observed in this study, together with previous data for Al 2 O 3 and TiO 2 , are discussed with reference to the melting points for the La 2 O 3 –Al 2 O 3 and La 2 O 3 –TiO 2 systems and the different local environments within the four crystal structures. Results suggest that there is an observable inverse correlation between T c and melting temperature ( T m ) in the two systems. More complex relationships exist between T c and crystal structure, with the stoichiometric perovskite LaAlO 3 being the most resistant to amorphisation.

During investigations of novel material types with uses in future nuclear technologies (ITER/DEMO and GenIV fission reactors), ternary carbides with compositions Ti{sub 3}AlC{sub 2} and Ti{sub 3}SiC{sub 2} have been irradiated with high Xe fluences, 6.25 x 10{sup 15} ions cm{sup -2} ({approx}25-30 dpa), using the IVEM-TANDEM facility at Argonne National Laboratory. Both compositions show high tolerance to damage, and give indications that they are likely to remain crystalline to much higher fluences. There is a visible difference in tolerance between Ti{sub 3}AlC{sub 2} and Ti{sub 3}SiC{sub 2} that can be related to the changes in bonding within each material. These initial findings provide evidence for a novel class of materials (+200 compounds) with high radiation resistance, while, significantly, both of these materials are composed of low-Z elements and hence exhibit no long-term activation.

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.

Thin crystals of rutile, brookite, anatase, and cassiterite were irradiated in situ in the transmission electron microscope using 1.0 MeV Kr ions at 50-300 K. Synthetic rutile and natural cassiterite, with 0.1-0.2 wt% impurities, remain crystalline up to a fluence of 5 x 10{sup 15} ions cm{sup -2} without evidence for amorphization at 50 K. Natural brookite and anatase, with 0.3-0.5 wt% impurities, become amorphous at fluences of 8.1 x 10{sup 14} and 2.3 x 10{sup 14} ions cm{sup -2}, respectively. We have also studied two natural rutile samples containing {approx}1.7 and 1.2 wt% impurities. These samples became amorphous at 9.2 x 10{sup 14} and 8.6 x 10{sup 14} ions cm{sup -2} at 50 K, respectively. Further analyses of the fluence-temperature data for natural brookite, rutile, and anatase give critical amorphization temperatures of 168 {+-} 11, 209 {+-} 8, and 242 {+-} 6 K, respectively. Results are briefly discussed with respect to several criteria for radiation resistance, including aspects of the structure, bonding, and energetics of defect formation and migration.

Polycrystalline synthetic samples of Y2Ti2−xSnxO7 with x = 0.4, 0.8, 1.2, and 1.6, together with Nd2Zr2O7, Nd2Zr1.2Ti0.8O7, and La1.6Y0.4Hf2O7, were irradiated in situ in the intermediate voltage electron microscope (IVEM)-Tandem Facility at Argonne National Laboratory using 1.0 MeV Kr ions at temperatures of 50 to 650 K. Determination of the critical amorphization fluence (Fc) as a function of temperature has revealed a dramatic increase in radiation tolerance with increasing Sn content on the pyrochlore B site. Nonlinear least-squares analysis of the fluence-temperature curves gave critical temperatures (Tc) of 666 ± 4, 335 ± 12, and 251 ± 51 K for the Y2Ti2−xSnxO7 samples with x = 0.4, 0.8, and 1.2, respectively. The sample with x = 1.6 appears to disorder to a defect fluorite structure at a fluence below 1.25 × 1015 ions cm−2 and remains crystalline to 5 × 1015 ions cm−2 at 50 K. Additionally, the critical fluence-temperature response curves were determined for Nd2Zr1.2Ti0.8O7 and La1.6Y0.4Hf2O7, and ...

The use of binders such as phosphoric acid to consolidate aluminosilicates to form refractory products has been reported since the 1940s [1]. Another class of materials formed by reacting concentrated alkaline silicate solutions with metakaolin (MK) has been termed geopolymers by Davidovits [2]. MK is made by heating (*750 C) of kaolin to render it X-ray amorphous and thus more reactive. In a geopolymer, the aluminosilicate is composed of cross-linked AlO4 and SiO4 tetrahedra, charge balanced with Na or K ions. It was shown by Cao et al. [3] that PO4 3can be incorporated in the geopolymer structure. Derrien et al. [4] added calcium phosphates to geopolymers, but they did not show whether the phosphate was part of the geopolymer structure. MacKenzie et al. [5] showed that the P occupied tetrahedral sites in the geopolymer with a different chemical shift from that of the aluminium phosphate reactants. Cao et al. [3] made nine compositions with Si/P molar ratios of 0.13–0.63 by adding H3PO4 to metakaolin and the maximum strength obtained was 55 MPa for the composition with Si/P = 0.21 molar ratio. Mackenzie et al. [5] made one composition of molar ratio of Si/P = 25 by adding a small amount of aluminium phosphate to an MK-based geopolymer, having molar ratios of Si/Al = 1.6 and Si/Na = 2.6. In the work reported here, the microstructure and the cold crushing strength (CCS) of the materials produced by alkaline-bonding and phosphoric acid-bonding of MK have been studied as a preliminary effort to develop these materials as replacements in some current uses and for future applications. Batches of 100 g of different compositions were made as listed in Table 1. The approximate chemical compositions of the nominal batch compositions based on the chemical analyses of the precursors from the suppliers resulted in molar ratios of Si/Al = 2 and Na/Al = 1 for MK-based geopolymers (MKGP). Similarly, the phosphoric acid-bonded MK (MKP) had molar ratios for Si/Al = 1 and Al/P = 1. MKGP (see Table 1) was prepared by adding MK to the sodium silicate solution. MKP was made by first mixing the deionised water (DIW) with 85 mass% H3PO4, then adding MK to the acid. Minimum amount of water was added to achieve the required workability, because any excess of water would increase the porosity and thus decrease strength. All the batches were mixed in a dental mixer (Renfert, Dental mixer, UK) for *5 min under vacuum at 300 rpm. To the MKGP and MKP batch compositions (see Table 1), 40 mass% sand was added before mixing (i.e. MKSGP and MKSP). Ordinary washed beach sand of size fractions, 81 mass% 250–500 lm, 17 mass% 125–250 lm and 2 mass%\125 lm, was used. Generally, sand is added in making mortar for building applications; hence, it was added for comparison with ordinary Portland cement mortar. The slurries produced in each instance were cast to form 25 mm dia 9 40 mm long cylindrical specimens in sealed polycarbonate containers for subsequent physical and mechanical testing. The cast items were kept at room temperature for 2 h before curing at 60 C for 24 h in an oven. After removing the seals, the samples were left at ambient temperature for 4 days before demoulding for MKGP. The MKP and MKSP samples were demoulded after 14 days when they were dry (they were still wet after D. S. Perera (&) J. V. Hanna J. Davis M. G. Blackford B. A. Latella Y. Sasaki E. R. Vance Australian Nuclear Science and Technology Organisation, PO Box 1, Menai, NSW 2234, Australia e-mail: pereradan@gmail.com; dsp@ansto.gov.au

By combining sol–gel technology with emulsion chemistry, it is possible to produce spherical particles with a designed microstructure based on a judicious choice of solvent/surfactant and sol–gel reaction parameters. When an active molecule is located in the aqueous droplet of a water-in-oil (W/O) emulsion, encapsulation occurs as the silicon precursors polymerise to build an oxide cage around the active species. By changing the solvent–surfactant combination, the particle size can be varied from 10 nm to 100 μm. The size of the particles is controlled by the size of the emulsion droplet, which acts as a nano-reactor for the sol–gel reaction. The release profiles can be tailored, independently of the particle size, by controlling the internal structure of the particles: pore volume, pore size, tortuosity, and surface chemistry (e.g. by introduction of trialkoxysilane). This can be easily achieved by controlling sol–gel processing parameters such as the water-to-alkoxide ratio, pH, alkoxide concentration, ageing, drying time and temperature.

Multilayer structures of alternating thin titanium and tungsten oxide layers having dimensions of ∼20 nm have been fabricated from titanium alkoxide and various tungstate precursor solutions using the dip coating technique. Single, double, and triple layer titanate and tungstate thin films were deposited on silicon substrates, and these films were initially annealed at 400 °C. Structural and microstructural aspects of the films were investigated using a variety of techniques, including X-ray reflectometry, grazing incidence X-ray absorption spectroscopy (GIXAS), cross-sectional transmission electron microscopy (TEM), and secondary ion mass spectrometry. The dimensions of the films and the character of the interfaces were principally gauged by cross-sectional TEM and X-ray reflectometery. All films were continuous on a local scale and had relatively low surface roughness. At the treatment temperature of 400 °C, only the tungsten oxide component showed appreciable crystallinity. The multilayer films had rel...

Titania thin films were prepared through the anodisation of titanium metal in a 1.0 M sulphuric acid solution at 80 °C utilising a series of pulsed dc constant currents of increasing magnitude. Films were then tested as a potential anode material for lithium batteries using a variety of techniques. Electrochemical testing revealed that the films (3.8 cm 2 ) offered good rate capabilities affording a constant capacity of 48 μAh for a constant current of 10 μA which decreased to 25 μAh on increasing the current to 1250 μA. Cyclic voltammetry was conducted over a range of scan rates from which capacitive currents were examined and rate constants, transfer coefficients and diffusion coefficients calculated. Electrochemical impedance spectroscopy was conducted over six potentials in the range 0.1–2.7 V with the experimental data successfully modelled using an equivalent circuit with the notation R(Q(RW))C. TEM observation of focussed ion beam milled cross-sections showed significant structural differences between the as-anodised film and those cycled in a lithium battery. Raman spectroscopy showed that the films had an anatase character that transformed into an unidentified lithium-containing, titanate phase on cycling. Based on a film thickness of 100 nm, and assuming density of 4 g cm −3 such films offered a stable capacity of 316 mAh g −1 .

Transmission electron microscopy of a geopolymer phase, derived from metakaolin and alkaline silicate solutions and having nominal Na/Al and Si/Al molar ratios of 1 and 2, respectively, showed it to be amorphous on the ∼1 nm scale after curing at 40°C. In samples containing 5 wt% Cs or Sr, Cs inhabited the amorphous phase, whereas Sr was incorporated only partly, being preferentially partitioned to crystalline SrCO3. Heating progressively to dewater the material had little effect on the overall structure for temperatures up to 500°C. From solid-state nuclear magnetic resonance in material cured at near-ambient temperatures, Cs, like Na, was found to be basically associated with pore water, but with significant linkage to the aluminosilicate framework, more so than for Na. Subsequent heating to 300°C increased the linkage of Cs and Na to the framework.

The speciation of Fe was studied in metakaolin-based geopolymers to which Fe was added as ferric nitrate solution or freshly precipitated ferric hydroxide. From Mossbauer and near-edge X-ray absorption spectroscopies, coupled with X-ray diffraction and electron microscopy, it was concluded that in as-cured geopolymers the Fe was present in octahedral sites, either as isolated ions in the geopolymer matrix or as oxyhydroxide aggregates which had not reacted with the starting geopolymer components. For material to which iron nitrate was added, heating to 900 °C allowed the formation of nepheline and a glass, both of which contained tetrahedrally coordinated, substituted Fe 3+ .

Medium-sulfur bituminous coal and a mixture of 95 wt.% coal plus 5 wt.% tire-derived fuel (TDF) in the form of shredded automotive tires were combusted in a stoker boiler under the same conditions. This paper presents quantitative chemical compositions of the fuels and of the gaseous and particulate emissions. The coal + TDF mixture is considerably richer in Zn than the pure coal as a result of the high Zn content of the shredded tires (∼1 wt.% Zn). Atmospheric emissions of Zn increased from 15 g/h to nearly 2.4 kg/h when coal + TDF was combusted. Similarly, emissions of most other metals and metalloids, as well as those of HCl increased when TDF (∼3000 ppm Cl) was added. The enhanced metal emissions might be due to formation of gaseous metal chloride species in the stack gases. On the other hand, emissions of CO decreased slightly, whereas those of NO x , SO 2 , and total particulate matter remained virtually unchanged. These results help in assessing the environmental impact of energy recovery from scrap tires in stoker boilers.

Novel mesoporous tungsten trioxide (WO 3 ) films were deposited on ITO-glass by continuous, cathodic electrodeposition. The electrolytes for the deposition were prepared by using the peroxy-tungstic acid (50 mM) in 50:50 water:2-propanol solution with varying amounts of sulfuric acid. It is observed that the morphology of the films could be controlled by varying the sulfuric acid concentration in the electrolytes. The most porous films were obtained at a pH of 0.8, and this had a thickness of 0.6 μm, average particle size of 12 nm, and was quasi-transparent. The surface morphology and the structure of the films were characterized by X-ray diffraction, SEM, TEM, and cyclic voltammetry for the hydrogen intercalation reaction. Using a chopped light source, the present mesoporous WO 3 films generated a photocurrent that was three times higher than transparent films.

We have characterized thermally annealed perovskite (CaTiO3) surfaces, both before and after aqueous dissolution testing, using scanning electron microscopy, cross-sectional transmission electron microscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. It was shown that mechanical damage caused by polishing was essentially removed at the CaTiO3 surface by subsequent annealing; such annealed samples were used to study the intrinsic dissolution behavior of perovskite in deionized water at RT, 90 °C, and 150 °C. Our results indicate that, although mechanical damage caused higher Ca release initially, it did not affect the long-term Ca dissolution rate. However, the removal of surface damage by annealing did lead to the subsequent spatial ordering of the alteration product, which was identified as anatase (TiO2) by both x-ray and electron diffraction, on CaTiO3 surfaces after dissolution testing at150 °C. The effect of Ca2+ in the leachant on the dissolution reaction of perovskite at 150 °C was also investigated, and the results suggest that under repository conditions, the release of Ca from perovskite is likely to be significantly slower if Ca2+ is present in ground water.

Neodynium-doped zirconolite was fabricated by hydrolysing a mixture of alkoxide with nitrate solutions followed by a series of drying, calcination, pressing and sintering steps. The material obtained was essentially zirconolite (99.5 vol% Ca 0.8 Nd 0.2 ZrTi 1.8 Al 0.2 O 7 ) with a minor ZrTiO 4 phase (0.5 vol%). The microstructure and composition of the zirconolite was characterised, before and after durability experiments, by SEM/EDS, SIMS, AFM and TEM. Chemical durability testing was carried out using the standard MCC-2 test at 150 °C for a series of four test durations - 1, 7, 28 and 84 days. The pH of the leachates was fairly constant with time (pH 5), and elemental releases reached apparent steady-state conditions within the first day of leaching. Thermodynamic calculations indicated that attainment of these steady-state conditions at this point could not be explained by thermodynamic equilibrium being reached between the leachates and the primary zirconolite phase. However, thermodynamic equilibrium between a possible layer of secondary hydroxides or a decalcified zirconolite and the leachates could explain the steady state of Ti, Zr and Al releases. Moreover, it is suggested that the steady-state conditions achieved by Nd, theoretically undersaturated in the leachates, is due to adsorption of Nd to this secondary layer, and is not a result of precipitation of a hydroxide form. Anatase, commonly observed during leaching of zirconotitanates, is also theoretically undersaturated in the leachates. When observed, it is possibly a product of local condensation of the hydroxide layer and not due to simply a dissolution/precipitation process. SEM and AFM investigations confirmed the formation of a passivation layer on the surface of the zirconolite. The layer was of the order of 10 nm, in accordance with the thickness calculated from leachate results.

The dissolution of synthetic brannerite in aqueous media at 40 and 90 °C under atmospheric redox conditions has been studied. At 40 °C, the presence of phthalate as a buffer component in the pH range of 2–6 has little effect on uranium release from brannerite. Bicarbonate increases uranium release and enhances the dissolution of brannerite. Compared to UO 2 , brannerite is more resistant to dissolution in bicarbonate solutions. In under-saturated conditions at 90 °C, the dissolution of brannerite is incongruent (preferential release of uranium) at pH 2 and nearly congruent at pH 11. TEM examinations reveal a polymorph of TiO 2 (pH 2 specimen) and a fibrous Ti-rich material (pH 11 specimen) as secondary phases. XPS analyses indicate the existence of U(V) and U(VI) species on the surfaces of specimens both before and after leaching, and U(VI) was the dominant component on the specimen leached in the pH 11 solution.

Amorphous precursor nanopowders of zirconolite (CaZrTi2O7) were prepared using a water-in-oil micro-emulsion synthesis, with Ti(O i C3H7)4, Zr(O n C3H7)4 and either Ca(OC2H5)2 or an aqueous Ca(NO3)2 solution as precursors. The stoichiometry and structural evolution of the nanoparticles were investigated using a range of techniques, including ICP-MS, TEM, gas adsorption and vibrational spectroscopy. The use of Ca(OC2H5)2 led to slightly sub-stoichiometric nanopowders (Ca x ZrTi2O6+x , x = 0.8), following washing. Lower values of x were obtained in the washed nanopowders when using Ca(NO3)2, with x = 0.004, 0.022 or 0.52 at pH 2, 7 or 13, respectively. In the latter system, a comparison between the washed and unwashed nanopowders revealed that 25% of the calcium was lost during washing. The Ca(NO3)2 was found to form unstable tetraamine complexes within the reverse micelles at high pH, which transformed into Ca(OH)2 on ageing. The Ca(OH)2 can then interact with the hydrolysed titanium/zirconium alkoxides, and thus be integrated chemically into the final nanoparticle structure.

Cerium titanate CeTi2O6 was prepared by a new soft chemistry route in aqueous solution. A suite of characterization techniques, including X-ray diffraction, thermal analysis, vibrational spectroscopy, and scanning and transmission electron spectroscopy, were employed to investigate the brannerite structure formation and its bulk properties. The synthesized powder formed the brannerite crystal structure upon calcination at temperatures as low as 800 °C. Samples sintered at 1350 °C possess a high level of crystallinity. X-ray absorption near-edge structure results indicate the presence of six-coordinated Ce4+ in the brannerite samples.

Nickel germanide formed on amorphous and crystalline germanium is investigated for material and electrical properties. The crystal quality of films formed is poorer for the germanides formed on amorphous germanium with a slight increase in sheet resistance. The grains of NiGe formed on amorphous germanium show a growth that is hexagonal like, extending into the substrate further than germanides grains formed on crystalline germanium. The NiGe formed on crystalline germanium has a much more uniform thickness and uniform grain size and shape. Hollow cone illumination shows that some recrystallisation of the amorphised region of germanium does occur.

Cerium titanate CeTi2O6 was prepared by a new soft chemistry route in aqueous solution. A suite of characterization techniques, including X-ray diffraction, thermal analysis, vibrational spectroscopy, and scanning and transmission electron spectroscopy, were employed to investigate the brannerite structure formation and its bulk properties. The synthesized powder formed the brannerite crystal structure upon calcination at temperatures as low as 800 °C. Samples sintered at 1350 °C possess a high level of crystallinity. X-ray absorption near-edge structure results indicate the presence of six-coordinated Ce(4+) in the brannerite samples.

We have shown that Ni metal particles when melted in the presence of C 60 form graphitic layers around their outer surface with the Ni remaining as pure metal without any evidence of carbide formation. Particles over several orders of magnitude in size with diameters in the range of ∼10 nm to several microns have been successfully encapsulated in this manner. The process has been observed taking place in real time using transmission electron microscopy (TEM). The electron beam served a dual purpose in this case by providing a means of observation as well as the source of thermal energy. High resolution transmission electron microscopy (HRTEM) shows the nature of the encapsulation to be graphitic. The process does not occur when graphite powder is used instead of C 60 powder and the Ni similarly heated to melting point. The encapsulation method using C 60 as a carbon source also occurs on heating a mixture in a conventional manner and shows the effect is thermal in nature although the electron beam does offer the ability to control the process for individual particles. Further research has shown the encapsulation process to occur at temperatures as low as 800°C by a catalytic pathway.