Australian Nuclear Science and Technology Organisation
Recent publications
Cosmogenic nuclide techniques have advanced the geosciences by providing tools for exposure age dating, burial dating, quantification of denudation rates and more. Advances in geochemistry, accelerator mass spectrometry and atom trap trace analyses are ushering in a new cosmogenic nuclide era, by improving the sensitivity of measurements to ultra-trace levels that now allow new applications of these techniques to numerous Earth surface processes. The advances in cosmogenic nuclide techniques have equipped the next generation of geoscientists with invaluable tools for understanding the planet, but addressing pressing needs requires rising to an even greater challenge: imbuing within the cosmogenic community, and the geosciences as a whole, a commitment to justice, equity, diversity and inclusion that matches our dedication to scientific research. In this Primer, we review the state of the art and recent exciting breakthroughs in the use of cosmogenic nuclide techniques, focusing on erosion factories over space and time, and new perspectives on ice sheet stability. We also highlight promising ways forward in enhancing inclusion in the field, as well as obstacles that remain to be overcome. Cosmogenic nuclide dating techniques provide tools for age dating, burial dating and denudation rates. Advances in accelerator mass spectrometry and atom trap trace analyses are improving measurement sensitivity. In this Primer, Schaefer et al. outline how to use cosmogenic nuclide dating across a range of applications.
Stable carbon and nitrogen isotope analyses were used to evaluate the contribution of five protein sources to the growth of juvenile slipper lobster Thenus australiensis. Protein sources tested were fish meal, krill meal, lupin meal, soybean meal and a squid by-product meal. A commercial in confidence basal mix was utilised to produce five experimental feeds containing 30% of each protein source. Juvenile lobsters were fed daily at 5% of their body weight for 12 weeks. Lobster performance was assessed by survival, feed intake and growth performance, and the effects of protein source on nutrient assimilation and discrimination factor were determined. The squid by-product meal, soybean meal, and krill meal produced better growth performance and survival. The specific growth rate on lupin meal was significantly (p < 0.05) lower than all the other protein sources. Apparent feed intake was significantly (p < 0.001) higher in squid by-product meal than lupin meal but with no significant differences in feed efficiency ratio. Protein source assimilation proportion in lobster ranged from 7% for soybean meal to 32% for squid by-product meal, whereby squid by-product meal and fish meal (29%) were the only protein sources assimilated at approximately their dietary inclusion level (30%). Overall, squid by-product meal had the best growth performance, high survival, and the highest assimilation into growth. This study demonstrated the potential of stable isotopic analysis to screen protein sources, evaluate the nutritional performance of the experimental feeds, and provide a deeper insight into ingredient utilisation. This study also provides the first whole-body isotopic discrimination factors for juvenile lobster, which can determine ingredient contribution to growth in future studies.
The role of microstructure in influencing fatigue crack growth behavior for laser powder bed fusion (LPBF) produced nickel superalloy 718 was examined. Two common post-build heat treatments were applied to produce two distinct microstructures, one which retained much of the solidification structure from additive manufacturing, while the other was mostly recrystallized. For both groups, residual stresses were assessed along the crack path by neutron diffraction. At low load ratios (R = 0.1), the non-recrystallized LPBF material had the lowest and most varied fatigue crack growth thresholds at 6-7.2 MPa m1/2. This is attributed to a reduction in crack path roughness induced crack closure and high superimposed residual stresses. The recrystallizing heat treatment coarsened and homogenized the grain structure substantially, thus increasing the threshold to 7.3-7.6 MPa m1/2 due to a substantially rougher crack path and completely relieved residual stresses. Both LPBF heat treatments showed negligible effect of build orientation and gave significantly lower fatigue thresholds compared to wrought material tested in the L-T orientation (∼11 MPa m1/2). At high load ratios, the difference in fatigue behavior between microstructures was reduced but still present and was attributed to differences in geometric shielding from crack path roughness, grain size, and degree of microstructural homogeneity.
Omicron, Ο-Ti2NbAl alloys have been under continuous development for more than 40 years as potential materials for the gas turbine engine; however, the crystal structure and phase transformations are still unclear. In this work, we clarified the crystal structure, atom positions and phase transformations of the Ο phase by in-situ neutron diffraction and high-temperature X-ray diffraction methods. From room temperature to the vanishing temperature of the Ο phase, the latter exposes a C m c m structure, with Ti and Nb atoms tending to respectively occupy the 8g and 4c2 positions, but with a certain disorder, introducing an order parameter. The phase transformation sequences of Ti-24.8Al-24.3Nb alloy are Ο(975 °C) → βo + Ο(997.5 °C) → βo(1165.5 °C) → β. Moreover, we have proven that a distinction of the omicron subvariants Ο1 and Ο2 is crystallographic nonsense as Ο1 must equal to α2 of P 63/m m c structure, and Ti2NbAl is a prototype structure by itself.
The accurate prediction of elevated-temperature creep behaviour of alloys is important for preventing catastrophic failure of systems operating under prolonged elevated temperature-stress conditions. Here, we couple the Kachanov-Rabotnov (K-R) creep model with a multi-objective genetic algorithm (MOGA) to predict the creep behaviour of Alloy 617 at 800 • C, 900 • C, and 1000 • C, under various stress conditions. It is shown that the MOGA-optimised K-R creep model can capture the overall elevated-temperature behaviour of the alloy at 800 • C under a wide range of stress conditions. However, at 900 • C and 1000 • C, oxidation leads to the atypical accumulation of creep plasticity, which the K-R model cannot account for. Nevertheless, it is shown that the proposed methodology of optimising the K-R model with a MOGA can consistently provide accurate results within the limits of the K-R model.
Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) are the only available experimental techniques to provide seamless non-destructive measurements of the geometry of the accessible and inaccessible pore structure of rocks from sub-nanopore size to the scale of macropores. They have therefore become the measurement of choice for tight reservoir rocks such as organic rich shales. A simplifying assumption in the analysis is, however, that during the path of neutrons through the sample each neutron is only scattered once. Shales are samples with a high scattering power and Multiple Scattering (MS) may occur which requires special modelling for deconvolution of the results. The approach to avoid MS is to simply reduce the sample thickness to <0.15–0.5 mm. Here, we present a systematic method on wavelength selection and preparation of samples to optimise extraction of microstructural data and minimise parasitic errors. Experimentally measured SAS transmission (TSAS) values are used as a practical criterion for estimation of the extent of MS. Generous beamtime allocations allowed robust testing revealing that sample thicknesses can be twice as thick as predicted using the standard protocol. Analysing thicker samples is particularly beneficial for statistically relevant characterisation of heterogeneous samples making the new protocol the method of choice for such samples.
The widespread application of lithium-ion batteries as the practice facility of energy storage has come alongside much unforeseen fire safety and thermal runaway issues that leads to increasing research interests. A comprehensive understanding of the thermal features of battery packs and the heat exchange process of energy storage systems is imperative. In this paper, a three-dimensional thermo-electrochemical model has been developed to simulate the detailed temperature distribution of battery packs. The numerical analysis of the cooling effect with both natural and forced air ventilation configurations are compared as well. Moreover, the artificial neural network (ANN) model was coupled with the computational fluid dynamics (CFD) simulation results to perform an optimization of a specific configuration battery system considering configuration dimensions and operating conditions simultaneously. The ANN model builds a relationship between battery spacing and ambient cooling properties. It was found that the changing of ambient pressure creates a larger temperature drop under the forced air cooling than that under natural ventilation. The optimum design for the battery pack can decrease the maximum temperature and the temperature difference by 1.94% and 17%, respectively. Overall, the present modelling framework presents an innovative approach to utilising high-fidelity CFD numerical results as inputs for establishing ANN training dataset, potentially enhancing the state-of-art thermal management of lithium-ion battery systems reducing the risks of thermal runaway and fire outbreak.
Materials science literature contains domain knowledge about numerous descriptors, which play a critical role in data-driven materials design. However, automatically extracting descriptors from literature remains challenging. Here, we develop an automatic descriptors recognizer based on natural language processing (NLP) to mine latent descriptors, which consists of a conditional data augmentation model incorporating materials domain knowledge (cDA-DK), coarse- and fine-grained descriptors subrecognizers (CGDR and FGDR). cDA-DK conducts augmenting training data of text mining model, which can significantly reduce the cost of manually labeling and enhance the robustness of its model. On this basis, CGDR recognizes coarse-grained descriptor entities automatically, and FGDR performs screening of fine-grained descriptors related to specific materials design. Following this, the activation energy of NASICON-type solid electrolytes, which is influenced by complicated descriptors, is taken as an example to demonstrate the potential utility of our recognizer. CGDR extracts 106896 descriptor entities from 1808 relevant articles with an accuracy (F1) of 0.87. Furthermore, with features from 408 descriptors screened by FGDR, six activation energy prediction models are constructed to perform experiments, achieving an optimal prediction performance (R2) of 0.96. This work provides important insight towards the understanding of structure-activity relationships, thus promoting materials design and discovery.
The Centre of Excellence for Dark Matter Particle Physics aims to measure ²¹⁰Pb (half-life of 22.2 years) in 1 kg of NaI via accelerator mass spectrometry (AMS) for the SABRE (Sodium iodide with Active Background REjection) South dark matter experiment. The first step is to find the optimal target material (chemical compound and binder) to produce the highest and most stable negative ion output. We initially studied the outputs from Pb3O4, PbO and PbF2 mixed 1:2 with Ag. The ²⁰⁸PbO2⁻ and ²⁰⁸PbF3⁻ currents were 0.5–1.2 μA with the procedural PbF2 compound performing slightly better. Based on these results, we explored the performance of PbF2 mixed with fluorinating agents such as AgF, AgF2 and SbF3 at different ratios. The 1:1 mixture was the best for all additives. The possibility of using either Fe (oxide/fluoride) or NaF as bulk material for the AMS target was also studied, however, none proved suitable.
Black carbon (BC) aerosols significantly contribute to radiative budgets globally, however their actual contributions remain poorly constrained in many under-sampled ocean regions. The tropical waters north of Australia are a part of the Indo-Pacific warm pool, regarded as a heat engine of global climate, and are in proximity to large terrestrial sources of BC aerosols such as fossil fuel emissions, and biomass burning emissions from Northern Australia. Despite this, measurements of marine aerosols, especially BC remain elusive, leading to large uncertainties and discrepancies in current chemistry-climate models for this region. Here, we report the first comprehensive measurements of aerosol properties collected over the tropical warm pool in Australian waters during a voyage in late 2019. The non-marine related aerosol emissions observed in the Arafura Sea region were more intense than in the Timor Sea marine region, as the Arafura Sea was subject to greater continental outflows. The median equivalent BC (eBC) concentration in the Arafura Sea (0.66 μg m⁻³) was slightly higher than that in the Timor Sea (0.49 μg m⁻³). Source apportionment modelling and back trajectory analysis and tracer studies consistently suggest fossil fuel combustion eBC (eBCff) was the dominant contributor to eBC across the entire voyage region, with biomass burning eBC (eBCbb) making significant additional contributions to eBC in the Arafura Sea. eBCff (possibly from ship emissions or oil and gas rigs and their associated activities) and cloud condensation nuclei (CCN) were robustly correlated in the Timor Sea data, whereas eBCbb positively correlated to CCN in the Arafura Sea, suggesting different sources and atmospheric processing pathways occurred in these two regions. This work demonstrates the substantial impact that fossil fuel and biomass burning emissions can have on the composition of aerosols and cloud processes in the remote tropical marine atmosphere, and their potentially significant contribution to the radiative balance of the rapidly warming Indo-Pacific warm pool.
We report a flux crystal growth of Ba2[(UO2)2Ti2O8] and subsequent structural and spectroscopic studies using multiple techniques. The layered crystal structure, built up with sheets of edge‐sharing dimeric uranyl pentagonal bipyramids and dimeric TiO5 square pyramids with interlayer Ba(II) ions, was revealed by synchrotron single crystal X‐ray diffraction and confirmed with electron diffraction using a transmission electron microscope. The presence of only hexavalent uranium was confirmed by both diffuse reflectance and X‐ray absorption near‐edge structure spectroscopies, consistent with the bond valence sum calculations. Its vibrational modes were revealed by Raman spectroscopy. In addition, its implications as a potential hexavalent uranium waste form for the immobilization of uranium‐rich radioactive wastes were discussed. This article is protected by copyright. All rights reserved
Oxynitride complex perovskites, BaMn0.2M0.8O2.6N0.4 (M = Nb, Ta), were prepared by reacting the layered oxides Ba5M4O15 with MnCl2, in the NH3 atmosphere. Both BaMn0.2M0.8O2.6N0.4 phases crystallized in orthorhombic symmetries, in contrast with previous Ba-based perovskite oxynitrides, BaMO2N and BaM'0.2M0.8O3−xNx (M′ = Li, Na, Mg; M = Nb, Ta), all of which were cubic. The thermogravimetry (TG) and differential scanning calorimetry (DSC) of AMn0.2M0.8O2.6N0.4 (A = Sr, Ba; M = Nb, Ta) suggested that the phase stability is higher for A = Ba and M = Ta than for A = Sr and M = Nb, respectively. Both BaMn0.2Nb0.8O2.6N0.4 and BaMn0.2Ta0.8O2.6N0.4 exhibited paramagnetic behavior with effective magnetic moments of 5.75 μB and 5.90 μB, respectively, well consistent with the high-spin Mn²⁺ state. All the four members of AMn0.2M0.8O2.6N0.4 had negative Weiss constants (θW's), indicative of the antiferromagnetic interactions. The variations of the θW among AMn0.2M0.8O2.6N0.4 were attributable to the differences in the Mn–O bond lengths (A = Sr vs. Ba) or to the distinct lattice covalency (M = Nb vs. Ta).
Reverse faulting in Otago, southern New Zealand, accommodates distributed tectonic convergence on the eastern side of the Australian‐Pacific plate boundary. Paleoearthquake records from some of the faults in the region show highly variable earthquake recurrence times, with long periods of quiescence separated by periods of earthquake activity. Here we develop a longer‐term context for these records, using cosmogenic radionuclide dating of faulted alluvial fan surfaces to characterize the late Quaternary slip rates on two significant faults within the system, the Hyde and Dunstan faults. We determine an average slip rate of 0.24 mm/yr (0.19–0.29 mm/yr at 95% confidence) for the Hyde Fault since about 115 ka, and an average slip rate of 0.16 mm/yr (0.12–0.21 mm/yr) for the Dunstan Fault since about 320 ka. Both faults show increases in slip rate of a factor of three to five times the average long‐term rate over timescales of 10 kyr. Increases in slip rate are out of phase on the two faults, supporting a hypothesis that strain is shared within the fault system over timescales on the order of 10 kyr. Over longer timescales, on the order of 100 kyr, slip rates can be well‐approximated by a linear fit, providing an upper limit on the variability of fault slip rates with time.
Small angle scattering affords an approach to evaluate the structure of dilute populations of macromolecules in solution where the measured scattering intensities relate to the distribution of scattering-pair distances within each macromolecule. When small angle neutron scattering (SANS) with contrast variation is employed, additional structural information can be obtained regarding the internal organization of biomacromolecule complexes and assemblies. The technique allows for the components of assemblies to be selectively ‘matched in’ and ‘matched out’ of the scattering profiles due to the different ways the isotopes of hydrogen—protium ¹H, and deuterium ²H (or D)—scatter neutrons. The isotopic substitution of ¹H for D in the sample enables the controlled variation of the scattering contrasts. A contrast variation experiment requires trade-offs between neutron beam intensity, q-range, wavelength and q-resolution, isotopic labelling levels, sample concentration and path-length, and measurement times. Navigating these competing aspects to find an optimal combination is a daunting task. Here we provide an overview of how to calculate the neutron scattering contrasts of dilute biological macromolecule samples prior to an experiment and how this then informs the approach to configuring SANS instruments and the measurement of a contrast variation series dataset.
The origin and early diversification of jawed vertebrates involved major changes to skeletal and soft anatomy. Skeletal transformations can be examined directly by studying fossil stem gnathostomes; however, preservation of soft anatomy is rare. We describe the only known example of a three-dimensionally mineralized heart, thick-walled stomach, and bilobed liver from arthrodire placoderms, stem gnathostomes from the Late Devonian Gogo Formation in Western Australia. The application of synchrotron and neutron microtomography to this material shows evidence of a flat S-shaped heart, which is well separated from the liver and other abdominal organs, and the absence of lungs. Arthrodires thus show the earliest phylogenetic evidence for repositioning of the gnathostome heart associated with the evolution of the complex neck region in jawed vertebrates.
We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr 14−x Ca x Cu 24 O 41 (SCCO) using Cu L 3-edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with high (x = 12.2) and without (x = 0) Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2 T) excitations (x = 0) to weakly-dispersive gapped modes at an energy of 280 meV (x = 12.2). Density matrix renormalization group (DMRG) calculations of the RIXS response in the doped ladders suggest that the flat magnetic dispersion and damped excitation profile observed at x = 12.2 originates from enhanced hole localization. This interpretation is supported by polarization-dependent RIXS measurements, where we disentangle the spin-conserving ΔS = 0 scattering from the predominant ΔS = 1 spin-flip signal in the RIXS spectra. The results show that the low-energy weight in the ΔS = 0 channel is depleted when Sr is replaced by Ca, consistent with a reduced carrier mobility. Our results demonstrate that off-ladder impurities can affect both the low-energy magnetic excitations and superconducting correlations in the CuO 4 plaquettes. Finally, our study characterizes the magnetic and charge fluctuations in the phase from which superconductivity emerges in SCCO at elevated pressures.
Coating a substrate with anisotropic nanoparticles such as cellulose nanocrystals (CNCs) confers some of their desirable physicochemical properties, such as strength, wettability, and barrier properties. The formation of monolayer coatings of CNCs via dip coating is affected by the enrichment of CNCs at both air–liquid and substrate–liquid interfaces. In this work, a surfactant‐free method for dip coating CNCs is presented through use of the hydrotrope tetraethylammonium chloride. Hydrotropes demonstrate a different mechanism for facilitating interfacial enrichment, adsorbing to CNCs and rendering them weakly hydrophobic, causing them to adsorb to both solid–liquid and air–liquid interfaces without affecting the surface tension of the system. This new coating mechanism may be more robust as adsorption onto the substrate from the bulk dispersion is less sensitive to the air–liquid interface. Adsorption at the solid–liquid interface showed two distinct CNC layers, with a tightly bound, close‐packed CNC layer at the interface, and a loosely associated outer layer. Adsorption of both layers is shown to be fully reversible after washing with ultra pure water, highlighting the potential of hydrotropes for facilitating new coating mechanisms. Small molecules called hydrotropes were shown to be able to facilitate the coating of nanoparticles onto surfaces, replacing surfactant molecules more typically used. Being much smaller, hydrotropes cause nanoparticles to deposit via a different mechanism, allowing for a deeper understanding and finer control of nanoparticle coatings and influencing their final properties when coating surfaces.
New heterometallic hydride complexes that involve the addition of {Mg–H} and {Zn–H} bonds to group 10 transition metals (Pd, Pt) are reported. The side‐on coordination of a single {Mg–H} to Pd forms a well‐defined σ ‐complex. In contrast, addition of three {Mg–H} or {Zn–H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X‐ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.
Perovskite multiferroics have drawn significant attention in the development of next-generation multifunctional electronic devices. However, the majority of existing multiferroics exhibit ferroelectric and ferromagnetic orderings only at low temperatures. Although interface engineering in complex oxide thin films has triggered many exotic room-temperature functionalities, the desired coupling of charge, spin, orbital and lattice degrees of freedom often imposes stringent requirements on deposition conditions, layer thickness and crystal orientation, greatly hindering their cost-effective large-scale applications. Herein, we report an interface-driven multiferroicity in low-cost and environmentally friendly bulk polycrystalline material, namely cubic BaTiO3-SrTiO3 nanocomposites which were fabricated through a simple, high-throughput solid-state reaction route. Interface reconstruction in the nanocomposites can be readily controlled by the processing conditions. Coexistence of room-temperature ferromagnetism and ferroelectricity, accompanying a robust magnetoelectric coupling in the nanocomposites, was confirmed both experimentally and theoretically. Our study explores the 'hidden treasure at the interface' by creating a playground in bulk perovskite oxides, enabling a broad range of applications that are challenging with thin films, such as low-power-consumption large-volume memory and magneto-optic spatial light modulator.
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299 members
Ivan Greguric
  • Biosciences
Max Avdeev
  • Australian Centre for Neutron Scattering
Tamim A Darwish
  • Australian Centre for Neutron Scattering
Anna Sokolova
  • Australian Centre for Neutron Scattering
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