The hydrogen storage properties of Hf1-xTixNbVZr high entropy alloys (HEAs) synthesized by arc melting have been investigated. The first hydrogenation of the alloys was performed at room temperature under 20 bars of hydrogen pressure. Results show an increase in gravimetric hydrogen content with Ti substitutions. Upon hydrogenation, the multiphase alloys (x = 0 and x = 0.25) exhibit a combination of faces-centred-cubic (FCC) hydride and C15 Laves phases, while single-phase alloys (x = 0.5, 0.75, and 1) display FCC structures. The crystal structure evolution during dehydrogenation of HfNbVZr (x = 0) and TiNbVZr (x = 1) HEAs was examined using in-situ neutron diffraction. The analysis demonstrates temperature-dependent desorption behaviour, with HfNbVZr displaying lower desorption temperatures compared to TiNbVZr. Additionally, in-situ neutron diffraction experiments during deuterium desorption indicate a two-step phase transition from FCC dihydride to BCT monohydride, followed by a transition to BCC.@en

Photocatalysis offers a sustainable solution for essential reactions such as CO2 conversion and water splitting, but constraints in catalyst properties like bandgap and active site availability often limit its efficiency. High-entropy oxides (HEOs), which incorporate five or more different cations, present significant potential for this application due to their elemental diversity. This study explores active HEO development for photocatalytic applications by integrating cations with d0 and d10 electronic configurations. A single-phase HEO with a monoclinic structure was successfully synthesized, comprising elements with d0 (titanium, zirconium, niobium and tantalum) and d10 (zinc) electronic configurations. Comprehensive analyses of its microstructure, chemical composition, optical properties and photocatalytic activity were conducted. The resulting TiZrNbTaZnO10 exhibited superior UV and visible light absorption, a low bandgap of 2.5 eV, minimal radiative electron–hole recombination and high stability under photocatalytic conditions. Remarkably, TiZrNbTaZnO10 outperformed the TiZrHfNbTaO11 photocatalyst which contains solely d0 electronic configuration. This enhanced performance is attributed to the mixed electronic configurations fostering heterogeneous chemical environments, which facilitate efficient charge carrier separation and transfer.@en

The evolution of metallurgy is a fundamental aspect related to the knowledge of the technological level of ancient civilizations, for which the information was mostly part of an oral tradition. The ancient, preserved artefacts are the only keepers of this long gone knowledge. Most advanced non-invasive techniques provide us the key to access it. Neutron techniques are nowadays the only available approach for revealing, non-destructively and with good spatial resolution, the morphological and microstructural properties within the whole volume of densely composed artefacts such as bronze statues. Application of neutron methods allows us to learn about ancient artefact manufacturing methods and to study at a very detailed level the current conservation status in their different parts. As part of a research project dedicated to the study of ancient Asian bronzes led by the Rijksmuseum Metal Conservation Department, four statues from the Rijksmuseum Asian collection were analysed using non-invasive neutron techniques. In this work, we present the investigation of a South Indian bronze statuette depicting Shiva in the form of Chandrasekhara (AK-MAK-1291, c. 1000–1200 A.D.) by means of white beam tomography, energy-selective neutron imaging (performed on CONRAD-2 at HZB, DE, and on FISH at TU-Delft, NL), and neutron diffraction (on ENGIN-X at ISIS, UK). The application of neutron imaging revealed the inner structure of the statue and allowed us to investigate the conservation state and potential cracking on the surface and in the bulk, to understand the interconnection of the different sections of the statue, and to obtain clues about the manufacturing processes. These morphological and microstructural results were employed to guide neutron diffraction analyses that allowed us to precisely characterize compositional differences, the presence of dendrites and columnar growth peak structures related to casting. This work is a complete non-invasive analytical investigation on an archaeological bronze artefact, providing outstanding results: from a quantitative analysis of the composition and microstructure to an in-depth morphological analysis capable of unveiling details on the ancient casting methods of the statue.

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We studied the corrosion of Roman copper alloy coins that experienced alternations or progressive changes in their burial environment. We used coins that were still embedded in soil or in a concretion selectedfrom three professional excataved sites - Berlicum and Krommenie in the Netherlands and Kempraten in Switserland. mCT scanning and neutron scanning were used to record the 3-D properties of these coins prior to (destructive) analyses. It proved possible to tentatively identify the coins. Microscope observations and SEM-EDX analyses revealed complex corrosion processes, related to changing burial environments. In soil horizon with fluctuating groundwater levels in a region with upwelling reducing, iron-rich groundwater, the copper in a gunmetal coin is essentially replaced by iron oxides while tin remains and forms tin-oxide bands. Fluctuating redox conditions in marine-influenced environments was shown to transform a copper-alloy coin into strongly laminated copper sulphides with embedded gypsum crystals, with an outer surface of copper and copper-iron sulphides. Burial of bronze in a charcoal rich layer probably caused temporary highly alkaline soil conditions. This caused most of the copper to leach from this coin, leaving behind a laminated tin-dominated mass, with only a limited amount of (malachite) corrosion products remaining in the surrounding groundmass. In all three cases, corrosion processes tend to be anisotropic, probably because of cold-hammering of the coins during their manufacture. Such corrosion processes on massive copper alloy coins may produce features that may lead to their incorrect classification as subferrati, i.e. copper alloy coins with an iron core. Our results may help in future to distinguish strongly corroded massive coins from subferrati. @en

The ANET project aims at developing 2D compact neutron collimators for neutron imaging applications. The results of the ANET collimator performances, presented in this communication, are based on data collected at the FISH beamline at TU-Delft. Two independent methods to evaluate the neutron radiography resolution are described and discussed, as well as a comparison of the beam divergence with or without the ANET collimator.

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De uiterst goede lensjes van zijn microscoopjes bezorgden Antoni van Leeuwenhoek wereldfaam als grondlegger van de microbiologie. Bij het maken van zijn microscoopjes zette Van Leeuwenhoek de lensjes vast tussen twee dichtgeklonken lensplaatjes. Daarom bleef het tot op heden erg lastig hun vervaardigingsmethodes en optische kenmerken te bepalen.@en

X-ray fluorescence spectroscopy (XRF) and X-ray micro computed tomography (μ-CT) were applied to the study of four archaeological glass objects from the collection of the Allard Pierson in Amsterdam, The Netherlands. Often, little is known about the provenience and provenance of archaeological glass objects, as documentation is regularly insufficient to assign a specific place and date of excavation or place of production. This paper demonstrates the value of μ-CT for visualising the internal structures of archaeological glass objects, providing insight into production techniques and condition. The XRF results presented are consistent with published glass compositions but are, as yet, insufficient to assign the glass objects to a specific place of production. Part of a broader research project to apply non-destructive techniques to the study of archaeological glass objects, the results presented here will be the basis for the future evaluation of less commonly applied methods, such as neutron tomography and gamma spectroscopy.@en

The structure of five rare filigree spheres from a seventeenth century shipwreck was examined in order to unravel their condition, manufacturing process and function. This study focuses on the application of non-invasive imaging techniques: optical microscopy, X-radiography, X-ray micro-computed tomography and neutron computed tomography. A valuation of different aspects of the applied techniques was made, aiding stakeholders in decision-making on research and conservation. The combination of theory and scientific information was used to obtain an improved understanding of the manufacturing process and function of the filigree spheres.@en

A rare find of a high-status 17th century oval box, retrieved from a shipwreck, provided a unique opportunity to research the construction and finishing layers of an object that is untouched for 350 years. This case study was used to demonstrate the extent of data that can be gained from analytical techniques prior to conservation. The amalgam-gilt brass object was studied by optical and electron microscopy, X-radiography, micro-computed X-ray tomography, neutron tomography, X-ray fluorescence, X-ray diffraction, Rutherford backscattering spectrometry, proton-induced X-ray emission and gas chromatography. The results have led to a characterisation of the manufacturing methods used on the box and to a better understanding of the practicality of modern analytical methods and techniques in (maritime) archaeological research.

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Iron is a promising, earth-abundant material for future energy applications. In this study, we use a neutron diffractometer to investigate the properties of an iron electrode in an alkaline environment. As neutrons penetrate deeply into materials, neutron scattering gives us a unique insight into what is happening inside the electrode. We made our measurements while the electrode was charging or discharging. Our key questions are: Which phases occur for the first and second discharge plateaus? And why are iron electrodes less responsive at higher discharge rates? We conclude that metallic iron and iron hydroxide form the redox pair for the first discharge plateau. For the second discharge plateau, we found a phase similar to feroxyhyte but with symmetrical and equally spaced arrangement of hydrogen atoms. The data suggest that no other iron oxide or iron (oxy)hydroxide formed. Remarkable findings include the following: (1) substantial amounts of iron hydroxide are always present inside the electrode. (2) Passivation is mostly caused by iron hydroxide that is unable to recharge. (3) Iron fractions change as expected, while iron hydroxide fractions are delayed, resulting in substantial amounts of
amorphous, undetectable iron phases. About 40% of the participating iron of the first plateau and about 55% of the participating iron for the second plateau are undetectable. (4) Massive and unexpected precipitation of iron hydroxide occurs in the transition from discharging to charging. (2), (3), and (4) together cause accumulation of iron hydroxide inside the electrode.@en

The technique of neutron tomography has, after 350 years, enabled a first look inside the iconic single-lens microscopes of Antoni van Leeuwenhoek. Van Leeuwenhoek's 17th-century discovery of "animalcules"marks the birth of microbiology. His skillfully self-produced microscope lenses remained unsurpassed for over 150 years. Neutron tomography now enabled us to reveal the lens types Van Leeuwenhoek used. We argue that Van Leeuwenhoek's instruments incorporate some innovations that testify to an awareness of concurrent developments. In particular, our analysis shows that for making his best-performing microscopes, Van Leeuwenhoek deployed a lens-making procedure popularized in 1678 by Robert Hooke. This is notable, as Hooke always wanted to find the secret of Van Leeuwenhoek's lenses, but never managed to do so. Therefore, Van Leeuwenhoek was far from the isolated scholar he is often claimed to be; rather, his secrecy about his lenses was motivated by an attempt to conceal his indebtedness to Hooke.

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The existence of a novel double-molybdate phase with a palmierite-type structure, Cs2Ba(MoO4)2, is revealed in this work, and its structural properties at room temperature have been characterized in detail using X-ray and neutron diffraction measurements. In addition, its thermal stability and thermal expansion are investigated in the temperature range 298-673 K using high-temperature X-ray diffraction, leading to the volumetric thermal expansion coefficient αV ≈ 43.0 × 10-6 K-1. The compound's standard enthalpy of formation at 298.15 K has been obtained using solution calorimetry, which yielded ΔfHm°(Cs2Ba(MoO4)2, cr, 298.15 K) = -3066.6 ± 3.1 kJ· mol-1, and its standard entropy at 298.15 K has been derived from low-temperature (2.1-294.3 K) thermal-relaxation calorimetry as Sm°(Cs2Ba(MoO4)2, cr, 298.15 K) = 381.2 ± 11.8 J K-1 mol-1.

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Neutron diffraction, X-ray absorption spectroscopy (XAS), and Raman spectroscopy measurements of the quaternary perovskite phase Ba₂NaMoO_5.5 have been performed in this work. The cubic crystal structure in space group Fm3¯ m has been refined using the Rietveld method. X-ray absorption near-edge structure spectroscopy (XANES) measurements at the Mo K-edge have confirmed the hexavalent state of molybdenum. The local structure of the molybdenum octahedra has been studied in detail using extended X-ray absorption fine structure (EXAFS) spectroscopy. The Mo-O and Mo-Ba distances have been compared to the neutron diffraction data with good agreement. The coefficient of thermal expansion measured in the temperature range of 303-923 K, using high temperature X-ray diffraction (HT-XRD) (α_V = 55.8 × 10^-6 K), has been determined to be ∼2 times higher than that of the barium molybdates BaMoO₃ and BaMoO₄. Moreover, no phase transition nor melting have been observed, neither by HT-XRD nor Raman spectroscopy nor differential scanning calorimetry, up to 1473 K. Furthermore, the standard enthalpy of formation (Δ_fH_m°) for Ba₂NaMoO_5.5(cr) has been determined to be -(2524.75 ± 4.15) kJ mol^-1 at 298.15 K, using solution calorimetry. Finally, the margin for safe operation of sodium-cooled fast reactors (SFRs) has been assessed by calculating the threshold oxygen potential needed, in liquid sodium, to form the quaternary compound, following an interaction between irradiated mixed oxide (U,Pu)O₂ fuel and sodium coolant.

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The formation of a thin layer, the so-called Joint Oxyde-Gaine (JOG), between the (U,Pu)O2 fuel pellets and the cladding has been observed in fast neutron reactors, due to the accumulation of volatile fission products. Cs2MoO4 is known to be one of the major components of the JOG, but other elements are also present, in particular tellurium and palladium. In this work, an investigation of the structural and thermodynamic properties of Cs2TeO4 and Cs2Mo1-xTexO4 solid solution is reported. The existence of a complete solubility between Cs2MoO4 and Cs2TeO4 is demonstrated, combining X-ray diffraction (XRD), neutron diffraction (ND), and X-ray absorption spectroscopy (XAS) results. High-temperature XRD measurements were moreover performed on Cs2TeO4, which revealed the existence of a α-β phase transition around 712 K. Thermal expansion coefficients were also obtained from these data. Finally, phase equilibra points in the Cs2MoO4-Cs2TeO4 pseudobinary phase diagram were collected using differential scanning calorimetry and used to develop a thermodynamic model for this system using a regular solution formalism.

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The hydride phase of Ti₅₀V₂₀Cr₃₀ alloy cast with 4 wt% of 7Zr+10Ni has been investigated. Pressure composition desorption isotherms were measured at 150 °C and 200 °C. These isotherms revealed same desorption of 1.5 wt% at 150 °C and 200 °C. The evolution of the crystal structure upon dehydrogenation was investigated by in-situ neutron diffraction. A sample was fully deuterated at room temperature under 2000 kPa pressure. Afterwards, the sample was heated from 120 °C to 266 °C under vacuum and neutron diffraction patterns were recorded as a function of temperature. It was found that the alloy started to desorb very quickly at 200 °C. The amount of fcc phase was monitored using the relative intensity of the fcc phase compared to a standard. At 266 °C only 10% hydride phase was seen, which was confirmed by X-ray diffraction. Besides the fcc phase, a minor aluminum phase due to the heating element was also observed in all patterns. Thermal expansion coefficient of Al and fcc phase were calculated. Using the aluminum peaks as reference, it was found that deuterium occupancy reflect the phase abundance of the fcc deuteride.

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A new concept named “rotating magnetocaloric effect (RMCE)” has been proposed and attracted more attention recently. Unlike the traditional MCE that is achieved by moving the magnetic refrigerant in and out of magnetic field, RMCE can be realized by rotating the anisotropic material within the static field, thus implying the possible higher efficiency and simpler device. However, most studies on RMCE are concentrated on single crystals, which are generally more expensive and difficult to prepare in comparison with polycrystals. Therefore, it is highly desirable to search polycrystalline materials with high RMCE. Here, the textured HoNiSi polycrystal is reported to show a giant RMCE, e.g., the rotating magnetic entropy change (−ΔS_R) are 18.5 and 26.7 J/kg K and rotating adiabatic temperature change (ΔT_R) are 7.0 and 13.4 K under 2 and 5 T, respectively. This giant RMCE over a wide temperature range especially under low field suggests textured HoNiSi as promising material for practical application of rotary magnetic refrigeration. Moreover, the large magnetic anisotropy of HoNiSi is explained by the single-ion magnetic anisotropy theory, and the coherent orientation of crystallographic texture and rare-earth ion moments leads to the large RMCE in the textured HoNiSi polycrystal. This work reveals that the strongly coherent orientation of crystallographic texture and rare-earth ion moments is a key to realize large RMCE in polycrystalline materials.

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