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Summary The spatiotemporal distribution of multiple components and phases governs their evaporation and condensation at the liquid-vapor interface. However, in situ methods to characterize the distribution remain challenging, despite the significance of understanding the ubiquitous mass transport phenomena. Here, we introduce high-resolution neutron imaging as a versatile method to quantify the composition of a sessile droplet in situ, under evaporation and condensation. To prove the concept, we perform a neutron transmittance analysis of a sessile heavy water (D2O) droplet and measure the fraction change of H2O to D2O by the sorption of ambient H2O vapor during the evaporation. Our observations are consistent with ex situ Fourier transform infrared spectroscopy measurements and our diffusion-based numerical model. Our results demonstrate that, with deuterated components having a physicochemical similarity with their hydrogenated counterparts, high-resolution neutron imaging can trace composition changes in nonequilibrium phenomena, such as evaporation and condensation.

The fuel rod claddings in nuclear light water reactors are made of zirconium alloys. Corrosion of these alloys during operation and in particular high temperature oxidation during nuclear accidents results in the production of free hydrogen. The cladding can absorb this hydrogen. It affects the mechanical properties of the cladding material. Hydrogen embrittlement of these materials provides the risk of brittle fracture of the cladding by thermo-shock during emergency cooling. At KIT the behaviour of cladding materials under different hypothetical nuclear accident scenarios was investigated. One focus was on hydrogen absorption and distribution/re-distribution in the alloys. The hydrogen distribution was determined mainly by neutron tomography. Examples for the determination of the 3D hydrogen distribution in cladding tubes after loss of coolant accident simulation tests are given and discussed.

Just after the start into the new millennium the concept for combined neutron and X-ray imaging was introduced by extending the standard configuration of the thermal neutron imaging NEUTRA instrument with a complementary 320 kV X-ray tube setup. Using essentially the same detector configuration for both neutron and X-ray imaging enables a pixel-wise (in radiography) and a voxel-wise (in tomography) correlation and combination of attenuation data. The optimal use and analyses of such complementary data sets depend on the specific investigation and research question and range from a combinatory interpretation of separately analyzed images to full data fusion approaches. Here, several examples from more than a decade of bimodal neutron and X-ray imaging at NEUTRA at PSI shall be reviewed.

Hydrogels are normally isotropic and weak, in contrast to their natural analogs that possess hierarchically oriented structure and excellent mechanical properties. Inspired by the unique structure of natural materials, we develop an approach for preparing highly anisotropic hydrogels with programmable oriented polymer structure and extraordinary mechanical properties. Our method is based on a novel welding technique for stretched cellulose hydrogel films, in which interfacial reconfiguration occurs, allowing full integration without compromising the highly aligned polymer orientation. We demonstrate the versatility of this method by fabricating four types of anisotropic tough multilayer hydrogels with differently oriented hierarchies: parallel lamination (‖), orthogonal lamination (⊥), axial rolling, and concentric rolling. These high-water-content hydrogels (∼68 wt%) exhibit extremely high anisotropy (birefringence ≥0.006, the highest reported for hydrogels) and superior mechanical properties (Young's modulus of ∼140 MPa, tensile strength of ∼47 MPa, and work of extension of ∼20 MJ m−3). Moreover, these hydrogels also show interesting anisotropic electrical conductivity and asymmetric shape deformation. Because this method is easy to apply and offers flexibility in designing complex hierarchical hydrogel structures, our work opens a new window to designing novel hydrogel materials for engineering and biomedical applications.

This paper reports on light yield enhancement of terbium-doped gadolinium oxysulfide based scintillator screens achieved by coating their substrates with thin layers of a high density and high atomic number material. For this purpose, iridium was chosen and layers of various thicknesses were applied by atomic layer deposition (ALD). We assessed newly developed scintillator screens for neutron absorption, light yield and spatial resolution and compared them to previously used non-iridium-coated scintillator screens. The addition of the iridium layer resulted in 65 % light yield enhancement in comparison to uncoated scintillator screens while the spatial resolution and absorption power remained unchanged., MethodsX, 6, ISSN:2215-0161

In metallurgical processing, non-metallic inclusions contaminating metallic materials are one highly relevant challenge. Bubble injection into molten metals boosts the inclusion control and removal, thus enhancing metal homogenisation and purification. Although this principle of bubble flotation has been used for a long time, the effects of bubble–inclusion interactions in molten metals are not yet well researched. Imaging measurements of multiphase metal flows are challenging for two main reasons: the metals’ high melting temperatures and their opaqueness for visible light. This work focuses on X-ray and neutron radiographic experiments employing low-melting gallium alloys laden with model particles smaller than 1 mm in diameter. Both, bubbles and particles, are visualised simultaneously with high spatial and temporal resolution in order to analyse their motions by tracking algorithms. We demonstrate the capability of time-resolved X-ray and neutron radiography to image multiphase flows in particle-laden and optically opaque liquid metals, thus contributing to pave the way for systematic investigations on bubble–inclusion interactions in molten metals.

We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with an intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented—stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions representative of the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our previously achieved results. Significant improvements are observed as well as the capacity to reliably extract physically meaningful information from measurements performed under highly adverse imaging conditions. The showcased image processing solution and separate elements thereof are readily extendable beyond the present application, and have been made open-source.

The electrosorption of Gd$^{3+}$ ions from aqueous 70 mM Gd(NO$_3$)$_3$ solution in monolithic carbon aerogel electrodes was recorded by dynamic neutron imaging. The aerogels have a bimodal pore size distribution consisting of macropores and mesopores centered at 115 nm and 15 nm, respectively. After the uptake of Gd$^{3+}$ ions by the negatively charged surface of the porous structure, an inhomogeneous magnetic field was applied to the system of discharging electrodes. This led to a convective flow and confinement of Gd(NO$_3$)$_3$ solution in the magnetic field gradient. Thus, a way to desalt and capture paramagnetic ions from an initially homogeneous solution is established.

Superabsorbent polymers (SAPs) are used to counteract self-desiccation in order to mitigate autogenous shrinkage, a problem in cementitious systems with a low water-to-cement ratio. The release kinetics during internal curing are of importance as not all SAP types are able to efficiently mitigate autogenous shrinkage. In this study, neutron tomography is used to study and visualize the water release kinetics over time. Per-voxel analysis of the time-attenuation curve was performed using piecewise-constant functions. Two different SAP types were studied, one being able to mitigate autogenous shrinkage and one quickly releasing its stored water after final setting. The tomography results correspond to autogenous shrinkage measurements and nuclear magnetic resonance tests. The visualization provides information on the time of water release by the SAPs after setting and the time window of internal curing. This opens additional insights towards the application of SAPs in the construction sector and provides information on the mechanism of internal curing.

The fast neutron imaging technique with recoil proton detection harbors significant potential for imaging of thick, large-scale objects containing high-Z elements. However, the challenge to find efficient fast neutron scintillators with high spatial resolution is ongoing. The list of requirements for such scintillators is long and demanding: a proton-rich, scattering-free material combining high light yield with the absence of light reabsorption. To meet these challenges, we look for a suitable material among a rising class of 0D organic-inorganic Pb(II) halide hybrids. The use of large organic cations, e.g., trihexyltetradecylphosphonium, results in room-temperature ionic liquids that combine highly Stokes-shifted (up to 1.7 eV), reabsorption-free, and efficient emission (photoluminescence quantum yield up to 60%) from molecularly small and dense (PbX2 molar fraction up to 0.33) emitting centers. We investigate the optical properties of the resulting ionic liquids and showcase their utility as fast neutron imaging scintillators. Concomitantly with good light yield, such fast-neutron scintillators exhibit both higher spatial resolution and lower γ-ray sensitivity compared with commercial ZnS:Cu-based screens., ACS Photonics, 8 (11), ISSN:2330-4022

Dynamic neutron radiography is used to observe the effect of a transverse magnetic field on argon bubbles rising through a thick layer of liquid gallium without interactions with the container walls.

Although of pivotal importance in heterogeneous hydrogenation reactions, the amount of hydrogen on catalysts during reactions is seldom known. We demonstrate the use of neutron imaging to follow and quantify hydrogen containing species in Cu/ZnO catalysts operando during methanol synthesis. The steady-state measurements reveal that the amount of hydrogen containing intermediates is related to the reaction yields of CO and methanol, as expected from simple considerations of the likely reaction mechanism. The time-resolved measurements indicate that these intermediates, despite indispensable within the course of the reaction, slow down the overall reaction steps. Hydrogen-deuterium exchange experiments indicate that hydrogen reduction of Cu/ZnO nano-composites modifies the catalyst in such a way that at operating temperatures, hydrogen is dynamically absorbed in the ZnO-nanoparticles. This explains the extraordinary good catalysis of copper if supported on ZnO by its ability to act as a hydrogen reservoir supplying hydrogen to the surface covered by CO2, intermediates, and products during catalysis.

This work presents the fabrication and experimental evaluation of instrumentation designed to enable higher spatial resolution neutron radiography for those performing research at neutron scattering facilities. Herein, we describe a proof-of-concept array of microstructured silicate fibers with 6Li doped cores that shows progress towards a design for μ m resolution neutron radiography. The multicore fiber was fabricated by drawing stacked unit elements of Guardian Glass (Nucsafe Inc., Oak Ridge, TN, USA), a 6Li scintillating core glass, and a silicate cladding glass. These structured fibers function as an array of sub-10- μ m waveguides for scintillation light. Measurements have shown a significantly increased integrated charge distribution in response to neutrons, and the spatial resolution of the radiographs is described by edge response and line spread functions of 48 ± 4 μ m and 59 ± 8 μ m , respectively.

High-resolution neutron radiography (∼10 μm) was utilized to quantify hydrogen diffusion under stress in Zircaloy nuclear fuel cladding materials. A notched Zircaloy-4 plate with ∼600 wppm hydrogen underwent a thermo-mechanical test to allow hydrogen in solid solution to diffuse solely under a stress raiser. After the test, neutron radiography revealed an elevated concentration field at the notch, with a hydrogen gradient detectable over 700 μm and a maximum elevation of 130 wppm. Finite element computation was then performed by employing the Cauchy stress tensor and hydrogen-induced anisotropic transformation trains as the driving force of hydrogen diffusion.

This article reports on the simultaneous measurement of foam structure and attached particles employing neutron imaging. An aqueous foam sample is placed in the NEUTRA beamline at the Paul Scherrer Institut, enabling a spatial resolution of less than 200 μ m to be achieved at a frame rate of more than 1 Hz. A forced drainage setup allows the liquid content of the foam to be controlled. The averaged attenuation of the neutrons is demonstrated to yield the liquid fraction of the foam. Hydrophobized gadolinium particles with a diameter of 200 μ m are added to the foam. Using two surfactants, different levels of hydrophobicity are achieved. Depending on the drainage flow and the hydrophobicity, the particles are washed out of the foam at different rates. An avalanche-like motion of particle clusters is observed. Neutron radiography is demonstrated to yield unique insights into the unsteady froth flotation process.

Hydrogen uptake by nuclear fuel claddings during normal operation as well as loss of coolant during design basis and severe accidents beyond design basis has a high safety relevance because hydrogen degrade the mechanical properties of the zirconium alloys applied as cladding material. Currently, claddings with enhanced accident tolerance are under development. One group of such accident tolerant fuel (ATF) claddings are zirconium alloys with surface coatings reducing corrosion and high-temperature oxidation rate, as well as the chemical heat and hydrogen release during hypothetical accidents. The hydrogen permeation through the coating is an important parameter ensuring material safety. In this work, the hydrogen permeation of Ti2AlC and Cr2AlC MAX phase coatings on Zircaloy-4 is investigated by means of neutron radiography. Both coatings are robust hydrogen diffusion barriers that effectively suppress hydrogen permeation into the matrix.

Hydrides precipitation has been induced by slow cooling of hydrogen-charged specimens of three different Zircaloy-2 claddings commonly used in boiling water reactors. The resulting hydrides distribution has been analysed by optical and scanning electron microscopy and neutron radiography. With the latter technique, it is possible to quantify radially the hydrogen concentration with a resolution of ±10 wppm and a spatial resolution of 10 µm. Hydrogenated samples were subjected to a temperature of 400°C and afterwards a cooling rate of 0.3°C/h and 10°C/h showed that practically a complete migration of the hydrogen towards the liner-cladding interface took place, leading to very high local hydrogen concentrations exceeding 2000 wppm.

Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell, NiO is reduced to Ni. When this process is conducted under external load, like also present in a stack assembly, significant deformations of NiO/Ni-YSZ composite samples are observed. The observed creep is orders of magnitude larger than the one observed after reduction during operation. This phenomenon is referred to as accelerated creep and is expected to have a significant influence on the microstructure development and stress field present in the Ni-YSZ in solid oxide electrochemical cells (SOCs), which is highly important for the durability of the SOC. In this work we present energy selective neutron imaging studies of the accelerated creep phenomenon in Ni/NiO-YSZ composite during reduction and also during oxidation. This approach allowed us to observe the phase transition and the creep behavior simultaneously in-situ under SOC operation-like conditions.

Neutron imaging of sub-10-micrometres spatial resolution has been recently achieved in 2D mode within the framework of the Neutron Microscope project at the Paul Scherrer Institut. Here we report on the development of the PSI Neutron Microscope instrument and the results of the first microtomographic imaging experiment of multifilament superconducting MgB 2 wire. The sample of MgB 2 superconducting 37 multifilaments embedded in copper-nickel matrix was investigated –in microtomographic mode– with the scientific interest regarding the distribution of boron within the individual superconducting filaments (about 40 μm in diameter). The resulting tomographic dataset revealed the distribution of boron within the entire 0.8 mm thick multifilamental wire with the isotropic voxel size of 2.6 micrometres.

During the growth of anodic Al oxide layers water incorporates in the film and therefore influences the intrinsic properties of the oxide formed. In this study, we propose a new approach, based on the use of high-resolution neutron imaging, to visualize and quantify the water content in porous Al oxides as a function of anodizing conditions. Water in these porous films is either incorporated directly in the oxide structure (structural) and/or fills the pores (morphological). This preliminary study demonstrates that the differences in water content of porous anodic Al oxide layers are strongly related to the oxide growth parameters but interestingly cannot be directly correlated to a specific change in the amorphous oxide structure or in the pore morphology. Due to the high sensitivity of high-resolution neutron imaging to small changes in the water content, we furthermore show that the morphological water content in Al oxides formed in sulfuric acid as well as in phosphoric acid is partially reversible upon heat treatment and immersion. High-resolution neutron imaging is also found to be highly sensitive to structural disorder and crystallographic orientations, allowing to identify different crystalline Al oxide samples based on their structural and morphological defect content. This offers new perspectives to study the effect of the hydrogen and/or water incorporation as well as oxide-related structural modifications on Al oxihydroxides in relation to growth parameters, stability, functionalization as well as properties tuning, highly relevant to surface protection and their use as templates.

Calcium aluminate cements are used for special applications but are nowadays banned for general structural purposes due to the calcium aluminate hydrate conversion, that has led, for concretes fabricated with high water contents, to building collapses. The stoichiometries of these conversion chemical reactions are relatively well established but the consequences in porosity, key to predict durability, were unknown. Here, we have used hard X-ray ptychographic nanotomography to study the hydration of CaAl2O4 at different temperatures and chiefly, at 4 °C and then at 50 °C to provoke conversion similar to field conditions. The mass densities of the resulting Al (OH)3 gels were 1.94, 1.98 and 2.23 g·cm−3, for samples hydrated at 4, 20 and 50 °C, respectively. These values are lower than that of gibbsite, 2.42 g·cm−3. Above all, this 3D imaging technique has allowed measuring the secondary water porosity developed in the conversion, which has an average pore dimension close to 140 nm.

The unique possibilities enabled by neutron imaging for in situ remote diagnostics of microstructural characteristics during crystal growth are demonstrated, even when the materials and surrounding structures are opaque to other more conventional interrogation techniques. Neutron radiography is implemented to image remotely the uniformity of elemental distribution (e.g. dopant concentration) during crystal growth, the location of the liquid/solid interface and the presence of macroscopic crystal defects (e.g. cracks), all with a temporal resolution of 5–7 s., Neutrons are known to be unique probes in situations where other types of radiation fail to penetrate samples and their surrounding structures. In this paper it is demonstrated how thermal and cold neutron radiography can provide time-resolved imaging of materials while they are being processed (e.g. while growing single crystals). The processing equipment, in this case furnaces, and the scintillator materials are opaque to conventional X-ray interrogation techniques. The distribution of the europium activator within a BaBrCl:Eu scintillator (0.1 and 0.5% nominal doping concentrations per mole) is studied in situ during the melting and solidification processes with a temporal resolution of 5–7 s. The strong tendency of the Eu dopant to segregate during the solidification process is observed in repeated cycles, with Eu forming clusters on multiple length scales (only for clusters larger than ∼50 µm, as limited by the resolution of the present experiments). It is also demonstrated that the dopant concentration can be quantified even for very low concentration levels (∼0.1%) in 10 mm thick samples. The interface between the solid and liquid phases can also be imaged, provided there is a sufficient change in concentration of one of the elements with a sufficient neutron attenuation cross section. Tomographic imaging of the BaBrCl:0.1%Eu sample reveals a strong correlation between crystal fractures and Eu-deficient clusters. The results of these experiments demonstrate the unique capabilities of neutron imaging for in situ diagnostics and the optimization of crystal-growth procedures.

We report a powerful method for capturing the time-resolved concentration profiles, liquid swelling and surface phenomena during the absorption of methane (CH4) in still liquid ethanol (C2D6O) and n-decane (n-C10D22) and at high spatial resolution (pixel size 21.07 μm) using neutron imaging. Absorption of supercritical methane was followed at two temperatures and two pressures of methane, namely 7.0, 37.8 °C and 80, 120 bar. Fick's second law, which was used in the liquid-fixed coordinates, enabled for an adequate parameterization of the observed concentration profiles and liquid levels using simple analytical expressions. For both studied liquids, anomalously slow diffusion was observed in the initial stage of the absorption experiment. This was ascribed to the slow formation of the surface excess on the interface, time constant ranged 130-275 s. The axial symmetry of the cell allowed for the tomographic reconstructions of the profiles of the menisci. Based on these profiles, contact angle and surface tension were evaluated using the Young-Laplace equation. Overall, neutron imaging made it possible to capture time- and space-resolved information from which the methane concentration, liquid level and meniscus shape under high-pressure conditions inside a cylindrical titanium vessel were quantitatively derived. Multiple characteristics of ethanol, a methane hydrate inhibitor, and n-decane, a model constituent of crude oil, were thus measured for the first time under industrially relevant conditions in a one-pot experiment.

In this work, for the first time, high-resolution neutron imaging (true spatial resolution of 13 μm) is used for irradiated nuclear fuel cladding, applying an adapted procedure for transfer, handling, and measurements of highly radioactive samples in combination with the neutron microscope detector at Paul Scherrer Institut. A sample container referred to as an active box for high-resolution neutron imaging of highly active spent nuclear fuel cladding sections was developed. Sections of unirradiated and irradiated cladding of duplex type, having a liner, with hydrogen average concentrations of 420 wppm and 450 wppm were investigated using this device. The irradiated cladding originated from a fuel rod operated for five cycles in a Swiss pressurized water reactor. The irradiated cladding sample was measured inside the active box. Long circumferential hydride accumulations were revealed together with notable hydride precipitation at the liner-substrate interface. Measurements of the unirradiated cladding in air and inside the active box delivered consistent results, confirming the applicability of the developed device for high-resolution neutron imaging.

Hydrogen distribution in zirconium nuclear fuel claddings can often be non-uniform because of the high mobility of hydrogen interstitial atoms, raising the risk to the fuel rod integrity. Therefore, the assessment of hydrogen migration behavior is of great importance when considering its potential detrimental effects during spent fuel storage. Here, we present the quantitative results of hydrogen redistribution measured by high-resolution neutron imaging in conjunction with thermodynamic modeling. A duplex cladding, with a 150 μm external layer of low-tin Zircaloy-4, so-called liner, bonded to an inner standard Zircaloy-4 substrate, underwent various cooling rates subsequent to hydrogenation and solution heat treatment. The tube segments were measured using a state-of-the-art neutron imaging setup of PSI Neutron Microscope with an effective spatial resolution of 9.6 μm. The hydrogen concentration was quantified across the cladding wall thickness with a precision of 9 wppm, revealing the effect of cooling rate on hydrogen migration from the substrate into the liner. Depending on the cooling rate, hydrogen accumulation in the liner near the interface reached more than 1000 wppm, which consisted primarily of intragranular hydrides in the accumulation strip. The equilibrium concentration during solid solution treatment was identified to be lower in the liner than in the substrate. The thermodynamic calculations reveal that the hydrogen migration into the liner is attributed to the composition-induced difference in the reference chemical potential between the liner and the substrate, and the high precipitation rate promoted hydride accumulation near the interface instead of the liner interior.

We demonstrate the feasibility of the production of isotopically-enriched gadolinium oxysulfide scintillator screens for the high spatial-resolution neutron imaging. Approximately 10 g of 157 Gd 2 O 2 S:Tb was produced in the form of fine powder (particle size approximately 2 µm). The level of 157 Gd enrichment was above 88%. Approximately 2.5 µm thick 157 Gd 2 O 2 S:Tb scintillator screens were produced and tested for the absorption power and the light output. The results are compared to the reference screens based on nat Gd 2 O 2 S:Tb. The isotopically enriched screens provided increase by a factor of 3.8 and 3.6 for the absorption power and the light output, respectively. The potential of the scintillator screens based on 157 Gd 2 O 2 S phosphor for the purpose of the (high-resolution) neutron imaging is discussed.

Here we present results stemming from the first prototype of the Neutron Microscope instrument at Paul ScherrerInstitut (PSI). The instrument is based on a very thin gadolinium oxysulfide (Gd2O2S:Tb+) scintillator screen and a magnifying optics. The Neutron Microscope prototype has been tested at the ICON and the BOA beamlines at PSI and sub-10 μm features can be clearly resolved on a focussed ion beam (FIB) enhance test object – a gadolinium-based Siemens star. The spatial resolution of the images of the gadolinium-based Siemensstar assessed by Fourier ring correlation was about 7.6 μm. The outlook for future improvement of the Neutron Microscope system is presented.

Ptychographic X-ray computed tomography (PXCT) allows for a non-destructive, three-dimensional mapping of the electron density. Its quantitativeness combined with a resolution in the 100 nm range makes it a suitable tool for the assessment of densities of the individual phases in complex materials, such as hardened cement pastes. Here we present results of an experiment performed on a cylindrical sample of epoxy-impregnated hardened cement paste of about 30 μm in diameter. Two-dimensional cross sections of the three-dimensional electron density map show a microstructure that bears distinct similarity to that observed by back-scattered scanning electron microscopy. Domains of various residues of cement grains, calcium hydroxide, calcium carbonate, epoxy-resin impregnated calcium silicate hydrates, epoxy-resin impregnated porosity, and unimpregnated porosity are revealed and are manifested as distinguishable peaks in the histogram of the three-dimensional electron density map. On assumptions of (i) a priori knowledge of the chemical composition and (ii) the purity of the analysed regions, the mass densities of the above mentioned individual material phases are estimated. The potential of PXCT for the science of cement and concrete is discussed.

Recent results of statistical nanoindentation testing on hardened cement pastes (HCP) reported in the literature show a multipeak response in the elastic modulus frequency plots. These peaks have been interpreted as indicating the true elastic modulus of two calcium silicate hydrate (C–S–H) phases of different densities. However, the application of statistical indentation for determining material properties of single phases in HCP appears to violate some of the basic principles of the technique. To elucidate this aspect, virtual experiments emulating statistical nanoindentation are performed and presented in this paper. They are based on 3D images of: (i) an idealized two-phase material and (ii) HCP acquired by focussed ion beam nanotomography (FIB-nt); within both 3D images, a marching object is sampled over a large number of positions. Based on the local phase composition within the marching object, a local stiffness is estimated by using simple composite models. Due to the large number of the investigated positions, the elastic modulus can be statistically evaluated in the same manner as in the real statistical indentation experiments. The results presented in this paper indicate that the homogenous C–S–H regions present in HCP are too small to cause independent and separated peaks in the elastic modulus plots. Moreover, the presence of phases other than C–S–H, namely unhydrated cement and calcium hydroxide, may also produce spurious peaks in the frequency plots. In conclusion, the presented results question the notion that the multipeak signature in statistical nanoindentation experiments on HCP can be explained only by the presence of two distinct C–S–H phases.

Amorphous binary (CoB, NiB) and ternary (CoBCr, NiBCr) alloys prepared by chemical reduction with NaBH4 were characterized by atomic absorption spectroscopy (AAS), nitrogen physisorption (BET), X-ray diffraction (XRD), temperature programmed desorption (TPD), temperature programmed reduction (TPR), hydrogen chemisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) and the influence of their properties on catalytic performance in the hydrogenation of unsaturated nitriles to unsaturated amines was studied. The hydrogenation over NiB(Cr) catalysts lead to preferential hydrogenation of the C C bond, whereas the hydrogenation over CoB(Cr) catalysts occurred preferentially to the unsaturated amine. Addition of chromium dramatically increased the activity of both NiB and CoB catalysts, due to its effect on the binding energy of adsorbed hydrogen and the adsorption strength of the nitrile functional group. Amorphous cobalt borides treated with sodium hydroxide can hydrogenate unsaturated nitriles to primary unsaturated amines with medium-to-high selectivity without the presence of ammonia.

International audience; Calcium silicate hydrates (C−S−H) are the most abundant hydration products in ordinary Portland cement paste. Yet, despite the critical role they play in determining mechanical and transport properties, there is still a debate about their density and exact composition. Here, the site-specific mass density and composition of C−S−H in hydrated cement paste are determined with nanoscale resolution in a nondestructive approach. We used ptychographic X-ray computed tomography in order to determine spatially resolved mass density and water content of the C−S−H within the microstructure of the cement paste. Our findings indicate that the C−S−H at the border of hydrated alite particles possibly have a higher density than the apparent inner-product C−S−H, which is contrary to the common expectations from previous works on hydrated cement paste.

The 3D structure of three individual aggregates composed of 165 nm polystyrene primary particles is revealed nondestructively by hard X-ray phase-contrast synchrotron nanotomography. Three-dimensional image analysis allows us for the first time to obtain the complex inner porosity of the entire aggregate. It is demonstrated that despite their rather compact structure, characterized by a fractal dimension equal to 2.7, the produced aggregates are still porous, with porosity increasing with its size. Generated pores have diameters from 100 nm to 3 μm and are almost completely interconnected.