Bragg edge imaging has been applied to multi-material laser powder-bed fusion (M2LPBF) samples of 316 L stainless steel and CuCrZr. A multilayer sample with interfaces perpendicular to the building direction and a bilayer sample with a parallel interface to the building direction were studied. The results demonstrate that this non-destructive approach does not only succeed in characterizing the different interdiffusion zones, but also strain and texture variations across the multiple material regions. In both samples the 316 L layers are found to display a strong (200) texture, while the CuCrZr layers exhibited either a random or weak (110) texture. In the multilayer samples, the difference in thermal expansion between CuCrZr and 316 L led to tensile residual strain in the steel layers and compressive residual strain in CuCrZr. The multilayer sample showed narrower intermixing zones at its horizontal interfaces, especially where CuCrZr was printed onto 316 L steel which is attributed to adjustments in the printing parameters that increase local heating in the formed layers. These results agree with conventional destructive characterizations used in this work. The non-destructive nature of the analyses can enable corresponding observations on the same sample before and after post treatments and/or mechanical testing, implying significant potential for future studies.

Bragg edge imaging experiments were carried out at the BOA beamline of the Paul Scherrer Institute on ring-shaped specimens cut at different axial positions of an unfinished, partially deformed, Zircaloy 4 tube. The height of the (101 0) and (112 0) Bragg edges was taken as indicative of the rotation of the grains around the c-axis during plastic deformation. Maps of these Bragg edge heights were constructed at each axial position to elucidate how this grain rotation changes along the hoop-radial plane. The results were consistent with neutron diffraction data, showing that the initial texture is dominated by the (112 0) // axial fiber, and during deformation the (101 0) // axial fiber became increasingly important at the expense of the first fiber.

Spectroscopic neutron imaging (SNI) is a chemically sensitive imaging technique for probing composition-dependent variations in a variety of systems, including hydrocarbon-based liquid battery electrolytes. This technique utilises wavelength-dependent transmission to distinguish between electrolyte components and H environments by leveraging incoherent scattering interactions in hydrogenous materials, revealing information about the physico-chemical state. Therefore, SNI has the potential to serve as a powerful tool for electrolyte engineering, enabling in situ studies of electrolyte dynamics, heterogeneity, and degradation within commercial lithium-ion battery (LIB) environments. To this end, detection limits for hydrogen and total neutron cross-sections, and , respectively, were evaluated across multiple spatial resolutions, achieving the detection of 10% fluoroethylene carbonate (FEC) in 1 M LiPF6 dissolved in 3:7 (w/w) ethylene carbonate (EC): ethyl methyl carbonate (EMC) electrolytes at a spatial resolution of 275 mu m. These findings establish a framework for applying SNI to electrolyte engineering, enabling the monitoring of solid electrolyte interphase (SEI) formation and characterisation of electrolyte degradation pathways. This framework will support the development of safer, more robust, advanced high energy-density electrochemical devices from LIBs and beyond.

We present a nested Wolter-I mirror design for a neutron condenser, which is based on established X-ray telescope technology. We demonstrate through simulations that it can increase the flux density at the ESS imaging instrument ODIN by up to two orders of magnitude. Experimental measurements of reflectivity and figure errors on a prototype mirror element confirm the technical feasibility of the approach. Then, we introduce design strategies for an imaging objective to fully exploit the condenser specifications while achieving spatial resolutions comparable to those of X-ray micro-computed tomography instruments. Analytically, we show that for monochromatic beams suitable solutions exist employing arrays of hundreds of identical objectives, realized either as compound refractive lenses (CRLs) or Fresnel zone plates (FZPs). To mitigate the inherent chromatic aberration of these optics, each individual objective could be replaced by an achromatic FZP/CRL combination. Key optical properties of the resulting microscope are estimated. This novel full-field microscopy concept for highly divergent, polychromatic neutron beams has the potential to improve temporal and spatial resolution for large samples and sample environments and to enable the simultaneous acquisition of hundreds of projections in neutron tomography.

In polymer electrolyte fuel cells (PEFCs), temperature gradients can exert a substantial influence on cell performance and durability. Monitoring these gradients without perturbing fuel cell operation is one of the main challenges. This study introduces a novel method for remotely mapping fuel cell temperature using ferromagnetic nanoparticles, such as nickel and iron. These nanomediators possess temperature-dependent magnetic properties, enabling neutron depolarization imaging (NDI) to provide insights into the internal fuel cell temperature. We extensively evaluated the main parameters pertaining to the utilization of these nanoparticles in powdered form for temperature sensing. This encompassed an assessment of the minimum detection concentration and temperature sensitivity. Our findings reveal that while the smallest nanoparticles yield the highest relative change in depolarization, they exhibit considerably lower absolute depolarization coefficients. Hence, larger particles emerge as strong candidates for signal detection. Despite the challenges posed by the considerable size of these sensors, which inhibits in-situ dispersion, there is an opportunity to enhance nanoparticle characteristics. Such improvements could be achieved by scaling up the size of the materials from the nanoscale while retaining high magnetic saturation and temperature sensitivity.

Optimizing hydrogen and oxygen transport within porous electrodes is essential for improving the efficiency of industrial alkaline electrolyzers. In this study, we utilize operando dynamic neutron radiographic measurements to investigate gas distributions and bubble dynamics within an alkaline electrolysis cell. Porous nickel foam was used as cathode and anode in the zero-gap cell configuration to replicate the gas evolution conditions occurring in industrial settings. Our results indicate that approximately 50 % of hydrogen and oxygen is generated within the innermost quarters of both the cathode and anode at the lower section of the electrolysis cell. Additionally, the findings imply that 4-8 % of the volume within the electrode compartments remains occupied by immobilized gas bubbles. These findings demonstrate the potential of neutron imaging as a powerful technique for quantitative mapping of gas volumes within electrolyzer systems.

Soft matter systems, such as colloids, emulsions, and polymer solutions, are common in nature and industry. A key feature is that their structures respond to external mechanical forces, such as shear flow, leading to complex non-linear behavior and flow-induced phase transitions. In this study, we explore the interplay between flow and microstructure in a Couette cell geometry. As a sample, we select a surfactant-free glycerol-in-silicone oil mixture, which was recently reported to form a stable emulsion, not coalescing over time. To probe the structural changes of this emulsion due to shear flow, we pioneer the use of in situ neutron dark-field imaging (DFI) using a single hexagonal grating, introducing a novel imaging technique capable of capturing spatially resolved anisotropic small-angle neutron scattering (SANS) signals. We demonstrate droplet elongation due to shear forces and the appearance of reversible bands with alternating droplet density. By simultaneously creating a full field map and measuring droplet deformation and orientation during shear, DFI enables in situ structural characterization of flowing soft matter. This structural mapping is complemented by the simultaneous monitoring of the macroscopic rheological response of the fluid, resulting in a multimodal probe for soft matter structure. We demonstrate DFI to be a powerful methodology to uncover in situ structural changes under flow, which can exploit common neutron contrast matching techniques. DFI can be applied to concentrated and opaque fluids, uncovering structures from the nanometer to the micrometer range, thereby complementing the typical sample and size limitations of SANS.

Hierarchical biomaterials embody nature's intricate design principles and offer multiple functionalities through the multi-level organization of their molecular and nanosized building blocks. However, 3D structural characterization over length scales ranging from nanometers to centimeters of biopolymer-based materials remains a challenge. Current limitations hinder understanding how macroscopic properties originate in the multiscale arrangement of nanoscale structures that cannot be fully captured from small sample volumes. Here, we demonstrate how multi-directional neutron dark-field tomography (MD-NDFT) provides structural information on multiple length scales in large volumes of heterogeneous hierarchical soft matter materials. By implementing 3D single-grid directional neutron dark-field reconstructions, we quantified the degree of preferential alignment of cellulose nanostructures in centimeter-sized assemblies of several nanocomposite foams simultaneously, probing structural features down to 50 nm through anisotropic ultrasmall-angle scattering, within a field of view greater than or similar to 40 cm2. The successful application of MD-NDFT to nanocellulose, which is inherently radiation-sensitive, prevalent in natural systems and widely used in nanotechnology, proves the relevance of MD-NDFT for multiscale characterization of hierarchical biobased and bioinspired materials.

Abstract Neutrons provide exceptional insight into materials, owing to their sensitivity to light elements, isotopic composition, magnetic moments, and high-penetration. However, neutron sources are polychromatic and of low brightness. Neutron optics provides a route to address these limitations by focusing, and to date, various types of neutron optics have been developed based on reflection, refraction, diffraction, and magnetism. Notably, compound refractive lenses and Fresnel zone plates have been demonstrated for imaging, yet their severe chromatic aberration under polychromatic beams has prevented their widespread use and limits progress towards true high-resolution neutron microscopy. Here, we demonstrate an achromatic neutron lens for full-field neutron microscopy. This development overcomes the intrinsic sample-detector distance constraint in pinhole-based radiography. The lens magnification enables the use of efficient detection systems without loss of spatial resolution and establishes a pathway towards high-resolution neutron microscopy. We anticipate the neutron achromat will advance a broad range of neutron methods.

Neutrons provide exceptional insight into the structure and dynamics of materials, owing to their sensitivity to light elements, isotopic composition, magnetic moments, and high-penetration capabilities. Neutron sources produce beams that are polychromatic and have low brightness. Neutron optics provides a promising route to mitigate these challenges by guiding and focusing neutron beams, and to date, various types of neutron optics have been developed based on reflection, refraction, diffraction, and magnetism. Notably, compound refractive lenses and Fresnel zone plates have also been demonstrated for imaging and focusing applications, yet their severe chromatic aberration under polychromatic beams has prevented their widespread use and continues to limit progress towards true high-resolution neutron microscopy. Here, we demonstrate an achromatic neutron lens combining a compound refractive lens and a Fresnel zone plate. We experimentally verify its achromatic behaviour and compare its performance to a Fresnel zone plate. We employ the achromatic neutron lens to realise a full-field neutron microscope. This development overcomes the long-standing trade-off between flux and spatial resolution that constrains neutron imaging in a pinhole-based radiography geometry and establishes a pathway towards high-resolution neutron microscopy. We anticipate that this new class of neutron optics will advance a broad range of neutron methods that require or benefit from focused neutron beams.

Microstructure and mechanical properties of tungsten/415 stainless steel samples manufactured by Laser Powder Bed Fusion (PBF-LB/M) were investigated. The influence of the parameters used to process tungsten was investigated, focusing on the resulting microstructure at the steel-tungsten interface and its vicinity. Chemical imaging techniques were employed, in particular scanning micro X-ray diffraction (mu XRD) and micro X-Ray Fluorescence (mu XRF) imaging. The microstructure at the interface between W and steel was analyzed using Electron Backscatter Diffraction and XRD, and the formation of crystalline phases in the area of the interface was also analyzed by operando XRD measurements. mu XRD-imaging showed the formation of retained austenite within the lower interface region, reaching up to 1 wt% locally and 0.4 wt% on average. Fe7W6 was identified as the major intermetallic phase at the interface. Its formation could be mitigated using a layer-wise energy grading strategy. The presence of tungsten within the steel lattice just below the intermetallic region was found to favor the formation of large martensitic grains by suppressing the formation of austenite during cooling. Neutron Bragg-Edge Imaging revealed the formation of a residual strain gradient in the steel domain, strongly depending on the energy density, heat input and energy gradient employed.

Metal additive manufacturing is a promising route for producing complex, highly customized embedded structures for nuclear fusion environments, such as breeding blankets and divertors. These applications require steels with high thermomechanical stability and resistance to irradiation, yet AM processing often leads to undesired microstructural heterogeneities, including the formation of metastable phases. In this work, we investigate the formation and spatial distribution of retained austenite in Laser Powder Bed Fusion (PBF-LB/M) - processed ferritic-martensitic stainless steel (AISI 415) using multimodal synchrotron-based characterization. Micron-resolution 2D and 3D synchrotron X-ray Diffraction and X-ray Fluorescence mapping, combined with operando XRD during PBF-LB/M, reveal the presence of retained gamma-phase in periodic mesostructures at concentrations up to 0.5 wt%, depending on scanning strategy. We demonstrated that this result, gained from volumetric measurements based on mu XRD scanning imaging, cannot be gathered by any surface-sensitive technique (e.g. EBSD) due to depth limitations and phase transformation artifacts during sample preparation. No correlation between gamma-phase formation and elemental segregation was observed. Operando XRD measurements show that cooling rates critically affect phase evolution: wall-like geometries exhibit rapid cooling (similar to 105 to 106 K/s) and complete martensitic transformation, whereas bulk samples cool more slowly (similar to 104 K/s), allowing up to 0.5 wt.% of gamma-phase to be retained. These results demonstrate the strong influence of both scanning strategy and thermal history on phase stability in PBF-LB/M steels, supporting the qualification of AM-built components for nuclear applications.

To develop durable and high-performance sodium-ion batteries, it is crucial to understand the degradation processes taking place during electrochemical cycling. This study presents the first demonstration of visualizing the effects of electrolyte degradation in sodium-ion batteries, via 2D and 3D neutron imaging thereby visualizing the degradation of the cells. The experiment was performed on a pristine sodium-based full cell, and two extensively cycled half cells differing only in the electrolyte composition. The different electrolytes, based on NaPF6, but differing in solvent (propylene carbonate and dimethoxyethane), are chosen for their different cycling properties, allowing us to induce two different plating mechanisms. Plating phenomena highly correlate with the accumulation of so-called "dead sodium", which is detrimental to battery functioning, as it can lead to battery failure upon electrode disconnection. We observe that the type of electrolyte is correlated to the plating mechanism, with the propylene carbonate-based cell showing bigger plating domains than the dimethoxyethane-based cell. Segmentation was performed by Python codes designed to extract features based on shape variation, as thresholding-based approaches were unsuccessful due to the relatively high incoherent scattering contribution. The study performed on the full cell allowed us to quantify voltage-induced electrolyte degradation, while in the study on the half-cells we performed the very first demonstration of visualizing the chemical reactions occurring at the surface of the sodium metal electrode by performing 3D neutron imaging on the plating domain of the electrode.

Many neutron techniques can greatly benefit from enhanced neutron lenses for focusing and imaging. In this work, we revisit the potential of diffractive optics for neutron beams, building on advanced high-resolution nano-lithography techniques developed for the fabrication of X-ray diffractive optics used at synchrotron facilities. We demonstrate state-of-the-art fabrication of nickel and silicon Fresnel zone plates and we report proof-of-concept experiments for full-field neutron microscopy and small angle neutron scattering. The advancement of neutron diffractive optics will open new opportunities for neutron techniques, improving both the efficiency and resolution of existing instruments.

This study investigates the development of residual stresses in textured 2205 duplex stainless steel during laser powder bed fusion additive manufacturing (LPBF AM). In situ and operando neutron diffraction experiments were conducted to study the transient and real-time evolution of stresses and strains during processing, using an AM machine designed for neutron studies. Additionally, Bragg-edge imaging was employed to investigate the crystallographic texture. The results showed that residual stress redistribution primarily occurs in the first set of added layers when further layers are added on top. The cube texture observed in the sample significantly affects residual stress determination, leading to inaccuracies up to 96 MPa if not accounted for. This highlights the need for orientation-dependent diffraction elastic constants in residual stress calculations. Furthermore, variations in texture intensity across the sample dimensions were found to be driven by changes in the local temperature history, which were deciphered from real-time strain measurements. Finally, this study demonstrates the potential of combining LPBF with neutron diffraction to investigate the underlying mechanisms of AM in the bulk of the sample.

Well-designed guidance of the magnetic field through electric steel sheets forming the rotor of electrical motors and generators is of utmost importance with regards to efficiency. Typically, this is achieved through tailored cutouts in the sheets. While fulfilling the magnetic guidance needs this strategy structurally weakens the rotor and ultimately limits the possible rotation speeds due to the mechanical forces these imply. Recently an alternative approach has been reported, in which the material is embossed in respective regions. The, thus, induced stresses act, based on the inverse magnetostrictive effect, as flux barriers without, unlike traditional cutouts, weakening the structure significantly. Here we propose to replace the embossing through laser shock peening, which can be controlled digitally and hence be applied flexibly, without the need for mechanical changes in the production lines, like in the case of a punch.

Wavelength-resolved neutron imaging for diffraction contrast often referred to as Bragg edge imaging is a neutron-based technique that has gained attention in recent years due to its promising ability to characterize the microstructure of polycrystalline materials with spatial resolution. This method relies on spatially resolved analyses of diffraction induced features in transmission spectra within the thermal neutron range. Assessable characteristics are e.g. phase fractions, lattice strains, and crystallographic texture. For the latter forward modelling of transmission spectra from known orientation distribution functions (ODFs) has been demonstrated for various materials. However, solving the inverse problem-retrieving crystallographic texture from transmission spectra-presents a more complex challenge. In recent years, the authors have developed two theoretical approaches to model the relationship between transmission spectra and texture, either by decomposing the ODF into individual orientation fractions or by expanding it into a Fourier series. Both approaches have shown excellent predictive capability for materials with different crystal symmetries, including hexagonal, FCC, and BCC structures. Here we present the comparison between the proposed models, highlighting the advantages and disadvantages of the direct method based on different approaches for the analysis of wavelength-resolved neutron transmission experiments of textured materials. Finally, we present the future trends in the inversion method, i.e., the estimation of the ODFs from transmission spectra in tomography experiments.

This work reports on the development of a downsized laser powder bed fusion device for operando neutron characterization. The design considerations, device configurations, and detailed setup are described. The device is optimized for installations at neutron diffraction and instruments for diverse studies of the structural and microstructural evolution and constitution of metallic components during printing. In conjunction with introducing the device, we provide examples of operando neutron diffraction for strain analysis and operando neutron imaging for defect characterization and temperature mapping at two different beamlines of the Swiss Spallation Neutron Source. By acquiring diffraction patterns of crack-susceptible materials and tracking the shift of a diffraction peak, the evolution of thermal contributions to elastic strains within a fixed volume can be determined, during processing. Bulk defect characterization is realized by continuously acquiring radiographs during manufacturing. The change in the neutron beam attenuation is correlated with the final microstructure and it confirms the capability of the technique to operando characterize defect formation within the probed bulk. We further demonstrate how using a Beryllium filter and, thus, the long wavelength part of a cold neutron spectrum, allows obtaining spatially and temporally resolved temperature maps during printing of bimetallic composites.

Steel-copper multi-material structures produced via Additive Manufacturing pose challenges in laser coprocessing and microstructural control. This work employs neutron imaging, Electron Backscatter Diffraction (EBSD), and Energy Dispersive Spectroscopy (EDS) mapping to characterize 316L-CuCrZr Functionally Graded Structures (FGS) fabricated via Laser Powder Bed Fusion. Polarization Contrast Neutron Imaging (PNI) tracks ferrite formation in 316L-CuCrZr premixtures, while Neutron Bragg Edge Imaging (BEI) examines the texture evolution of the 316L-CuCrZr mixtures. PNI and EBSD phase mapping confirm ferrite formation in mixtures exceeding 50 wt% CuCrZr, appearing as spherical particles that locally increase hardness, as shown by nanoindentation mapping. The ferrite fraction peaks between 70-80 wt% CuCrZr. Simultaneously, BEI and EBSD Inverse Pole Figures (IPF) mapping reveal a crystallographic texture transition and grain refinement for mixtures containing more than 50 wt% CuCrZr. Microstructure analysis shows cracks in 10-40 wt% CuCrZr mixtures, while compositions with more than 50 wt% CuCrZr result in crack-free structures. EDS mapping and thermodynamic modeling suggest ferrite formation mechanisms in both liquid and solid states. This study highlights how FGS engineering enables precise control over crack formation, microstructure, and crystallographic texture in steel-copper multi-material structures.