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(a) Example measurement of the open beam with BB grid. (e) Resulting interpolated background image using the BB grid at 16 different positions. (f) Vertical intensity profile of the measured background. Fine grid corresponds to 16 different BB grid positions and coarse grid to one single position.
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We propose a method for improving the quantification of neutron imaging measurements with scintillator-camera based detectors by correcting for systematic biases introduced by scattered neutrons and other sources such as light reflections in the detector system. This method is fully experimental, using reference measurements with a grid of small bl...
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A wavelength resolved measurement technique used in neutron imaging applications is known as energy-resolved neutron transmission imaging. This technique of reconstructing residual strain maps provides high spatial resolution measurements of strain distribution in polycrystalline materials from sets of Bragg edge measurement images. Strain field re...
Citations
... The scattering correction was performed using established black body methodology, 21,22 for which a set of 26 black-body sample projections evenly distributed over 360°(angular step of 14.4°) and 10 open beam black body images were acquired. ...
Hybrid implants consisting of a permanent Ti-based part combined with a degradable Mg part, are promising solutions to design superior implants by combining the advantages of both materials. In these implants Ti provides high strength while a degradable Mg part is used for temporary structural support, bone growth stimulation or drug delivery purpose. As Mg degrades hydrogen gas is released which can ingress into the Ti part, leading to changes in its properties. The profile of hydrogen distribution is a critical parameter for mechanical stability of Ti, especially in long-term applications. To investigate this in microscopic length scale, Ti6Al4V–Mg0.6Zn0.5Ca hybrid samples prepared using metal injection molding were subjected to saline degradation for a period of 0 to 120 hours. Neutron tomography, synchrotron X-ray tomography and diffraction, SEM and gas fusion technique were used to study the ingress of hydrogen in 3D after the degradation of MgZnCa. A uniform distribution of hydrogen was seen radially while the profile along height matched with macroscopic measurements. Synchrotron XRD confirmed that the room temperature diffusion of hydrogen led to lattice expansion of the BCC β-phase in Ti6Al4V, while no hydride phases were present.
... These tubes were subject to the methane pressure step, the diffusion of methane into the liquid was imaged. After applying filters and corrections 29,30 , the radiographs were reconstructed at the central plane of the sample via the onion-peeling algorithm 31 . The resulting tomographic reconstructions at the central plane of the sample (Fig. 1) are matrices of the overall linear attenuation coefficient (Σ) for the individual pixels. ...
Bulk properties of two-phase systems comprising methane and liquid p-xylene were derived experimentally using neutron imaging and theoretically predicted using molecular dynamics (MD). The measured and predicted methane diffusivity in the liquid, Henry’s law constant, apparent molar volume, and surface tension compared well within the experimentally studied conditions (273.15 to 303.15 K, ≤ 100 bar). Since MD is a physical model, extrapolations of the two-phase systems properties were performed for a broader temperature range (260 to 400 K, ≤ 100 bar). Moreover, the species diffusivities in single phases formed by infinitely diluted p-xylene in methane were predicted under conditions relevant to the methane liquefaction (90 to 290 K, 50 bar). The predicted p-xylene diffusivity in the supercritical methane was one order of magnitude higher than that calculated using Wilke–Chang and He–Yu correlations. This study provides novel experimental and MD-simulated characteristics for this industrially relevant system, for which intensive freeze-out formation from the supercritical methane is predicted.
... The utility of neutron imaging for gas bubble detection is potentially of interest to development efforts for conventional all-liquid batteries, since these frequently employ foam current collectors -very similar in structure to the diaphragms investigated here -submerged in molten mixtures of halides [14]. [15] that are usually used to quantify the effect of scattered neutrons. c) Comparison between the potentials needed to charge cells with bubbles that totally (red) and partially (blue) cover their diaphragms, at 100mA and 400mA. ...
Electrochemical cells employing Sodium (Na) and Zinc (Zn) electrodes and a chloride salt electrolyte have been imaged by neutron radiography during cycling. The use of such abundant raw materials confers a very low energy-normalised cost to the Na-Zn system, but its operation requires them to be entirely molten, and therefore to be operated at 600 {\deg}C. To suppress the self-discharge that results from this all-molten configuration, porous ceramic diaphragms are used to partition the electrolyte and thereby impede the movement of the Zn2+ ions responsible towards the Na electrode. Neutron images reveal large gas bubbles trapped beneath these diaphragms, formed during the cell fabrication process due to the large volume change that accompanies melting/solidifying of the electrolyte. Cycling data confirm that these bubbles interfere with cell operation by substantially increasing ohmic resistance. They indicate the need for either a new diaphragm design, or a cell fabrication process that prevents their formation in the first instance.
... More recently, researchers from the Paul Scherrer Institute introduced a method to correct for systematic biases reported in Boillat et al [32] and Carminati et al [33]. The method relies on the use of an ordered array of black bodies (BBs) i.e. objects of known geometry with very high neutron absorption positioned before the sample with respect to the neutron beam. ...
... The same methodology can be extended to tomography where each angular projection is corrected in the same manner, prior to the reconstruction of the 3D attention fields. The method was shown to be highly effective in eliminating the artefacts caused by scattering [32][33][34]. Wissink et al [35] further improved the performance of this method in removing scattering artefacts by presenting a new method for the fabrication of the BB grids with an optimized design tailored to the particular experimental setup. ...
... The practical application of neutron imaging for measuring the concentrations and distribution/thickness of highly scattering elements (e.g. containing hydrogen) can lead to measurable deviations from true concentrations. This study has set out to address these deviations, in particular with water as a percolating medium, by applying a correction methodology first proposed in Boillat et al [32]. The effectiveness of the correction in ensuring accurate measurements during both 2D and 3D neutron imaging was investigated through a series of calibration acquisitions performed at the NeXT instrument (ILL, Grenoble, France), with the aim of providing a database and guidelines for future studies. ...
Neutron imaging has gained increasing attention in recent years. A notable domain is the in-situ study of flow and concentration of hydrogen-rich materials. This demands precise quantification of the evolving concentrations. Several implementations deviate from the ideal conditions that allow the direct applicability of the Beer–Lambert law to assess this concentration. The objective of this work is to address these deviations by applying both calibration and correction procedures to ensure and validate accurate quantitative measurements during 2D and 3D neutron imaging conducted at the cold neutron source at the NeXT instrument of the Institute Laue–Langevin, Grenoble, France. Linear attenuation coefficients and non-linear correlations have been proposed to measure the water concentration based on the sample-to-detector distance. Furthermore, the effectiveness of the black body grid correction method, introduced by Boillat et al (2018 Opt. Express 26 15769), is evaluated which accounts for spurious deviations arising from the scattering of neutrons from the sample and the surrounding environment. The applicability of the Beer–Lambert law without any data correction is found to be reasonable within limited equivalent thickness (e.g. below 4 mm of water) beyond which the correction algorithm proves highly effective in eliminating spurious effects. Notably, this correction method maintains its effectiveness even with transmissions below 1%. We examine here the impact of grid location and resolution with respect to sample heterogeneity.
... More information about the FISH neutron imaging station can be found elsewhere [33]. The scattering corrections have been performed using an established black bodies methodology [34,35]. ...
The steel–concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete’s opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to elucidate the mechanism of steel corrosion in concrete. The study demonstrates that the segmentation of the specimen components of relevance—steel, cementitious matrix, aggregates, voids, corrosion products—obtained through bimodal X-ray and neutron imaging is more reliable than that based on the results of each of the two techniques separately. Further, we suggest the combination of tomographic in-situ imaging with ex-situ SEM analysis of targeted sections, selected based on the segmented tomograms. These in-situ and ex-situ characterization techniques were applied to study localized corrosion in a very early stage under laboratory chloride-exposure conditions, using reinforced concrete cores retrieved from a concrete bridge. Several interesting observations were made. First, the acquired images revealed the formation of several corrosion sites close to each other. Second, the morphology of the corrosion pits was relatively shallow. Finally, only about half of the total 31 corrosion initiation spots were in close proximity to interfacial macroscopic air voids, and > 90% of the more than 160 interfacial macroscopic air voids were free from corrosion. The findings have implications for the mechanistic understanding of corrosion of steel in concrete and suggest that multimodal in-situ imaging is a valuable technique for further related studies.
Supplementary Information
The online version contains supplementary material available at 10.1617/s11527-024-02337-7.
... A comparison between the measured Δc Gd and data from the potentiostat is shown in Fig. 7. The gaps in the data were caused by an attempt to correct for scattering contributions with a black-body grid [38]. This correction was not used in the end ...
Neutron imaging was employed to track the uptake of Gd3+ ions by the sub 2 nm micropores of charged activated carbon cloth electrodes from an aqueous Gd(NO3)3 solution. The transmitted neutron intensity evinces the persistent presence of Gd3+ in the micropores during the discharge cycle, which is caused by the adsorption of oppositely charged ions. The charge efficiency of the activated carbon cloth system was determined by direct comparison with the imaged Gd3+ concentration changes, with which the influence of ion swapping and resistive losses on capacitive deionization cells can be ascertained.
... For this research, the images were processed using Kiptool, a multiplatform general purpose software to process 2D and 3D imaging data [31]. The importance of appropriate data correction for useful results (namely removing sample and set-up scattering by means of black bodies) has been highlighted in previous research [32,33] and was applied here. The steps for image acquisition were as follows: open beam (10 images), dark current (10 images) and black body images (10 images) were obtained for each series to perform the corresponding corrections (neutron beam intensity, camera noise, background scattering). ...
During capillary imbibition, there are changes in the pore structure that reduce the water ingress rate, leading to anomalous behaviour. However, the relation of those deformations with the C-S-H content is still unclear. We performed simultaneous measurements of external deformations and water ingress through neutron radiography. Cement pastes of water/cement of 0.4 and 0.6, using both Portland and white cement were tested after 1 year curing. Porosity and calcium silicate hydrate (C-S-H) content of the pastes were determined. Strain gauges were attached perpendicular and parallel to the water flow. Results indicate that the degree of internal restriction of the mix influences the shape of the water profile and that C-S-H deformations affect internal changes more than external. Water ingress visualisation indicated the lack of a sharp front during imbibition and the saturation degree variation at the position of the strain gauges. We propose a model to address the dynamic porosity.
... Various methods were also proposed in the literature to estimate the background and sample scattering, e.g., the Quantitative Neutron Imaging (QNI) approach based upon estimations of scattering point spread functions (PScF) [58,63]. In this study, a fully experimental method for correcting for both the background and the sample scattering [58,64] was used. According to this method, BB radiographs collected with and without specimens were needed. ...
The drying process has a prominent impact on the volume changes, crack propagation and durability of concrete structures. This study is to quantify the moisture distribution in real-time drying cement mortars. Mortar prisms with different water-to-cement ratios (w/c) and superabsorbent polymers (SAP) amounts were cut into slices and prepared with distinct lengths of cut notches. They were subjected to accelerated drying during neutron radiography measurements. In mortars with higher w/c, the coarser pores accelerate water transport and lead to more rapid drying. The large voids and the SAP in the bulk of the specimens are emptied well before the exposed surface starts to dry out. The presence of notches enhances drying. However, the moisture loss through the notches is less efficient than through the external surfaces. The competition between evaporation from the surfaces and moisture transport within the material, in both liquid and gas forms, governs the moisture distribution evolution.
... A CCD camera with a field of view of 15×15 cm capturing the capillary rise of liquid at a pixel size of 58 µm was used. Acquired images were scatter corrected using a black body bias correction procedure (Boillat et al., 2018), normalized, spot cleaned and filtered (Kaestner and Schulz, 2015). Attenuation coefficients of water and ethanol were derived from liquid of specific thickness between the edge of aluminium containers and the aluminium channel (see Fig. 1) filled with the respective liquid to initiate liquid imbibition. ...
... To further improve data accuracy, the SBKG was computed by interplating regions among 5mm-thick Cd black body (BB) stripes at the bottom, top, and top border of the FoV. The SBKG correction was applied to each framewise image [49]. To account for intensity fluctuations of the beam throughout the experiment, the area between the last set of BBs was defined as a non-changing region (open beam within the sample in the FoV). ...
