Neutron Imaging Techniques Research Articles

Quantitative Analysis of Active Lithium Loss and Degradation Mechanism in Temperature Accelerated Aging Process of Lithium‐Ion Batteries

AbstractQuantifying the aging mechanisms and their evolution patterns during battery aging is crucial for enabling renewable energy. Here, key factors are monitored and quantified affecting the aging processes of LiFePO4//graphite battery by a combination of mass spectrometry titration (MST), nuclear magnetic resonance (NMR), cryogenic transmission electron microscopy (cryo‐TEM), and neutron imaging techniques. Electrochemical analysis reveals the loss of active lithium inventory drives battery aging as temperature increases. It is shown that temperature‐induced accelerated decaying rate is 2.01 and 3.45 times at 45 and 65 °C compared with that of rate at 25 °C. Quantitative analysis indicates that irreversible formation of LixC6 (x ≤ 1), LiF, ROCO2Li, LiH, Li2C2, and RLi (R = CH3, C2H3, C2H5, C3H5) are the primary components of inactive lithium. The solid eletrolyte interpahse (SEI), excluding LixC6, constitutes over 70% of the total inactive lithium. With increasing cycles, SEI shows a decreasing proportion of LiF and an increasing proportion of ROCO2Li. The coupled effects of substantial SEI growth, increased irreversible formation of LixC6, and worsened conductivity result in the rapid aging of batteries tested at high temperatures. In this work, a research toolbox for the quantitative study of aging mechanisms in practical batterysystems has been provided.

Wavelength-Resolved Neutron Imaging Technique for Metal Material Analysis

Wavelength-Resolved Neutron Imaging Technique for Metal Material Analysis

Stochastic modeling of a neutron imaging center at the Brazilian Multipurpose Reactor

Neutron imaging is a non-destructive technique for analyzing a wide class of samples, such as archaeological or industrial material structures. In recent decades, technological advances have had a great impact on the neutron imaging technique, which has meant an evolution from simple radiographs using films (2D) to modern tomography systems with digital processing (3D). The 5 MW research nuclear reactor IEA-R1, which is located at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) in Brazil, possesses a neutron imaging instrument with 1.0×106n/cm2s in the sample position. IEA-R1 is over 60 years old and the future of neutron science in Brazil, including imaging, will be expanded to a new facility called the Brazilian Multipurpose Reactor (RMB, Portuguese acronym), which will be built soon. The new reactor will house a suite of instruments at the Neutron National Laboratory, including the neutron imaging facility, viz., Neinei. Inspired by recent author’s works, we model the Neinei instrument through stochastic Monte Carlo simulations. We investigate the sensitivity of the neutron imaging technique parameter (L/D ratio) with the neutron flux, and the results are compared to data from the Neutra (PSI), Antares (FRM II), BT2 (NIST) and DINGO (OPAL) instruments. The results are promising and provide avenues for future improvements.

STUDY OF FLUID MOTIONS AND THERMAL PERFORMANCE OF WATER AND ACETONE OSCILLATING HEAT PIPES USING NEUTRON IMAGING

Quantitative analysis of fluid motion in an oscillating heat pipe (OHP) is essential to better understand fluid flow and heat transfer mechanisms in an OHP. Two copper OHPs filled with water and acetone respectively were investigated by a neutron imaging technique to visualize the fluid motions in the OHP. Temperatures on the OHP surface were measured while neutron images were taken simultaneously. Algorithms to determine the degree of activity and the interface passing count were developed to analyze fluid motions quantitatively from the neutron images. Then, the degree of activity and the interface passing count were compared with temperatures. The results showed that there are patterns of temperature change before and after start-up of the oscillation motions. The acetone OHP showed better thermal performance at a similar heat input, while the water OHP showed better thermal performance at a similar degree of activity. Interfaces in the acetone OHP oscillate more frequently and travel further. Low latent heat at low heat input, low viscosity, and high thermal conductivity are preferred for the working fluid to achieve better thermal performance.

(Invited) Neutrons as a Powerful Tool for Better Understanding Electrochemistry on Various Length and Time Scales

Today, sophisticated methods are applied to gain a deeper understanding of processes in in-situ electrochemistry. There are few ways to study electrochemically relevant processes on different length and/or time scales without affecting the processes themselves. Probes that cover a sufficient volume of the sample non-destructively and are sensitive to the important charge carriers are in great demand. For such purposes, neutrons are an ideal candidate to perform this task because they have relatively high sensitivity to the light chemical elements, can distinguish neighboring elements of the periodic table, have a large beam cross-section, and possess high penetration depth for many types of materials.Therefore, many open questions are addressed to unique neutron techniques tailored to solve the open problems. This article gives an overview of some examples to show the advantages of using neutrons for special questions on different length and time scales [1]. For surface investigations of electrodes, the neutron depth profiling method (NDP) is suitable for characterizing the Li distribution up to the nano range [2]. Neutron diffraction is a powerful tool to better understand cylindrical cells at the atomic level, e.g. during the intercalation process [3]. Another strong field of neutrons is the monitoring of the wetting process during the electrolyte filling of prismatic hard case cells on the macroscopic length scale using the neutron imaging technique [4].

Time-of-flight polarization contrast neutron imaging for enhanced characterization of ferritic phase fractions in Fe-Mn-Si shape memory alloys

The determination of the amount and distribution of different phase fractions in additively manufactured shape memory alloys processed with laser powder bed fusion is crucial for understanding the correlation between processing parameters, microstructure, and mechanical properties. Neutron imaging techniques, such as Bragg edge imaging and polarization contrast neutron imaging (PNI), have been introduced to complement and overcome the limitations of traditional characterization methods, which are often destructive and limited to surface analyses and small-sized specimens. Bragg edge imaging can distinguish and quantify crystallographic phase fractions with spatial resolutions of a few tens of micrometers, while PNI is highly sensitive to crystallographic phases and is particularly suited for sub-percent phase fractions and in-situ, time-resolved, and tomographic analyses. In this work, we present a time-of-flight PNI method that enables simultaneous measurements of phase fractions.

Preface

The International Topical Meeting on Neutron Radiography Buenos Aires, 17th – 21th October 2022 The International Topical Meeting on Neutron Radiography (ITMNR-9) was held in Buenos Aires, Argentina, during October 17-21, 2022, sponsored by the Argentine Neutron Beam Laboratory (LAHN) of the Atomic Energy Commission of Argentina (CNEA). This was the 9th meeting in the ITMNR series coordinated by the International Society for Neutron Radiography (ISNR), initiated in 1990 in Pembroke, Canada. ITMNR-9 followed the meeting held in Beijing in 2016, and it was originally planned for 2020, but it was postponed due to the COVID-19 pandemic. After evaluating the possibility of organizing a virtual meeting, the ISNR board decided to postpone it to 2022, in order to hold a completely in-person meeting.ITMNR-9 was a forum for scientists working with neutron imaging techniques to share their experiences and expertise, through technical presentations describing the latest advances on neutron imaging applications to an ever-increasing number of problems in science and technology. A total of 99 participants from 17 countries including Argentina, Australia, Bolivia, Canada, Czech Republic, France, Germany, Hungary, Italy, Japan, South Africa, South Korea, Switzerland, Thailand, The Netherlands, United Kingdom and United States.The conference program included 58 oral presentations, with 2 Keynote and 9 Invited speakers, on topical sessions dedicated to applications in Nuclear Materials, Hydrogen & Processes, Materials Science & Engineering, Electrochemistry, and Miscellaneous Applications, which included contributions in Cultural Heritage, Paleontology, Earth sciences, Boron Neutron Capture Therapy and Education. Besides this, 6 technical oral sessions were dedicated to presentations of the latest advances in Neutron Imaging and Tomography Methods, Instrument Projects, and Novel Software and Detector systems. There were also 2 sessions dedicated to 47 posters presentations. Hence, after a week of intense activity, the ITMNR-9 participants returned home with many new ideas to continue with their projects.The conference organizing committee thanks the financial support of CNEA, the International Atomic Energy Agency, the Argentine Agency for Promotion of I+D+i, and Fundación Balseiro. It also greatly thanks the companies that sponsored the meeting: Swiss Neutronics, Phoenix, Tibidabo, Mirrotron, Tritec, Amsterdam Scientific Instruments and Volume Graphics, which sent representatives who had the opportunity to present their products and interact with the participants during the breaks.These proceedings present 37 peer-reviewed contributions to the ITMNR-9 meeting, divided in 7 areas: Material Science & Engineering, Nuclear Materials, Tomography Applications, Instruments, Software & Tomography, Methods & Analysis, and Instrumentation & Detectors.Aureliano TartaglioneFlorencia MalamudSergio SoriaJavier Santisteban ITMNR-9 Editorial Committee Picture of participants in the last day of the ITMNR-9 meeting.Picture of ITMNR-9 participants visit to the RA-10 multi-purpose reactor site in the outskirts of Buenos Aires, which will host the Argentine Neutron Beam Laboratory (LAHN) and the cold neutron imaging instrument ASTOR.List of Pictures, Scientific Program Committee and Organizing Committee are available in this pdf.

How can Neutron Imaging contribute to Heritage Science? An overview at the ISIS Neutron and Muon Source

Heritage Science HS spans a large variety of objects and materials, as well as anything that has historic, artistic, anthropological, and natural significance. This paper aims to bridge the gap between the physical and natural sciences and the humanities, and divulge neutron imaging techniques to a wider community. Here we give an introduction of the neutron imaging capabilities at the ISIS Neutron and Muon Source (UK), and a brief overview of some research activities in HS carried out at the facility in recent years, from neutron tomography to elemental imaging.

The VENUS imaging beamline at the Spallation Neutron Source: layout, expected performance and status of the construction project

Located at the Spallation Neutron Source, VENUS is an instrument optimized for wavelength-dependent neutron imaging techniques, namely Bragg edge and resonance imaging, across a broad range of neutron energies (from meV to hundreds of eV). The VENUS construction project started in Fall 2018, establishing a conceptual design of the major components and timeline for purchasing, testing, and installation. Completion of the VENUS instrument is anticipated late 2024. This instrument comprises components such as a set of boron carbide apertures designed for both thermal/cold and epithermal neutrons, a suite of choppers (T0 and single disks), beam collimators, and a cadmium filter. The time-of-flight detector at VENUS will be the micro-channel-plate Timepix detector and will be positioned 25 m away from the source. This manuscript describes the instrument general layout, explains the choice of the moderator, and specifies the VENUS key capabilities. It also provides the status of the construction project with installed components. Discussions about software development are also presented.

NEUTRA 2.0 – Upgrade of a pioneering instrument

After more than 25 years of successful operation of the thermal neutron imaging instrument NEUTRA, the NEUTRA 2.0 upgrade project has been approved. This upgrade implies a complete reconstruction of the instrument including a redesign of the shielding bunker. The inner usable area of the bunker will be increased thus creating ample space required in modern neutron imaging instruments for complex set-ups with bulk sample environments. Likewise, full access to an upstream measuring position, MP1, of the beamline will allow utilizing about half an order and one order of magnitude higher flux than at the currently accessible measurement positions MP2 and MP3, respectively. These measures will enable higher temporal resolution neutron imaging investigations and the use of the Neutron Microscope detector at NEUTRA. Together with more available space the higher flexibility of the interior arrangement will enable accommodating components for advanced neutron imaging techniques such as in-situ simultaneous bimodal neutron/x-ray imaging, time-of-flight imaging and thermal neutron grating interferometry. While the upgrade will enable advanced neutron imaging capabilities at NEUTRA 2.0, the instrumentation and techniques that were pioneered at NEUTRA in the past, like the XTRA option for in-line bimodal neutron/X-ray imaging and the NEURAP insert for neutron imaging of highly radioactive samples will be retained in the suite of the available modalities at the beamline.

Water liquid distribution in a bioinspired PEM fuel cell

Water management is a key factor in the operation of hydrogen fuel cells since its formation may lead to significant mass transport losses, oxygen diffusion limitation and membrane durability issues. In this work, the effect of different operating conditions on the liquid water distribution inside a 50 cm2 active area bio-inspired PEM fuel cell has been studied. Therefore, a set of experiments was designed varying cell pressure, the reactants relative humidity (anode and cathode), temperature, and cell current density. Liquid water distribution for each operating condition was determined using neutron imaging technique as it has been proved to be an excellent technique for this purpose, including quantitative analysis and water profiles in the different areas of the bio-inspired flow field. The results show that high relative humidity of the inlet gas flows, high pressure, low temperatures and low current density favor the accumulation of water in the flow field channels and GDL. Specifically, water accumulates preferentially in the anode side that make contact with the low part of the cathode foams inserted in the flow field, instead of blocking the closest area to the gases outlets points. This is due to permeation from the cathode foams to the anode side.

Neutron imaging based vapor fraction measurements in an inductively heated boiling packed bed

During a loss of coolant accident, the formation of porous heat-generating debris bed causes concerns with the further progression of accident through inadequate removal of the decay heat. The sustainable heat removal or cooling of the porous debris bed using emergency coolant water poses limitations on the cooling mechanisms by imposing a maximum removable heat flux, also known as the dryout heat flux. Modeling debris bed cooling and the dryout heat flux requires the use of parameters that are non-linear functions of the vapor fraction in the two-phase flow. These models need high resolution vapor fraction data for validation, which is currently lacking in literature. This paper presents first of a kind high-resolution vapor fraction measurements in an inductively heated debris bed using a non-optical and non-intrusive neutron imaging technique. The neutron beam from TRIGA Mark II reactor at Kansas State University was used to image the packed bed test section and gather vapor fraction data. The vapor fraction measurements are presented for a range of heat fluxes up to the limiting dryout heat flux. Images showing the formation of a dryout zone for heat fluxes higher than the limiting dryout heat flux are also presented. The measured vapor fractions are compared with predictions from the classical 1D Lipinski model. The mean absolute deviation between the model predictions and the measured vapor fractions is found to be less than 10%, providing the first validation of the classical 1D Lipinski model.

Monte Carlo simulation-aided design of a thermal neutron generator system from 241Am-Be isotopic sources

Collimated thermal neutron beams are obtained from neutron extraction channels in nuclear reactors for various applications in research and technology, such as neutron imaging techniques (neutron radiography, neutron radioscopy, neutron tomography, and neutron-based autoradiography). Practical setups for neutron radiography using ion beams from particle accelerators and radioisotopic sources of fast neutrons have been also developed. However, only radioisotopic sources enable autonomous and transportable thermalization systems that can produce thermal neutron collimated beams. This work presents the performance results for a prototype of a compact system that generates a collimated beam of thermal neutrons using low-activity isotopic 241Am-Be sources. It was designed with the aid of Monte Carlo simulation using the PHITS v 3.17 program. Experimental measurements of the fluence of the neutron beam produced by the built prototype showed good agreement with the simulated values by the Monte Carlo method.

From superhydrophilicity to superhydrophobicity: high-resolution neutron imaging and modeling of water imbibition through porous surfaces treated with engineered nano-coatings

This paper reports on a superhydrophilic to superhydrophobic transformation of TiO2 nanoparticles doped zinc phosphate coating systems when a hydrophobic agent is applied. The objective of the reported research was to demonstrate the feasibility of a neutron imaging technique for evaluating the performance of the proposed nano-coating system and reveal the differences in water ingress mechanisms which are specific to plain, superhydrophilic, overhydrophobic, and superhydrophobic specimens. The engineered nano-coatings were designed to improve hydrophobic response with inducing the required roughness pattern and introducing the photocatalytic performance. The effectiveness of the coatings was assessed using high-resolution neutron imaging (HR-NI), SEM, CLSM, and XRD techniques. High-resolution neutron imaging revealed that the superhydrophobic coating effectively prevents water ingress into the porous ceramic substrate, whereas water imbibition was observed for superhydrophilic coating during the test duration. The moisture transport kinetics was modeled based on the Richards equation for plain ceramic and superhydrophilic specimens using obtained penetration depth values from HR-NI. SEM, CLSM, and XRD studies confirm the desired TiO2-doped zinc phosphate coatings with increased surface roughness, photocatalytic reactivity, and chemical bonding. The research results demonstrated that a two-layer superhydrophobic system is capable of creating effective water barriers on the surface with contact angles of 153°, which remained effective even after surface damage.

Neutron Imaging of Al6061 Prepared by Solid-State Friction Stir Additive Manufacturing

Solid-state Friction Stir Additive Manufacturing has recently gained attention as a result of its capacity to fabricate large-scale parts while preserving the mechanical properties of the feedstock material. However, the correlation between the quality of layer-by-layer bonding of the deposited metal and processing parameters has remained unknown. Neutron imaging techniques, with 90% total transmission per cm, are employed for Al6061 parts fabricated by MELD® Technology as a non-destructive evaluation approach for the first time to investigate the layer-by-layer structure of a stadium-shaped ingot in different sections. The post-processed results show the fabricated parts with an optimized set of processing parameters are void-free. However, the hydrocarbon-based feedstock lubricant segregates between the layers, which consequently may lead to non-uniform weaker mechanical properties along the build direction and stimulate crack initiation during mechanical loading. The tensile test results show 14% lower strain-to-failure values in alleged contaminated areas in transmission imaging results. Additionally, layer bonding is significantly impacted by hot-on-hot and hot-on-cold layer deposition schemes, especially for larger layer thicknesses.

Experimental studies on nuclide identification radiography with a CMOS camera at Back-n white neutron source

As an advanced neutron imaging technique, nuclide identification radiography (NIR) using neutron resonance or cross-section differences is a promising technique for investigating nuclide spatial distribution inside samples. Since its proposal in 1980s, this technique has advanced very slowly due to many limitations in neutron source, detector efficiency and resolution. At the Back-n white neutron source at China Spallation Neutron Source, the NIR technique based on gated CMOS camera has been developed by taking the advantage of very high neutron flux and suitable energy spectrum of the Back-n neutron beam. Heavy nuclides, medium-mass nuclides and light nuclides have been tested to validate the effectiveness of the technique, covering the resonances from eV to MeV regions. Typical heavy elements such as Ag, In, Au and W, medium-mass elements such Al, Fe and Cu, light elements such as O have been used for experiments. The study shows, that nuclides with resonance peaks in the eV region can be easily identified, while the nuclides with resonance peaks above keV are difficult to be identified individually due to their narrow resonance peaks affecting the signal-to-noise ratio in the camera measurements. However, these nuclides can be differentiated for imaging by using adjacent multiple resonance peaks or distinct cross-section differences over wider energy ranges. The experiments are perhaps the first ones that demonstrate the NIR technique for the identification and imaging of nuclides with cross-section resonances covering from eV to several MeV.

Dual-energy fast neutron imaging using tunable short-pulse laser-driven sources.

A novel dual-energy fast neutron imaging technique is presented using short-pulse laser-driven neutron sources to leverage their inherent adaptive spectral control to enable 3D volume segmentation and reconstruction. Laser-accelerated ion beams incident onto secondary targets create directional, broadband, MeV-class neutrons. Synthetic radiographs are produced of multi-material objects using ion and neutron spectra derived from analytic and numerical models. It is demonstrated that neutron images generated from small changes to the neutron spectra, controlled by altering the initial laser conditions, are sufficient to isolate materials with differing attenuation coefficients. This is first demonstrated using a simplistic combinatorial isolation method and then by employing more advanced reconstruction algorithms to reduce artifacts and generate a segmentation volume of the constituent materials.

Quantification of Hydrogen in Metals Applying Neutron Imaging Techniques

Quantification of Hydrogen in Metals Applying Neutron Imaging Techniques

High-speed 4D neutron computed tomography for quantifying water dynamics in polymer electrolyte fuel cells

In recent years, low-temperature polymer electrolyte fuel cells have become an increasingly important pillar in a zero-carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. The performance improvement is a particular focus of research and engineering roadmaps, with water management being one of the major areas of interest for development. Appropriate characterisation tools for mapping the evolution, motion and removal of water are of high importance to tackle shortcomings. This article demonstrates the development of a 4D high-speed neutron imaging technique, which enables a quantitative analysis of the local water evolution. 4D visualisation allows the time-resolved studies of droplet formation in the flow fields and water quantification in various cell parts. Performance parameters for water management are identified that offer a method of cell classification, which will, in turn, support computer modelling and the engineering of next-generation flow field designs.

A study of the influence of novel scan strategies on residual stress and microstructure of L-shaped LPBF IN718 samples

Process parameters in laser-based powder bed fusion (LBPF) play a vital role in the part quality. In the current study, the influence of different novel scan strategies on residual stress, porosities, microstructure, and crystallographic texture has been investigated for complex L-shape parts made from nickel-based superalloy Inconel 718 (IN718). Four different novel scanning strategies representing total fill, re-melting, and two different sectional scanning strategies, were investigated using neutron diffraction, neutron imaging, and scanning electron microscopy techniques. These results were compared with the corresponding results for an L-shape sample printed with the conventional strategy used for achieving high density and more uniform crystallographic texture. Among these investigated novel strategies, the re-melting strategy yielded approximately a 25% reduction in surface residual stress in comparison to the reference sample. The other two sectional scanning strategies revealed porosities at the interfaces of the sections and due to these lower levels of residual stress were also observed. Also, variation in crystallographic texture was observed with different scan strategies.