Nano-computed Tomography Research Articles

3D microfracture network and seepage characteristics of low-volatility bituminous coal based on nano-CT

Microfractures in the coal reservoir contribute greatly to the exploitation of coalbed methane. In this study, the 3D microfracture structure of low-volatility bituminous coal is characterized by using nano-computed tomography (nano-CT), and the seepage characteristic of the single-phase water flow in the microfracture network is simulated by Avizo and Comsol. The result shows that the low-volatility bituminous coal HB02 has significant structural heterogeneity and is dominated by type D microfractures on the nanoscale. By pore network modeling analysis, the connected microfracture network consists of 4945 pore bodies and 7194 pore throats, and the connected porosity is 1.96%. Additionally, as the pore diameter increases, the coordination number of the connected pores increases, but the shape factor decreases, indicating that larger pores have a better permeability and much rougher surface. Seepage simulation shows that the permeability of the microfracture network are strong anisotropic, and the microfracture structure has strong controlling effect on seepage. The permeability value in the horizontal (X-axis and Y-axis) direction is higher than that in the vertical (Z-axis) direction.

Additive manufacturing of high loading concentration zirconia using high-speed drop-on-demand material jetting

Zirconia-based ceramic has generated considerable interest in specialist structural/engineering ceramics. Among current available additive manufacturing methods for fabrication of ceramic components, the conventional material jetting systems are able to create local deposition of thin layers, dense green bodies, and complex shapes. However, this method is mainly limited to low viscous ceramic inks (mostly in the range of 20–40 mPa/s) with often less than 25 vol% solid loading which has restricted the widespread adoption of this technique. In this work, we employed a novel in-house developed hybrid drop-on-demand material jetting system (DODMJ) to deposit a highly viscous paste (up to 72 wt% solid content, a viscosity of 2100 mPa/s) of yttria-stabilized-zirconia (YSZ), with approximately 20 times higher speed than the current material jetting methods, for the first time. For this study, tetragonal zirconia polycrystal containing 8 wt% Y2O3 (5Y-TPZ), which is commonly used to produce dental restorations by subtractive manufacturing, was utilized. The printability of several visible light–curable zirconia pastes was studied in terms of the rheology, paste composition, solid content, and printing parameters. The density and porosity measurements as well as a two-stage sintering process to achieve fully dense and crack-free parts were carried out. The microstructure and internal features of the printed parts were also explored by X-ray nano-computed tomography (CT) scanning and scanning electron microscopy (SEM). In this work, standard test methods were also utilized to study the Vickers hardness and fracture toughness of the sintered 5Y-TPZ parts for the first time. The results showed that specimens produced with the paste containing 62.3 wt% solid loading yielded a relative density of 99.5% and presented an average fracture toughness and micro-hardness of 5.62 MPa/m0.5 and 1516 HV, respectively. Overall, the outcomes presented in this work confirmed that the novel DODMJ technique adopted for this study has great potential in the development of a feasible, high-speed, and cost-effective manufacturing system to produce zirconia ceramic parts with adequate mechanical and structural properties that meet the demanding requirements for various applications such as dental crowns restoration.

Making Fe-Si-B amorphous powders as an effective catalyst for dye degradation by high-energy ultrasonic vibration

Synthetic dyes have caused serious ecological and environmental threats in our daily lives. Effective and inexpensive dye-degradation methods are desperately perused for decades. In this work, ultrasonic-vibration treatment is found as an effective approach that can dramatically improve the degradation performance of industrial Fe78Si9B13 amorphous powders towards methylene blue. As demonstrated by synchrotron X-ray nano-computed tomography and scanning electron microscope combined with X-ray photoelectron spectroscopy, the micro-channels on the surface or inside of Fe78Si9B13 particles offer a shortcut for fast mass transfer and supply plenty of reactive sites with low density and high energy due to the structural rejuvenation after ultrasonic vibration. It leads to the reduction of the reaction activation energy of degradation under the pseudo-first-order kinetic model and an exceptional decomposition capacity. Our work not only extremely drives down the current costs of wastewater treatments, but also provides a promising approach for tuning the effectivity of alloying catalysts via manipulating the potential energy state of metallic glasses based on the high-frequency mechanical vibration technique.

Impacts of operational parameters on the morphological structure and uranium bioleaching performance of bio-ore pellets in one-step bioleaching by Aspergillus niger

The impacts of operational parameters on the morphological structure and uranium bioleaching performance of the bio-ore pellets obtained in one-step bioleaching by Aspergillus niger were investigated. The uranium recovery of over 80% was achieved under the optimized conditions. Furthermore, the morphological changes of ore particles before and after bioleaching were characterized by scanning electron microscope. The results showed more reactive surfaces were generated by the wrap and adherence of mycelia and the corrosion of metabolites. Finally, the three-dimensional structures of bio-ore pellets were detected by X-ray full-field nano-computed tomography. The results showed the bio-ore pellet structures could be classified into one type of bilayer structure and two types of three-layer structures. The bio-ore pellets with bilayer structure that the mycelia and ore particles were evenly distributed presented preferable uranium bioleaching capability.

Self-Standing and Binder Free Cathode: Facile and Scalable Fabrication with MWCNT for Recyclable and Sustainable Application of Li-O2 Battery

It’s well known that the Li-O2 battery can achieve theoretically1 ten times as much energy density (5200Wh/kg) as Li-ion battery but often limited in reality on the capacity and the cycling. In this system, the carbon cathode provides merely a framework for the lithium peroxide deposition but is not an active material. The dissolved oxygen in the electrolyte is indeed the active material. In other words, the capacity depends on the porosity and the framework architecture. Our previous X-ray tomographic study2 pointed out that a sparse structure is needed to increase the capacity by impeding the pore clogging and oxygen depletion. The conventional fabrication by evaporating the solvent of a slurry can only provide ~20% porosity which is insignificant. Other templating fabrications3,4 are often reported in the literature, but procedures are tedious. To fabricate sparse and self-standing cathode with the multi-wall carbon nanotubes (MWCNTs), we propose a facile and scalable two steps Buchner approach.The MWCNTs are firstly dispersed in a solvent by sonification. A direct filtration with the separator of a battery can omit a stacking step in the battery assembling (Figure 1). Preceded by a drying process, the cathode is then investigated in the overall cell for electrochemical performance and cyclability. The data of X-ray nano-Computed Tomography acquired in APS synchrotron (ID32) shows that the material is highly porous and the pores are fully filled with the discharge product Li2O2 which conducts to a capacity improvement. Impedance is utilized alongside with tomography data for a complementary understanding of the dominance between lithium ion and oxygen depletion during the discharge.The self-standing and flexible properties of such cathode even without polymer binder are beneficial for industrial application. We demonstrate the possibility of loading other particles with our approach. A gain of specific surface area for the deposition of lithium peroxide can be obtained with the loading at a price of the mechanical property detriment. Thereby, several percentages of loading are studied to obtain the best trade-off. Besides, bared carbon-nanotube framework with loaded particle trends to loss the structural stability. A sandwich-like structure is hence investigated for the efficiency of the particle confinement.Finally, our approach is highly eco-friendly. The solvent for nanotube dispersion can be reused after the filtration. And the aged cathode is entirely recyclable by proceeding a low-cost acid retreatment then ultrasonic re-dispersion. The impact of the recycling in terms of electrochemistry and pressure evolution have also been studied.Figure 1. (a) image of the homogeneous laid out cathode in a Buchner (b) SEM image of the intersection separator and cathode and (c) sandwich structure (d) electrochemical curve with pressure evolution Reference:(1) Abraham, K. M. A Polymer Electrolyte-Based Rechargeable Lithium/Oxygen Battery. Journal of The Electrochemical Society 1996, 143 (1), 1. https://doi.org/10.1149/1.1836378.(2) Su, Z.; De Andrade, V.; Cretu, S.; Yin, Y.; Wojcik, Michael. J.; Franco, Alejandro. A.; Demortière, A. X-Ray Nano-Computed Tomography in Zernike Phase Contrast for Study 3D Morphology of Li-O2 Battery Electrode. ACS Applied Energy Materials (submitted)(3) Cho, S. A.; Jang, Y. J.; Lim, H.-D.; Lee, J.-E.; Jang, Y. H.; Nguyen, T.-T. H.; Mota, F. M.; Fenning, D. P.; Kang, K.; Shao-Horn, Y.; et al. Hierarchical Porous Carbonized Co 3 O 4 Inverse Opals via Combined Block Copolymer and Colloid Templating as Bifunctional Electrocatalysts in Li-O 2 Battery. Advanced Energy Materials 2017, 7 (21), 1700391. https://doi.org/10.1002/aenm.201700391.(4) Gaya, C.; Yin, Y.; Torayev, A.; Mammeri, Y.; Franco, A. A. Investigation of Bi-Porous Electrodes for Lithium Oxygen Batteries. Electrochimica Acta 2018, 279, 118–127. https://doi.org/10.1016/j.electacta.2018.05.056. Figure 1

3D microstructure design of lithium-ion battery electrodes assisted by X-ray nano-computed tomography and modelling

Driving range and fast charge capability of electric vehicles are heavily dependent on the 3D microstructure of lithium-ion batteries (LiBs) and substantial fundamental research is required to optimise electrode design for specific operating conditions. Here we have developed a full microstructure-resolved 3D model using a novel X-ray nano-computed tomography (CT) dual-scan superimposition technique that captures features of the carbon-binder domain. This elucidates how LiB performance is markedly affected by microstructural heterogeneities, particularly under high rate conditions. The elongated shape and wide size distribution of the active particles not only affect the lithium-ion transport but also lead to a heterogeneous current distribution and non-uniform lithiation between particles and along the through-thickness direction. Building on these insights, we propose and compare potential graded-microstructure designs for next-generation battery electrodes. To guide manufacturing of electrode architectures, in-situ X-ray CT is shown to reliably reveal the porosity and tortuosity changes with incremental calendering steps.

Revisiting Silica Networks by Small-angle Neutron Scattering and Synchrotron Radiation X-ray Imaging Techniques

The silicone rubber composites present remarkable mechanical properties due to the double network structure constructed with molecular network of matrix and filler network of silica. Nevertheless, the filler network structure and corresponding reinforcement mechanism are still under debate and need to be further probed with the aid of applicative advanced analysis techniques. Herein, small-angle neutron scattering (SANS) and synchrotron radiation X-ray nano-computed tomography (Nano-CT) techniques are employed to explore the evolution of filler networks of fumed, precipitated and sol-gel silica, respectively. Our studying results reveal the formation of filler network constructed by the interconnecting of branched silica aggregates. And the silica with highly associated structure, pertaining to amorphous morphology, small size, and large surface area, presents short distance and effective molecular chain bridge between aggregates, thus forming strong and steady filler networks. This work would provide deep-seated revisiting of filler networks and corresponding reinforcement mechanism and offer guidance for optimizing the mechanical properties of silicone rubber.

Tetralin and Decalin H-Donor Effect on Catalytic Upgrading of Heavy Oil Inductively Heated with Steel Balls

The Toe-to-Heel Air Injection (THAI) combined with catalytic upgrading process in situ (CAPRI) has demonstrated it can simultaneously extract and upgrade heavy oil in situ. This paper reports the investigation of augmenting temperature deficit and suppressing coke formation in the CAPRI section through the incorporation of induction heating and H-donor solvents. An induction-heated catalytic reactor was designed and developed, heated with steel balls in a mixed bed of NiMo/Al2O3 catalyst (66% v/v) to 425 °C temperature, 15 bar pressure and 0.75 h−1 LHSV (Liquid Hourly Space Velocity). The catalyst surface area, pore volume and pore size distribution were determined by using nitrogen adsorption–desorption, while the location of coke deposits within the microstructure of the pelleted spent catalyst was analyzed with X-ray nano-Computed Tomography (X-ray nano-CT). Findings showed that induction heating improved the catalyst performance, resulting in a 2.2° American Petroleum Institute (API) gravity increase of the upgraded oil over that achieved with the conventional heating method. The increment in API gravity and viscosity reduction in the upgraded oils with nitrogen gas only, N2 and H-donor solvents, and hydrogen gas environments can be summarized as follows: decalin > H2 gas >= tetralin > N2 gas. Meanwhile, the improvement in naphtha fraction, middle distillate fractions and suppression of coke formation are as follows: decalin > H2 gas > tetralin > N2 gas. The X-ray nano-CT of the spent catalyst revealed that the pellet suffers deactivation due to coke deposit at the external surface and pore-mouth blockage, signifying underutilization of the catalyst interior surface area.

Comparison of calcified cartilage between normal and osteoarthritis human knee specimens based on 3D synchrotron nano-computed tomography images with phase contrast: a preliminary study

Purpose: The articular cartilage is organized into distinct regions, from superficial to deep zones and calcified cartilage. In osteoarthritis (OA), a thickening of the calcified cartilage zone was observed based on a histological approach. The interaction (crosstalk) between cartilage and subchondral bone is thought to be a central feature of the OA process. A better understanding of this process will help to improve therapeutic strategies: to target bone or cartilage or modify the crosstalk? A preliminary study performed in our group indicates that there are thicker subchondral plates with lower porosity in case of OA compared to controls subjects but the differences were not significant, due to a lack of precision of conventional micro-computed tomography performed with a voxel size of 10 μm, too coarse given the small size of pores.

Plate-nanolattices at the theoretical limit of stiffness and strength

Though beam-based lattices have dominated mechanical metamaterials for the past two decades, low structural efficiency limits their performance to fractions of the Hashin-Shtrikman and Suquet upper bounds, i.e. the theoretical stiffness and strength limits of any isotropic cellular topology, respectively. While plate-based designs are predicted to reach the upper bounds, experimental verification has remained elusive due to significant manufacturing challenges. Here, we present a new class of nanolattices, constructed from closed-cell plate-architectures. Carbon plate-nanolattices are fabricated via two-photon lithography and pyrolysis and shown to reach the Hashin-Shtrikman and Suquet upper bounds, via in situ mechanical compression, nano-computed tomography and micro-Raman spectroscopy. Demonstrating specific strengths surpassing those of bulk diamond and average performance improvements up to 639% over the best beam-nanolattices, this study provides detailed experimental evidence of plate architectures as a superior mechanical metamaterial topology.

Comparison of structure and composition of a fossil Champsosaurus vertebra with modern Crocodylidae vertebrae: A multi-instrumental approach

Information on the adaptation of bone structures during evolution is rare since histological data are limited. Micro- and nano-computed tomography of a fossilized vertebra from Champsosaurus sp., which has an estimated age of 70–73 million years, revealed lower porosity and higher bone density compared to modern Crocodylidae vertebrae. Mid-infrared reflectance and energy dispersive X-ray mapping excluded a petrification process, and demonstrated a typical carbonate apatite distribution, confirming histology in light- and electron microscopy of the preserved vertebra. As a consequence of this evolutionary process, the two vertebrae of modern Crocodylidae show reduced overall stiffness in the finite element analysis simulation compared to the fossilized Champsosaurus sp. vertebra, with predominant stiffness along the longitudinal z-axes.

Effect of laminae development on pore structure in the lower third member of the Shahejie Shale, Zhanhua Sag, Eastern China

Similar to mineral composition and organic geochemical features, laminae development significantly influences pore structure. Taking the lower third member of the Shahejie Shale (Es3l), Zhanhua Sag, Eastern China as the research object, we introduced various methods to analyze the influence of laminae development on pore structure, including thin section observations, field emission scanning electron microscopy, gas adsorption, high-pressure mercury injection, nano-computed tomography (CT), quantitative evaluation of minerals by scanning electron microscopy, and spontaneous imbibition. We draw the conclusions that various minerals present a mixed distribution in nonlaminated shale, whereas laminated shale is characterized by alternating bright and dark laminae. Dark laminae comprise clay and quartz, whereas bright laminae consist of calcite. Microfractures are abundant at the edges of the bright and dark laminae. Nonlaminated shale possesses a pore volume (PV) of [Formula: see text] and a specific surface area (SSA) of [Formula: see text]. In contrast, laminated shale has a PV of [Formula: see text] and an SSA of [Formula: see text] with good reservoir property. Pores, especially macropores and micropores, are much more developed in laminated shale than in nonlaminated shale. Interconnected pores in sheet form are extremely developed in laminated shale, whereas most of the interconnected pores in nonlaminated shale are distributed in isolated spherical and tubular forms. Because of the abundant interconnected pores and throats, laminated shale presents good connectivity. The slopes of the spontaneous imbibition curves in the first and second stages for laminated shale are greater than those for nonlaminated shale. Laminae development could provide microfractures as dominant pathways for fluid migration as well as promote the interconnection of pores, greatly increasing the connectivity of shale reservoirs.

纳米计算机断层扫描成像技术进展综述

纳米计算机断层扫描成像技术进展综述

In situ observation of void evolution in 1,3,5-triamino-2,4,6-trinitrobenzene under compression by synchrotron radiation X-ray nano-computed tomography.

The formation and development of voids in 1,3,5-triamino-2,4,6-trinitrobenzene crystals under compression were characterized in situ by X-ray nano-computed tomography. Benefiting from high spatial resolution (30 nm) and excellent imaging contrast, the X-ray nano-computed tomography images revealed the presence of a small fraction of inhomogeneous structures in the original crystal (volume ratio ∼1.2%). Such an inhomogeneity acts as a nucleation of voids and produces stress concentration during compression, which leads to continuous growth of the voids under loading. Meanwhile, the results further reveal that the developing voids are not isotropic: voids with higher surface roughness and irregular structures are easier to break and form new micro-voids. These new voids with higher irregular structures are weaker and easier to break into smaller ones compared with the originals, leading to the development of voids along these weak zones. Finally large voids form. The experiments allow direct investigation of void formation and development, which helps in studying the mechanisms of void development and energetic materials deterioration during manufacturing and transporting.

The Imaging Resolution and Knudsen Effect on the Mass Transport of Shale Gas Assisted by Multi-length Scale X-Ray Computed Tomography

The spatial resolution of 3D imaging techniques is often balanced by the achievable field of view. Since pore size in shales spans more than two orders of magnitude, a compromise between representativeness and accuracy of the 3D reconstructed shale microstructure is needed. In this study, we characterise the effect of imaging resolution on the microstructural and mass transport characteristics of shales using micro and nano-computed tomography. 3D mass transport simulation using continuum and numerical physics respectively is also compared to highlight the significance of the Knudsen effect on the reconstructed solid surface. The result shows that porosity measured by micro-CT is 25% lower than nano-CT, resulting in an overestimated pore size distribution and underestimated pore connectivity. This leads to a higher simulated intrinsic permeability. An overestimated diffusive flux and underestimated permeability are obtained from the continuum mass transport simulation compared to the numerical ones when the molecular-wall collision is accounted, evidenced by the large deviation of the measured Knudsen tortuosity factor and permeability correction factor. This study is believed to provide new knowledge in understanding the importance of imaging resolution and gas flow physics on mass transport in porous media.

Preparation and evaluation of microfluidic magnetic alginate microparticles for magnetically templated hydrogels

Our aim is to develop a hydrogel-based scaffold containing porous microchannels that mimic complex tissue microarchitecture and provide physical cues to guide cell growth for scalable, cost-effective tissue repair. These hydrogels are patterned through the novel process of magnetic templating where magnetic alginate microparticles (MAMs) are dispersed in a hydrogel precursor and aligned in a magnetic field before hydrogel crosslinking and subsequent MAM degradation, leaving behind an aligned, porous architecture. Here, a protocol for fabricating uniform MAMs using microfluidics was developed for improved reproducibility and tunability of templated microarchitecture. Through iron quantification, we find that this approach allows control over magnetic iron oxide loading of the MAMs. Using Brownian dynamics simulations and nano-computed tomography of templated hydrogels to examine MAM chain length and alignment, we find agreement between simulated and measured areal densities of MAM chains. Oscillatory rheology and stress relaxation experiments demonstrate that magnetically templated microchannels alter bulk hydrogel mechanical properties. Finally, in vitro studies where rat Schwann cells were cultured on templated hydrogels to model peripheral nerve injury repair demonstrate their propensity for providing cell guidance along the length of the channels. Our results show promise for a micro-structured biomaterial that could aid in tissue repair applications.

New Insights into the Three-Dimensional Anatomy of the Facial Mimetic Muscles Related to the Nasolabial Fold: An Iodine Staining Technique Based on Nano-computed Tomography.

This study aimed to introduce a novel approach to study the facial mimetic muscles (FMMs) in relation to the nasolabial fold (NLF) and realize the visualization of complex three-dimensional (3D) structures and spatial relationships of the FMMs. Nano-computed tomography (nano-CT) and iodine staining techniques were used to obtain the two-dimensional (2D) radiographs of the FMMs. Materialise Mimics software was then used to reconstruct the 3D model of the FMMs. The zygomaticus major muscle (ZMM) was divided into trunk fibers and branch fibers. The trunk fibers of the ZMM were subdivided into branch fibers layer-by-layer. Adipose tissue in the cheek was not a mass of unorganized fat. It was separated and fixed by branch fibers. Moreover, the trunk fibers of the ZMM were directly connected to the levator anguli oris (LAO), not the skin. On the contrary, the ZMM was connected to the skin by its subdivided branch fibers indirectly. The muscle fibers in the modiolus were organized, rather than disorganized. In other words, the terminal of the trunk fibers of the ZMM was located in the LAO. Moreover, the terminal of the trunk fibers of the LAO was located at the terminal of the trunk fibers of the musculus depressor anguli oris at the corner of the mouth. Furthermore, the levator labii superioris alaeque nasi was not directly connected to the orbicularis oris muscle. It was connected to the combination of the LLS and the rhinaeus. Although nano-CT has many disadvantages, it enabled the 3D anatomical study of the FMMs in relation to the NLF when combined with iodine staining. We imported the 2D images obtained by nano-CT scanning into the Mimics software, successfully reconstructed the FMMs, and finally obtained images of complex 3D structures of the FMMs. The shapes, positions, and 3D spatial relationships of the FMMs were clearly visualized. The novel insights into the 3D anatomy of the FMMs may help understand the formation of the NLF. Finally, the results of this study may help improve the rejuvenation surgery of the NLF soon. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Ovariectomy increases RANKL protein expression in bone marrow adipocytes of C3H/HeJ mice.

Estrogen deficiency induces bone loss by increasing bone resorption, in part through upregulation of receptor activator of nuclear factor-κB ligand (RANKL). RANKL is secreted by osteoblasts and osteocytes, but more recently bone marrow (pre)adipocytes have also been shown to express RANKL. Estrogen deficiency increases bone marrow adipose tissue (BMAT). The aim of this study was to determine the effect of ovariectomy (OVX) on RANKL protein expression by bone marrow adipocytes in C3H/HeJ mice. Fourteen-week-old female C3H/HeJ mice (n = 20) were randomized to sham surgery (Sham) or OVX. After 4 wk animals were euthanized. BMAT volume fraction (BMAT volume/marrow volume) was quantified by polyoxometalate-based contrast-enhanced nano-computed tomography. The percentage of RANKL-positive bone marrow adipocytes (RANKL-positive bone marrow adipocytes/total adipocytes) and the percentage of RANKL-positive osteoblasts covering the bone surface (bone surface covered in RANKL-positive osteoblasts/total bone surface) were quantified in the distal metaphysis of immunohistochemically stained sections of the left femur. The effects of OVX were analyzed by Student's t test or Mann-Whitney U test. RANKL was detected in osteoblasts, osteocytes, and bone marrow adipocytes. OVX significantly increased mean percentage of RANKL-positive bone marrow adipocytes [mean (SD): Sham 42 (18)%; OVX 64 (12)%; P = 0.029] as well as BMAT volume/marrow volume [median (interquartile range): Sham 1.4 (4.9)%; OVX 7.2 (7.3)%; P = 0.008] compared with Sham. We show that OVX increased both the percentage of RANKL-positive bone marrow adipocytes and the total BMAT volume fraction in C3H/HeJ mice. Therefore, RANKL produced by bone marrow adipocytes could be an important contributor to OVX-induced bone loss in C3H/HeJ mice.

Rock properties from micro-CT images: Digital rock transforms for resolution, pore volume, and field of view

Digital Rock Physics is a promising approach for achieving more, cheaper, and faster rock property characterization of digital images of rock samples. To successfully deliver on this potential, we must correctly interpret the digitally derived properties in the context of the limitations imposed by imaging constraints. To this end, we show that a combination of limited image resolution, a biased segmentation of images with coarse resolution, and a finite field of view of images, generated by the present micro-Computed Tomography (micro-CT) technology, leads to systematic underestimation of porosity (down to a factor of 0.5) and overestimation of permeability (up to a factor of 10) calculated using the Digital Rock Physics (DRP). We demonstrate these imaging limitations can be overcome by identifying good measures of image resolution and representative elementary volume and applying appropriate transforms. These transforms expand the operating envelop of DRP. Transforms for finite image resolution and limited field of view can be estimated directly from the micro-CT images. However, implementation of transforms related to errors in image segmentation require either a higher resolution image (e.g., nano-computed tomography, scanning electron microscopy) or laboratory measured constraints (Mercury injection capillary pressure, NMR porosity). Additionally, we suggest how insights from these transforms can be used to define operating envelopes and optimize imaging resolution and field of view to achieve more reliable results from digital rock characterization and simulations.

(Invited) Latest Advances in 2D and 3D Microstructural Characterization of Fuel Cell Components

Fuel cells are complex systems whose performance and degradation depend on a number of factors spreading over multiple scales. At the lowest spatial scale are nano-sized Pt-group or Pt-group-metal-free (PGM-free) catalysts, various types of catalyst supports, proton-conducting nanometer-thin ionomer film, and gas-transporting nano-pores, all contained within the electrodes of a membrane electrode assembly (MEA). Their properties, composition and spatial distribution largely determine fuel cell performance and affect degradation trends. At the next scale are electrodes, membrane and gas diffusion layer, dictating mass, electrical and thermal transport at the micron-scale. Finally, millimeters-thick flow field plates and larger system components affect the gas transport, water and overall system management. Understanding how all of these factors affect fuel cell performance and degradation is of crucial importance, and it is only possible by applying highly correlated efforts in testing, structural characterization and mathematical modeling. The focus of this talk is to present the latest advancements in the structural characterization approaches for fuel cells at multiple scales. In the recent years, a whole suite of novel 2D and 3D characterization approaches have been developed to provide information ranging from nano-sized catalysts used in the electrodes to macro-level flow field plates. This talk will give an overview of a number of advanced characterization techniques used for fuel cell analysis, starting from some more typically used, such as scanning electron microscopy (SEM), to highly sophisticated techniques such as 3D electron tomography. Techniques such as 2D and 3D high-resolution transmission electron microscopy (HR-TEM), 2D and 3D scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS), 3D focused-ion beam SEM (FIB-SEM), electron energy loss spectroscopy (EELS), scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), and micro- and nano-computed tomography (CT), as well as developed in-situ techniques will be discussed. Challenges in characterization, ranging from sample preparation, ionomer and water imaging, image processing and quantification will be addressed. Finally, the author’s work on advanced characterization of fuel cells will be reported. Multi-scale approach in 3D imaging and property modeling, utilizing electron tomography, FIB-SEM and micro-CT, will be presented with encountered challenges [1]. Advanced 2D STEM characterization with quantification and its application for analysis of fuel cell degradation will be discussed [2]. Lastly, a collaborative work on in-situ water imaging using X-ray synchrotron imaging and revealed effect on membrane changes during operation at high current densities will be shown [3]. The talk will close by discussing the challenges and plan forward for continuing development of fuel cell characterization approaches. Jankovic, S. Zhang, A. Putz, M. S. Saha, D. Susac, Multi-scale imaging and transport modeling for fuel cell electrodes, (invited) Journal of Materials Research, 34 (4) (2019).Kneer, J. Jankovic, D. Susac, A. Putz, N. Wagner, M. Sabharwal, M. Secanell, Correlation of changes in electrochemical and structural parameters due to voltage cycling induced degradation in PEM fuel cells, Journal of The Electrochemical Society, 165 (6) F3241-F3250 (2018).N. Ge, R. Banerjee, D. Muirhead, J. Lee, H. Liu, P. Shrestha, A.K.C. Wong, J. Jankovic, M. Tam, D. Susac, J. Stumper, A. Bazylak, Membrane dehydration with increasing current density at high inlet gas relative humidity in polymer electrolyte membrane fuel cells, Journal of Power Sources, 422 (2019) 163-174.