FIB SEM Research Articles

(Invited) Numerical Simulation of Sintering Process in Solid Oxide Fuel Cell Anode

Solid oxide fuel cell (SOFC) is expected as a promising energy conversion device because of its high efficiency and fuel flexibility. It is widely known that electrode microstructures are of great importance for attaining high performance as well as high reliability of SOFCs. In the SOFC fabrication processes, sintering of sub-micron scale ceramic and metallic powders is one of the most important step to achieve efficient and reliable electrodes. In addition, microstructural changes in SOFC anodes associated with particle sintering during high temperature operation may lead to severe performance degradation. Thus, in order to develop more reliable electrodes of SOFC, a method that can offer quantitative information of sintering behavior at the sub-micron scale is highly demanded.Accurate prediction of microstructure evolution during sintering, even in single-phase systems, is still very challenging. This is because sintering behavior is deeply affected by the three-dimensional (3D) complex geometries of the powder compacts, such as grain and pore size distributions, their shapes, relative density and coordination number, etc. Among many types of numerical approaches, a mesoscale kinetic Potts Monte Carlo (KMC) method has the potential to overcome this difficulty [1]. This method is capable of capturing three dimensional microstructural evolution from the initial to the final stages of solid-state sintering. However, the underlying kinetics at the sub-micron scale are not yet completely understood. Validation of the results using quantitative 3D microstructure data is indispensable to develop a numerical simulation tool which can reproduce proper sintering trajectory of real powder sintering. In the present study, KMC simulations of nickel (Ni) and nickel oxide - yttria stabilized zirconia (NiO-YSZ) composite are carried out starting from the green powder microstructure obtained using focused ion beam - scanning electron microscopy (FIB–SEM). Quantitative topological changes during sintering of real powder compacts are obtained by FIB–SEM. This technique offers a great advantage because of its high resolution, which is sufficient to capture the 3D geometric nature of sub-micron-sized powder compacts (typically < 1/10 of the powder size). The simulated temporal trajectories of microstructural parameters are compared with the experimental data from FIB-SEM to verify the numerical modeling results. [1] Hara, S., Ohi, A. and Shikazono, N., Sintering Analysis of Sub-Micron-Sized Nickel Powders: Kinetic Monte Carlo Simulation Verified by FIB-SEM Reconstruction, J. Power Sources, 276, pp. 105-112 (2015).

Modeling reaction–diffusion processes within catalyst washcoats: II. Macroscale processes informed by microscale simulations

This paper first develops a two-dimensional Thiele-type cylindrical-pore model that predicts catalytic washcoat performance, albeit for idealized cylindrical pores. The primary purpose for the cylindrical-pore model is to serve as a basis of comparison with three-dimensional models of catalytic performance in actual geometrically complex washcoat pores that are tomographically reconstructed from focused-ion-beam–scanning-electron-microscopy (FIB–SEM) measurements. In both models, the reaction–diffusion processes are characterized by a Damköhler number that is based on a pore diffusion coefficient and a single first-order reaction rate. Performance metrics include effective product flux from the pores, pore effectiveness, and reaction depth within the pore. In all cases, the models are generalized by casting the conservation equations and performance metrics as dimensionless variables. The paper then derives expressions to upscale individual pore performance to full-scale washcoats. The new understanding that emerges from these studies provides qualitative and quantitative insight that can assist the design and fabrication of improved washcoat microstructures.

Modeling reaction–diffusion processes within catalyst washcoats: I. Microscale processes based on three-dimensional reconstructions

This paper develops a detailed analysis of reaction–diffusion processes within a porous rhodium-alumina catalyst washcoat. Focused-ion-beam–scanning-electron-microscope (FIB–SEM) techniques are developed and applied to reconstruct the actual catalyst-support microstructure. Three-dimensional transport processes within washcoat micro-pore structures are modeled using a dimensionless representation of reaction and diffusion rates based on the Damköhler number. Three-dimensional computational solutions for particular porous microstructures are modeled and interpreted. In a companion paper, these microstructural results are used to assist development of larger-scale models that can be incorporated into reactor-scale simulations.

3-D Analysis of a Copper Flip-Chip Interconnection Using FIB-SEM Slice and View

Abstract A detailed analysis based on FIB etching and SEM image capture was conducted on a flip-chip solder joint deep inside a tablet PC. 3D views reconstructed from SEM images show what appears to be a copper pillar with a solder cap connected to a copper trace on the substrate. The investigators believe the joint was formed by thermal compression bonding with a preapplied underfill. The analysis also revealed the presence of voids and intermetallic compounds along with signs of filler entrapment.

Layered double hydroxides: Efficient fillers for waterborne nanocomposite films

Using Layered double hydroxides (LDH) nanoparticles and film-forming latexes, waterborne nanocomposite films were produced by simply a heterocoagulation and solvent casting process. Self-standing and transparent films with LDH contents from 2.5 to 15vol% were prepared. The structure, microstructure and mechanical behavior were thoroughly investigated by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), scanning electron microscopy (FIB–SEM) and dynamic mechanical analysis (DMA). Favorable electrostatic interactions between pristine LDH and the latex ensured a good dispersion of the bidimensional LDH platelets in the films. Above a certain content of LDH, the formation of a well-defined cellular LDH network following the starting latex morphology was observed. Such a percolating microstructure induces a large mechanical reinforcement significant of a mechanical percolation behavior.

Editorial

Traditionally microscopy has been separated into materials and biological applications, but these divisions break down in fields such as nanotechnology and tissue engineering where there is a need to understand actions of materials components at the cellular and intracellular level. Microanalytical techniques with their ability to identify elemental content at the nm scale offer considerable promise in these areas of research, but their application is not always straightforward. Routine procedures developed for specific applications in one field are not always appropriate when applied in another, and may cause misleading results. This issue of J Microsc. brings together a number of papers dealing with the application of microanalysis at the interface between materials science and biology. The subjects dealt with include the effects of standard fixation and embedding procedures on nanoparticle composition, (Cross et al.), the inadvisability of using standardless quantitation routines with biological specimens (Warley), problems encountered in SEM analysis of cells cultured on biocompatible substrates (Tylko) and correlation of results produced from FIB SEM with those from TEM to overcome sampling problems that occur in thin section TEM studies (Hondow et al.). Lawrence et al. present their results achieved using soft X-rays as the source of X-ray excitation, the advantage of this technique being that minimal specimen preparation is required. Whilst Zeitvogel et al. present a plug in for Image J to tackle the problem of extracting information from the large data sets that can be produced from microanalytical studies. Together these papers tackle different aspects of problems that may be encountered when undertaking analysis at the materials biology interface and should provide a very useful reference point for workers in the field.

Mineral Formation Pathways in Bone

Event Abstract Back to Event Mineral Formation Pathways in Bone Steve Weiner1, Anat Akiva1, Michael Kerschnitzki1, Natalie Reznikov1 and Lia Addadi1 1 Weizmann Institute, Structural Biology, Israel The mineralization of bone involves the sequestering of calcium and phosphate ions from the food, and its transport to the extracellular environment, where carbonated hydroxyapatite crystals grow within the preformed collagenous organic matrix. Mammalian bone is composed of two different types of mineralized materials: the ordered material dominated by aligned bundles of collagen, and the disordered material that fills in the spaces between bundles and is composed of individual collagen fibrils, mineral and “ground mass”. Studies of the forming embryonic zebrafish tail bones and mouse long bones show that osteoblasts, as well as other cells sometimes located at some distance from the forming bone surface, contain vesicles with numerous mineral particles. In vivo Raman spectroscopy as well as EDS, indicate that the mineral phase inside cells in close association with the mineralizing matrix is OCP-like, with some ACP, and showing a Ca/P ratio very close to one. The presence of a transient disordered mineral phase on the surfaces of the forming bones of zebrafish has been documented using micro-Xray diffraction. The intracellular mineral phase is exocytosed into the extracellular pre-formed collagen fibril matrix. Here the disordered mineral aggregates disaggregate and particles enter into the fibril arrays, and crystallize. A cryo-SEM and FIB SEM serial sectioning study of the chicken embryonic bones, reveals the presence of abundant calcium phosphate mineral bearing vesicles inside cells in the proximity of the forming bones, but most significantly also within blood vessels. This implies that as yet unidentified cells at an unknown distant location are producing solid mineral for transport to the bone. This view of bone mineral pathways involving many cell types, some at great distance from the final depositional site, is consistent with observations of mineralization of embryonic sea urchins, raising the possibility that this is a widespread strategy. Keywords: cell, Calcium phosphate, Bone repair, acellullar matrix Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: New Frontier Oral Topic: Mechanobiology of cells on biomaterials Citation: Weiner S, Akiva A, Kerschnitzki M, Reznikov N and Addadi L (2016). Mineral Formation Pathways in Bone. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.00282 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Steve Weiner Anat Akiva Michael Kerschnitzki Natalie Reznikov Lia Addadi Google Steve Weiner Anat Akiva Michael Kerschnitzki Natalie Reznikov Lia Addadi Google Scholar Steve Weiner Anat Akiva Michael Kerschnitzki Natalie Reznikov Lia Addadi PubMed Steve Weiner Anat Akiva Michael Kerschnitzki Natalie Reznikov Lia Addadi Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Labyrinths, columns and cavities: new internal features of pollen grain walls in the Acanthaceae detected by FIB-SEM.

External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants, especially the Acanthaceae which are noted for pollen diversity. However internal pollen wall features have received far less attention due to the difficulty of examining the wall structure. Advancing technology in the field of microscopy has made it possible, with the use of a focused ion beam-scanning electron microscope (FIB-SEM), to view the structure of pollen grain walls in far greater detail and in three dimensions. In this study the wall structures of 13 species from the Acanthaceae were investigated for features of potential systematic relevance. FIB-SEM was applied to obtain precise cross sections of pollen grains at selected positions for examining the wall ultrastructure. Exploratory studies of the exine have thus far identified five basic structural types. The investigations also show that similar external pollen wall features may have a distinctly different internal structure. FIB-SEM studies have revealed diverse internal pollen wall features which may now be investigated for their systematic and functional significance.

Tuning the plasmonic behavior of metallic nanowires

The Localized Surface Plasmon Resonance (LSPR) of metallic nanowire arrays was studied as a function of wire thickness and composition. Ripple-like periodic structures on polymer foils were produced using an excimer laser. Nanowire arrays were prepared on these nano-patterned polymer surfaces via vacuum evaporation of silver and gold at grazing angle of incidence. Different widths of the wires were obtained by a second grazing incidence evaporation process on the still uncoated side of the polymer ridges. Using different metals for each deposition step, mixed nanowires were prepared. The sample geometry was analyzed by FIB–SEM. The optical properties of the nanowires were studied by polarization resolved optical transmission spectroscopy revealing systematic shifts of the plasmon peak with respect to composition and width of the wires.

Advancing FIB assisted 3D EBSD using a static sample setup

A new setup for automatic 3D EBSD data collection in static mode has been developed using a conventional FIB–SEM system. This setup requires no stage or sample movements between the FIB milling and EBSD mapping. Its capabilities were tested experimentally on a coherent twin boundary of an INCONEL sample. Our result demonstrates that this static setup holds many advantages in terms of data throughput and quality as compared with other ones requiring stage/sample movements. The most important advantages are the better slice alignment and an improved orientation precision in 3D space, both being prerequisite for a reliable grain boundary characterization.

A New In-line Laser-based Acoustic Technique for Pillar Bump Metrology

The drive to reduce the interconnect pitch and increase the number of connections for packaging in mobile devices has led to the development of copper pillar bumps. The key drivers for the adoption of copper pillars are improved performance, reduced form factor and lower cost. In this paper, we present a laser-based acoustic technique for the characterization of multi-layer pillars. This non-contact technique has a high sensitivity for materials characterization with micron-scale spatial resolution. Absorption of laser light causes excitation of elastic waves that propagate through the pillar and are reflected by the pillar walls, exciting vibrational modes in the structure. We have demonstrated that our approach is sensitive to the thicknesses of individual layers in bi-layer and tri-layer copper pillar stacks. Focused ion beam scanning electron microscopy (FIB SEM) has been used to optimize the model and to validate the accuracy of the technique.

3D FIB SEM imaging of oil filled chalk: What are the challenges?

In Europe, fresh groundwater and oil resources are hosted in chalk, which is a sedimentary rock, dominated by calcite (CaCO3) precipitated by marine organisms. The calcite particles have remained small during millions of years of compaction and weathering, creating a complex microstructure with low permeability in spite of often high porosity. Knowledge about pore architecture is required to simulate fluid flow, which can be used to predict how contaminants would behave in groundwater aquifers, or how easily oil could be extracted.

Rapid switching and ultra-responsive nanosensors based on individual shell–core Ga2O3/GaN:Ox@SnO2 nanobelt with nanocrystalline shell in mixed phases

Research on semiconducting oxide nanocrystals will likely remain one of the leading topics in condensed matter physics and advanced functional materials. Looking beyond this field, chemically heterogeneous nanocrystals systems based on mixed phases have been assembled as reported here for shell–core Ga2O3/GaN:Ox@SnO2 nanocables, i.e. long and single crystalline SnO2 belts/wires as core surrounded with a shell composed of GaN:Ox and Ga2O3 nanoparticles. Subsequently, nano- and micro-sensors from an individual shell–core Ga2O3/GaN:Ox@SnO2 nanocable on the chip have been realized via localized maskless growth of metal using dual-beam FIB–SEM instrument. In contrast to pure SnO2 nanowire-based sensor, here fabricated nano- and micro-devices on individual hybrid nano- or micro-cables on chip are quite stable, highly sensitive (the current ratio IUVON/IOFF>104), higher and faster switching in UV photodetection, as well as air/vacuum and temperature sensing capabilities. The SnO2 nano- and microbelts/wires networks were synthesized by the flame transport synthesis and a shell layer composed of Ga2O3/GaN:Ox nanoparticle was deposited on them by magnetron sputtering. The scanning electron microscopy and transmission electron microscopy results revealed that the Ga2O3/GaN:Ox nanocrystallite shells are uniformly deposited on SnO2 networks. The detailed TEM structural studies on the as-grown and annealed structures confirmed that the nanocable is made from mixed phases by an excellent agreement with the standard data for rutile SnO2, amorphous GaN:Ox and monoclinic β-Ga2O3. Herein, we resolve two essential problems regarding the nano-construction of an efficient nanosensor. First, the simplest process fabrication of the highly protected shell–core nanocables with improved electrical properties is achieved by cost-effective synthesis in a controlled manner. Second, construction of a non-planar 3D nanoscale double-heterojunctions with a large surface area is realized via an efficient technique. It allows surface protection of nanosensors during its fabrication and operation in different ambient conditions. The developed nanomaterial sparks interest for further studies on different hybrid semiconducting oxides as promising candidates for fabricating multifunctional nano- and micro-sensors and photodetectors.

High frequency reciprocating sliding wear behavior and mechanisms of quaternary metal oxide coatings

Wear resistant coatings based on quaternary metal oxides were studied with comparisons made to more traditional ternary metal oxides. While much is known about ternary metal oxide wear behavior and mechanisms from room to higher temperatures, little is known about quaternary oxides; for instance, the role of the fourth element in determining the coating crystalline state and defect structure and how they control tribological properties. To this end, the system (ZnTiZr)xOy was deposited by atomic layer deposition (ALD) and compared to previously studied wear resistant nanocrystalline ALD ZnTiO3 coatings. X-ray diffraction determined that both as-deposited and ex situ 550°C annealed ternary and quaternary coatings exhibit ZnTiO3 phase or solid solution Zn(Ti,Zr)O3 phase only, respectively. However, the coatings have completely different growth structures where the ternary ZnTiO3 coatings exhibit textured (104) nanocolumnar grains and the quaternary Zn(Ti,Zr)O3 coatings are predominantly amorphous with some nanocrystalline grains. High frequency reciprocating sliding on these coatings revealed that the growth structure did not influence the wear rate (~1×10−6mm3/Nm). However, the crystal structure-dependent deformation mechanisms were different as revealed by FIB–SEM and HRTEM analyses inside worn surfaces. It was determined that both coatings show surface deformation due to ductile layering/smearing with no evidence of brittle fracture. Wear reduction of the ZnTiO3 coating was due to nanoscale sliding-induced plastic deformation when (104) stacking faults were sheared along the sliding direction resulting in an intrafilm shear velocity accommodation mode. Conversely, wear reduction in the quaternary Zn(Ti,Zr)O3 coating was a result of a tribofilm/mechanically mixed layer, composed of amorphous transferred silica from the sliding Si3N4 counterface and refined nanocrystalline Zn(Ti,Zr)O3 grains from the coating. Both wear surfaces contained solid cylindrical rolls or roll-ups often found in ceramic–ceramic reciprocating sliding. New insights revealed that the rolls originate in the tribofilm, with similar composition and structure, and evolve to the surface with continued sliding.

Change of an anode's microstructure morphology during the fuel starvation of an anode-supported solid oxide fuel cell

A RedOx cycle is one of the most dangerous factors of anode degradation due to microstructure changes. In this paper, the evolution of anode microstructure during a RedOx cycle caused by a fuel starvation process was studied using electrochemical measurements. After a power generation experiment, the anode microstructure was reconstructed using a combination of focused ion beam and scanning electron microscopy (FIB–SEM). The microstructure changes were quantified for parameters such as the tortuosity factor, tripe phase boundary density, volume fraction, connectivity and average grain size. The three dimensional microstructure reconstruction indicated that the fuel starvation condition might cause significant changes in microstructure morphology.

Synthesis, characterization and sorption capacities toward organic pollutants of new β-cyclodextrin modified zeolite derivatives

The functionalization of zeolite Y (Faujasite) with β-cyclodextrin (CD) was realized by using 3-glycidoxypropyltrimethoxysilane (GPTS) as linker. Two different strategies were followed: grafting of the linker on β-CD and then reacted with zeolite or grafting of the linker on zeolite and then reacted with β-CD. Obtained materials were characterized by several complementary methods including, focused ion beam–scanning electron microscopy–energy dispersive X-ray spectrometry (FIB–SEM–EDX), Thermogravimetric analysis and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmet–Teller (BET) analysis. The decrease in surface area compared to native zeolite indicated clogging of the zeolite pores while sorption capacities of functionalized zeolite toward two model pollutants (toluene and methyl orange) were greater than native zeolite. Moreover, the first strategy led to better sorption capacities than the second one. These new materials are potential sorbents for remediation purpose toward gaseous or aqueous effluent.

The Bacterial Spore as an Energy-Rich Adaptive Material

Stimuli responsive materials are in high demand for myriad applications within the fields of biomedicine, adaptive-architecture, robotics, and alternative energy. The non-pathogenic bacterial spores of Bacillus subtilis have the ability to swell as much as 12% in response to humidity gradients. Within the spore unique biomaterials drive this dynamic response, resulting in energy densities greater than 10 MJ∗m−3, more than a hundred times the potential of existing synthetics. We hypothesize that the spore's cortex, a protective layer surrounding the genetic core, is largely but not solely responsible for this peculiar water-responsive behavior. To evaluate the spore's constituent biomaterials we developed AFM techniques that assay individual spores during a thermodynamic cycle of varied applied force and relative humidity. This method resulted in energy density and strain profiles for multiple spore variants and structural mutants. Electron microscopy (FIB SEM) was then used to ascribe radial dimensions to biomaterial layers within the spore. Quantifying precise substructural contributions to the spore's hygrodynamics will allow for in vitro optimization of composite spore biomaterials and may even facilitate artificial synthesis in the future. The bacterial spore's inherent ability to form monolayers and superior performance in highly efficient energy conversion and actuation qualifies it as an intriguing material worthy of broad development.

Imaging and characterization of γ′ and γ″ nanoparticles in Inconel 718 by EDX elemental mapping and FIB–SEM tomography

Microstructural characterization of Inconel 718 superalloy after three different heat treatment variants was performed by electron microscopy and electron tomography techniques, taking advantage of recent development in quantitative electron microscopy. Distribution maps of the chemical elements, collected by ChemiSTEM™ EDX system, offer a clear contrast between γ′, γ″, and the γ matrix. It was found that the γ′ phase contains mainly Ni, Al, and Ti, while the γ″ phase contains Ni, Nb, and Ti. Thus application of the Al and Nb STEM–EDX elemental maps enables identification and size measurements of γ′ and γ″ nanoparticles. 3D morphology of γ′ and γ″ precipitates was examined by electron microscopy and FIB–SEM tomography. Employed methods revealed that in all three heat treatment variants the γ′ particles are almost spheroidal while the γ″ precipitates are mainly elongated-disc shaped. However, the precipitate sizes differed for each variant contributing to differences in the yield strength. Tomographic images were used for estimation of the volume fraction of the both strengthening phases.

Sintering analysis of sub-micron-sized nickel powders: Kinetic Monte Carlo simulation verified by FIB–SEM reconstruction

Since sintering of sub-micron-sized particles is a critical phenomenon affecting the electrochemical performance and reliability of solid oxide fuel cell systems, a better understanding of this microstructure-related process is of great importance. In this study, we show that kinetic Potts Monte Carlo modeling is capable of quantitatively predicting the three-dimensional (3D) microstructure evolution over an entire stage of nickel sintering at the sub-micron scale. This is achieved through direct comparison of simulation results and 3D microstructural analysis using focused ion beam–scanning electron microscopy. We show that grain boundary diffusion is the dominant mechanism on densification, while surface diffusion has an impact on the coarsening during sub-micron scale sintering, only acting as one of the multiple mechanisms of sintering.

Three‐Phase Multiscale Modeling of a LiCoO2 Cathode: Combining the Advantages of FIB–SEM Imaging and X‐Ray Tomography

LiCoO2 electrodes contain three phases, or domains, each having specific‐intended functions: ion‐conducting pore space, lithium‐ion‐reacting active material, and electron conducting carbon‐binder domain (CBD). Transport processes take place in all domains on different characteristic length scales: from the micrometer scale in the active material grains through to the nanopores in the carbon‐binder phase. Consequently, more than one imaging approach must be utilized to obtain a hierarchical geometric representation of the electrode. An approach incorporating information from the micro‐ and nanoscale to calculate 3D transport‐relevant properties in a large‐reconstructed active domain is presented. Advantages of focused ion beam/scanning electron microscopy imaging and X‐ray tomography combined by a spatial stochastic model, validated with an artificially produced reference structure are used. This novel approach leads to significantly different transport relevant properties compared with previous tomographic approaches: nanoporosity of the CBD leads to up to 42% additional contact area between active material and pore space and increases ionic conduction by a factor of up to 3.6. The results show that nanoporosity within the CBD cannot be neglected.