Plasma Focused Ion Beam Research Articles

Transport Properties of Iridium Oxide Catalyst Layers for Proton Exchange Membrane Water Electrolyzers

One of the current challenges of proton exchange membrane (PEM) water electrolyzers (PEMWE) is to reduce the high costs associated with iridium as the anode catalyst material. In commercial PEMWE membrane electrode assemblies (MEAs), loadings of iridium are as high as 2 to 3 mgIr/cm2. However, for PEMWE systems to match global energy demand, the Ir-specific power density must increase by ~ 50-fold [1, 2]. This can be achieved by decreasing iridium loadings and increasing the utilization of iridium. Previous work has determined that homogeneity of anode catalyst layers is generally favorable and even necessary for good electrochemical performance at lower iridium loadings [1-3]. However, gaining a better understanding of the important micro- and nano-scale features of iridium oxide (IrO2) catalyst layers is still needed for informing fabrication methods and achieving higher Ir-specific power density operation. Our previous work used nano-scale X-ray computed tomography (nano-CT) and plasma-focused ion beam cross sectioning with scanning-electron microscopy (pFIB-SEM) to characterize several IrO2 catalyst layers varying in coating methods and steps along the fabrication and testing lifetime, finding differences in morphological properties particularly of the pore size distributions. Our current work expands on this image-based characterization to elucidate transport properties between catalyst layers fabricated with different coating methods and iridium loadings. Using modeling and simulation techniques, effective transport properties for pore and solid phases such as oxygen diffusivity, conductance, and tortuosity will be examined using the high-resolution image-based data. The results presented in this work will help elucidate the transport phenomena through the IrO2 catalyst layer and the relationship between fabrication, morphology, and performance.This conference presentation was developed based upon funding from the Alliance for Sustainable Energy, LLC, Managing and Operating Contractor for the National Renewable Energy Laboratory for the U.S. Department of Energy.[1] Bernt, M., Siebel, A., & Gasteiger, H. A. (2018). Analysis of Voltage Losses in PEM Water Electrolyzers with Low Platinum Group Metal Loadings. Journal of The Electrochemical Society, 165(5), F305–F314. https://doi.org/10.1149/2.0641805jes[2] Kulkarni, D., Huynh, A., Satjaritanun, P., O’Brien, M., Shimpalee, S., Parkinson, D., Shevchenko, P., DeCarlo, F., Danilovic, N., Ayers, K. E., Capuano, C., & Zenyuk, I. v. (2022). Elucidating effects of catalyst loadings and porous transport layer morphologies on operation of proton exchange membrane water electrolyzers. Applied Catalysis B: Environmental, 308. https://doi.org/10.1016/j.apcatb.2022.121213[3] Taie, Z., Peng, X., Kulkarni, D., Zenyuk, I. v., Weber, A. Z., Hagen, C., & Danilovic, N. (2020). Pathway to Complete Energy Sector Decarbonization with Available Iridium Resources using Ultralow Loaded Water Electrolyzers. ACS Applied Materials and Interfaces, 12(47), 52701–52712. https://doi.org/10.1021/acsami.0c15687

Characterization of local deformation around hydrides in Zircaloy-4 using conventional and high angular resolution electron backscatter diffraction

Zircaloy-4 is used as a fuel cladding material for water reactors, as it has good mechanical properties, corrosion resistance, and a low thermal neutron absorption cross section. However, the mechanical performance of Zircaloy-4 can be reduced during service due to hydrogen uptake and hydride formation. These hydrides are brittle, and often reduce the strength and toughness of materials as well as increase susceptibility to delayed hydride cracking (DHC). In this work, large grain Zircaloy-4 with hydrides was prepared and then cross sectioned using cryo-ion beam polishing, using plasma focused ion beam (pFIB) and broad ion beam (BIB) approaches to enable the preparation of a very high quality flat surface with no preferential etching of either the hydride or zirconium metal (typically metallographic polishing preferentially removes hydrides). Conventional and high angular resolution electron backscatter diffraction (EBSD) analysis were then used to explore morphology, deformation fields, and orientation relationships between the zirconium matrix and hydrides. Four maps were collected for analysis which included hydrides near grain boundaries: (a) where the hydride smoothly decorates across two of the connecting boundaries near a triple junction; (b) where the hydride smoothly decorates the boundary; (c) a mixture of smooth decoration of the interface and protrusion into the grains; (d) fine scale hydride that protrudes into one grain. This work highlights that incompatibility of the hydride within the zirconium matrix is strongly linked to the orientation relationship of the hydride and matrix, and the grain boundary character. These results may enable enhanced understanding of the role of hydrides in fracture as well as stress-induced hydride reorientation and DHC susceptibility.

Evaluation of Lithium Metal Anode Volumetric Expansion through Laser Plasma Focused Ion Beam Cross-Sectional Imaging

Lithium metal is an ideal anode for high energy density batteries, however the implementation of lithium metal anodes remains challenging. Beyond the development of highly efficient electrolytes, degradation processes restrict cycle life and reduce practical energy density. Herein lithium volumetric expansion and degradation pathways are studied in half cells through coupling electrochemical analysis with cross-sectional imaging of the intact electrode stack using a cryogenic laser plasma focused ion beam and scanning electron microscope. We find that the volumetric capacity is compromised as early as the first cycle, at best reaching values only half the theoretical capacity (1033 vs 2045 mAh cm−3). By the 101st electrodeposition, the practical volumetric capacity decreases to values ranging from 143 to 343 mAh cm−3.

Assessing the Quality of Oxygen Plasma Focused Ion Beam (O-PFIB) Etching on Polypropylene Surfaces Using Secondary Electron Hyperspectral Imaging.

The development of Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) systems has provided significant advances in the processing and characterization of polymers. A fundamental understanding of ion-sample interactions is still missing despite FIB-SEM being routinely applied in microstructural analyses of polymers. This study applies Secondary Electron Hyperspectral Imaging to reveal oxygen and xenon plasma FIB interactions on the surface of a polymer (in this instance, polypropylene). Secondary Electron Hyperspectral Imaging (SEHI) is a technique housed within the SEM chamber that exhibits multiscale surface sensitivity with a high spatial resolution and the ability to identify carbon bonding present using low beam energies without requiring an Ultra High Vacuum (UHV). SEHI is made possible through the use of through-the-lens detectors (TLDs) to provide a low-pass SE collection of low primary electron beam energies and currents. SE images acquired over the same region of interest from different energy ranges are plotted to produce an SE spectrum. The data provided in this study provide evidence of SEHI's ability to be a valuable tool in the characterization of polymer surfaces post-PFIB etching, allowing for insights into both tailoring polymer processing FIB parameters and SEHI's ability to be used to monitor serial FIB polymer surfaces in situ.

Bridging macro to micro-scale fatigue crack growth by advanced fracture mechanical testing on the meso-scale

Fatigue and fracture mechanics testing is strictly regulated by standards that specify a minimum specimen size. However, when component sizes or material volume decrease below this limit, test methods need to be adapted for small scales. In fatigue crack growth studies, experiments become complex and challenging. Thus, there is lack of systematic scale-bridging studies from meso- to micro-scales on ductile materials. This study outlines a method to bridge this scale gap by performing meso-scale studies. Cantilver bending specimens with a cross section of 50x50µm2 and a lever arm length of 200µm of nanocrystalline nickel, as a model material, are milled by Xe plasma focused ion beam technique and tested following ASTM E647 standard. The gathered da/dN-curves are highly reproducible. The threshold stress intensity factor ΔKth is obtained by step-wise load reduction and discussed in context of crack closure. So, not only the gap between macro and micro-scaled testing was bridged, but also a pre-cracking step was shown to be essential for obtaining reliable data, and a new method to determine the intrinsic threshold stress intensity factor was introduced.

A Multi-scale Understanding of the Three-dimensional Microstructure of the Cornea Using Oxygen Plasma Focused Ion Beam, Scanning Transmission Electron Microscopy and Micro-CT Techniques.

A Multi-scale Understanding of the Three-dimensional Microstructure of the Cornea Using Oxygen Plasma Focused Ion Beam, Scanning Transmission Electron Microscopy and Micro-CT Techniques.

Understanding Ion-Beam Damage to Air-Sensitive Lithium Metal With Cryogenic Electron and Ion Microscopy.

It is essential to understand the nanoscale structure and chemistry of energy storage materials due to their profound impact on battery performance. However, it is often challenging to characterize them at high resolution, as they are often fundamentally altered by sample preparation methods. Here, we use the cryogenic lift-out technique in a plasma-focused ion beam (PFIB)/scanning electron microscope (SEM) to prepare air-sensitive lithium metal to understand ion-beam damage during sample preparation. Through the use of cryogenic transmission electron microscopy, we find that lithium was not damaged by ion-beam milling although lithium oxide shells form in the PFIB/SEM chamber, as evidenced by diffraction information from cryogenic lift-out lithium lamellae prepared at two different thicknesses (130 and 225 nm). Cryogenic energy loss spectroscopy further confirms that lithium was oxidized during the process of sample preparation. The Ellingham diagram suggests that lithium can react with trace oxygen gas in the FIB/SEM chamber at cryogenic temperatures, and we show that liquid oxygen does not contribute to the oxidation of lithium process. Our results suggest the importance of understanding how cryogenic lift-out sample preparation has an impact on the high-resolution characterization of reactive battery materials.

Investigation of the residual strain and deformation mechanisms in laser-welded Eurofer97 steel for fusion reactors

A fusion power plant requires not only the control of high energy plasma but also advanced techniques for maintenance and assembly to generate electricity consistently and safely. Laser welding is a promising technique for cutting and joining pipes and in-vessel components made of Eurofer97, a European baseline structural material. However, the substantial residual strain induced during post-weld cooling degrades the mechanical properties and reduces the lifespan of engineering components. Establishing the underpinning mechanistic connection between residual strain, microstructure, and tensile behaviour is critical to lifetime assessments of engineering components. Here, the heterogeneous strain evolution in laser-welded Eurofer97 joint is quantitatively evaluated using in situ neutron diffraction at the lattice-scale, nanoindentation at the microscale, and digital image correlation (DIC) at a macroscale. The residual strain in the loading direction is characterised via neutron diffraction and validated using a plasma-focused ion beam (PFIB-DIC) ring-core method. Superimposing the microstructural strengthening, the highest residual tensile strain (0.6×10−3με) accelerates the accumulation of tensile deformation around the fusion line (FZ/HAZ interface), whereas residual compressive strain (−1×10−3με) hinders the tensile strain evolution around the heat-affected zone and the base material interfaces, increasing the localised yield strength to 506 MPa. Residual strain is the primary strengthening mechanism during the initial deformation stage, although the microstructural strengthening then dominates as deformation increases. This work reveals the critical role of residual strain, and the results provide insight into managing structural integrity and developing predictive tools for lifetime assessment.

Detectability of Small True-T Hole Image Quality Indicators by Digital Radiographic Techniques

Image quality indicators (IQIs) are used to ensure quality in radiography. The requirements for hole-type IQIs have changed from MIL-STD-453-C (US DOD 1984) to ASTM E1742 and E1025 (ASTM 2018a, 2018b). For materials thinner than 0.50 in., the 2-2T hole does not represent 2% sensitivity. E1025 introduced true-T hole IQIs, where the 2-2T hole represents 2% sensitivity. Stainless steel true-T hole IQIs were fabricated using drills and a plasma-focused ion beam instrument. They were imaged using digital radiography (DR), computed radiography, and X-ray film to determine the limit of their visibility. DR was able to detect holes on the order of 2 to 3 pixels in diameter. All three techniques were able to detect the 2T hole in the number 4 IQI while DR was able to detect it in the number 3 IQI. These hole sizes are near the limit where geometric magnification would be required. The better sensitivity of DR is probably a result of being able to minimize fixed structural noise. Presently, for materials thinner than 0.50 in., there is the option to use IQIs defined by either E1742 Annex A1 or E1025. It is recommended that inspection procedures require a particular sensitivity percent that would necessitate the use of a specific IQI.

Investigation of the milling characteristics of different focused-ion-beam sources assessed by three-dimensional electron diffraction from crystal lamellae.

Three-dimensional electron diffraction (3DED) from nanocrystals of biological macromolecules requires the use of very small crystals. These are typically less than 300 nm-thick in the direction of the electron beam due to the strong interaction between electrons and matter. In recent years, focused-ion-beam (FIB) milling has been used in the preparation of thin samples for 3DED. These instruments typically use a gallium liquid metal ion source. Inductively coupled plasma (ICP) sources in principle offer faster milling rates. Little work has been done to quantify the damage these sources cause to delicate biological samples at cryogenic temperatures. Here, an analysis of the effect that milling with plasma FIB (pFIB) instrumentation has on lysozyme crystals is presented. This work evaluates both argon and xenon plasmas and compares them with crystals milled with a gallium source. A milling protocol was employed that utilizes an overtilt to produce wedge-shaped lamellae with a shallow thickness gradient which yielded very thin crystalline samples. 3DED data were then acquired and standard data-processing statistics were employed to assess the quality of the diffraction data. An upper bound to the depth of the pFIB-milling damage layer of between 42.5 and 50 nm is reported, corresponding to half the thickness of the thinnest lamellae that resulted in usable diffraction data. A lower bound of between 32.5 and 40 nm is also reported, based on a literature survey of the minimum amount of diffracting material required for 3DED.

A robust approach for MicroED sample preparation of lipidic cubic phase embedded membrane protein crystals

Crystallizing G protein-coupled receptors (GPCRs) in lipidic cubic phase (LCP) often yields crystals suited for the cryogenic electron microscopy (cryoEM) method microcrystal electron diffraction (MicroED). However, sample preparation is challenging. Embedded crystals cannot be targeted topologically. Here, we use an integrated fluorescence light microscope (iFLM) inside of a focused ion beam and scanning electron microscope (FIB-SEM) to identify fluorescently labeled GPCR crystals. Crystals are targeted using the iFLM and LCP is milled using a plasma focused ion beam (pFIB). The optimal ion source for preparing biological lamellae is identified using standard crystals of proteinase K. Lamellae prepared using either argon or xenon produced the highest quality data and structures. MicroED data are collected from the milled lamellae and the structures are determined. This study outlines a robust approach to identify and mill membrane protein crystals for MicroED and demonstrates plasma ion-beam milling is a powerful tool for preparing biological lamellae.

An open source framework for advanced Multi-physics and multiscale modelling of solid oxide fuel cells

Solid oxide fuel cells are high-efficiency renewable energy devices and considered one of the most promising net-zero carbon energy technologies. Numerical modelling is a powerful tool for the virtual design and optimisation of the next-generation solid oxide fuel cells but needs to tackle issues for incorporating the multi-scale character of the cell and further improving the accuracy and computational efficiency. While most of solid oxide fuel cell models were developed based on closed source platforms which limit the freedom of customisation in numerical discretization schemes and community participation. Here, an open source multi-physics and multiscale platform for advanced SOFC simulations consisting of both cell- and pore-scale performance models was developed using OpenFOAM. The modelling aspects are elucidated in detail, involving the coupling of various physical equations and the implementation of the pore-scale electrode in the performance model. The entire platform was carefully validated against experimental data and the other numerical models which were implemented in commercial software ANSYS Fluent and based on the lattice Boltzmann method. The cell-scale model is subsequently employed to study the effects of different fuels, i.e., pure hydrogen and different ratios of pre-reformed methane gas under various operating temperatures. It is found that the cell-scale model reasonably predicts the effects of these parameters on the cell performance, aligning well with the Fluent model. This study further identified the size of representative element volume with respect to the current density for the anode via the pore-scale model where the realistic microstructures reconstructed by a Xe plasma focused ion beam–scanning electron microscopy are employed as computational domains. It is found that a volume element size of 1243 voxels is sufficient to yield the representative current density of the whole. All these numerical investigations show that OpenFOAM is a potential multi-physics and multi-scale computational platform that is capable of accurately predicting both cell-scale and pore-scale performance and spatial information of solid oxide fuel cells. The developed models are also made public in GitHub to inspire community to further develop around it.

A Detailed Analysis of the Microstructural Changes in the Vicinity of a Crack-Initiating Defect in Additively Manufactured AISI 316L

The fatigue life of metals manufactured via laser-based powder bed fusion (L-PBF) highly depends on process-induced defects. In this context, not only the size and geometry of the defect, but also the properties and the microstructure of the surrounding material volume must be considered. In the presented work, the microstructural changes in the vicinity of a crack-initiating defect in a fatigue specimen produced via L-PBF and made of AISI 316L were analyzed in detail. Xenon plasma focused ion beam (Xe-FIB) technique, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were used to investigate the phase distribution, local misorientations, and grain structure, including the crystallographic orientations. These analyses revealed a fine grain structure in the vicinity of the defect, which is arranged in accordance with the melt pool geometry. Besides pronounced cyclic plastic deformation, a deformation-induced transformation of the initial austenitic phase into α’-martensite was observed. The plastic deformation as well as the phase transformation were more pronounced near the border between the defect and the surrounding material volume. However, the extent of the plastic deformation and the deformation-induced phase transformation varies locally in this border region. Although a beneficial effect of certain grain orientations on the phase transformation and plastic deformability was observed, the microstructural changes found cannot solely be explained by the respective crystallographic orientation. These changes are assumed to further depend on the inhomogeneous distribution of the multiaxial stresses beneath the defect as well as the grain morphology.

Improved Methodology of Cross-Sectional SEM Analysis of Thin-Film Multilayers Prepared by Magnetron Sputtering

In this work, an improved methodology of cross-sectional scanning electron microscopy (SEM) analysis of thin-film Ti/V/Ti multilayers was described. Multilayers with various thicknesses of the vanadium middle layer were prepared by magnetron sputtering. The differences in cross sections made by standard fracture, focused ion beam (FIB)/Ga, and plasma focused ion beam (PFIB)/Xe have been compared. For microscopic characterization, the Helios NanoLab 600i microscope and the Helios G4 CXe with the Quanta XFlash 630 energy dispersive spectroscopy detector from Bruker were used. The innovative multi-threaded approach to the SEM preparation itself, which allows us to retain information about the actual microstructure and ensure high material contrast even for elements with similar atomic numbers was proposed. The fracture technique was the most noninvasive for microstructure, whereas FIB/PFIB results in better material contrast (even than EDS). There were only subtle differences in cross sections made by FIB-Ga and PFIB-Xe, but the decrease in local amorphization or slightly better contrast was in favor of Xe plasma. It was found that reliable information about the properties of modern nanomaterials, especially multilayers, can be obtained by analyzing a two-part SEM image, where the first one is a fracture, while the second is a PFIB cross section.

Okapi-EM: A napari plugin for processing and analyzing cryogenic serial focused ion beam/scanning electron microscopy images.

An emergent volume electron microscopy technique called cryogenic serial plasma focused ion beam milling scanning electron microscopy (pFIB/SEM) can decipher complex biological structures by building a three-dimensional picture of biological samples at mesoscale resolution. This is achieved by collecting consecutive SEM images after successive rounds of FIB milling that expose a new surface after each milling step. Due to instrumental limitations, some image processing is necessary before 3D visualization and analysis of the data is possible. SEM images are affected by noise, drift, and charging effects, that can make precise 3D reconstruction of biological features difficult. This article presents Okapi-EM, an open-source napari plugin developed to process and analyze cryogenic serial pFIB/SEM images. Okapi-EM enables automated image registration of slices, evaluation of image quality metrics specific to pFIB-SEM imaging, and mitigation of charging artifacts. Implementation of Okapi-EM within the napari framework ensures that the tools are both user- and developer-friendly, through provision of a graphical user interface and access to Python programming.

Observation of Focused Ion Beam-Induced Artifacts in Transmission Electron Microscopy Samples Leading to the Epitaxial Growth of AlGaSb Quantum Dots on the GaSb Substrate

Abstract We report an unusual artifact induced by Ga+ or Xe+ focused ion beam (FIB) preparation in transmission electron microscopy (TEM) samples with epitaxial layers on a GaSb substrate. The Ga+ FIB-ed TEM samples with a quantum structure made of Al/AlSb/GaSb/InAs/Al0.33Ga0.67Sb multilayers on a GaSb substrate are found to undergo phase modifications under certain conditions related to the beam energy. Dependent on the voltage used during thinning, the Al islands initially on top of the multilayer stack are gradually replaced by Ga, leading to the epitaxial formation of AlxGa1-xSb (AlGaSb) quantum dots (QDs) whose shapes are conformed to the initial Al islands. A similar effect is observed when the top Al islands are capped by an amorphous As layer. The artifacts can be avoided by extensive thinning at 5 kV followed by 2 kV polishing. Further experiments using Xe+ plasma FIB (PFIB) also produce similar artifacts, and those effects are eliminated by Xe+ PFIB under cryogenic conditions regardless of the beam conditions. The mechanism for forming the epitaxial AlGaSb QDs is investigated, and potential use of this phenomenon for QD fabrication is discussed.

High Resolution Characterization of Proton Exchange Membrane Water Electrolysis Anodes

The current use of expensive and geographically-limited precious metal catalysts, typically iridium, in proton exchange membrane water electrolyzer (PEMWE) anodes is necessary to accelerate the sluggish oxygen evolution reaction (OER). However, high loadings of iridium catalyst drastically increase the capital costs of PEM electrolysis, while low loadings of iridium lead to a significant decline in the efficiency of hydrogen production. Thus, PEMWE anode fabrication methods must be optimized to achieve the highest performance with lower iridium loadings. Using high resolution characterization methods, we show nanoscale differences in anode morphology between different IrO2 anode fabrication methods, such as spray coated versus blade coated anodes. We also explore the evolution of the electrode morphology throughout its fabrication and testing lifetime. The characterization methods used in this work include high resolution nanoscale X-ray computed tomography (nano-CT) as well as plasma-focused ion beam cross-sectioning and scanning electron microscopy (pFIB-SEM). Additionally, we present quantitative data such as solid particle and pore size distributions as well as pore network extractions derived from our image-based characterizations to elucidate the morphological differences between IrO2 anodes.This conference presentation was developed based upon funding from the Alliance for Sustainable Energy, LLC, Managing and Operating Contractor for the National Renewable Energy Laboratory for the U.S. Department of Energy.

Three-dimensional high-resolution crystallographic observation of the entire volume of microstructurally small fatigue cracks in Ni-Co based superalloy

The crystallographic features of microstructurally small fatigue cracks (MSFCs) in a Ni-Co-based superalloy were analyzed by using a Xe plasma focused ion beam scanning electron microscope (PFIB-SEM) system in conjunction with electron backscatter diffraction (EBSD) analysis. The crystallographic orientation of the three-dimensional (3D) fatigue crack growth path was successfully observed using a large-volume, high-resolution 3D image. The major parts of the crack surface were close to the {111} slip plane. Our results indicated that the Mode II fatigue crack growth mechanism is locally more predominant than the general blunting-resharpening Mode I fatigue crack growth mechanism, not only in the Stage I region but also in the larger part of the Stage II region of MSFC growth process.

Rethinking radiation effects in materials science using the plasma-focused ion beam

A new methodology for fundamental studies of radiation effects in solids is herein introduced by using a plasma Focused Ion Beam (PFIB). The classical example of ion-induced amorphization of single-crystalline pure Si is used as a proof-of-concept experiment that delineates the advantages and limitations of this new technique. We demonstrate both the feasibility and invention of a new ion irradiation mode consisting of irradiating a single-specimen in multiple areas, at multiple doses, in specific sites. This present methodology suggests a very precise control of the ion beam over the specimen, with an error in the flux on the order of only 1%. In addition, the proposed methodology allows the irradiation of specimens with higher dose rates when compared with conventional ion accelerators and implanters. This methodology is expected to open new research frontiers beyond the scope of materials at extremes such as in nanopatterning and nanodevices fabrication.

Development of a new, fully automated system for electron backscatter diffraction (EBSD)-based large volume three-dimensional microstructure mapping using serial sectioning by mechanical polishing, and its application to the analysis of special boundaries in 316L stainless steel.

We report the development of a fully automatic large-volume 3D electron backscatter diffraction (EBSD) system (ELAVO 3D), consisting of a scanning electron microscope (ZEISS crossbeam XB 1540) with a dedicated sample holder, an adapted polishing automaton (Saphir X-change, QATM), a collaborative robotic arm (Universal Robots UR5), and several in-house built devices. The whole system is orchestrated by an in-house designed software, which is also able to track the process and report errors. Except for the case of error, the system runs without any user interference. For the measurement of removal thickness, the samples are featured with markers put on the perpendicular lateral surface, cut by plasma focused ion beam (PFIB) milling. The individual effects of both 1μm diamond suspension and oxide polishing suspension polishing were studied in detail. Coherent twin grain boundaries (GBs) were used as an internal standard to check the removal rates measured by the side markers. The two methods for Z-spacing measurements disagreed by about 10%, and the inaccurate calibration of the PFIB system was found to be the most probable reason for this discrepancy. The angular accuracy of the system was determined to be ∼2.5°, which can be significantly improved with more accurate Z-spacing measurements. When reconstructed grain boundary meshes are sufficiently smoothed, an angular resolution of ±4° is achieved. In a 3D EBSD dataset of a size of 587 × 476 × 72μm3, we focused on the investigation of coincidence site lattice ∑9 GBs. While bearing predominantly a pure tilt character, ∑9 GBs can be categorized into three groups based on correlative 3D morphologies and crystallography.