Evaporated amorphous Si protective coatings for dual FIB/SEM preparation of high-quality lamellae for S/TEM analysis.

The metal layer deposition technologies have been revolutionized throughout the years. One of the most common forms of thin metal film deposition techniques is Physical Vapor Deposition (PVD). Within the category of PVD, there are many modifications based on the source of deposition. Among all PVD variations, the Electron Beam Physical Vapor Deposition (EB-PVD) has the advantages of higher deposition rates, the ability to deposit a wide range of high purity metals for high purity films, and the creation of continuous film layers. [1,3]. EB-PVD is better known as a thermal vaporization technique. Thermal Vaporization focuses on a source, in this case an Electron Beam (EB), which bombards the desired source material with electrons. The electron beam increases the temperature of the porous metal source until it reaches its vapor phase. The metal vapor is then condensed onto the surface of the substrate holder perpendicular to the source material. While EB-PVD is known for its advantages of higher material utilization efficiency, higher deposition rates, and better step coverage [1], it lacks in its ability to penetrate into the volume of Porous Transport Layer (PTL) or coat surfaces that are not perpendicular to the source. This is important as the PTL is in contact with a corrosive environment, which causes metal corrosion and degradation of the PTL at the surfaces that are not protected by the coating.A key aspect plaguing the thin film deposition techniques is the ability to penetrate deep into the volume of a PTL and provide full coating of the porous material, including surfaces not perpendicular to the source. In an attempt to find a solution to this challenging task, we explored the capability of the Reactive Spray Deposition Technology (RSDT) to deposit precious metal nanoclusters directly onto all surfaces in the volume of the sintered titanium material [2]. The studied metal coating of interest is Gold (Au). In this work, we have deposited Au coatings of various thicknesses onto the Ti-PTLs by using both EB-PVD and RSDT techniques. The Au thin film deposits are characterized by scanning electron microscopy (SEM), digital optical microscopy, inductively coupled plasma (ICP), and focused ion beam scanning electron microscopy (FIB-SEM) [2]. The optimal deposition parameters for thin and continuous Au films with precisely controlled thicknesses have been identified. In addition, the depth of penetration of the deposits in the volume of the PTL as a function of the deposition parameters have been studied in detail, and the results will be reported at the ECS 242 meeting.

In this chapter we describe three different approaches for three-dimensional imaging of electron microscopic samples: serial sectioning transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) tomography, and focused ion beam/scanning electron microscopy (FIB/SEM) tomography. With these methods, relatively large volumes of resin-embedded biological structures can be analyzed at resolutions of a few nm within a reasonable expenditure of time. The traditional method is serial sectioning and imaging the same area in all sections. Another method is TEM tomography that involves tilting a section in the electron beam and then reconstruction of the volume by back projection of the images. When the scanning transmission (STEM) mode is used, thicker sections (up to 1 μm) can be analyzed. The third approach presented here is focused ion beam/scanning electron microscopy (FIB/SEM) tomography, in which a sample is repeatedly milled with a focused ion beam (FIB) and each newly produced block face is imaged with the scanning electron microscope (SEM). This process can be repeated ad libitum in arbitrary small increments allowing 3D analysis of relatively large volumes such as eukaryotic cells. We show that resolution of this approach is considerably improved when the secondary electron signal is used. However, the most important prerequisite for three-dimensional imaging is good specimen preparation. For all three imaging methods, cryo-fixed (high-pressure frozen) and freeze-substituted samples have been used.

Analysis of cellular ultrastructure has been dominated by transmission electron microscopy (TEM), so images collected by this technique have shaped our current understanding of cellular structure. More recently, three-dimensional (3D) analysis of organelle structures has typically been conducted using TEM tomography. However, TEM tomography application is limited by sample thickness. Focused ion beam-scanning electron microscopy (FIB-SEM) uses a dual beam system to perform serial sectioning and imaging of a sample. Thus FIB-SEM is an excellent alternative to TEM tomography and serial section TEM tomography. Animal tissue samples have been more intensively investigated by this technique than plant tissues. Here, we show that FIB-SEM can be used to study the 3D ultrastructure of plant tissues in samples previously prepared for TEM via commonly used fixation and embedding protocols. Reconstruction of FIB-SEM sections revealed ultra-structural details of the plant tissues examined. We observed that organelles packed tightly together in Nicotiana benthamiana Domin leaf cells may form membrane contacts. 3D models of soybean nodule cells suggest that the bacteroids in infected cells are contained within one large membrane-bound structure and not the many individual symbiosomes that TEM thin-sections suggest. We consider the implications of these organelle arrangements for intercellular signalling.

Identification of interdendritic phases in Ni[sbnd]30Cr weld metal with additions of tantalum and molybdenum using electron diffraction pattern and high-resolution scanning transmission electron microscopy image analysis

In this study, the effects of plasma assistance on the electron beam physical vapour deposition (EB-PVD) process were investigated using an industrial coater (Smart Coater ALD Vacuum Technologies GmbH) equipped with a dual hollow cathode system. This configuration enabled the generation of a plasma environment during the deposition of the ceramic top coat onto a metallic substrate. The objective was to assess how plasma assistance influences the microstructure and thickness distribution of 7% wt. yttria-stabilised zirconia (YSZ) thermal barrier coatings (TBCs). Coatings were deposited with and without plasma assistance to enable a direct comparison. The thickness uniformity and columnar morphology of the 7YSZ top coats were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties of the deposited coatings were verified by the scratch test method. The results demonstrate that, in the presence of plasma, columnar grains become more uniformly spaced and exhibit sharper, well-defined boundaries even at reduced substrate temperatures. XRD analysis confirmed that plasma-assisted EB-PVD processes allow for maintaining the desired tetragonal phase of YSZ without inducing secondary phases or unwanted texture changes. These findings indicate that plasma-assisted EB-PVD can achieve desirable coating characteristics (uniform thickness and optimised columnar structure) more efficiently, offering potential advantages for high-temperature applications in aerospace and power-generation industries. Continued development of the EB-PVD process with the assistance of plasma generation could further improve deposition rates and TBC performance, underscoring the promising future of HC-assisted EB-PVD technology.

Although shale gas systems constitute a new target for commercial hydrocarbon production, only a little attention has been paid to the evolution of these unconventional systems with increasing thermal maturation. This study reports the characterization of samples of the Lower Toarcian (Lower Jurassic) Posidonia Shale from northern Germany at varying levels of thermal maturity. Observations were made using an original combination of focused ion beam-scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM). The paper documents the formation of microfracture-filling bitumen in close assotiation with kerogen residues with increasing maturity. Porosity evolves from mostly submicrometric interparticle pores in immature samples to intramineral and intraorganic pores in overmature (gas mature) samples. This intraorganic nanoporosity has most likely come about by the exsolution of gaseous hydrocarbon and been hydrocarbon wet during the thermal maturation processes. Although FIB-SEM and TEM images are small compared to field size, this study emphasizes the need for nanoscale imaging to better constrain hydrocarbon generation processes in gas shale systems.

BioSpotlight

Thermal barrier coatings (TBCs) are being developed for the key technology of gas turbine and diesel engine applications. In general, 8 mass% Y2O3–ZrO2 (8YSZ) coating materials are used as the top coating of TBCs. The development of hafnia-based TBC was started in order to realize the high reliability and durability in comparison with 8YSZ, and the 7.5 mass% Y2O3–HfO2 (7.5YSH) was selected for coating material. By the investigation of electron-beam physical vapor deposition (EB-PVD) process using 7.5YSH ceramic ingot, 7.5YSH top coating with about 200 µm thickness could be formed. The microstructure of the 7.5YSH coated at coating temperature of 850 °C showed columnars of laminated thin crystals. On the other hand, the structure of the 7.5YSH coated at coating temperature of 950 °C showed solid columnars. From the result of sintering behavior obtained by heating test of 7.5YSH coating, it was recognized that the thermal durability of 7.5YSH coating was improved up to about 100 °C in comparison with 8YSZ coating. This tendency was confirmed by the experimental result of the thermal expansion characteristics of sintered 7.5YSH and 8YSZ.©2003 Elsevier Science Ltd. All rights reserved.

Caudofoveates are benthic organisms that reside in the deep waters of continental slopes in the world. They are considered to be a group that is of phylogenetic and ecological importance for the phylum Mollusca. However, they remain poorly studied. In this work, we revealed the structure of the spicules of Caudofoveatan mollusks Falcidens sp. The spicules presented a hierarchical organization pattern across different length scales. Various imaging and analytical methods related to light and electron microscopy were employed to characterize the samples. The primary imaging methods utilized included: low voltage field emission scanning electron microscopy (FEG-SEM), focused ion beam-scanning electron microscopy (FIB-SEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and electron diffraction. In addition, we performed a physicochemical analysis by electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDS). A crucial factor for successfully obtaining the results was the preparation of lamellae from the spicules without damaging the original structures, achieved using FIB-SEM. This allowed us to obtain diffraction patterns of significant areas of well-preserved sections (lamellae) of the spicules in specific directions and demonstrate for the first time that the bulk of these structures is organized as a single crystal of calcium carbonate aragonite. On the other hand, AFM imaging of the spicules’ dorsal surface revealed a wavy appearance, composed of myriads of small, pointed crystallites oriented along the spicules’ longer axis (i.e., the c-axis of the aragonite). The organization pattern of these small crystallites, the possible presence of twins, the relationship between confinement conditions and accessory ions in the preference for mineral polymorphs, and the single crystalline appearance of the entire spicule, along with the observation of growth lines, provide support for further studies employing Caudofoveata spicules as a model for biomineralization studies.

The three-dimensional structure of thermal barrier coatings has an important effect on its performance. Thermal barrier coatings prepared by electron beam physical vapor deposition (EB-PVD) was investigated, and a hightemperature oxidation experiment at 1050℃ was carried out, three-dimensional(3D) imaging were performed by micro- CT and focused ion beam-scanning electron microscopy, and the three-dimensional structure of EB-PVD thermal barrier coatings was obtained. Three-dimensional distribution of thermally grown oxide, inter-diffusion zone, pores, microcracks were obtained, and the thickness of TGO and micro-cracks were quantitatively analyzed. The results show that the TGO thickness analyzed by micro-CT and FIB-SEM are consistent with SEM results, the average depth of microcracks is 0.14 μm, and the micro-cracks only can be observed by a higher resolution micro-CT.

Artificial bright spots, which appear in some atomic resolution high-angle annular dark field scanning transmission electron microscope (HAADF STEM) images, have been accounted for by simulations based on Bloch wave description. This is illustrated with Si and SrTiO3 images. The simulation reveals that bright spots on no-atomic columns in [011]-orientated Si images are produced by thermal diffuse scattering from Si atoms on their surrounding atomic columns, which are under the subsidiary peaks in the incident convergent electron probe. Similarly, bright spots on oxygen columns in [001]-orientated SrTiO3 images are ascribed to Sr and Ti atoms in their surrounding atomic columns rather than O atoms in the O columns. The probe function, therefore, provides a simple explanation for the appearance of these artificial spots.

Energy storage devices allow us to use energy in a flexible, high efficient and eco-benign way, which has profoundly shaped our everyday life. The most successful energy storage device is lithium-ion battery (LIB), which has dominated the portable electronic devices and are now penetrating deep into vehicle markets. However, the limited reserves of lithium and cobalt in the earth crust cannot fulfill the huge demand gap of electrochemical energy storage, and the fast expansion of LIB industry has already led to accelerated cost rising. Therefore, worldwide research programs strategically encourage the development of energy storage devices beyond LIB, among of which, sodium ion battery (SIB) is a very attractive one. Sodium is much more natural abundance and more importantly SIB industry can share facilities and technologies from LIB because of the similarities of physical and chemical properties between Li and Na. To achieve superior performance of SIB, high performance cathode material plays a critical role. Among of variety of cathode candidates, layered NaxTMO2 (TM refers to transition metal) oxides are promising and widely studied, which can be grouped into two families, P2-type and O3-type structures. However, one critical drawback for both P2-type and O3-type layered oxides is the multi-phase-transition reactions during charge/discharge, which leads to the annoying multi-voltage-plateaus in voltage-capacity profiles. Various ordering processes (TM ordering, charge ordering and Na-vacancy ordering) and structure transitions (P2-O2, O3-P3, et al) have been identified previously. The structural ordering will result in sluggish Na-ion transportation kinetics and it can further couple with the structural transformation to collectively cause structural instability, significantly plaguing the cycling performance. Therefore, many efforts have been taken to suppress the structural ordering and transformation, namely eliminating the multi-voltage-plateaus in the charge/discharge profile. Particularly for P2-Na2/3Ni1/3Mn2/3O2 (NNM), doping electrochemically inactive elements (Li, Mg, Cu or Zn) is proven to be an effective approach to suppress the P2-O2 phase transition and Na-vacancy ordering to achieve improved electrochemical performance. In this work, by virtue of variety of analytical tools, such as X-ray diffraction (XRD), focused ion beam/scanning electron microscopy (FIB/SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF) imaging, we conduct systematic investigations on the degradation mechanisms of P2-NNM and find that P2-O2 phase transition induced grain cracking is the main cause of performance decay. Our further investigations on the role of dopant on P2-Na0.67Ni0.33-xMn0.67MgxO2 (x=0, 0.05, 0.1) (P2-NMMx) and find that doping electrochemically inactive elements can suppress intragranular cracking to improve cycle stability of P2-NM. we show that dopants segregation is more effectively to suppress intragranular crack and improve cycling stability than dopant uniform distribution in TM layer. By virtue of variety of analytical tools and simulation, dopant segregation have been characterized comprehensively and come up a new strategy, precipitation strengthening mechanism, to alleviate electrochemomechanical degradation and enhance stability of layered cathode operating at high voltage.

Franckeite (˜FeSn3Pb5Sb2Si14) has a complex modulated structure containing alternating layers of different composition. The complex composition and structure, lack of a well-defined unit cell, incommensurate character, and poor quality of crystals has made it difficult to study by standard X-ray and electron-diffraction methods. High-angle annular dark-field (HAADF) STEM imaging provides a way of mapping the compositional distributions directly and with atomic resolution. For thin regions of the sample, the intensity of the electrons scattered at high angles depends strongly on the atomic number of the scatterer. This unique property makes HAADF imaging powerful for studying compositional modulations on the atomic scale. By comparing the structure as viewed by high-resolution imaging to the compositional information provided by the HAADF technique, we have been able to obtain an improved understanding of crystal structures with displacive and compositional modulations, such as franckeite. We use the HAADF technique to test the assumption that in franckeite two kinds of layers (SnS2 and PbS) are stacked along the a axis with a 1.73 nm repeat, and that Sb and Fe produce structural modulations in the c direction.

Several kinds of thermal barrier coatings (TBCs) deposited by electron beam physical vapor deposition (EB-PVD) were produced as a function of electron beam power in order to evaluate their strain tolerance. The deposition temperatures were changed from 1210 K to 1303 K depending on EB power. In order to evaluate strain tolerances of the EB-PVD/TBCs, a uniaxial compressive spallation test was newly proposed in this study. In addition, the microstructures of the layers were observed with SEM and Young’s moduli were measured by a nanoindentation test. The strain tolerance in as-deposited samples decreased with an increase in deposition temperature. In the sample deposited at 1210 and 1268 K, high-temperature aging treatment at 1273 K for 10 h remarkably promoted the reduction of the strain tolerance. The growth of thermally grown oxide (TGO) layer generated at the interface between topcoat and bondcoat layers was the principal reason for this strain tolerance reduction. We observed TGO-layer growth even in the as-deposited sample. Although the thickness of the initial TGO layer in the sample deposited at high temperature was thicker, the growth rate during aging treatment was smaller than those of the other specimens. This result suggests that we can improve the oxidation resistance of TBC systems by controlling the processing parameters in the EB-PVD process.

The effect of both composition and substrate temperature on the structure and properties of quasicrystalline Al–Cu–Fe coatings obtained by high-rate (˜100 nm s−1) electron beam physical vapour deposition (EBPVD) was studied. An icosahedral phase has been observed in thick coatings in a much wider concentration range compared with in cast alloys. A lowering of substrate temperature results in a decrease of grain size of the quasicrystalline coating (down to nanosized scale) and an increase of the concentration of vacancy-type defects in the quasicrystalline structure. The features of the quasicrystalline structure of the coatings are shown to have an influence on their mechanical behaviour at both static and alternate loadings.