Microscopy Conference 2023

Prof. Dr.

Session chairs

Prof.

Combining electron tomography of dislocations and continuum mechanics to investigate the rheology of minerals

Abstract text (incl. figure legends and references) Transmission electron microscopy is the most precise technique to characterize dislocation microstructures. Several techniques are available to determine Burgers vectors be it via extinction contrast, by thickness fringes, or with LACBED. As a linear defect, a dislocation is also determined by its geometry, which gives important information on the deformation mechanisms like glide, climb, or cross-slip. In comparison to Burgers vectors, characterization of line orientations are less common and rely often on the use of the stereographic projection following tilting experiments. Although applications of tomography in the transmission electron microscope (TEM) date back to the 70s, it is only in 2006 that it has been applied to dislocations [1]. The difficulty lies in the need to cover a large range of tilt while keeping the diffraction contrast rigorously constant. Using electron tomography of dislocations in the TEM provides a quantitative volumetric characterization of the dislocation microstructure. In this presentation, we show how this possibility can be exploited to build an interface with continuum mechanics. This allows in particular to identify the non-zero components of the strain tensor [2] or to determine the Nye tensor of dislocations. A further step is to implement the dislocation microstructure in a Dislocation Dynamics code (DD), NuMoDis [3] to investigate the temporal evolution of the microstructure under stress. We present applications in quartz and olivine which are important mineral phases of the crust and the mantle respectively. Quartz presents the additional challenge of being very sensitive to electron irradiation which requires an adapted tilted series acquisition strategy. [1] Barnard, J. S., Sharp, J., Tong, J. R., &amp; Midgley, P. A. (2006). High-resolution three-dimensional imaging of dislocations. Science, 313(5785), 319-319. [2] Mussi, A., Gallet, J., Castelnau, O., &amp; Cordier, P. (2021). Application of electron tomography of dislocations in beam-sensitive quartz to the determination of strain components. Tectonophysics, 803, 228754. [3] Drouet, J., Dupuy, L., Onimus, F., Mompiou, F., Perusin, S., Ambard, A. (2014): Dislocation dynamics simulations of interactions between gliding dislocations and radiation induced prismatic loops in zirconium. J. Nucl. Mater., 449, 252-262.

IM 5: Quantitative image and diffraction data analysis

MS 6: Geoscience and construction materials, cultural heritage

Poster

Application of microscopic methods in the field of structural diagnostics: the drift seal of the Morsleben repository

Abstract text (incl. figure legends and references) According to the multi-barrier concept, radioactive waste is isolated in geological repositories by the host rock and engineered barriers (seals). One group of sealing materials are concretes. During the emplacement and hardening of the concrete, processes can occur that could impair the effectiveness of the seals. As long as the mixture is fluid, the components can separate and air bubbles can escape. The heat of the chemical reactions results in a temperature rise and fall that could lead to volume changes, stresses, and cracking. Moreover, stresses and volume changes can be the result of mineral transformations and the build-up of a grain structure. During the closure of the Morsleben repository drift seals will be erected. When using salt concrete, the contact zones to the host rock will be grouted. A pilot seal was built to investigate the spatial distribution of the sealing materials, their structure as well as the occurrence of cracks and their spatial distribution. The investigations included microscopic analyzes of the core seal, the contact zone to the host rock and the adjacent rock salt. Thick and thin sections were prepared from drill cores from all areas. For better visualization of cracks, the specimens were vacuum impregnated with blue colored resin and the surfaces of the specimens were polished. All specimens were examined with digital light microscopes. The non-transparent grout and concrete were viewed in reflected light. Moreover, thin section analysis and computed tomographic analysis were carried out. Rock salt could be viewed in reflected and transmitted light. The work can be divided into an image analysis and a crack analysis. The aim of the image analysis was, for example, to describe the distribution of aggregates in the salt concrete (concrete edge zone), the shape of the contact area with the host rock and the spatial distribution of the grout. The blue-colored resin made it possible to draw conclusions about the depth of damage to the rock salt. In order to draw conclusions about the permeability of the damaged area, information on the extent, thickness, spatial position and cross-linking of the cracks is required. This task included the crack analysis. The basis of the analysis were sets of photos. The technique of image stacking was used to improve the depth of field (cf. Engelhardt 2016). Measurement values of crack orientations were analyzed by the the numeric computing platform MATLAB. Photo stitching was used to get an overview of larger sample areas. Anaglyphs were made to get a three-dimensional impression of the structure of the rock salt. The ImageJ/Fiji software package was used for image and crack analysis. The application is an example of the combined and successful use of microscopic methods in the field of structural diagnosis. Engelhardt, H.-J. (2016) Der Einsatz von Focus-Stacking bei der Untersuchung von Flüssigkeitseinschlüssen im Steinsalz. Mikroskopie, 3 (07): 166-172. Von Borstel, L.E.; Engelhardt, H.-J. &amp; Köhler, M. (2012) Präparationstechnik zur Visualisierung des Porenraumes von kompaktiertem Salzgrus mittels Dünnschliffen. Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften (SDGG), Heft 80, GeoHannover 2012, 1.–3.10.2012, p. 552.

LS 4: Image analysis of large data sets

Discovering Baltic networks using TEM: Comparative material analysis on medieval age brass ornaments

Abstract text (incl. figure legends and references) Introduction: Modern nano analysis can affectively help understand the material culture in the past societies by analyzing the excavated artefacts. In the recent past, increasingly sophisticated analytical methods have been used to study ancient artefacts to test various hypotheses related to the material aspects of these artefacts. In this research work advanced material analysis methods have been utilized to investigate the medieval age artefacts from East Baltic regions and Eastern Europe using nano analytical technique such as transmission electron microscopy (TEM). Objectives The objective of this research work is to test the hypotheses of possible immigration of population from East Baltic regions to Ostriv (present day Ukraine). Strong similarities between the physical attributes of the excavated artefacts from the two regions led to believe of a possible connection between the two regions. To explore this possible connection between the regions, laboratory analysis of the artefacts was planned to compare the production mechanism of the artefacts found in East Baltic regions and Ostriv. Materials and Methods: Two sets of samples belonging to the 11-12th century copper alloys were used such as fibulas, penannular brooches and flat ladder brooches. The first set of items was found in a cemetery by a group of Ukrainian scientists in Ostriv (Ukraine) within the skeletal graves. The other set of samples was received from Berlin Museum for Pre- and Early History that belonged to the East Baltic regions. The ornaments were studied by means of Energy Dispersive X-Ray (EDX) Spectroscopy in a Jeol JEM-2100 equipped with an EDX detector (Si/Li, EDAX). The analysis was performed on lamellae prepared from the surface of the ornaments into a depth of ca. 10 µm via Focused Ion Beam (FIB). EDX point measurements and elemental maps were performed in STEM mode. Results: The EDX analysis showed the presence of brass in the artefacts from Ostriv, however, the artefacts from East Baltic regions consisted of pure copper, brass and bronze. Additional surface limited signals from carbon, iron, lead, chlorides, sulphates, oxides and phosphates were also observed. TEM-EDX on the FIB lamellae showed Cu and Zn as the major constituents with traces of organic compounds and oxidation possibly as a result of secondary alteration. Astonishingly, the same physical features in the artefacts from East Baltic and Ostriv regions do not translate into same production mechanisms. The zinc content in the artefacts is also varying in the brass ornaments found in Ostriv cemetery. Conclusion: The advanced methodology for analyzing the archaeological artefacts is shown in this study. The study demonstrated the comparison of chemical compositions between the medieval age brass ornaments from East Baltic and Ostriv regions. The authors further demonstrate the modification of surface and subsurface of the archaeological artefacts, that are buried under the soil for thousands of years. The similar physical features but different elemental composition could suggest the transfer of technology through the population that migrated from East Baltic regions to Ostriv. Material composition of archaeological artefacts served as an important identifier to unearth technology exchange and network between medieval Baltic population.

MS 2: Metals and alloys

A full-field quantitative analysis of grain boundary sliding using digital image correlation (DIC) inside a transmission electron microscope

Abstract text (incl. figure legends and references) Abstract In experimental mechanics, the digital image correlation (DIC) technique using scanning transmission electron microscope (SEM) images has been extensively used for quantitative deformation analysis [1]. In order to increase the sensitivity of DIC toward nanoscale strain detection, efforts are made to couple the DIC with transmission electron microscopy (TEM) images. At present, there are only a few experimental DIC studies available based on TEM [2, 3], hence exploiting this direction on various materials is desirable. In the present work, the grain boundary sliding deformation mechanism in olivine is investigated through the DIC technique coupled with TEM to get enhanced spatial resolution for mapping the small localized strain onset of the grain boundary sliding. For this purpose, forsterite nano-tensile specimens containing a single grain boundary or a triple point are prepared from synthetic forsterite (Mg-rich end member of olivine) by focused ion beam (FIB) after grain orientation mapping using ASTAR (see Fig. 01). Further, the surface of the tensile samples is decorated with nano-Pt particles during FIB. The in-situ nanomechanical test performed inside TEM uses high-angle annular dark field (HAADF) imaging to minimize the dynamical contrast. We demonstrate that during the deformation, strain localized at the grain boundaries triggers the sliding activity. These full-field quantitative nanoscale deformation investigations provide insight into the mechanisms that influence the macroscopic response. [1] A. Weidner and H. Biermann, "Review on Strain Localization Phenomena Studied by High-Resolution Digital Image Correlation," Adv. Eng. Mater., vol. 23, no. 4, 2021, doi: 10.1002/adem.202001409. [2] X. Wang, Z. Pan, F. Fan, J. Wang, Y. Liu, Scott X. Mao, T. Zhu, and S. Xia, "Nanoscale deformation analysis with high-resolution transmission electron microscopy and digital image correlation," J. Appl. Mech. Trans. ASME, vol. 82, no. 12, pp. 1–9, 2015, doi: 10.1115/1.4031332. [3] Y. Zhang, L. Feng, S. Dillon, and J. Lambros, "Full-field deformation measurements in the transmission electron microscope using digital image correlation and particle tracking," Mater. Charact., vol. 183, no. July 2021, p. 111598, 2022, doi: 10.1016/j.matchar.2021.111598. Fig. 01 Sample preparation and in-situ TEM nanomechanical experiment (a) FIB lamella showing the different grain boundaries and inset showing the ACOM-TEM from the selected area for cutting the tensile specimen (b) Push-To-Pull (PTP) device for in-situ TEM. A diamond flat punches the semicircular end on the top and opens the middle gap to strain the specimen. Inset shows the forsterite tensile specimen having a triple junction grain boundary before the fracture.

MS 7: Ceramics and composites

Miss

The structure, character, and relative energies of grain boundaries in Mg­2SiO4

Abstract text (incl. figure legends and references) Mg&shy;2SiO4 is a ceramic with geological and engineering relevance. It is the most abundant mineral in the Earth's upper mantle, meaning its properties dominate mantle behaviour. Additionally, it is a refractory material with applications in microwave dielectric devices and promising bio-compatible properties. It has been shown that the grain boundary energy is inversely correlated to the total area of that interface in a system(Li et al., 2009). The Grain Boundary Character Distribution (GBCD) shows the proportion of different types of interfaces in a system and is key to understanding melt extraction, texture formation, creep regimes, and electrical and optical properties of materials. It has also been shown that the relative grain boundary energy varies with grain size(Bojarski et al., 2013). In this study we aim to investigate these relationships in the Mg&shy;2SiO4 system, with studies of specific interfaces to determine their complexions. Synthetic Mg&shy;2SiO4 samples with grain sizes of 0.4, 3.4, 7.8 and 5.4 μm were synthesised by vacuum sintering(Koizumi et al., 2010) and subsequently characterized with Electron Backscatter Diffraction (EBSD) and Atomic Force Microscopy (AFM). Over 230,000 grain boundary segments were extracted from EBSD maps encompassing over 70,000 grains to extract the Grain Boundary Character Distribution (GBCD) of each sample. Thermal etching was used to reveal grain boundary grooves which were mapped using AFM to extract their depth profile. From this data the relative grain boundary energy for different grain sizes was determined using a simplified Young's Equation. Finally, thin sections were prepared using mechanical and ion polishing for HRTEM imaging of individual interfaces. Analysis of thermal grooves shows a decrease in average relative grain boundary energy with increasing grain size from 0.48 arbitrary units for 0.4 μm grain size to 0.41 for an average grain size of 7.8 μm. Furthermore we observe a difference in the relative grain boundary energy between normal and abnormally grown grains. We will discuss these results in relation to the GBCD and structure. Bojarski, S. A., Knighting, J., Ma, S. L., Lenthe, W., Harmer, M. P., &amp; Rohrer, G. S. (2013). The relationship between grain boundary energy, grain boundary complexion transitions, and grain size in Ca-doped Yttria. Materials Science Forum, 753, 87–92. https://doi.org/10.4028/www.scientific.net/MSF.753.87 Koizumi, S., Hiraga, T., Tachibana, C., Tasaka, M., Miyazaki, T., Kobayashi, T., Takamasa, A., Ohashi, N., &amp; Sano, S. (2010). Synthesis of highly dense and fine-grained aggregates of mantle composites by vacuum sintering of nano-sized mineral powders. Physics and Chemistry of Minerals, 37(8), 505–518. https://doi.org/10.1007/s00269-009-0350-y Li, J., Dillon, S. J., &amp; Rohrer, G. S. (2009). Relative grain boundary area and energy distributions in nickel. Acta Materialia, 57(14), 4304–4311. https://doi.org/10.1016/j.actamat.2009.06.004

Networks of partially open grain and phase boundaries in magmatic and metamorphic rocks

Abstract text (incl. figure legends and references) TEM/FIB-based investigations have shown that grain and phase boundaries of various minerals in different metamorphic and magmatic rocks are lastingly open on the nanometer scale and partly to totally filled with secondary minerals [1, 2]. The most likely reason for opening is the exhumation of rocks and the associated temperature and pressure decrease, which leads to volume reduction and internal stresses on the grain scale and causes fracturing and opening of the boundaries. This is confirmed by 3D numerical modelling, combining contact mechanics and finite-element method [3]. It is assumed that opening starts below the temperature threshold for dislocation creep in the different minerals. TEM investigations are restricted to small material volumes. Therefore, scanning electron microscopy (SEM) is applied to cm-large thin-section areas. The drastically enlarged data set provides statistically reliable information about conditions of opening and filling of boundaries in grain aggregates with different size and crystallographic orientation of grains. Investigated rocks and minerals include contact-metamorphic quartzite, deformed vein quartz, metagabbro, lherzolite, garnet-sillimanite rock, felsic granulite, calcsilicate rock, jadeite quartzite, syntectonic granitoid, and marble. Over entire thin-section areas, roughly 90% of the boundaries are continuously open or partly filled with secondary minerals, independently of mineral type, and grain size, shape and crystallographic orientation. This confirms previous TEM investigations on a much broader data basis. The two crystal faces of an open boundary are mostly strictly parallel to each other. The width of opening remains generally constant between triple junctions, i.e., typically over tenth of micrometers. However, boundary kinks show that movement directions are often not perpendicular but oblique to the boundary. Open space is also developed between filling and crystal faces. This points to more than one stage of opening. Particularly in quartz, micrometer-large, often conical voids frequently occur along open boundaries indicating dissolution-precipitation processes. For quartz, a weak correlation exists between grain size and boundary opening width, however, is absent for the crystallographic orientation of boundaries and opening width. This confirms that cracking and opening of boundaries are controlled in a complex way by the development of stress on the grain scale and movements in the grain aggregate. In general, these findings demonstrate that grain and phase boundaries are completely or partly open in all types of magmatic and metamorphic rocks and form pathways for fluid migration on thin-section scale but most likely also on larger scales. This represents a ubiquitous structural phenomenon of crystalline materials under at least upper-crust to surface conditions. It controls not only various physical properties of crystalline material but also governs its behavior during different natural and technical conditions as well as in experiment. [1] Kruhl, J.H., Wirth, R., Morales, L.F.G., 2013. JGR Solid Earth. https://doi.org/10.1002/jgrb.50099 [2] Wirth, R., Kruhl, J.H., Morales, L.F.G., Schreiber, A., 2020. J. Metam. Geol. https://doi.org/10.1111/jmg.12610 [3] Raghami, E., Schrank, C., Kruhl, J.H., 2020. Tectonophysics. https://doi.org/10.1016/j.tecto.2019.228242

PS 20
Poster session MS 6: Geoscience and construction materials, cultural heritage

Appointment

Session chairs

Programme

PS 20Poster session MS 6: Geoscience and construction materials, cultural heritage

Appointment

Session chairs

Programme

PS 20
Poster session MS 6: Geoscience and construction materials, cultural heritage