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    Environmental and in-situ scanning electron microscope
    The direction of the Hamburg University of Technology towards becoming a sustainable institution with research excellence has significantly defined the new research structure with five strategic research fields. Several of these fields, e.g. "Advanced Materials & (Bio-) Processes" and "Environmental & Energy Systems" are directly reflected in the currently planned large-scale research projects, the Collaborative Research Center 1615 "Smart Reactors", the Federal Cluster of Excellence "BlueMat: Water-Driven Materials" and the extension of the Research Training Group 2462 "Processes in Natural and Engineered Particle-Fluid Systems". These projects and those described in this proposal rely on the analysis of sample systems in environments with dynamically changing parameters. Key requirements of these projects for sample investigations at the microscopic level include, in addition to humid environments, oxidizing and reducing conditions at temperatures ranging from -20 °C to 1400 °C. To ensure such investigations, an environmental and in-situ scanning electron microscope is required. Especially the possibility to perform temperature- and gas-controlled experiments of electron-transparent samples with a structural resolution of a few nanometers in scanning transmission mode by means of a field emission cathode and a special holder is a necessary condition for the analysis of nanoporous systems, such as aerogels. Also, wetting studies of electron-transparent building material or nanoporous silicon samples are only possible with scanning transmission mode in an environmental and in-situ scanning electron microscope and are not feasible with, for example, in-situ liquid holders for transmission electron microscopes. Additionally, to achieve an improved image quality even under high temperatures and partial pressures, imaging by means of absorbed electron beam current is necessary. A mass spectrometer is intended as an important component for constant monitoring of the gas environment. The Electron Microscopy Unit is the user-based equipment center for electron microscopy at Hamburg University of Technology. The continuous modernization of the Electron Microscopy Unit since 2011 with powerful electron microscopes as well as equipment for sample preparation and tomography was a key prerequisite to enable competitive research, e.g. for the Collaborative Research Center 986. Numerous current and future research projects in materials science, process engineering and building materials technology are based on high-performance electron microscopy in the form of individual or joint projects. With the environmental and in-situ scanning electron microscope applied for here, it will be possible to carry out the planned research projects that rely on the analysis of sample systems in changing environmental conditions.
      6
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    SPP 2020: Cyclic deterioration of High-Performance Concrete in an experimental-virtual lab
    Extensive advances in concrete technology have led to the development of high performance concretes with significantly expanded application possibilities. Examples include self-compacting, high-strength and ultra-high-strength concretes with steel-like strengths or fiber-reinforced and textile-reinforced concretes with highly ductile behavior. These concretes allow very slender, aesthetic and resource efficient concrete structures, which are more susceptible to vibration due to their reduced weight. Even outside of the classical construction industry, the range of applications for high-performance concretes will undergo considerable development, for example in mechanical and plant engineering, where they can become an alternative to metallic and ceramic materials. All of these structures are subjected to highly cyclical loading, so that the fatigue behavior is crucial for their design and thus for the feasibility of innovative concrete applications. However, there is any basic knowledge of material degradation of concrete under fatigue stress hardly available. Because of these gaps in knowledge, the use of modern high-performance concretes is already considerably hindered, sometimes even prevented.The designed aim of this priority program is to capture, understand, describe, model and predict the material degradation of high-performance concretes using the newest experimental and virtual numerical methods. Since the damage processes occur on a very small scale, they cannot be entirely observed during the load tests. The recording of suitable damage indicators during the experiments make the time-consuming fatigue tests already very demanding. To this extent, the desired results will be developed from a close cooperation between the building material science and the computational mechanics knowledge, which is the interconnection of experiment and computation in the Experimental-Virtual-Lab.An SPP is the perfect framework to resolve the pressing issues of material degradation across locations. The collaboration is designed in such a way that in addition to an intensive exchange of experimental techniques, damage indicators and modeling approaches, a multiple use of the experimental data and a close interaction between experiment and simulation is achieved. Due to the complex experimental technique and the necessity of a fundamental further development of material models, a strong cooperation of the participating locations is promoted with special structural arrangements. Only in this way the existing barriers to the use of fatigue-stressed high-performance concretes can be overcome and an innovation boost for building with concrete and for concrete applications outside of the classical construction industry can be triggered. The new knowledge will also enable to extend the service life of existing fatigue-stressed structures such as bridges and wind turbines.
      174
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    3D FIB/SEM Untersuchung von Salzbetonen
    Im Auftrag der Technischen Universität Braunschweig und in Zusammenarbeit mit der Bundesgesellschaft für Endlagerung (BGE) in Peine wird die Mikro- und Nanoporosität verschiedener Salzbetone mittels Focused Ion Beam (FIB) Tomographie untersucht.
      57
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    SFB 986: Subproject B09 - Microstructure-based classification and mechanical analysis of nanoporous metals by machine learning
    In this research project mathematical methods will be developed to characterize precisely and comprehensively the complex microstructure of nanoporous metals. Based on such characterization, on the one hand machine learn-ing will be used to classify nanoporous metals with regard to their microstructure, which will allow quantitative statements how different production processes affect the microstructure and thus the physical properties of nanopo-rous metals. On the other hand, a new approach will be developed that combines the finite element method with machine learning in order to enable substantially acceler-ated micromechanical simulations of nanoporous metals. The scientific objective of this project is to develop ad-vanced computational methods that can help to unravel the relation between processing, microstructure and me-chanical properties in nanoporous metals. These methods can be used in other projects of the SFB 986, in particular in the projects B2 and B4, to better understand and optimize the favorable properties of nanoporous metals.
      252
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    Subproject of SPP 2020: High resolution electron microscopy of fatigue behavior in high performance concrete and multiscale modelling using a bonded particle model
    The project focuses on two topics: firstly, the examination of structural damage caused by fatigue in cementitious high performance materials using high resolution analytical electron microscopy. The correlation with the inhomogeneities within the material, for example the residues of the plasticizers in the hydrated material, is of special interest. It is our working hypothesis, that in high performance concretes without capillary porosity, the initiation of cracks is caused by such inhomogeneities, whereas in normal strength concrete the initiation of cracks is linked to capillary porosity and the pores within the transition zone. Secondly, the aim of the project is the multiscale modelling of fatigue in high performance concrete using a bonded particle model (BPM). The project concentrates on concrete without capillary pores. The analysis of the structural damage requires very small specimens Tension tests on such small specimens will be performed in a transmission electron microscope. The results of these mechanical tests will be linked to the spatial distribution of the phases within the concrete. The examination of the crack propagation is performed on macroscopic specimens damaged by fatigue. Parts of these specimens will be analyzed by FIB-tomography. This method allows a three-dimensional reconstruction of the structure with very high resolution. Therefore, a large portion of the scientific work will be the development of methods for analyzing concrete with high resolution electron microscopy. These methods will then be made available for the whole DFG priority program. In addition, these examinations will produce fundamental results with regard to structural damage, crack formation and crack propagation in the case of fatigue, for the own modelling as well as for the modelling work of other projects within the DFG priority program.The numerical research work is focused on the development of a multiscale BPM-based simulation approach and on the validation of meso- and macro-scale models for the description of fatigue behavior. The new approach should be able to predict the influence of cyclic loading on mechanical properties; consider the influence of mesoscopic concrete structure on macroscopic behavior; describe initiation and coalescence of micro- and growth of macro cracks, which lead to material destruction.The modeling of investigated samples will be performed with the self-developed simulation framework MUSEN, which will be extended with new calculation algorithms and rheological models. The validation of the simulation results and the estimation of the model parameters will be made based on data experimentally obtained for high-performance concrete and its components. Thereby, information not only about macroscopic material behavior will be used, but also data obtained from electron microscopy will be applied to create, adjust and validate the models.
      965
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    SFB 986: Subproject Z03 - Electron Microscopy of Multi-scale Materials Systems
    The production of multi-scale materials systems is one focus of the SFB 986. Another focus lies in the analysis and characterization of the newly acquired materials via scanning and transmission electron microscopy(SEM/TEM). The task and the purpose of the service project Z3 is to provide classic sample preparation methods as well as modern sample preparation by a focused ion beam(FIB) for electron microscopy. Using the existing sample preparation methods and microscopes, the structure and chemical nature of multi-scale materials can be efficiently analyzed and characterized at middle and high magnification. The findings will serve as a basis for characterizing the materials used in SFB, for assessing production methods and production parameters, and furthermore for conducting more complex investigations, e.g., by high resolution transmission electrons microscopes(HRTEM), scattering method, or micro-tomography.
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