The particular innovative potential of the Collaborative Research Centre is its ability to develop macroscopic materials - structured in a multi-scale way, designed "on the drawing board". Owing to their design, such materials will have tailor-made mechanical, electrical and photonic properties. Predominantly, the materials are assembled from single building blocks of distinct discrete length scales. This hierarchical composition opens up possibilities to exchange building units in a concerted way in order to discretely alter materials properties and, thus, to achieve entirely new materials functions. In addition to the required experimental methods and based on their results, theoretical materials models are refined. Hence, the Collaborative Research Centre not only gains experimental expertise but also a theoretical understanding of how a hierarchical composition determines materials behaviour. To this end, theoretical modelling includes atomistic, meso-scale and continuum models. For the hierarchical structures, the single building blocks are comprised of polymers, ceramics, metals and carbon (in form of carbon nanotubes and aerographites). Those assemble and form structured and functionalised units from the atom to the macro-scale, their form being core-shell structures or cavities filled with polymers. The three project areas of the Collaborative Research Centre use different materials systems and vary both the multi-scale structure and the functionalised properties: area A is concerned with quasi-self-similar structures with multi-functional properties; area B aims at integrated nano-structured multi-phase materials systems, which - due to the design of their microstructure - combine strength and functional properties (in particular, electrical ones); area C focusses on highly ordered, hierarchical, periodic and aperiodic structures and their photonic properties at high temperatures. One question unites all three project areas: How can we influence and control the macroscopic mechanical, electrical and photonic properties of materials by shaping their hierarchical composition? By answering this question, the Collaborative Research Centre can develop hierarchical materials with tailor-made properties in a systematic way.
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- ProjectSFB 986: Subproject A03 - Fabricating of higher hierarchical levels of material systems with the fluidized bed spray granulation and Discrete Element Modeling of materialsThe most important aim of this subproject is the fabrication and coating of ceramic polymer and ceramic metal composite materials with improved mechanical strength and toughness and ultra-high packing density by using the spouted fluidized bed spray granulation process in a novel miniaturized plant. The fabricated granules are assembled afterwards to bulk materials by hot pressing and final mechanical properties are characterized. The fabricated composites consist of a hard disperse phase (ceramic, metal) and a soft continuous phase (high performance polymer). The envisaged structure of composites is hierarchically designed. The pre-structured granules are supplied from projects A1, A2, and A6. A multiscale simulation strategy including the discrete element modeling (DEM) for determination of mechanical properties and microstructure of the produced composite materials is applied, where two hierarchical levels will be modeled. The additional coupling with CFD simulations of the fluid phase will allow optimizing and analyzing the influence of the process parameters on the particle formulation and the transport processes. Main material parameters are composition, shape and size of the particles as well as type of polymer. A further extensive part of the subproject is, in cooperation with subproject C5, to simulate sintering and thermal expansion of thermal barrier coatings occurring in photonic structures using DEM. The DEM allows to predict the influence of different conditions on the material behavior as well as to consider influence of the material microstructure. The research in this area is focused on optimization of the geometric and structural parameters of photonic structures to avoid material collapse, such as debonding and crack formation. In order to validate simulation results experimental data are obtained in subproject C5 is used.Acronym:CompositesStart Date:2012-07-01End Date:2024-06-30
- ProjectSFB 986: Subproject A04 - Ab-initio-based modeling and control of mechanical properties of hybrid interfacesWithin this project, hybrid interfaces between oxide surfaces (Fe3O4, TiO2) and organic molecules (carboxylic acids, phosphonates, etc.) are investigated at the atomic length scale. The main goal is to obtain model systems which allow understanding, quantifying, and predicting material properties such as the thermodynamic stability. To this end, quantum-mechanics-based computational methods, mainly density functional theory (DFT), are employed to study the electronic and atomic structure of various interfaces. On top of DFT calculations, further methods like the cluster-expansion (CE) approach and Monte-Carlo (MC) simulations are used to scan configuration spaces exhaustively, to gain access to larger length scales, or to account for finite temperature effects. Key questions such as the structure, stability, and mechanical properties of the aforementioned hybrid interfaces including the influence of defects and co-adsorbates, or the shape of nanoparticles due to the presence of different ligands during their growth are addressed in close collaboration with the experimental projects A1, A6, A7 and other simulation projects like A5. This comprehensive approach allows us to gain fundamental knowledge on hybrid materials. A better understanding of their properties and phenomena at involved interfaces in the atomistic and nano domain will also facilitate the tailoring of properties of novel materials performed by various other projects on different hierarchical levels.
- ProjectSFB 986: Subproject A06 - Synthesis and characterization of hierarchical, multifunctional ceramic/metal-polymer materials systemsThe aim of this project is creating new bioinspired materials, through the design, synthesis and characterization of hierarchically structured composites. Such materials consist of hard (ceramic/metal) and soft phases (polymers and organic ligands). Pre-structured functionalized nanoparticles received from projects A1 and A2 are assembled into a material of progressively higher hierarchical levels. The processing steps involve self-assembly, hot-pressing and spouted bed spray granulation (with projects A2 and A3). The objective for the highest hierarchical level is an anisotropic brick-and-mortar structure, analogous to the one characterizing nacre and other exceptionally strong and tough natural materials. The composites, as well as their individual hierarchical levels, will be characterized both structurally (in collaboration with projects A7, Z2 and Z3) and mechanically (in collaboration with projects Z2 and Z3), from the nano- to the macro-scale. The key scientific question to be addressed concerns the role played by each building unit, at the different length scales, in the material’s macroscopic features. To do so, it is imperative to determine which properties and arrangements of the building units (polymeric, ceramic, metallic and nanocomposite particles) are necessary and sufficient to attain the desired mechanical and multifunctional characteristics in the final bulk material. Gaining this knowledge will ultimately lead to the tailored design of novel nanocomposites.
- ProjectSFB 986: Subproject A08 - Molecular dynamics simulation of the self-assembly of polymer coated metal/ceramic nanoparticlesNaturally occurring materials, such as nacre or enamel, usually have significantly better properties than classic materials due to their hierarchical structure. The elucidation of the influence of the structure of these materials on all hierarchical levels - from the atomistic to the macroscopic scale - makes it possible to produce materials that can be individually adapted to the specific requirements by employing a bottom-up design strategy. Molecular dynamic (MD) simulations and advanced simulation techniques to estimate free energies are used in this subproject to investigate functionalized nanoparticles (NP) produced in the project area A and to understand their properties and structure on the nanoscale. This includes, for example, the self-assembly of the ligands on iron oxide (Fe3O4) and titanium oxide (TiO2) NPs and the assembly of the functionalized NPs into super crystals. The basis for reliable results in simulations are realistic models. Consideration and implementation of structural information obtained experimentally and from ab-initio modelling in A1, A4, A6, A7 and Z3 will thus improve the quality of the simulation models. Those models will be used to investigate the process of self-assembly of the nanoparticles with simultaneous volatilization of the solvent - as carried out experimentally in A6 - and to clarify the influence of various parameters, e.g. the degree of surface coverage, on the mechanical stability of the nanocomposites.Start Date:2018-07-01End Date:2024-06-30Principal Investigator:
- ProjectSFB 986: Subproject B04 - Micromechanical behavior of hierarchical materialsDas Teilprojekt (TP) B4 befasst sich mit der Untersuchung der mechanischen Eigenschaften von hierarchischen Materialien mit dem Fokus auf die Mikroskala. Der Einfluss von Größeneffekten und Grenzflächeneigenschaften steht dabei im Vordergrund. Die in TP B4 entwickelten inversen Methoden zur Bestimmung des nichtlinearen mechanischen Verhaltens einzelner Phasen und Grenzflächen sowie die gewonnenen Erkenntnisse leisten einen wichtigen Beitrag zum Verständnis, wie die Mikromechanik das makroskopische Verformungs-, Versagens- und Bruchverhalten kontrolliert. Das TP B4 unterstützt mit diesen Erkenntnissen die Entwicklung der hierarchischen Materialien im SFB im Hinblick auf optimale makroskopische Eigenschaften.
- ProjectSFB 986: Subproject B06 - Computational modeling of metal-polymer-nanocompositesThis project is focused on the modeling and simulation of novel and hierarchical metal-polymer composites at the nanoscale. Within the framework of advanced non-linear continuum mechanics, fundamental mathematical and thermodynamic principles are used to develop suitable material models which allow for precise numerical prediction of the micromechanical behavior of materials under the consideration of the relevant underlying physical processes. One important aspect is the variation of elastic composite properties due to an applied electrical voltage. Special emphasis is placed on the validation of the material model using experimental data and by close collaboration with other subprojects which have an experimental orientation.
- ProjectSFB 986: Subproject B07 - Polymers in interfacial-dominated geometries: Structure, dynamics and function in planar and in porous hybrid systemsThis project focuses on investigations of Polypyrol (PPy) inside tubular pores in a micro-, meso-, and macro-porous Silicon (PSi). PPy offers the possibility to modify the electrical conductivity of PSi in a controlled way. It furthermore opens up sensoric and actoric applications for the PPy/PSi hybrid system. The experiments with the 1D system will be complemented by investigations in the planar 2D geometry, permitting to differentiate the sole influence from the geometric confinement inside the pores from the interfacial coupling at the interface. The combination of hard Si walls and soft polymer filling represents an interesting material with novel structural, functional and dynamical properties that will be characterized and optimized by various experimental techniques including optical birefringence, mechanical-dynamical analysis, indentation, temperature-dependent conductivity measurements as well as by X-ray diffraction, and modelled together with B6. This combined approach permits to establish PPy/PSi as a multiscale hybrid model system within the SFB, and at the same time it opens up application-oriented developments.
- ProjectSFB 986: Subproject B09 - Microstructure-based classification and mechanical analysis of nanoporous metals by machine learningIn 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.
- ProjectSFB 986: Subproject C01- Multiscale photonic materials with adjustable absorption and thermal emissionProject C1 focuses on the description of the optical properties of metal-dielectric multiscale material systems. The new proposal will be dealing with both adjustment and tunability of the absorption and emission of such material systems, which are interesting as tunable structural color, smart windows or switchable thermal emitters. This will be done by adjustment of the structure design and by the tunability of the dielectric function of metals via surface modification, phase transformations and temperature. In order to tailor efficient TPV-emitters which match specific photovoltaic receivers we realize spectrally selective emitters that show an emission close to that of a black body at short wavelengths, but substantially reduced emission at long wavelengths. We demonstrate such band-edge emitters based on a W-HfO2 refractory metamaterial in cooperation with C7  and a monolayer of monodisperse ZrO2-spheres on a tungsten substrate in cooperation with C4 and C6 . Both structures are stable up to 1000°C. The study of near field emission concentrates on the thermal radiation in hyperbolic materials  and across nanometer vacuum gaps.
- ProjectSFB 986: Subproject C04 - Additive manufacturing by selfassembly of colloidal suspensions for tailor-made photonic propertiesTP C4 aims at the fabrication of multi-scale and multiphase photonic coatings by combining methods of additive fabrication with the self-assembly of colloidal suspensions and thus combining principles of colloidal self-organization with the scalability and form flexibility of direct writing. We expect that this will enable us to control the particle arrangement in the µm to nm scale on planar and curved cm-sized substrates and to produce ceramic photonic structures for adaptable photonic properties, structural colors and high temperature applications.