23. December 2016
New EAM strategy for the development of materials in the post-empirical age
a-c: TEM analysis of α-Fe2O3 particles with: a) pseudo-cubic; b) nanorod; c) apple-like morphology. i - iii: Different models used to describe the particles and simulate their optical properties. RI = refractive index; LC = linear combination of RI of hematite and organic matrix;
Today the empirical approach is still widely used to develop materials with new properties for a variety of applications. This approach has been very successful in the past, considering the many advances made in science and technology through serendipity over the last centuries. However, another approach of designing advanced materials by function has been gathering momentum. Given a pre-defined property, for instance, an optical response, the structure of the best performing material is then rigorously designed under this approach. To advance development strategies for new materials to the post-empirical age, it is crucial to understand and predict the properties of materials based on their structures. Understanding the relationship between structure and function is the topic of a recent paper on hematite hierarchical structures published in the Journal of Quantitative Spectroscopy and Radiative Transfer. This publication is the result of an interdisciplinary EAM collaboration coordinated by Dr. Monica Distaso between Particle Technology (LFG), Electron Microscopy (CENEM), Physics (Institute of Optics, Information and Photonics), Applied Mathematics II, and in cooperation with Lanxess Deutschland GmbH, a world leader in the production of iron oxide pigments.
The first stage of the project was the fabrication of hierarchically structured hematite nanocomposites of various morphologies, controlled size distributions, and optical properties. Transmission electron microscopy (TEM) characterization showed the particles were constituted of primary crystallites in the nanometer size regime (< 100 nm) embedded in a polymer matrix, and organized into secondary structures with diameters of at least 100 nm (Fig. 1).Next, electrodynamic simulations of the (measurable) extinction spectra were carried out using various methods. The less intensive methods treated the particles as homogeneous or, using a socalled effective medium theory, rationalized the inhomogeneous structure as a homogeneous one with fictive optical properties (Fig. 2i and 2iii). The more intensive method used (T-Matrix approach) could represent the inhomogeneous nature of the particles (Fig. 2ii).
The results show that an excellent approximation of the experimental spectra could only be obtained when the results of the structural characterization were taken into account rigorously either through the Maxwell-Garnett effective medium theory or through the T-matrix approach (Fig. 3).The collaboration between EAM researchers from Research Areas A1, A2, A3 and C led to the development of an interdisciplinary methodological approach for the prediction of the spectral properties of nanocomposite materials and set a basis for the development of rigorous product design approaches for hierarchical materials.
Interaction of light with hematite hierarchical structures: Experiments and simulations
Research Areas A1, A2, A3, C
Monica Distaso, Oleksander Zhuromskyy, Benjamin Seemann, Lukas Pflug,
Mirza Mačković, Ezequiel Encina, Robin Klupp Taylor, Rolf Müller,
Günter Leugering, Erdmann Spiecker, Ulf Peschel, Wolfgang Peukert
Journal of Quantitative Spectroscopy & Radiative Transfer, 2017, 189, 369 – 382
Fig. eprinted from Journal of Quantitative Spectroscopy & Radiative Transfer, Copyright (2016), with permission from Elsevier