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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - SFB 1109

Research

Materials based on metal oxides are of crucial importance for a multitude of present and emerging technical and consumer applications. In such applications, ranging from medical implants to surface coatings and construction materials, metal oxides are very often in contact with water during use and typically they are also produced from aqueous solution. Thus, a detailed understanding of the metal oxide/water interactions, which determine oxide formation and dissolution, is indispensable for the design of oxides with desirable properties and for ensuring the stability of these materials over time (i.e. resistance to degradation and corrosion). Such a fundamental understanding has not been reached yet, and one reason for this is the profoundly multi-scale nature of metal oxide/water chemistry: a comprehensive description of the behaviour of oxide/water interfaces has to account for processes occurring on length scales ranging from individual molecules, clusters and nanoparticles to extended crystalline and amorphous bulk materials. However, analytical and computational methods have developed rapidly within the last decades. Thus, the elementary processes that control metal oxide/water interactions can now be studied on all relevant length scales, and this will be pursued within the proposed CRC.

We will thus gain a previously unavailable comprehensive understanding of the complex atomic scale processes underlying oxide formation, structural evolution and dissolution and how these change as a function of oxide complexity and water amount. Exemplarily, silica, alumina and iron oxides will be studied as metal oxides with the highest natural abundance and application relevance. Moreover, ternary systems composed of these oxides will be investigated to account for the complexity encountered in many real applications.

To investigate the different stages of oxide assembly and dissolution from or in the aqueous phase, respectively, the CRC will employ combinations of state-of-the-art methods in computational chemistry, chemical synthesis and spectroscopy, including time-resolved in-situ spectroscopy. It is structured into four research areas reflecting a) the aggregation level of the studied oxides (molecules and cluster vs. particles and extended bulk materials) and b) the concentration of water (individual and solvated water molecules vs. liquid water). Each investigated metal oxide system will be studied by an interdisciplinary research team that unites the required expertise from the four research areas.

The initial phase of the CRC will focus on the investigation of the initial stages of oxide formation and of oxide dissolution. The derived chemical understanding will evolve through the subsequent CRC phases to finally describe the complete oxide formation and dissolution process of each studied oxide within one mechanistic framework. Thus, also similarities and differences between respective formation and solution intermediates, reactions and oxides will be revealed.

The proposed CRC clearly aims at fundamental insights. However, the obtained knowledge will also pave the way for the rational synthesis of metal oxides with predetermined properties on demand – e.g. desired dissolution/corrosion characteristics, affinity for particular solutes and nanostructure – and also provide access to compositionally or structurally novel materials.

Research Areas

A: Molecular compounds in contact with pure water and binary mixtures

B: Solid materials at the interface with liquid water

C: Interactions of solid materials with water at low concentrations

D: Molecular compounds interacting with small numbers of water molecules