Precipitation kinetics of superparamagnetic nickel and cobalt crystals in silicate glasses controlled by redox potential

• Applicants: Professor Dr.-Ing. Joachim Deubener; Professor Dr. Thomas Höche
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Synthesis and Properties of Functional Materials
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 316146333

Colloids of the transition metals cobalt and nickel of high number densities (>1E20 m-3) shall be synthesized via redox potential induced precipitation in silicate glasses. The initial focus of this research is constituted by the kinetics of these processes, as well as by the analysis of microstructure-property relationships. Due to the nanosized scale of the precipitated metal phases, plasmon resonance based phenomena and, in particular, super-paramagnetic behavior can be expected from these novel metal-glass composites. In order to tailor the materials' microstructure, the kinetics of the involved precipitation and crystallization processes have to be controlled. Preliminary work showed a feasible path to produce a nanoscaled microstructure via complex redox reactions, which has been adopted from enamel technology. Therefore, it is anticipated that within this project, an alternative synthesis route for the generation of magnetic Co- and Ni- nanoparticles can be established, which is different from the usually used synthesis schemes (e.g., chemical precipitation reac-tion or hydrothermal synthesis). If nanoparticles are established via the envisioned precipitation route, they are intrinsically embedded in the silica matrix, thus protected against corrosive attack (oxidation), and bear a high potential e.g. for information storage applications. A huge level of scientific knowledge gain is expected by the project, since the factors which control the involved solution, degradation and precipitation reactions of Ni and Co metals are not reported in literature yet. This scientific "new ground" is broken via a combination of work packages considering both glass technology - on the side of glass syntheses - and micro-structural diagnostics - on the side of nanoanalytics - to gain a knowledge-based understanding of the relevant precipitation phenomena. The planned project may lead to a generalization of the ceramization of glasses, since through a control of the redox state of glass constituents, nanoscaled metal phases in a silicate network are expected to be synthesized. In contrast to the standard state-of-the-art glass ceramming technologies that rely on the crystallization of functional oxide phases via the preliminary precipitation of nucleation agents, this approach is entirely novel. It can be expected that it can provide a basis for the development of novel functional composite materials.

• DFG Programme: Research Grants