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Fertigungsorientierte Herstellung nanostrukturierter Schichten

Fachliche Zuordnung Produktionsautomatisierung und Montagetechnik
Mechanische Verfahrenstechnik
Förderung Förderung von 2012 bis 2018
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 223406962
 
Erstellungsjahr 2019

Zusammenfassung der Projektergebnisse

The performance of catalysts, batteries, gas-sensors, and many other devices is often limited to interfacial transport processes. For this reason, active materials with high surface to volume ratio have become an absolute necessity and the production of nano-scaled particles has turned into a central objective in the development of various industries. In this project, the manufacturing process of nanostructured deposition coating is explored by focusing on a relatively young production technique known as flame spray pyrolysis (FSP). In FSP, organometallic precursors are dissolved in flammable liquid hydrocarbons. Afterwards, the liquid mixture is pumped into a nozzle where it is atomized into a spray of fine droplets under the aid of gaseous oxygen. A pilot flame provides additional heat to accelerate droplet evaporation and allows for the simultaneous ignition of the spray. The metal precursor species evaporate from the droplet, react with oxygen inside the high-temperature flame and form metal oxide products which nucleate, condense and grow into primary nanoparticles. Due to the lower temperatures in the process downstream, sinter/coalescence mechanisms become negligible at certain distances from the burner which causes the formation of weakly bonded agglomerated particle structures that can be collected on filters. During the different stages of this project a new experimental laboratory with contact-free, laser-based in situ and online diagnostics was established to collect an extensive amount of information from the process. In cooperation with the Brazilian partners one objective of this project was the development of a theoretical model of the FSP process to facilitate complete evaluation of relevant process parameters in a 2D or 3D environment. The growth of particles is realized by a user defined code that was implemented in a commercial computational fluid dynamics (CFD) software and enables the direct estimation of nanoparticle diameters without relying on specific experimental input data to run the simulation. The model was validated with locally measured data, i.a. droplet size, velocity, temperature, nanoparticle size, etc., which were collected on a lab-scaled FSP reactor that is utilized in numerous international laboratories and considered as a suitable benchmark setup. In the later course of the project, double flame reactors, industrial scaled flame sprays and even novel co-flow concepts were suggested and successfully investigated. The outcome of this work demonstrates that accurate flame reactor design is indeed possible by employing the developed numerical models. To meet the demands for the commercial production of metal oxide nanoparticles via FSP it transpired to minimize the expenses emerging from the use of organometallic precursors. Substituting the expensive precursors with low-cost alternatives, e.g. metal nitrates, seems plausible but is also known to result in distinctly larger particles and multiple crystal phases that both are undesirable for most applications. With emphasis on battery materials, a set of lithium-based precursors was investigated, and it was found that high quality nanoparticles with single crystal phase composition can be obtained directly from the flame without applying any expensive precursors or inconvenient post-processing. Latest efforts have focused on simplifying the manufacturing of battery cell production by regarding the simultaneous synthesis and deposition of lithium-based metal oxides and carbon-based nanoparticles on electrode current collectors demonstrating the potential of modified double FSP reactors. In conclusion, the research findings obtained during the term of this project covered the modelling and characterization of the flame spray pyrolysis and illustrate significant contributions to the fundamental understanding of the process. The studies describe deep fundamental research of flame-made nanopowders with an application-oriented endeavor in overcoming technical and economic issues that exist in the industrial production of lithium-ion battery materials.

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