Hetero aggregates – building blocks for many applications
Essential key technologies, for example in the context of digitalization for Industry 4.0 (sensor technology), energy conversion (catalysis) and energy storage as well as e-mobility (battery technology) or also life science, depend on functional disperse particle systems with very specific functional properties. Particles are rarely present individually and isolated, but mostly as powder or heap. Interactions occur between the various particles at their points of contact. If particles of different materials (for example A and B) are present, contacts between different (hetero: A-B) particles can occur. These hetero contacts (A-B) are of fundamental importance for the functional properties and essential for many applications. But how can such hetero contacts be created specifically by mixing A and B in the gas phase and how can these contacts be made visible or measurable?
In our work the preparation and formulation of hetero-contacts in the gas phase is realized through the combination of two nanoparticle aggregate producing flames in a double and triple flame spray pyrolysis (DFSP) setup. The product functionality depends on the degree of mixing that determines the number of hetero-contacts and on the hetero-contact quality. The hetero-contact quality significantly depends on the contact area and on the atomic structure of the interface including lattice strain and defect chemistry, if interfacial transport processes govern the functionality. The variation of DFSP process parameters enables the adjustment of the mixing process and resulted in improved functionalities in various applications. However, the characterization of the hetero-contacts on the aggregate and particle scale is far from understood, where the small size of the primary particles of about 10 nm requires the use of transmission electron microscopy (TEM) imaging coupled with AI to achieve a sufficient resolution and statistics.
Nanoparticle and Surface Engineering with Aerosols for Chemical Sensors
Aerosol technologies are exceptionally versatile for the synthesis of nanostructures, offering precise control over particle size, composition, and phase across a wide functional materials space. This versatility has enabled the scalable fabrication of high-performance molecular sensors, where steep thermal gradients and high particle concentrations in combustion-derived aerosols give access, for instance, to metastable phases and high surface defect densities. In this lecture, I will discuss our recent progress in nanoparticle using aerosol technology, with a particular emphasis on surface engineering to tune the sensitivity, selectivity and reversibility of molecular sensors. We will start with the atomic-scale design of highly reactive surface sites to control interfacial chemistry. This will be followed by the interfacing of functional nanoparticles with microelectronic circuitry and integration into devices for health and environmental monitoring in terrestrial and space applications. I will conclude by highlighting key challenges and opportunities for translating aerosol-based chemical sensors from laboratory to industry based on my first-hand experience with the start-up company Alivion AG
Real and virtual particle and aerosol transport in wildfires: the underlying science and the business case
Fast wildfire propagation and its effects on land, property, and human health, especially in the wildland-urban interface (WUI), are devilishly complex due to a combination of combustion mechanisms (convection, radiation, embers, smoke and haze transport), fluid mechanical aspects (turbulence, buoyancy, heat release modifications on the wind, aerosol dynamics), materials and construction choices (the fuels, house hardening, landscaping), and response actions (water, retardants, aerial bombardment). A comprehensive modelling framework that includes enough placeholders for all these has been developed at the University of Cambridge and Imperial College, and has been recently commercialised. The talk will delve briefly into the pertinent fundamentals and how these shape the requirements for the underlying data analysis and will focus on how modelling can inform firefighter response, preventive measures, and risk assessment. The connections with the business and policy ecosystem around wildfires will also be discussed and in particular how modelling can optimise resources and quantify risk with high granularity.
