Scale-up classification numbers for the high-throughput generation of crystalline sub-micrometer spheres by pulsed laser melting in liquids in a continuous flat-jet flow-through reactor

• Applicant: Professor Dr.-Ing. Stephan Barcikowski
• Subject Area: Chemical and Thermal Process Engineering ; Technical Chemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555646461

Crystalline, sub-micrometer-spheres (SMS) are interesting for optical, thermal, and mechanical applications. Laser melting in liquids (LML) using irradiation of colloidal particles with pulsed lasers at moderate fluence is often the only synthesis route for crystalline SMS. Though the LML mechanism is well understood, systematic studies on the scale-up of LML are missing. We will define a universal matrix of process variables to scale up the synthesis of SMS by LML by several orders of magnitude (tens of g/h). We will use boron carbide (B4C) as model material and a flat-jet flow-through reactor allows homogeneous laser irradiation. B4C-SMS throughput, ruled by the mass concentration in the product flow and the mass yield of monodisperse and monomodal SMS, will be the main readout. We will examine how the optical process variables I) laser fluence (determines SMS diameter) and II) pulse energy (defining irradiated volume at fixed fluence) influence SMS throughput. Then, we will study energy input variables, particularly, how many pulses per volume element (PPV) are required for SMS formation and which combination of volume flow rate and laser repetition rate can maximize throughput. Next, the impact of B4C mass concentration (mass flow) is investigated. Finally, we will use the experimental data to deduce dimensionless classification numbers (CN) for I) optical, II) energy, and III) mass input variables. These CN will be implemented into a generalized reactor design equation combining power-specific SMS throughput with relevant input variables.

• DFG Programme: Research Grants