Project Details
Projekt
Synthesis and purification of highly functional nanoparticles: a controlled process chain from sol-gel synthesis to dead-end ultrafiltration
Subject Area
Mechanical Process Engineering
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 504545992
The development of functional semiconductor nanomaterials with tunable properties is vital for advancing energy conversion, electronics, and optoelectronics. Due to the growing demand for sustainable technologies and limited rare-earth resources, alternatives like aluminum- and indium-doped zinc oxide (AZO, IZO) have emerged as promising transparent conductive oxides (TCOs) to replace indium tin oxide (ITO). While gas-phase methods like sputtering yield high-quality films, they are expensive and inefficient due to multi-step lithographic processing. In contrast, sol-gel synthesis offers an affordable, scalable liquid-phase alternative compatible with various printing techniques and model-based control. In Phase 1, the project focused on sol-gel synthesis of AZO nanocrystals in a closed batch reactor. Multiscale characterization (SAXS, DLS, EDX, UV-Vis, and electron microscopy) was used to study particle structure, concentration and optoelectronic properties. Temperature-dependent synthesis enabled control over nucleation and growth. A first-principles model using reaction kinetics and population balance equations was developed and parameterized. For real-time application, a reduced-order model was derived via dynamic mode decomposition with control, enabling soft sensor design and model predictive control (MPC) of particle size distribution (PSD). AZO films with bandgaps up to 3.42 eV and conductivities ~0.2 S/cm were achieved. However, EDX showed Al segregation at particle surfaces, affecting doping uniformity and conductivity. Purification via offline centrifugation further limited process feedback and scalability. Phase 2 aims to address these issues by integrating a dead-end ultrafiltration unit for real-time purification and online bandgap measurement via UV-Vis spectroscopy. The process chain will be modeled to include filtration dynamics and time delays using time-delay differential equations. A semi-batch strategy with stepwise aluminum precursor addition will reduce segregation and improve dopant incorporation. WP1 focuses on constructing the process chain and model extension. WP2 addresses data generation, including bandgap analysis, machine learning-based prediction, and solubility studies. WP3 integrates hardware and implements soft sensor-based MPC. Advanced control methods such as backstepping and Smith predictors will be evaluated to manage system delays. This project establishes a robust process chain from synthesis to purification and control of semiconductor nanoparticles, enabling scalable, reproducible production of high-performance AZO/IZO nanoparticles and a transferable platform for other functional nanomaterials.
DFG Programme
Priority Programmes
