Development of Aerosol Measurement and Synthesis Technology for Functional Materials

Nanomaterials are used widely for their improved material properties, compared to bulk, and there are multiple ways of manufacturing them. Aerosol methods are versatile and up-scalable, making them one of the most promising routes to produce contaminant free nanomaterials. As more sophisticated applications emerge, the precise control over the whole process becomes more necessary. The process steps are interlinked in the sense that altering the precursor can have profound effects on the performance of the final application and without measurements, it is hard to say what changes actually took place.

This thesis considers the whole synthesis process of generating nanoparticles in gas phase and presents not only new results that improve different steps in this process, but also functionalized surfaces, prepared by depositing nanoparticles made with flame aerosol generation method.

One big problem in nanoparticle synthesis, when spraying is involved, is the generation of residual particles that consume most of the produced mass, decreasing the number of nanoparticles produced. The generation process was optimized by tuning the precursor solution to increase the heat of combustion, which enables the evaporation of the residual particles. This process was characterized with aerosol instrumentation and the absence of residual particles verified with gravimetric analysis and electron microscopy. Structural information was gained by measuring the effective density of the generated particles.

Building upon the usefulness of the density measurement, a new sensor-type instrument, density monitor (DENSMO) was developed. Here it is presented for synthesis monitoring purposes. The density of particles is monitored during synthesis to evaluate the stability of the system as well as characterize the shape of the generated particles. Further tuning of the produced nanoparticles’ morphology is conducted with real-time monitoring.

Two kinds of surface functionalization were achieved with the deposition of nanoparticles: anti-icing and anti-bacterial. The anti-icing surface was accomplished with a slippery liquid-infused porous surface (SLIPS) structure, where a silicone oil is held on the surface by a porous nanoparticle layer. The wetting behavior of the surface can also be changed with this kind of coating. The produced SLIPS is shown to exhibit excellent anti-icing performance. The anti-bacterial coating is implemented on a fiber filter by the deposition of silver nanoparticles. The performance of the prepared material is tested against Staphylococcus aureus and Escherichia coli bacteria. Further optimization on the antibacterial property is required in order to eradicate the S. aureus bacteria, but the material here was quite effective against E. coli, showing the viability of the presented method.

The utilized methods are tunable and scalable, therefore these results create a foundation for countless options for future materials and applications.