Physical characterization of engineered aerosol particles

This thesis will explore parts of the life of engineered nanoparticles, from generation in research environments andprocess monitoring, to emissions in an industrial setting. The aim is to give insights into how the particles can becharacterized in different settings and how different characterization methods can be applied depending on need ordemand.Airborne nanoparticles have been around forever but the use of them in specialized materials has increaseddramatically during the past decades. The new materials bring improvements to old applications, and brand new usesas the world of nanotechnology expands. It is, however, not only one-sided positive effects from this increase in use;some of these materials have properties previously experienced as health hazards. The physical size and amounts ofmaterial handled during the production can be different from what has been experienced before and with that, newhazards might arise. In order to assess these hazards, careful characterization of the particle behavior can be utilized incontrolled environments to further the knowledge on how the particles might behave out in the real world during use andapplication. Particles can be characterized in many different ways and aspects. Finding out which path that suits acertain situation is a key to make a successful measurement campaign or experiment. The systems used to producethese particles also need to be well characterized. In addition to safe handling, well characterized generation systemswill also allow for new uses and exploration of materials previously not investigated.In this thesis, I have characterized the initial stages of particles generated with spark discharge discovering how theparticles evolve depending on process parameters milliseconds after generation. I further dive deeper into the sparkdischarge characterization and show how the emitted light from the discharge can be correlated with the particles beingproduced and show how the input power doesn’t linearly correlate with particles produced in this process. In the samesystem, I successfully generate particles of InSb. It is demonstrated how a reducing atmosphere during generation iscritical for the formation of pure particles of this material. Several different characterization techniques to determine theproperties of the generated particles are described.One of the most interesting properties of nanoparticles from a toxicological view point is surface area. Knowing thesurface area of complex particles is, however, not always straightforward and is often difficult to measure directly. Ipresent an overview of a set of models that can be used to estimate the surface area of agglomerated particlesgenerated from different particle sources. The input to the methods relies on online measurements of mobility diameter,mass, and offline characterization of morphology via microscopy samples.No matter how harmful particles with specific properties are to humans, there is no harm unless people get exposed tothe particles. I present results from an extensive workplace campaign in which we utilized online aerosol instruments tocharacterize the emissions. A new method for classifying carbon nanotube materials via electron microscopy from filtersamples, as well as from surface sampling with adhesive tape, is further introduced.From this campaign release of engineered nanoparticles at several occasions during the work day was found. It wasevident that online methods alone would not enable us to discern carbon nanotubes from other particles but with thecombination of online time resolved characterization of emissions and extensive microscopy analysis emission eventswere identified. It was also revealed that the surface contamination of engineered particles were extensive. Severalsampled surfaces showed contamination by not only carbon nanotubes but also of nanomaterial which were nothandled during the time of the measurements.From this thesis it is clear that measuring nanoparticles is as difficult as you make it. It is possible to measure withsimple means to yield results that are sufficient to give an indication that some things needs to improve. In this thesis Iwill also show that an extensive arsenal of equipment can yield results which complement and build upon each other.While it is possible to measure all kinds of data on the same aerosol given enough time and resources, it is clear thatthe optimization and tailoring of a study might be the real challenge. (Less)