Material specific on-line surface characterization of gas-borne particles

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Although the surface of particles determines to a large extent their processing properties such as wettability and cohesion, there is currently no in situ technique available for the surface characterization of gas-borne particles. While electron spectroscopic surface analysis techniques rely on ultra high vacuum, laser based methods are elaborate and expensive and cannot distinguish between surface and volume properties. Since particles can also undergo structral changes during wetting, size related measurements such as mobility spectrometry are not applicable either. Therefore, the proposed research project aims at the in situ characterization of the surface of aerosol particles using a combination of aerosol photoemission spectroscopy and diffusion charging. By relating the photoemission signal to the diffusion charging signal size related effects such as restructuring cancel out and the mere surface properties are measured. Employing defined condensation experiments the wettability of the gasborne particles can be measured in situ. Finally, using a thermodenuder adsorbates on the particles will be characterized by applying temperature ramps.