Nanoparticles produced in technical aerosol processes exhibit often dendritic structures, composed of primary particles. Surprisingly, a small but consistent discrepancy was observed between the results of common aggregation models and in situ measurements of structural parameters, such as fractal dimension or mass-mobility exponent. A phenomenon which has received little attention so far is the interaction of agglomerates with admixed gases, which might be responsible for this discrepancy. In this work, we present an analytical series, which underlines the agglomerate morphology depending on the reducing or oxidizing nature of a carrier gas for platinum particles. When hydrogen is added to openly structured particles, as investigated by tandem differential mobility analysis (DMA) and transmission electron microscopy (TEM) analysis, Pt particles compact already at room temperature, resulting in an increased fractal dimension. Aerosol Photoemission Spectroscopy (APES) was also able to demonstrate the interaction of a gas with a nanoscaled platinum surface, resulting in a changed sintering behavior for reducing and oxidizing atmospheres in comparison to nitrogen. The main message of this work is about the structural change of particles exposed to a new environment after complete particle formation. We suspect significant implications for the interpretation of agglomerate formation, as many aerosol processes involve reactive gases or slightly contaminated gases in terms of trace amounts of unintended species.

A low pressure impactor is used to measure triboelectric charging behavior of metallic nanoparticles. Ag nanoparticles, produced by spark discharge, were impacted onto Pt sputtered targets. The influence of the impaction angle and impaction velocity on the triboelectric charging was investigated. While for perpendicular impaction the charge transfer behavior of previous work was confirmed, the oblique impaction revealed new phenomena. Additional charge transfer was observable, which increases with obliqueness. The possibility of mass transfer between particle and target due to the high‐energy collisions was also investigated. SEM characterization and Auger spectroscopy indicate mass transfer from the particle to the target surface.

Die elektrohydrodynamische Zerstäubung von flüssigen Präkursoren gekoppelt mit der Flammensprühpyrolyse erlaubt die Synthese von verschiedenartigen, metalloxidischen Nanopartikel. Ein Aufbau bestehend aus einem definiert verfahrbaren Brenner und einer Probennahme in der Flamme eröffnet dabei die Möglichkeit der Erfassung von Partikelgrößenverteilungen entlang der Flammenhöhe. Die Bildung von Eisenoxid- und Siliziumdioxid-Partikel in einer Flamme konnte so mithilfe eines 1nm-SMPS-Aufbaus (Scanning Mobility Particle Sizer) auch in den Frühstadien der Partikelbildung erfasst werden. Hierbei zeigte sich, dass auch für einfache Präkursorlösungen bei hinreichend kleinen Tropfen hochwertige, homogene Nanopulver erzeugt werden können.