TY - GEN AB - In order to standardize spray flame synthesis (SFS) studies, intensive work has been done in recent years on the design of burner types. Thus, in 2019, the so-called SpraySyn1 burner was introduced (SS1), which was subsequently characterized in numerical and experimental studies. Based on this research, a modification of the nozzle design was proposed, which has now been considered in the successor model, SpraySyn2 (SS2). As little is known about the effect of the nozzle adaptation on the particle formation, we operated both burners under identical operating conditions to produce maghemite. The final powder comparison showed that SS2 yielded considerable higher specific surface areas (associated with smaller primary particle sizes), lower polydispersity, and higher phase purity. To obtain further information on the size distributions of aggregates and agglomerates generated by SS2, aerosol samples were extracted by hole in a tube (HIAT) sampling and characterized by scanning mobility particle sizing (SMPS). Samples were extracted along the centerline at different heights above the burner (HAB) above the visible flame tip (>7 cm), and quenching experiments were performed to extract the aerosol samples at different dilution rates. Thereby, it was demonstrated that performing detailed quenching experiments is crucial for obtaining representative HIAT-SMPS data. In particular, agglomerates/aggregate sizes were overestimated by up to ~70 % if samples were not sufficiently diluted. If sufficient dilution was applied, distribution widths and mean particle mobility diameters were determined with high accuracy (sample standard derivation <5 %). Our data suggested the evolution of primary particle sizes was mostly completed <7 cm HAB and it was shown aggregates/agglomerates present above the visible flame were compact in structure (non- fractal). The mean diameter of the particle ensemble grew along the centerline from 6.9 nm (7 cm) to 11.4 nm (15 cm), while distribution widths grew from 1.42 to 1.52. ED - Tischendorf, Ricardo ED - Massopo, Orlando ED - Schmid, Hans-Joachim ED - Pyrmak, Olek ED - Dupont, Sophie ED - Fröde, Fabian ED - Pitsch, Heinz ED - Kneer, Reinhold ID - 51133 KW - Flame Spray Pyrolysis KW - SpraySyn2 KW - Spray flame synthesis KW - Maghemite nanoparticles KW - Gas to particle-conversion KW - Hole in a tube sampling T2 - Applications in Energy and Combustion Science TI - Maghemite nanoparticles synthesis via spray flame synthesis and particle characterization by hole in a tube sampling and scanning mobility particle sizing (HIAT-SMPS) ER - TY - GEN AB - Estimating the infection risks in indoor environments comprises the assessment of the behavior of virus-laden aerosols, i.e. spreading, mixing, removal by air purifiers etc. A promising experimental approach is based on using non-hazardous surrogate aerosols of similar size, e.g. salt particles, to mimic the virus aerosol behavior. This manuscript addresses the issue how a successful transfer of such experiments can be accomplished. Corresponding experiments in two very different environments, a large community hall and a seminar room, with optional use of air purifiers in various constellations were conducted. While high particle concentrations are advantageous in terms of avoiding influence of background aerosol concentrations, it is shown that appropriate consideration of aggregation and settling are vital to theoretically describe the experimentally determined course of particle concentrations. A corresponding model equation for a well-mixed situation is derived and the required parameters are thoroughly determined in separate experiments independently. It is demonstrated that clean air delivery rates (CADR) of air purifiers determined with this approach may differ substantially from common approaches not explicitly taking into account aggregation. AU - Beimdiek, Janis AU - Schmid, Hans-Joachim ID - 51731 KW - surrogate aerosols KW - indoor air cleaners KW - ultra-fine particles KW - COVID-19 KW - test method KW - field experiments: clean air delivery rate T2 - Atmosphere TI - Evaluation of Surrogate Aerosol Experiments to Predict Spreading and Removal of Virus-Laden Aerosols ER - TY - JOUR AU - Beimdiek, Janis AU - Schmid, Hans-Joachim ID - 52357 IS - 3 JF - Atmosphere KW - surrogate aerosols KW - indoor air cleaners KW - ultra-fine particles KW - COVID-19 KW - test method KW - field experiments: clean air delivery rate SN - 2073-4433 TI - Evaluation of Surrogate Aerosol Experiments to Predict Spreading and Removal of Virus-Laden Aerosols VL - 15 ER - TY - GEN AU - Neukötter, Moritz AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 44102 TI - Instabilities of Polymer Melt Suspensions under Uniaxial Extension (Poster) ER - TY - JOUR AB - AbstractThe use of structured measuring systems to prevent wall slip is a common approach to obtain absolute rheological values. Typically, only the minimum distance between the measuring surfaces is used for further calculation, implying that no flow occurs between the structural elements. But this assumption is misleading, and a gap correction is necessary. To determine the radius correction $$\Delta r$$ Δ r for specific geometries, we conducted investigations on three Newtonian fluids (two silicon oils and one suspension considered to be Newtonian in the relevant shear rate range). The results show that $$\Delta r$$ Δ r is not only shear- and material-independent, but geometry-dependent, providing a Newtonian flow behaviour in a similar viscosity range. Therefore, a correction value can be determined with only minute deviations in different Newtonian fluids. As the conducted laboratory measurements are very time-consuming and expensive, a CFD-approach with only very small deviations was additionally developed and compared for validation purposes. Therefore, simulation is an effective and resource-efficient alternative to the presented laboratory measurements to determine $$\Delta r$$ Δ r for the correction of structured coaxial geometries even for non-Newtonian fluids in the future. AU - Josch, Sebastian AU - Jesinghausen, Steffen AU - Dechert, Christopher AU - Schmid, Hans-Joachim ID - 36983 JF - Rheologica Acta KW - rheology KW - rheometry KW - suspension KW - coaxial KW - correction SN - 0035-4511 TI - Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems ER - TY - GEN AU - Rüther, Torben AU - Schmid, Hans-Joachim ID - 43236 KW - CDMA TI - CDMA: Centrifugal Differential Mobility Analyzer - Ein Messprinzip zur Bestimmung von Multidimensionalen Partikeleigenschaften (Vortrag) ER - TY - JOUR AB - Abstract The accessibility to rheological parameters for concrete is becoming more and more relevant. This is mainly related to the constantly emerging challenges, such as not only the development of high-strength concretes is progressing very fast but also the simulation of the flow behaviour is of high importance. The main problem, however, is that the rheological characterisation of fresh concrete is not possible via commercial rheometers. The so-called concrete rheometers provide valuable relative values for comparing different concretes, but they cannot measure absolute values. Therefore, we developed an adaptive coaxial concrete rheometer (ACCR) that allows the measurement of fresh concrete with particles up to d max = 5.5 mm {d}_{{\rm{\max }}}=5.5\hspace{.5em}{\rm{mm}} . The comparison of the ACCR with a commercial rheometer showed very good agreement for selected test materials (Newtonian fluid, shear thinning fluid, suspension, and yield stress fluid), so that self-compacting concrete was subsequently measured. Since these measurements showed a very high reproducibility, the rheological properties of the fresh concrete could be determined with high accuracy. The common flow models (Bingham (B), Herschel–Bulkley, modified Bingham (MB) models) were also tested for their applicability, with the Bingham and the modified Bingham model proving to be the best suitable ones. AU - Josch, Sebastian AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 43034 IS - 1 JF - Applied Rheology KW - Condensed Matter Physics KW - General Materials Science SN - 1617-8106 TI - Development of an adaptive coaxial concrete rheometer and rheological characterisation of fresh concrete VL - 33 ER - TY - JOUR AU - Rüther, Moritz Johannes AU - Klippstein, Sven Helge AU - Ponusamy, SathishKumar AU - Rüther, Torben AU - Schmid, Hans-Joachim ID - 43128 JF - Powder Technology KW - General Chemical Engineering SN - 0032-5910 TI - Flowability of polymer powders at elevated temperatures for additive manufacturing VL - 422 ER - TY - GEN AU - Ponusamy, SathishKumar AU - Schmid, Hans-Joachim ID - 44244 TI - Dynamisch-mechanische Polymerpartikelverrundung zur Verbesserung der Fließfähigkeit für das selektive Lasersintern ER - TY - GEN AU - Neukötter, Moritz AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 44103 TI - Particles as Seeds for Instabilities in Uniaxially Elongated Polymer Suspension Filaments (Presentation) ER - TY - JOUR AB - In this work, the influence of the filler–matrix adhesion on the tensile properties of laser-sintered parts built with Polyamide 613 filled with glass beads was investigated. For this purpose, dry blends of glass beads with and without organosilane coupling agents and polyamide powder were prepared and processed into tensile specimens on an EOS P396 laser sintering system. The samples were tested both in the dry state and after an accelerated conditioning in a climate chamber. Furthermore, finite element method (FEM) simulations were performed to model the extreme cases of optimum adhesion and no adhesion. By correlating the tensile tests with the simulation results and by analyzing the fracture surfaces, it was shown that the filler–matrix adhesion is sufficient in the dry state but is strongly degraded by conditioning. Even the presence of various organosilane thin films could not prevent a strong deterioration of the filler–matrix adhesion and the associated deterioration of the mechanical properties. Since a comparison with an injection-molded sample of the same polymer filler combination shows identical behavior after conditioning, it is assumed that this problem is not limited to additively manufactured parts. AU - Kletetzka, Ivo AU - Kosanke, Maren AU - Meinderink, Dennis AU - Neßlinger, Vanessa AU - Grundmeier, Guido AU - Schmid, Hans-Joachim ID - 46815 JF - Progress in Additive Manufacturing KW - Industrial and Manufacturing Engineering SN - 2363-9512 TI - Influence of the filler–matrix adhesion and the effects of conditioning on tensile properties of laser-sintered parts built with polyamide–glass bead dry blends ER - TY - JOUR AB - In the laser sintering technology, the semi-crystalline polymer material is exposed to elevated temperatures during processing, which leads to serious material ageing for most materials. This has already been investigated intensively by various authors. However, the ageing of the material at ambient temperatures during shelf life has not been the focus so far. The need to analyse the shelf life can be derived from an ecological and economic point of view. This work is focusing on the shelf life of PA2200 (PA12). To reduce the potential influences of powder production fluctuations, two different powder batches stored for 5.5 years and 6.5 years are investigated and compared to a reference powder produced 0.5 years before these investigations. Multiple powder analyses and part characterisations have been performed. A significant yellowing and molecular chain length reduction can be derived from the measurement results. Whereas the influence on mechanical part performance was minor, the parts built with the stored powders are more yellowish. As it is most likely that this is due to the consumption of polyamide stabilisers, it can be assumed that these parts will be subject to significantly faster ageing. Therefore, it is still not recommended to use the stored powders for critical parts or light intense and humid environments. AU - Klippstein, Sven Helge AU - Kletetzka, Ivo AU - Sural, Ilknur AU - Schmid, Hans-Joachim ID - 43046 JF - The International Journal of Advanced Manufacturing Technology KW - Selective laser sintering KW - Shelf life KW - Polyamide 12 KW - powder KW - PA2200 KW - material ageing TI - Influence of a prolonged shelf time on PA12 laser sintering powder and resulting part properties ER - TY - CHAP AU - Menge, Dennis AU - Milaege, Dennis AU - Hoyer, Kay-Peter AU - Schmid, Hans-Joachim AU - Schaper, Mirko ED - Horwath, Illona ED - Schweizer, Swetlana ID - 46870 SN - 2703-1543 T2 - Climate Protection, Resource Efficiency, and Sustainable Engineering TI - Case Study IV: Individualized Medical Technology using Additive Manufacturing ER - TY - GEN AU - Rüther, Moritz Johannes AU - Klippstein, Sven Helge AU - Schmid, Hans-Joachim ID - 47626 SN - 0083-5560 T2 - PARTEC International Congress on Particle Technology - Book of Abstracts TI - Correlation between SLS-Powder processability and particle properties ER - TY - CONF AB - Polymer composites represent the industry standard in injection molding for the production of plastic components with increased requirements in terms of heat resistance and stiffness. In the field of laser sintering (LS), these materials are less common so far. In order to extend the available material variety for the LS process, new ceramic-filled Polyamide 613 powders are investigated within the scope of this work. Here, the resulting properties from two different powder production methods are compared. One filled powder is produced by dry blending and the other powder with the same filler and filling ratio is produced by encapsulating the filler particles inside the polymer particles within the dissolution-precipitation process. It was found that encapsulating the filler particles can provide certain benefits for the processability, for example an improved powder flowability or better filler dispersion. However, encapsulating the filler also alters the thermal properties of the precipitated powder. AU - Kletetzka, Ivo AU - Neitzel, Fabian AU - Schmid, Hans-Joachim ED - Beaman, Joseph ID - 46764 T2 - Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium TI - Assessing the Impact of the Powder Production Method on Ceramic-filled Polyamide Composites made by Laser Sintering VL - 34 ER - TY - CONF AB - The high flammability of components manufactured by laser sintering (LS) using standard polyamide 12 (PA12) powder still severely restricts their use in industries such as electronics, aviation, and transportation. A key factor for the further establishment of LS is the expansion of the material portfolio with, for example, refreshable and halogen-free flame-retardant (FR) powder materials. Accordingly, various halogen-free FRs are investigated in this work and evaluated with respect to their use in LS. First, their decomposition behavior and mode of action are examined. Subsequently, the additives are dry blended with PA12 to investigate properties relevant for LS, such as particle morphology, thermal behavior and melt viscosity. Afterwards, test specimens for UL94 vertical flame-retardancy tests are produced by processing the dry blends on an EOS P3 LS system. Finally, the process stability of the process-aged powder blends is investigated by again examining the thermal behavior and melt viscosity. AU - Neitzel, Fabian AU - Kletetzka, Ivo AU - Schmid, Hans-Joachim ED - Beaman, Joseph ID - 46862 KW - Additive Manufacturing KW - Laser Sintering KW - Flame Retardant KW - Polyamide 12 T2 - Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium TI - Halogen-Free Flame Retardant Powder Materials for Laser Sintering: Evaluation and Process Stability Analysis ER - TY - GEN AB - Iron oxide nanoparticles are very interesting for many applications in different industrial sectors. A promising process to manufacture these nanoparticles is flame spray pyrolysis (FSP). A lack of understanding of the individual sub-processes in FSP makes it challenging to tailor nanoparticle properties. This work provides insights into the formation of iron oxide nanoparticles in a turbulent spray flame using Large Eddy Simulations (LES), which are based on a comprehensive model, including customized submodels. Highlights are the adaption of a turbulent combustion model and a bivariate hybrid method of moments for modeling nanoparticle dynamics. The work focuses on the SpraySyn burner, which is a standardized laboratory burner and was operated with a precursor-solvent mixture of ethanol and iron(III) nitrate nonahydrate. For studying the relevance of precursor chemistry, LES using an evaporation-limited precursor chemistry model is compared with a model that includes detailed iron chemistry. A further novelty is the inclusion of adsorption in the simulation, which defines a third model for comparison. Sufficient validation is achieved for the undoped LES using experimental data from the literature. A strong impact of the detailed iron chemistry and adsorption is found on the precursor consumption and the aggregate and primary particle formation. Comparing the particle diameters with experimental measurements from the literature and data generated for this work is found unsuitable to asses the precursor chemistry model and revealed an urgent need for future experimental and numerical research. This work serves as a step forward in realizing a reliable model. ED - Fröde, Fabian ED - Grenga, Temistocle ED - Pitsch, Heinz ED - Dupont, Sophie ED - Kneer, Reinhold ED - Tischendorf, Ricardo ED - Massopo, Orlando ED - Schmid, Hans-Joachim ID - 51136 KW - Flame spray pyrolysis KW - Iron oxide formation KW - Large eddy simulation KW - Method of moments KW - SpraySyn T2 - Applications in Energy and Combustion Science TI - Large eddy simulation of iron oxide formation in a laboratory spray flame ER - TY - GEN AU - Massopo, Orlando AU - Tischendorf, Ricardo AU - Schmid, Hans-Joachim AU - Fröde, Fabian AU - Grenga, Temistocle AU - Pitsch, Heinz AU - Bieber, Malte AU - Reddemann, Manuel AU - Kneer, Reinhold ID - 51147 KW - Flame Stability KW - Particle Sample Extraction KW - SMPS KW - Impurities TI - Influence of atomization on the particle formation in spray flame pyrolysis (Presentation) ER - TY - GEN AU - Massopo, Orlando AU - Schmid, Hans-Joachim AU - Gonchikzhapov, Munko AU - Kasper, Tina ID - 51145 KW - Absolute particle concentration KW - Flame Spray Pyrolysis KW - SMPS KW - Mass Spectrometry TI - Nanoparticle Concentration Measurement in Flame Spray Pyrolysis (Poster) ER - TY - GEN AU - Massopo, Orlando AU - Tischendorf, Ricardo AU - Schmid, Hans-Joachim AU - Fröde, Fabian AU - Pitsch, Heinz AU - Reddemann, Manuel AU - Grenga, Temistocle AU - Kneer, Reinhold ID - 51142 KW - SpraySyn KW - Flammenspraypyrolyse KW - Maghemite Nanopartikel KW - Gas to particle-Syntheseweg KW - Probennahme KW - Verunreinigung TI - Einfluss der Zerstäubung auf diePartikelbildung bei der Sprayflammenpyrolyse (Vortrag) ER -