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 -