@inproceedings{30225, author = {{Rüther, Moritz Johannes and Schulze, Dietmar and Schmid, Hans-Joachim}}, location = {{digital}}, title = {{{Flowability Measurements of Different SLS Materials at Elevated Temperatures with a Modified Schulze Ring Shear Tester}}}, year = {{2021}}, } @inproceedings{24160, abstract = {{In automotive and other fields of application media-carrying components often have complex, flow-optimized geometries and are made of plastics for reasons of weight and cost. Therefore, the laser sintering technology is predestinated to manufacture these components as it offers a very high degree of design freedom and good mechanical properties. For industrial applications the long-term properties of the SLS material in contact with liquid media are important and were therefore investigated for PA12, PP and PA613. Hereby, different media such as motor oil or Glysantin based coolant were tested with different temperatures and immersion times of up to 26 weeks. The mechanical properties were tested after immersion and compared to injection molded samples. Furthermore, laser sintering design guidelines for media-carrying components were developed. These guidelines for instance include the minimum wall thickness to ensure media tightness and the removal of powder from channels with a high length to diameter ratio.}}, author = {{Kletetzka, Ivo and Kummert, Christina and Schmid, Hans-Joachim}}, booktitle = {{Proceedings of the 32nd Annual International Solid Freeform Fabrication Symposium}}, location = {{Austin}}, publisher = {{Laboratory for Freeform Fabrication and University of Texas}}, title = {{{Laser Sintering Design Guidelines for media transmitting Components}}}, doi = {{http://dx.doi.org/10.26153/tsw/17548}}, volume = {{32}}, year = {{2021}}, } @article{26095, abstract = {{Luftreiniger werden derzeit häufig als mögliches Hilfsmittel zur Minimierung des Infektionsrisikos im Rahmen der COVID-19-Pandemie diskutiert. Dabei taucht oft die Frage auf, ob Luftreiniger grundsätzlich in der Lage sind, Viren oder virenbeladene Tröpfchen abzuscheiden. Ziel dieses Artikels ist es, die wesentlichen Grundlagen der Wirkungsweise von Luftreinigern und Filtern zu beschreiben, Methoden zur Messung der Reinigungswirkung im Größenbereich von Viren und virenbeladenen Tröpfchen aufzuzeigen sowie typische Szenarien zum Betrieb von Luftreinigern in einem mathematischen Modell zu erfassen. Darauf basierend können die Möglichkeiten und Grenzen von Luftreinigern für reale Anwendungsfälle besser eingeschätzt werden.}}, author = {{Schumacher, Stefan and Asbach, Christof and Schmid, Hans-Joachim}}, issn = {{0949-8036}}, journal = {{Gefahrstoffe}}, pages = {{16--28}}, title = {{{Effektivität von Luftreinigern zur Reduzierung des COVID-19-Infektionsrisikos/ Efficacy of air purifiers in reducing the risk of COVID-19 infections}}}, doi = {{10.37544/0949-8036-2021-01-02-18}}, year = {{2021}}, } @inproceedings{27553, author = {{Ludwig, Janis and Schmid, Hans-Joachim}}, title = {{{Synthese und asymmetrische Funktionalisierung von submikronen Janus-Polymer-Partikeln in der Gasphase (Poster)}}}, year = {{2021}}, } @inproceedings{24475, author = {{Neukötter, Moritz and Jesinghausen, Steffen and Schmid, Hans-Joachim}}, location = {{Online}}, title = {{{Theoretische Beschreibung des Tropfenbildungsprozesses bei der Filament Extension Atomization: Entwicklung eines Vorhersagemodells für die Tropfengröße (Poster)}}}, year = {{2021}}, } @inproceedings{30221, author = {{Neukötter, Moritz and Jesinghausen, Steffen and Schmid, Hans-Joachim}}, location = {{Online}}, title = {{{Filament Extension Atomization – A novel Process for Powder Production? (Presentation)}}}, year = {{2021}}, } @inproceedings{27551, author = {{Ludwig, Janis and Kykal, Carsten and Schmid, Hans-Joachim}}, booktitle = {{Book of abstracts for the 2021 European Aerosol Conference}}, keywords = {{aerosol spreading, SARS-CoV-2, indoor air filtration}}, title = {{{Assessing spreading and removal of virus laden aerosols in different settings using an aerosol method (oral presentation)}}}, year = {{2021}}, } @techreport{24943, author = {{Menge, Dennis and Klippstein, Sven Helge and Schmid, Hans-Joachim}}, pages = {{130}}, title = {{{Additive Leichtbaustrukturen für die Flugzeugkabine}}}, year = {{2020}}, } @article{24241, abstract = {{For gas phase nanoparticle production, hot wall reactors are widely used. In this article, we will describe the fundamental design considerations for a hot wall reactor system able to produce oxide nanoparticles. The system is outstanding in its ability to produce mostly spherical nanoparticles at particle sizes of up to 100 nm and even larger at mass outputs in the order of grams per hour by being able to rapidly quench the aerosol. While high production rates or larger particle sizes are already easily obtained with hot wall reactors, it is very challenging to produce these spherical particles at high mass rates. We will show in this research that the temperature and the particle number concentration are the major aspects influencing the particle morphology at the end of the process. Investigation on the performance of the setup shows good control over the temperature and the particle production stability. A representative particle characterization using SEM and scanning mobility particle sizer showed that particles are mostly spherical, while the particle size distribution had a geometric standard deviation close to 1.5. In addition to the aspects mentioned above, a possibility to manipulate the aggregation downstream of the reactor is to be presented as well. We found that applying electrical charges to the aerosol particles (in opposite polarity) can significantly foster aggregation.}}, author = {{Rasche, David B. and Tigges, Lena and Schmid, Hans-Joachim}}, journal = {{Review of Scientific Instruments}}, pages = {{055104}}, publisher = {{AIP Publishing}}, title = {{{An Apparatus to Synthesize Ceramic Nanoparticles with a Precisely Adjusted Temperature History and a Significant Mass Output}}}, doi = {{10.1063/1.5133438}}, volume = {{91}}, year = {{2020}}, } @inproceedings{22182, author = {{Kummert, Christina and Diekmann, Wolfgang and Tews, Katrin and Schmid, Hans-Joachim}}, booktitle = {{29th Annual International Solid Freeform Fabrication Symposium}}, pages = {{735--744}}, title = {{{Influence of Part Microstructure on Mechanicl Properties of PA6X Laser Sintered Specimens}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2019/063%20Influence%20of%20Part%20Microstructure%20on%20Mechanical%20Pro.pdf}}, volume = {{29}}, year = {{2020}}, } @inproceedings{25062, author = {{Tischendorf, Ricardo and Schmid, Hans-Joachim and Bieber, M. and Reddemann , M. and Kneer, R. and Fröde, F. and Grenga, T. and Pitsch, H.}}, location = {{Duisburg}}, publisher = {{4th International Symposium Gas‐Phase Synthesis of Functional Nanomaterials}}, title = {{{Influence of differing nozzle configurations on the final particle characteristics and particle structure evolution in spray flames}}}, year = {{2020}}, } @article{21949, abstract = {{This paper presents the results of an interlaboratory study of the rheological properties of cement paste and ultrasound gel as reference substance. The goal was to quantify the comparability and reproducibility of measurements of the Bingham parameters yield stress and plastic viscosity when measured on one specific paste composition and one particular ultrasound gel in different laboratories using different rheometers and measurement geometries. The procedures for both in preparing the cement paste and carrying out the rheological measurements on cement paste and ultrasound gel were carefully defined for all of the study’s participants. Different conversion schemes for comparing the results obtained with the different measurement setups are presented here and critically discussed. The procedure proposed in this paper ensured a reasonable comparability of the results with a coefficient of variation for the yield stress of 27% and for the plastic viscosity of 24%, despite the individual measurement series’ having been performed in different labs with different rheometers and measurement geometries.}}, author = {{Haist, Michael and Link, Julian and Nicia, David and Leinitz, Sarah and Baumert, Christian and von Bronk, Tabea and Cotardo, Dario and Eslami Pirharati, Mahmoud and Fataei, Shirin and Garrecht, Harald and Gehlen, Christoph and Hauschildt, Inga and Ivanova, Irina and Jesinghausen, Steffen and Klein, Christopher and Krauss, Hans-W. and Lohaus, Ludger and Lowke, Dirk and Mazanec, Oliver and Pawelczyk, Sebastian and Pott, Ursula and Radebe, Nonkululeko W. and Riedmiller, Joachim Jürgen and Schmid, Hans-Joachim and Schmidt, Wolfram and Secrieru, Egor and Stephan, Dietmar and Thiedeitz, Mareike and Wilhelm, Manfred and Mechtcherine, Viktor}}, issn = {{1359-5997}}, journal = {{Materials and Structures}}, keywords = {{Rheology, Wall Slip, Slip, apparent slip, suspension, cement, concrete}}, title = {{{Interlaboratory study on rheological properties of cement pastes and reference substances: comparability of measurements performed with different rheometers and measurement geometries}}}, doi = {{10.1617/s11527-020-01477-w}}, year = {{2020}}, } @article{21948, abstract = {{Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there is no flow behind this distance. However, several studies show that this is not true. Therefore, the measuring gap needs to be corrected by adding the effective gap extension δ to the prescribed gap height H in order to obtain absolute rheological properties. In this paper, we determine the effective gap extension δ for different structures and fluids (Newtonian, shear thinning, and model suspensions that can be adjusted to the behavior of real fluids) and compare the corrected values to reference data. We observe that for Newtonian fluids a gap- and material-independent correction function can be derived for every measuring system, which is also applicable to suspensions, but not to shear thinning fluids. Since this relation appears to be mainly dependent on the characteristics of flow behaviour, we show that the calibration of structured measuring systems is possible with Newtonian fluids and then can be transferred to suspensions up to a certain particle content.}}, author = {{Pawelczyk, Sebastian and Kniepkamp, Marieluise and Jesinghausen, Steffen and Schmid, Hans-Joachim}}, issn = {{1996-1944}}, journal = {{Materials}}, keywords = {{wall slip prevention, effective gap height, parallel-plate system, structured surfaces, model suspensions, cement paste, fresh concrete}}, title = {{{Absolute Rheological Measurements of Model Suspensions: Influence and Correction of Wall Slip Prevention Measures}}}, doi = {{10.3390/ma13020467}}, year = {{2020}}, } @techreport{24628, author = {{Menge, Dennis and Walter, Rolf and Schmid, Hans-Joachim and Breuer, Ulf Paul}}, pages = {{77}}, title = {{{FVA-Nr. 813 I - Generative Verfahren zur Herstellung von Polymerbauteilen}}}, volume = {{1338}}, year = {{2019}}, } @inbook{26098, abstract = {{Since, in the presence of humidity the inter-particle processes are dominated by capillary forces, a fundamental understanding of the water adsorption and the capillary bridge formation is very important. However, the adsorbed water structure and thus the capillary bridge formation is influenced by various parameters like the particle morphology (e.g. particle size, roughness) as well as the surface chemistry (surface energy, adsorbate structure) and therefore needs to be analyzed on a submicroscopic or even molecular basis. A multi-scale approach ranging from experiments on an individual particle level (AFM and liquid bridge simulation) and investigations on small particle ensembles (combined QCM-D/FTIR) up to macroscopic description of bulk behavior is presented in this chapter. In this context, the combined in situ QCM-D/FTIR experiments are bridging the gap between experiments on an individual particle level and macroscopic bulk behavior. Variation of surface chemistry by means of adsorption of functional organic molecules allows for the correlation of macroscopic particle behavior to nanoscopic effects like the presence and structure of adsorbate layers as well as the formation of capillary bridges while keeping the disperse properties constant. Besides extensive experimental work, simulations of capillary bridges formed by condensation from humid air are presented. It is clearly shown that well known approximations which have been introduced for micron-sized particles are not valid any more for nano-scaled particles. The forces between nanoparticles by static liquid bridges and their dependency on particle size, contact angle, humidity and interparticle distance are discussed in detail. Furthermore, capillary forces during separation of particles are studied thoroughly and a constitutive law based on a contact stiffness allows the transfer to DEM simulations of wet powders. Finally, it is demonstrated by comparison to Molecular Dynamics simulations, that the used continuum approach to simulate capillary bridges might even be used down to particle sizes of a few nanometers, if some additional effects are considered correctly.}}, author = {{Schmid, Hans-Joachim and Grundmeier, Guido and Dörmann, Michael and Orive, Alejandro González and de los Arcos, Teresa and Torun, Boray}}, booktitle = {{Particles in Contact}}, title = {{{Understanding and Manipulation of Nanoparticle Contact Forces by Capillary Bridges}}}, doi = {{10.1007/978-3-030-15899-6_2}}, year = {{2019}}, } @inproceedings{22198, abstract = {{Zuverlässige, wiederholbare Bauteileigenschaften sind unabdingbar um das Herstellungsverfahren Polymer Lasersintern im industriellen Prozess-Portfolio vieler Firmen aufnehmen zu können. Einige Unternehmen und Institute haben sich daher in jüngster Zeit mit dem Thema der reproduzierbaren Bauteileigenschaften beschäftigt. Mit der hier vorgestellten und angewandten Methodik wird nicht nur der Prozessablauf vom Bauteil bis zu Nachbearbeitung betrachtet, sondern auch die Maschinenperformance in einem Ringversuch und über einen längeren Zeitraum geprüft. Rückgrat dieser Untersuchung bildet hierbei der aus der Six Sigma Lehre stammende DMAIC (Define - Measure - Analyse - Improve - Control) Verbesserungszyklus. Hierfür wird ein Standard-Prozess definiert. Diesem folgend werden die für die Industrie oder den Anwender interessanten Messungen aufgenommen und analysiert. Anschließend wird der Prozess sowie die Messmethodik optimiert und auch Kontrollmethoden definiert. Für die Anwendung der entwickelten Methodik wird exemplarisch der Maschinentyp EOS P396 mit PA2200 untersucht. Daten für die Bestimmung der Mechanik, der Optik und der Haptik sowie für die Dimensionen und die Bauteildichte werden als Qualitätskriterium aufgenommen und über einen längeren Zeitraum analysiert. Weiteres Ziel ist es, den Messaufwand zu reduzieren und die Qualitätssicherung im Serienbtrieb zu gewährleisten.}}, author = {{Klippstein, Sven Helge and Schmid, Hans-Joachim}}, booktitle = {{Proceedings of the 16th Rapid.Tech Conference}}, title = {{{Methodik zur Qualifizierung des Lasersinter Prozesses für die Serienfertigung}}}, doi = {{10.3139/9783446462441.025}}, year = {{2019}}, } @inproceedings{24515, author = {{Tischendorf, Ricardo and Bieber, M. and Kneer, R. and Schmid, Hans-Joachim}}, keywords = {{FSP, nanoparticle synthesis, in situ measurements}}, location = {{Nürnberg}}, publisher = {{PARTEC 2019 International Congress on Particle Technology}}, title = {{{Representative Sample Extraction from Spray Flames for SMPS and HR-TEM Measurements}}}, year = {{2019}}, } @inproceedings{22202, abstract = {{Structural parts for aviation have very high demands on the development and production process. Therefore, the entire process must be considered in order to produce high-quality AM metal parts. In this case study, a conventional part was selected to be optimized for AM. The process presented includes component selection, design improvement with a novel approach for topology optimization based on the AMendate algorithm as basis of MSC Apex Generative Design,component production on a SLM 250 HL and post-processing including heat treatment and surface smoothing. With the topology optimization a weight reduction of ~60 % could be realized, whereby the stress distribution is more homogeneous. Furthermore, the challenges of support optimization and post-processing have to be addressed, in order to produce competitive parts.}}, author = {{Klippstein, Sven Helge and Duchting, Anne and Reiher, Thomas and Hengsbach, F. and Menge, Dennis and Schmid, Hans-Joachim}}, booktitle = {{30th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1932--1945}}, title = {{{Devolopment, Production and post-processing of a topology optimized aircraft bracket }}}, volume = {{30}}, year = {{2019}}, } @article{22541, abstract = {{Monodisperse micron-sized silica particle monolayers deposited onto plasma-grown SiOx-ultra-thin films have been used as reference systems to investigate wetting, water adsorption and capillary bridge formation as a function of silica surface functionalization. 1H,1H, 2H,2H perfluorooctyltriethoxysil (FOTS) monolayers, have been deposited on the respective surfaces by means of chemical vapor deposition resulting in macroscopically low energy surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) reflection absorption spectroscopy confirmed the monolayer formation. Water adsorption isotherms were studied by a combination of in-situ FTIR reflection spectroscopy and quartz crystal microbalance (QCM) while macroscopic wetting was analysed by contact angle measurements. The comparative data evaluation indicates that the macroscopic wetting behaviour was changed as expected, however, that water nanodroplets formed both at intrinsic defects of the FOTS monolayer and at the FOTS/SiOx interface. Capillary bridges of liquid water are dominantly formed in the confined particle contact areas and between surface asperities on the particles. The comparison of wetting, adsorption and capillary bridge formation shows that the hydrophobization of porous materials by organosilane monolayers leads to the formation of morphology dependent nanoscopic defects that act as sites for preferential capillary bridge formation.}}, author = {{Giner, Ignacio and Torun, Boray and Han, Yan and Duderija, Belma and Meinderink, Dennis and Orive, Alejandro González and de los Arcos de Pedro, Maria Teresa and Weinberger, Christian and Tiemann, Michael and Schmid, Hans-Joachim and Grundmeier, Guido}}, issn = {{0169-4332}}, journal = {{Applied Surface Science}}, pages = {{873--879}}, title = {{{Water adsorption and capillary bridge formation on silica micro-particle layers modified with perfluorinated organosilane monolayers}}}, doi = {{10.1016/j.apsusc.2018.12.221}}, year = {{2019}}, } @article{26103, abstract = {{Pore-scale filtration simulations require high spatio-temporal resolutions and significant computational effort, hence, keeping the domain size to a minimum is desirable. Previous studies have considered domains based on Brinkman length, or are limited by computing power, and little information is available for conditions involving high fluid saturation – typical of steady state mist filtration. In this study, simulations are performed to characterize the effect of domain size on pressure drop, residual saturation, liquid film thickness and interfacial area concentration, using virtual nonwoven and foam filters with similar micro-structural properties. Further, experiments using micro-CT are performed to validate the present computational simulations. It is found that two phase flow through filters are more sensitive to local geometric variations or mesh resolution in the porous media than single phase flow. Statistical uncertainties in the steady state quantities of less than +-10% can be expected to cope with the increase in computing power required for practical mesh sizes. A computational domain size of about 50–100xd (where d is the strut or fibre diameter) was found to be required for CFD for the operating conditions considered.}}, author = {{Abishek, S. and King, A.J.C. and Schuler, J. and Kasper, G. and Schmid, Hans-Joachim and Mullins, B.J.}}, issn = {{1383-5866}}, journal = {{Separation and Purification Technology}}, pages = {{344--352}}, title = {{{Representative domain size for the simulation of coalescence filtration in nonwoven and foam media}}}, doi = {{10.1016/j.seppur.2018.06.051}}, year = {{2018}}, }