@article{63830, abstract = {{ This study investigates the effect of dispersion gas (DG) flow on the formation and properties of maghemite (γ-Fe2O3) nanoparticles using standardized SpraySyn burners (SS1 and SS2). Several diagnostics were employed to characterize the spray and nanoparticles. Increasing DG flow (6 - 12 slm) results in smaller droplet sizes (DS), cooler flame temperatures, shorter high-temperature droplet/particle residence times, and smaller agglomerates in the size range of 5 - 12 nm with narrower primary particle size distribution, corresponding to higher mass fractal dimensions, as supported by TEM and SMPS analysis, resulting in more compact agglomerates. BET and TEM confirmed decreasing primary particle sizes with increasing DG flow. Raman and XRD analyses predominantly identified maghemite, which shows a bimodal distribution of crystallite sizes, while SS1 samples have a greater proportion of larger crystallites. The self-preserving size distributions of agglomerates with a geometric standard deviation of 1.5 are reached faster with increasing DG flow. The barrier effect of DG observed in SS1 leads to slower droplet combustion kinetics, higher temperatures, and delayed precursor release, which, along with downstream flow recirculation, result in significantly higher agglomeration rates outside the visible flame. SS2 demonstrates improved atomization, more stable flames, and finer, uniform nanoparticles with less carbonaceous residues (CR). Conversely, SS1 showed broader DS distributions and higher CR levels on the γ-Fe2O3 surface, especially at higher DG flow. This work highlights the essential role of DG flow and nozzle geometry in controlling droplet evaporation, flame stability, and nanoparticle growth, offering insights for optimizing SFS and validating numerical models. }}, author = {{Massopo, Orlando and Tischendorf, Ricardo and Gonchikzhapov, Munko and Kasper, Tina and Augustin, Peter and Özer, Burak and Reddemann, Manuel and Kneer, Reinhold and Sheikh, Mohammed-Ali and Mert, Aydan Akyildiz and Wiggers, Hartmut and Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, keywords = {{Spray flame synthesis, iron oxide nanoparticle, SpraySyn burner, Dispersion gas, Coaxial atomization, HiaT-SMPS}}, publisher = {{Elsevier BV}}, title = {{{Influence of dispersion gas flow on the spray characteristics and γ-Fe2O3 nanoparticles formation and properties in reference SpraySyn burners}}}, doi = {{10.1016/j.powtec.2025.121992}}, volume = {{470}}, year = {{2025}}, } @article{43128, author = {{Rüther, Moritz Johannes and Klippstein, Sven Helge and Ponusamy, SathishKumar and Rüther, Torben and Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, keywords = {{General Chemical Engineering}}, publisher = {{Elsevier BV}}, title = {{{Flowability of polymer powders at elevated temperatures for additive manufacturing}}}, doi = {{10.1016/j.powtec.2023.118460}}, volume = {{422}}, year = {{2023}}, } @article{26107, abstract = {{Capillary forces are very important considering the handling of powders as they, in general, exceed other adhesion forces. These capillary forces are dependent on several different parameters. Especially the distance between the particles is an important parameter. For example, in moving bulk solids a large variety of distances between particles will occur. Therefore, the distance-dependence of capillary bridges was investigated with a numerical simulation method, assuming thermodynamic equilibrium which is attained very fast for small particles. This method uses the Kelvin equation and the Young-Laplace equation to calculate numerically the shape of the capillary bridge without any assumption regarding the shape. The force is eventually derived from the meniscus shape. The distance becomes extremely important when the capillary liquid bridge between two surfaces is only determined by capillary condensation depending on relative humidity. Only a slight increase of the distance within the fraction of a nanometer changes the behaviour of the capillary force significantly. Furthermore, the influence of the force on the separation of particles will be presented. The force decreases almost linearly with increasing distance for a wide range of distances and consequently, a contact stiffness for capillary bridges could be derived. These results may e.g. be used in DEM models. Also, the maximum separation distance of capillary bridges in thermodynamic equilibrium and the correlation with the according bridge volume was investigated. As two limiting cases for capillary bridges at varying distances one can assume either a constant curvature, i.e. infinitely fast attainment of equilibrium, or a constant volume, i.e. infinitely slow attainment of equilibrium. Therefore, a comparison of these two possibilities will be presented and discussed as well.}}, author = {{Dörmann, Michael and Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{175--183}}, title = {{{Distance-dependency of capillary bridges in thermodynamic equilibrium}}}, doi = {{10.1016/j.powtec.2017.01.012}}, year = {{2017}}, } @article{21192, author = {{Engelkemeier, Katja and Grydin, Olexandr and Schaper, Mirko}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{204--209}}, title = {{{Structured zinc oxide powder materials: Synthesis and further investigations of their thermal morphological stability}}}, doi = {{10.1016/j.powtec.2017.06.031}}, year = {{2017}}, } @article{26123, abstract = {{The precipitation of sticky and ultrafine particles has become increasingly important. Biomass burners are one important example for ultrafine dust emission sources with ever growing importance. Therefore, a baghouse filter has been developed, which combines excellent separation efficiency (> 99%, clean air dust loading of < 1 mg/m3) with convenience in operation. However, in order to prevent clogging of the filter cloth by sticky and ultrafine particles, it is necessary to use a precoat layer (e.g. hydrated limestone powder). If this technology is applied to larger scale processes, e.g. biomass burning for industrial drying processes, the reuse of the precoat material can generate significant savings. Therefore, extended tests on recycling of used precoat material have been performed. Particularly, the influence of precoat injection parameters and various mixing strategies of used and virgin powder for refreshing the precoat material have been investigated. Different mixtures have been characterised by their ability to disintegrate, flowability and filtration behaviour. It is clearly demonstrated that upon redispersing the used precoat fine dust mainly adheres to the coarse precoat with only a limited number of dust agglomerates being produced in addition. For each kind of precoat a minimum amount is determined in order to ensure a long-term stable process. This way a saving potential of between 40–67% has been found. An economic and ecologic process has been developed to precipitate ultrafine dust in a baghouse filter system using precoat materials.}}, author = {{Schiller, Sascha and Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{96--105}}, title = {{{Highly efficient filtration of ultrafine dust in baghouse filters using precoat materials}}}, doi = {{10.1016/j.powtec.2015.03.048}}, year = {{2015}}, } @article{26129, abstract = {{Because of the large surface area of colloids interface effects are dominant in contrast to volume effects. The study presents experimental results of the direct transfer of magnetite nanoparticles from an aqueous to a non-miscible organic phase. The starting point is a water-based colloid that is synthesized through a precipitation reaction. The transfer is based on the adsorption of surfactants onto the particle surface at the liquid–liquid interface. While penetrating the liquid–liquid interface, the particles are covered with surfactants and a partial de-agglomeration is initiated. The intention is to produce a stable organic colloid, which has important applications in industry. The optimized process parameters for the successful phase transfer process, the adsorption reactions at the liquid–liquid interface and the stabilization of primary particles in the organic phase are demonstrated.}}, author = {{Erler, Jacqueline and Machunsky, Stefanie and Grimm, Philipp and Schmid, Hans-Joachim and Peuker, Urs A.}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{265--269}}, title = {{{Liquid–liquid phase transfer of magnetite nanoparticles — Evaluation of surfactants}}}, doi = {{10.1016/j.powtec.2012.09.047}}, volume = {{247}}, year = {{2013}}, } @article{26142, abstract = {{Modeling of particle deposition on adjacent walls is a key issue in various applications like separation or transport processes. The present paper focuses on the modeling of turbophoretic deposition of particles in the micron size range. The first step is to evaluate the important range where turbophoresis plays an important role in comparison to other mechanisms e.g. gravity or electrostatic separation. The disadvantages of commonly used models will be analyzed and overcome by implementing a more sophisticated approach considering damping of turbulent fluctuations in the wall-boundary layer. In contrast to previous work, commonly used turbulence models are applied to solve the mean flow field of the examples under consideration. The results will show a good prediction of particle deposition in comparison to experimental values [B.Y.H. Liu, J.K. Agarwal, Experimental observation of aerosol deposition in turbulent flow, Aerosol. Sci. 5 (1974) 145–155.] by using the advanced model.}}, author = {{Horn, M. and Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, number = {{3}}, pages = {{189--198}}, title = {{{A comprehensive approach in modeling Lagrangian particle deposition in turbulent boundary layers}}}, doi = {{10.1016/j.powtec.2007.11.048}}, volume = {{186}}, year = {{2008}}, } @article{26156, abstract = {{Electro-hydrodynamic two-phase flows are encountered in various applications, e.g. electrically enhanced coating, electrostatic precipitation or toner application. In all cases there is a complex interaction between a turbulent flow field, a strong electric field, a corona discharge and the particle motion. This paper starts with an overview and classification of possible modelling approaches for all major phenomena. Afterwards the manuscript focuses on the modelling of particle dynamics: A Lagrangian, continuous random walk model is compared with an Eulerian approach for a number of test cases. The study is mostly focused on fine particles, i.e. roughly smaller than 100 μm in diameter for the Lagrangian approach and smaller than about 10 μm in the case of Eulerian modelling. It is shown that a local turbulent dispersion coefficient may be derived based on flow field calculations with a constant of proportionality identical to the Lagrangian random walk model. In this case the turbulent dispersion is equally described by both models even for inhomogeneous turbulence. For a superimposed particle drift velocity a model equation introduced by Csanady gives a reasonable agreement. Finally it is shown that modelling of the charging kinetics is a very crucial point in Eulerian modelling. This is demonstrated for the example of electrostatic precipitation where good agreement between Lagrangian and Eulerian modelling is achieved only if local particle charging kinetics is accounted for. Even though Lagrangian particle tracking is still superior in terms of physical modelling of electro-hydrodynamic particulate flows, it is shown that an Eulerian approach may lead to reasonable results with substantially reduced numerical effort.}}, author = {{Schmid, Hans-Joachim and Vogel, Lutz}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{118--135}}, title = {{{On the modelling of the particle dynamics in electro-hydrodynamic flow-fields: I. Comparison of Eulerian and Lagrangian modelling approach}}}, doi = {{10.1016/j.powtec.2003.08.009}}, volume = {{135/136}}, year = {{2003}}, } @article{26157, abstract = {{A simulation method is applied to calculate particle dynamics in electrostatic precipitators as characterised by particle flux density and concentration profiles in arbitrary channel cross-sections and flux density profiles of dust precipitated at the collecting electrodes (CEs). A simple statistical model allows the determination of confidence intervals for flux profiles. First, a ‘standard case’ considering full coupling of all physical phenomena occurring in this problem, i.e., electric field, flow field and particle dynamics is simulated. Subsequently, this standard case is compared to simulations with one quantity (e.g., electric field strength, turbulence intensity) substituted by a mean value which is homogeneously distributed in the precipitation zone. This reveals the relevance of the various physical phenomena: It turned out that the secondary flows had only a minor influence on the overall particle precipitation although they cause some ‘patterning’ of local precipitation. Turbulence inhomogeneity shows a stronger effect on particle dynamics. However, the electric field appears to be by far the most important quantity in simulating particle dynamics. Consequently, in order to achieve most reasonable simulation results for a given numerical effort most attention has to be devoted to field calculations, including correct boundary conditions.}}, author = {{Schmid, Hans-Joachim}}, issn = {{0032-5910}}, journal = {{Powder Technology}}, pages = {{136--149}}, title = {{{On the modelling of the particle dynamics in electro-hydrodynamic flow fields: II. Influences of inhomogeneities on electrostatic precipitation}}}, doi = {{10.1016/j.powtec.2003.08.010}}, volume = {{135/136}}, year = {{2003}}, }