Fritsching, Udo
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Item type:Publication, Impact of process flow conditions on particle morphology in metal powder production via gas atomizationAdditive manufacturing processes as for instance selective laser melting or electron beam melting are becoming more common and just turning into standard manufacturing processes for metal components. Nevertheless, these processes are still new compared to classic powder metallurgy manufacturing routes such as pressing and sintering. Hence not all necessary requirements for the powders in use are fully known yet. This makes an increase in control of the powder properties a crucial task to achieve. To reach this goal one must understand the different influences on the powder production process from the beginning of the whole production route. In this work, the influence of the spray chamber flow on the particle morphology is examined. The nozzle system used to produce the metal powders is a close-coupled atomization system with a convergent-divergent gas nozzle configuration. The particle morphology as well as the particle size distribution have been analyzed to examine the influence of the atomization gas flow compared to an additional use of a coaxial gas flow. To review the changes of the flow patterns, computational fluid dynamic simulations have been performed. The particle trajectories were calculated to assess the change in particle behavior as well. Atomization experiments have been conducted with an AISI 52100 (1.3505) steel in a small batch atomization plant to evaluate the influence of the change in flow on the particle size distribution and circularity. The experimental results show that a use of additional coaxial gas leads to an increase in particle circularity up to 10% for relevant particle sizes. An approach for the quantification of satellite occurrence is given by examination of the shift of the particle size distribution to smaller diameters.journal articleBand:31Heft:183 122 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Formulation of blast-furnace slag for use in hydraulically bound construction materialsDry powder granulation of slag melts by gas atomization offers a means of reducing the resource expenditure associated with the conventional wet processing of blast furnace slags (BFS). Slags are a by-product of the iron production process and are subsequently processed to create a fine powder, which is then used in the manufacture of building materials. The melt atomization process, which is widely used in metal powder production, was adapted to process the slag into fine, amorphous and spherical particles. Therefore, this study investigates the development of an adapted high-temperature atomization process utilizing a new developed atomizer, the resulting properties of the slag particles, and the suitability of atomized blast furnace slag powders (ABFS) for use in building materials. It is demonstrated that BFS can be properly atomized to form spherical, amorphous particles that exhibit excellent flowability and a low Carr-Index. The utilization of heated atomization gas and high atomizing gas pressure increases the content of small particles below 200 μm in diameter with up to 60 % of the powder mass. The atomized slag powder exhibits comparable latent hydraulic properties as ground slag powders. The utilization of the atomized slag powder fraction below 90 μm in concrete approaches the results of formulations containing conventionally processed slag. In this way, the requisite water content in concrete formulations can be diminished, and the concrete formulation's CO2 footprint may be reduced. Consequently, liquid BFS can be directly processed into spherical and amorphous particles through hot gas atomization and the resulting slag powder can be utilized in building materials.journal articleBand:45163 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Stability of multiple emulsions under shear stressMultiple liquid emulsions of the water in oil in water (W1/O/W2) type are used in a variety of consumer or technical applications, for instance in the encapsulation of certain active ingredients. The encapsulation process and release mechanisms of the inner phase of the carrier drops are important in order to properly process and formulate such liquid-liquid systems. In this work the stability and breakage of multiple W1/O/W2 emulsions under mechanical shear stress are investigated for emulsions with different surfactants and surfactant concentrations of the internal emulsion. Stressing the emulsions in a mechanical stirring process is compared to the membrane emulsification process. The membrane emulsification process results in higher encapsulation efficiencies than the stirring process. The emulsion droplets were subjected to shear stress below and above the critical capillary number for drop breakup. The results show that stable inner emulsions with sufficient surfactant concentrations increase the overall encapsulation efficiency for multiple emulsions subjected to shear stress, although the effect is not prominent. The depletion of the carrier oil droplets could be achieved for Ca numbers below the critical limit, reducing the encapsulation efficiency below 10 %. This shows that even a low shear stress can result in content release from the internal droplet phase. The experimental emulsion release study is supported by a numerical simulation of drop deformation and break-up under shear stress.journal articleBand:98Heft:1105 151 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Premix membrane emulsification using flat microfiltration inorganic membranes with tailored structure and composition(Elsevier, 2020-04-20); ; ; ; Uniform oil-in-water emulsions were prepared using MCT (medium-chain fatty acid triglyceride, 10 wt%) as the oily dispersed phase and polysorbate 80 as the surfactant (1 wt%). The emulsification process was performed via premix membrane emulsification (PME) using 3 flat microfiltration ceramic membranes with different mean pore sizes (dm): borosilicate (symmetric, commercial, dm: 1.39 μm); SiOC (symmetric, manufactured, dm: 1.76 μm); and mullite (asymmetric, manufactured, dm: 1.18 μm). The droplets size and their distribution varied according to the membrane type and number of permeation cycles (up to a limit of 2 passes). All prepared emulsions presented a tendency to monomodal droplet distribution with span values in the range of 0.82–0.97. The coarse emulsion (premix) droplets were reduced from 6.30 to 4.50–2.17 μm. The asymmetric membrane (mullite) exhibited the highest permeation fluxes at constant relative pressure for both water (43.1 × 10−3 m3 m−2 s−1) and premix (Pass 1: 4.6 × 10−3 m3 m−2 s−1; Pass 2: 5.3 × 10−3 m3 m−2 s−1), still maintaining satisfactory emulsification results.journal article132 129 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Formulation and Rheological Characterization of Premix EmulsificationFormulation and Rheological Characterization of Premix Emulsificationjournal articleBand:87Heft:8120 109 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Proceedings SPRAY 2010, 3.-5. Mai 2010, Heidelberg(2010); Gutheil, EvaSPRAY 20109. Workshop über Sprays, Techniken der Fluidzerstäubung und Untersuchungen von SprühvorgängenHeidelberg, 3. - 5. Mai 2010Die Spray-Workshops sollen Ingenieuren und Wissenschaftlern aus Forschung und Industrie Gelegenheit bieten, sich mit aktuellen Problemen und Lösungsansätzen der Fluidzerstäubung, den entsprechenden Messtechniken sowie der physikalischen Modellbildung von Sprayprozessen und deren numerischer Behandlung auseinander zu setzen. Der Workshop Spray 2010 in Heidelberg war der neunte in dieser Reihe.In den Spray-Workshop 2010 integriert war das Jahreskolloquium des DFG-SPP Prozess-Spray: Herstellen funktionaler Feststoffpartikeln in Sprühverfahren von den Anforderungen an das Pulver und an seine Eigenschaften zum geeigneten Prozess. Die Proceedings zu diesem Workshop mit den eingereichten Tagungsbeiträgen sind nach dem Modus des Open Access auf dem E-Lib Server der Staats- und Universitätsbibliothek der Universität Bremen elektronisch publiziert und über ihre URN (uniform resource name) zitierfähig.E. Gutheil / U. Fritschingconference paper510 1077 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Energie- und Ressourceneffizienz in der Wärmebehandlung und ThermoprozesstechnikDie effiziente Nutzung von Energie und Rohstoffen gewinnt in den allen Produktionsprozessen zunehmend an Bedeutung. Steigende Energiepreise und Umweltanforderungen sowie der zunehmende Kostendruck durch die Globalisierung zwingen auch klein- und mittelständische Unternehmen, sich mit dem Thema Energie- und Ressourceneffizienz verstärkt auseinanderzusetzen. Potentielle Effizienzsteigerungen in Prozessen und Anlagen gründen nach dem Stand der Technik auf innovativen Prozessen und Produkten und wesentlich aus der Optimierung ganzer Prozess- und Fertigungsketten, der effizienten Verknüpfung von Verfahrens- und Prozessschritten sowie einer ganzheitlichen Optimierung bereits etablierter Produktionsabläufe. Um den Austausch von Know-how und Erfahrungen im Bereich energie- und ressourceneffizienter Fertigungs- und Prozessketten in der Wärmebehandlung und Thermoprozesstechnik voranzutreiben werden im Seminar u.a. folgenden Bereiche vorgestellt: Anlagen der Wärmebehandlung und Thermoprozesstechnik Vernetzung von Stoff- und Energieflüssen Bilanzierung von Stoff- und Energieströmen Möglichkeiten der Stoff- und Energieeinsparung Analyse und Optimierung der Prozessführung Optimierung von Steuer- und Regelkreisen Bewertung von Maßnahmen bezgl. Einspar- und Verwertungspotential Strategien und Prozessführung für Kühl- und Heiz- / Erwärmprozesse von Bauteilen in Thermoprozessen. Das Seminar richtet sich an Ingenieure und Techniker sowie Praktiker aus den Bereichen Entwicklung und Konstruktion und insbesondere die Betreiber von Thermoprozessanlagen in der Härtereitechnik und der Wärmebehandlung. Die Vortragenden sind Anwender und Entwickler/Anlagenbauer aus der Wärmebehandlung, der Werkstoff- und Thermoprozesstechnik.conference paper386 325 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Phase-selective laser–induced breakdown spectroscopy in flame spray pyrolysis for iron oxide nanoparticle synthesisThe flame spray pyrolysis of iron oxide nanoparticles using the new reference nozzle SpraySyn is a key step towards the understanding of the coupling of physicochemical steps such as precursor atomization, spray evaporation, combustion, particle formation and growth. Owing to the countless available solvents and precursors, systematic investigations are necessary to fully understand the impact of precursor formulation on the reaction route and, hence, the particle properties. In this work, the recently developed phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique is applied to an external mixing spray flame reactor in order to study iron oxide particle formation along the axial centerline of the spray under varying precursor solutions. The addition of 2-ethylhexanoic acid (EHA) to precursors is investigated and significant differences in the evolution of the atomic emission spectra are observed, enabling the differentiation between droplet-to-particle and gas-to-particle routes in situ. The observations from PS-LIBS are in good agreement with TEM images and XRD, where haematite (α-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) were observed. Raman spectroscopy (RS) in particle-free spray-flames revealed a significant gas-phase temperature difference of about ΔT∼500 K under addition of EHA to the spray and demonstrated accurate temperature measurements up to droplet rates of 103 Hz. The experimental results allow deep insights into the spray flame combustion and particle nucleation kinetics. Moreover, they can be coupled with population balance models and be used for the validation of numerical simulations.journal articleBand:38Heft:123 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Proceedings SPRAY 2012, 21.-22. Mai 2012, Berlin(2012); Drusch, StephanSPRAY 2012, 21.-22. Mai 2012, Berlin Die Spray-Workshops sollen Ingenieuren und Wissenschaftlern aus Forschung und Industrie Gelegenheit bieten, sich - über ihre jeweiligen Einsatzgrenzen hinweg - mit aktuellen Problemen und Lösungsansätzen der Fluidzerstäubung, den entsprechenden Messtechniken sowie der physikalischen Modellbildung von Sprayprozessen und deren numerischer Behandlung auseinander zu setzen. Die Spray-Workshops werden seit 1994 in loser Reihenfolge im deutschsprachigen Raum durchgeführt. Der aktuelle Workshop Spray 2012 ist der 10. in dieser Reihe. In den aktuellen Spray-Workshop integriert ist das Jahreskolloquium des DFG-SPP Prozess-Spray: Herstellen funktionaler Feststoffpartikeln in Sprühverfahren von den Anforderungen an das Pulver und an seine Eigenschaften zum geeigneten Prozess. Durch diese Einbindung soll das Thema der Fluidzerstäubung und seine aktuellen Entwicklungen und der Fortschritt im SPP in breiter Anwendung vorgestellt und diskutiert werden. Die Proceedings zu diesem Workshop mit den eingereichten Tagungsbeiträgen sind auf CD erschienen und werden nach dem Modus des Open Access auf dem E-Lib Server der Staats- und Universitätsbibliothek der Universität Bremen elektronisch publiziert. Sie sind damit dauerhaft und stabil archiviert und werden über eine dauerhaft verfügbare Internetadresse mittels URN (uniform resource name) zitierfähig. S. Drusch / U. Fritschingconference paper314 1913