TY - JOUR A1 - Nöske, Markus A1 - Müller, Jannes A1 - Nowak, Christine A1 - Li, Kangqi A1 - Xu, Xiaolu A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Multicomponent Comminution within a Stirred Media Mill and Its Application for Processing a Lithium-Ion Battery Slurry JF - Processes N2 - This study presents an approach for targeted comminution of component mixtures within a wet-operated stirred media mill. In the first step, a general understanding of the interactions between individual components on the grinding result with mixtures could be gained with basic experiments and following our former research work. In particular, a protective effect of the coarser particles on the fines could be elucidated. These findings were used to develop a process for the production of a battery slurry containing fine ground silicon particles as well as dispersed carbon black and graphite particles. By a tailored sample preparation applying a combination of particle dissolution and separation, the particle size distributions of carbon black and graphite particles were analyzed separately within the produced battery slurries. Based on the selective particle size analysis, the slurry preparation could be transferred from a complex multistage batch process using a dissolver to a stirred media mill, which was finally operated in a continuous one-passage mode. The prepared slurries were subsequently further processed to silicon-rich anodes using a pilot scale coating and drying plant. Afterward, the produced anodes were electrochemically characterized in full cells. The cell results prove a comparable electrochemical behavior of anode coatings derived from a dissolver- or mill-based slurry production process. Therefore, we could demonstrate that it is possible to integrate the mixing process for the production of multicomponent slurries into the comminution process for the preparation of individual materials upstream. Even with nearly identical starting sizes of their feed materials, the targeted particle size distributions of the single components can be reached, taking into account the different material-dependent particle strengths and sequential addition of single components to the multicomponent comminution process. KW - multicomponent comminution KW - stirred media mill KW - battery slurry KW - silicon anode Y1 - 2022 U6 - https://doi.org/10.3390/pr10112309 SN - 2227-9717 VL - 10 IS - 11 PB - MDPI AG ER - TY - JOUR A1 - Sterling, David A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Improved energy transfer model for mechanistic scale-up of stirred media mills JF - Powder Technology N2 - Wet-operated stirred media mills are commonly used in the field of fine and ultra-fine grinding. Depending on the application, there are different mill geometries, sizes and mill equipment materials of which the grinding chamber lining and the stirrer are made. Increasing energy prices demand an energy-efficient mill operation for a desired product, which can be achieved with mechanistic stress models. Here, besides the mill geometry and volume, the process parameters and various energy-transfer-coefficients are of importance. In this work, the impact of different mill equipment materials affecting the mill-related-energy-transfer-coefficients on performance prediction and scale-up using the advanced stress model are investigated. It was found that the mill-related-energy-transfer-coefficients as well as the improved grinding-media-energy-transfer-coefficients have a significant effect on the prediction precision of the comminution times and specific energies for chosen target particle sizes. KW - Stirred media mill KW - Scale up KW - Mechanistic model KW - Mill equipment materials KW - Advanced stress model KW - Energy transfer coefficient KW - Energy efficiency Y1 - 2024 U6 - https://doi.org/10.1016/j.powtec.2024.119978 SN - 0032-5910 VL - 444 PB - Elsevier BV ER - TY - JOUR A1 - Peppersack, Christoph A1 - Flach, Frederik A1 - Prziwara, Paul A1 - Damm, Cornelia A1 - Breitung-Faes, Sandra A1 - Peukert, Wolfgang A1 - Kwade, Arno T1 - Conceptual stabilizer selection for nanomilling based on dispersibility parameters JF - Advanced Powder Technology N2 - The choice of stabilizers to prevent particle agglomeration during nanomilling is an elaborate process which is often based on empirical rules and experience. Usually, extensive screening studies are required to find an appropriate stabilizing additive. The present study shows how the selection of polymeric stabilizers can be narrowed down to a couple of additives based on Hansen solubility parameters. The stabilizing capability was found to be a function of the difference between solubility parameters of additive and particulate species. Solubility parameters of different additives and two particle species were determined by inverse gas chromatography and the stabilization performance was evaluated by nanomilling experiments conducted with a stirred media mill. It is shown that a certain difference of solubility parameters between particle and additive is necessary in order to provide colloidal stability of small particles after milling. On the one hand, the additive needs a certain affinity to the particle surface, while on the other hand it also has to be compatible with the solvent. Based on experimental data, a solubility parameter difference in the range of 7.5–10 MPa0.5 was identified as a good measure for a proper stabilizer selection. The approach was proved for two organic particle species and represents a promising tool for a more efficient formulation development of drug nanosuspensions. KW - Nanomilling KW - Colloidal stability KW - Hansen solubility parameter KW - Inverse gas chromatography Y1 - 2023 U6 - https://doi.org/10.1016/j.apt.2023.104197 SN - 0921-8831 VL - 34 IS - 10 PB - Elsevier BV ER - TY - JOUR A1 - Peppersack, Christoph A1 - Kwade, Arno A1 - Breitung-Faes, Sandra T1 - Selective particle size analysis in binary submicron particle mixtures using density dependent differential sedimentation JF - Advanced Powder Technology N2 - Particle size characterization of heterogeneous mixtures is a challenging task, as it is not feasible to assign the measured signals to the individual components. Within this framework, the study proposes a method that applies the working principle of differential centrifugal sedimentation (DCS) in order to simultaneously separate and measure the denser component within a binary material mixture of submicron particles. The method was validated using a model system consisting of polyvinyl chloride (PVC) and diamond particles in a size range of 0.5 – 1.5 µm. The results proved that by applying a proper density gradient fluid, the diamond particles can be selectively analyzed by hindering the sedimentation of the lighter PVC component. Furthermore, a very promising application could be found with respect to wet fine grinding processes in stirred media mills. In fact, the approach was utilized to individually determine the particle size distribution of the grinding media wear within an ultrafine organic product. Despite the low quantity of wear particles, it was possible to separate them from the organic product under appropriate density conditions. The size distributions of both the wear and the product particles were validated with SEM images, confirming the feasibility of the method. KW - Grinding media wear KW - Differential centrifugal sedimentation KW - Selective particle size analysis KW - Heterogeneous mixtures KW - Stirred media milling Y1 - 2021 U6 - https://doi.org/10.1016/j.apt.2021.09.010 SN - 0921-8831 VL - 32 IS - 11 SP - 4049 EP - 4057 PB - Elsevier BV ER - TY - JOUR A1 - Sterling, David A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Experimental evaluation of the energy transfer within wet operated stirred media mills JF - Powder Technology N2 - Wet-operated stirred media mills are commonly used in the field of fine and ultra-fine grinding. Depending on the application, there are different mill geometries and mill equipment materials of which the grinding chamber lining and the stirrer are made. Polyurethane and ceramics are frequently implemented materials. Besides the process-relevant effects such as cooling and wear prevention, an energy efficient mill operation is intended, which can be achieved, by using mechanistic stress models. Here, besides the mill geometry, the process parameters, various energy-transfer-coefficients are also determined. In this work, the effect of different mill equipment materials on the mill-related-energy-transfer-coefficient are investigated by experiments while operating different mills only with water and grinding media but without feed material. It was found that the mill equipment material has a significant effect on the power consumption and thus, the energy transfer within the mill as a result of friction between different materials. KW - Stirred media mill KW - Grinding chamber and stirrer materials KW - Advanced stress model KW - Energy transfer coefficient KW - Energy efficiency Y1 - 2023 U6 - https://doi.org/10.1016/j.powtec.2023.118579 SN - 0032-5910 VL - 425 PB - Elsevier BV ER - TY - JOUR A1 - Peppersack, Christoph A1 - Wermbter, Karsten A1 - Kwade, Arno A1 - Garnweitner, Georg A1 - Breitung-Faes, Sandra T1 - Top-Down Formulation of Goethite Nanosuspensions for the Production of Transparent, Inorganic Glass Coatings JF - Coatings N2 - This study presents a simple but effective process route for the production of transparent coatings on glass substrates from inorganic pigment goethite. For this purpose, coating suspensions were prepared by wet milling with a stirred media mill. A water/ethanol mixture was used as the liquid medium to take advantage of the resulting low surface tension for the coating process. In this manner, stable suspensions with particles of down to 50 nm in size were obtained, which already showed a significant increase in transparency. With regard to grinding characteristics, particularly low stress energies proved to be energetically reasonable. The coating step was performed by wet film deposition, achieving coating thicknesses in a range of 0.5–2.5 µm via dip coating. Highly transparent coatings were obtained by applying small particles of 50 nm, which exhibited a significantly lower scattering loss of light (≈3%) in comparison to particles of around 300 nm (70–80%). Additionally, the film color could be adjusted through a variation of the drying temperature due to a conversion of goethite to hematite by dehydration. Since transparency was not affected, this provides an easy-to-implement process adaptation for controlling coating colors. KW - goethite KW - stirred media milling KW - top-down formulation KW - transparent coating KW - dip coating Y1 - 2022 U6 - https://doi.org/10.3390/coatings12030330 SN - 2079-6412 VL - 12 IS - 3 PB - MDPI AG ER - TY - JOUR A1 - Sterling, David A1 - Schons, Didier A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Effects of axial grinding media distribution on the disc wear behavior of a stirred media mill JF - Minerals Engineering N2 - Stirred media mills are commonly used process units for wet fine grinding and dispersing. During operation the grinding media and the feed material can cause wear to the process units of the stirred media mill. One typical representative of horizontal stirred media mills is the IsaMillTM, in which an internal classifier diverts the grinding media away from the discharge and implies a counteracting current force to the drag forces caused by the suspension flow. In this work, the disc wear of a pilot scale horizontal mill was investigated with regard to the axial grinding media distribution and other process parameters. In order to create quickly and well visible disc wear patterns, manufactured aluminum discs instead of the original polyurethane discs were specially used. For each set of operating parameters, a separate new pair of discs was installed. A radiometric densitometer was installed to measure the axial grinding media filling degree lengthwise to the M4 IsaMillTM. This method allows the determination of the local filling degree by correlation of the attenuation of gamma radiation from a Cs137 nuclide. The experiments showed that the disc wear per energy input increases with rising stress energy. With respect to the axial grinding media distribution, higher wear rates were observed in areas of increased grinding media filling ratios. As a result, it can be stated that the wear is a function of the local grinding media distribution and of the stress energy. In zones with a higher local grinding media filling degree, an increased disc wear is evident. Consequently, mills on a production scale could theoretically realize longer plant operating times and lower maintenance costs by securing a more homogeneous grinding media distribution. KW - Disc and stirrer wear KW - Stirred media mill KW - Axial grinding media filling degree KW - Radiometric density measurement Y1 - 2022 U6 - https://doi.org/10.1016/j.mineng.2022.107702 SN - 0892-6875 VL - 185 PB - Elsevier BV ER - TY - JOUR A1 - Cai, Yingying A1 - Peng, Wentao A1 - Song, Qingyuan A1 - Pluta, Denis A1 - Peppersack, Christoph A1 - Breitung-Faes, Sandra A1 - Kwade, Arno A1 - Bigall, Nadja C. A1 - Vana, Philipp T1 - Nanoengineering of Egyptian Blue Nanosheets: Advantages and Limitations for Near-Infrared Photoluminescence Applications JF - ACS Applied Optical Materials N2 - The ancient inorganic pigment Egyptian Blue is a fluorophore with outstanding near-infrared (NIR) performance and is thus considered as an emerging optical material that meets the current demand for cheap, efficient, and nontoxic NIR nanofluorophores. Herein, we present a protocol for the quick mass production of Egyptian Blue (CaCuSi4O10) nanosheets (EBNSs) with lateral size down to ∼100 nm by applying state-of-the-art ball-milling techniques. A systematic decay of the NIR photoluminescence behavior with decreasing size of the EBNSs was found, which challenges the desired application of EBNSs as bioimaging markers and other nanoapplications. To pave the way to surface modifications of EBNSs, we deposited a thin layer of silica on the surface of the EBNSs. Taking advantage of this modification, we subsequently performed surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization in order to grow both hydrophilic and hydrophobic polymer brushes from EBNSs, which enhanced dispersibility of the nanosheets and even delivered function. By matching the refractive index of the EBNS with its polymer shell, the quality of the NIR photoluminescence of the EBNS could significantly be improved, since disturbing light scattering at the interface could effectively be suppressed. Our results provide a clear picture of the advantages and limitations of EBNSs as optical nanomaterials for NIR fluorescence applications. KW - cuprorivaite KW - NIR fluorophore KW - NIR photoluminescence KW - nanocomposite KW - Layered silicate KW - surface modification KW - surface-initiated polymerization KW - silica coating Y1 - 2022 U6 - https://doi.org/10.1021/acsaom.2c00114 SN - 2771-9855 VL - 1 IS - 1 SP - 465 EP - 472 PB - American Chemical Society (ACS) ER - TY - JOUR A1 - Kwade, Arno A1 - Möller, Marcel A1 - Müller, Jannes A1 - Hesselbach, Jutta A1 - Zellmer, Sabrina A1 - Doose, Stefan A1 - Mayer, Julian A1 - Michalowski, Peter A1 - Powell, Malcolm A1 - Breitung-Faes, Sandra T1 - Comminution and Classification as Important Process Steps for the Circular Production of Lithium Batteries JF - KONA Powder and Particle Journal N2 - Lithium-ion batteries (LIBs) provide the largest source of electrical energy storage today. This paper covers the use of comminution processes and, thus, crushers and mills for particle breakage and dispersing, as well as classifiers for particle separation within the process chain, from the raw material to the final lithium battery cell and its recycling at end of life. First of all, the raw materials for the active material production have to be produced either by processing primary raw materials, or by recycling the spent lithium batteries. The end-of-life battery cells have to be shredded, the materials separated and then milled in order to achieve the so-called black mass, which provides a secondary material source with very valuable components. Using these materials for the synthesis of the cathode active materials, milling has to be applied in different stages. The natural graphite, increasingly used as anode material, has to be designed in mills and classifiers for achieving targeted properties. Nanosized silicon is produced by nanomilling using stirred media mills as a primary option. Conductive additives for LIBs, like carbon black, have to be dispersed in a solvent with machines like planetary mixers, extruders or stirred media mills. In the future, mechanochemical synthesis of solid electrolytes will especially require additional application of comminution processes. KW - graphite KW - silicon KW - battery recycling KW - active material synthesis KW - solid state batteries KW - electrode production Y1 - 2023 U6 - https://doi.org/10.14356/kona.2023006 SN - 0288-4534 VL - 40 IS - 0 SP - 50 EP - 73 PB - Hosokawa Powder Technology Foundation ER - TY - JOUR A1 - Altun, Okay A1 - Prziwara, Paul A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Impacts of process and design conditions of dry stirred milling on the shape of product size distribution JF - Minerals Engineering N2 - A grinding technology should consider the physical properties of the material, i.e., size, shape, which have effects on the product specifications, i.e., quality, strength or overall process efficiency. In this respect, this study aimed at evaluating the variations in the shape of product size distribution of a stirred media mill as the attention on this technology has been growing in the recent years. Within the scope of the research, series of grinding tests were performed at different operating conditions, i.e. bead size, bead type, tip speed, feed rate and mill design, with a laboratory scale continuously operated horizontal stirred media mill. The investigations proved that the use of coarser and denser beads as well as adjusting higher tip speeds resulted in obtaining narrower product size distribution for the same mean size. For a better understanding of the process, the stress energy and mean residence time evaluations were also undertaken. It was found that the stress energy and its normalization with the mean residence time are directly proportional to the slope of the distributions. As a conclusion, the dry stirred media mill is able to adjust the shape of the distribution, which may be beneficial regarding to the mechanical properties of the end products (cement manufacturing) or efficiency of the mineral beneficiation processes. KW - Grinding media KW - Dry stirred media milling KW - Process optimization KW - Product size distribution Y1 - 2021 U6 - https://doi.org/10.1016/j.mineng.2021.106806 SN - 0892-6875 VL - 163 PB - Elsevier BV ER - TY - JOUR A1 - Prziwara, Paul A1 - Thake, Simon A1 - Breitung-Faes, Sandra A1 - Kwade, Arno T1 - Comparison of open and closed circuit mode using a dry horizontal stirred media mill with special regard to the powder flowability and residence time distribution JF - Minerals Engineering N2 - A dry operated, horizontal stirred media mill was used for the fine grinding of limestone and compared in open and closed circuit modes. It was found that the choice of grinding aids as well as the stirrer tip speed are crucial for the mill operation, especially in terms of the grinding efficiency and the transport behavior through the mill. Independent of the process mode, both a too low and an excessive additive-induced flow behavior led to unfavorable stress conditions inside the mill, and thus, inefficient grinding. In the open circuit, especially high flowabilities turned out to be crucial, as thereby the stress conditions are negatively affected as a consequence of the material transport in combination with the overlapping impact of a mill- internal deflector wheel. Different important aspects were seen for the closed circuit grinding; especially when aiming for high finenesses or using high tip speeds, it is essential to ensure both a minimum flowability and a sufficient particle stabilization to ensure a fast removal of fine particles from the mill. High flowabilities in turn are not as critical during closed circuit grinding, but are accompanied by high material recirculations. KW - Dry continuous fine grinding KW - Open and closed circuit KW - Dry KW - Operated stirred media mill KW - Grinding aids KW - Powder behavior Y1 - 2021 U6 - https://doi.org/10.1016/j.mineng.2021.106781 SN - 0892-6875 VL - 163 PB - Elsevier BV ER - TY - JOUR A1 - Breitung-Faes, Sandra A1 - Oldhues, Victor A1 - Dobreva, Desislava A1 - Borchardt, Lars A1 - Kwade, Arno ED - Breitung-Faes, Sandra T1 - Influence of different stress types on the mechanochemical CaCO3-synthesis JF - Powder Technology N2 - Mechanochemistry is considered a green alternative to conventional wet-chemistry. Several reactions have been reported to be feasible via the mechanochemical route, while detailed insight in the mechanistic background of mechanochemical reactions is still elusive. Certain is a significant role of the mechanical stress applied, but the influence of the stress type is rarely addressed. This study uses different simple setups to apply isolated impact, compressive and shear stress to the reactants of the mechanochemical CaCO3-synthesis. Measuring of the energy inputs and modelling of the stressing conditions allowed correlation of the specific energies in the setups with the chemical conversion of the inorganic model reaction. For the same specific energy, impact stressing was found to be most successful in yielding product and the stress intensity could be identified to play a crucial role. A lower stress intensity was beneficial during initiation of the reaction, whereas a progressed reaction state could take advantage of higher stress intensities. This change is ascribed to the energy utilisation, which is limited in the beginning, but rises in an advanced reaction state due to the formation of product layers and an increased local temperature. Based on the results, a hypothesis on the influencing factors and procedure of the mechanochemical CaCO3-synthesis was formulated. KW - Mechanochemistry Mechanical stress types Stress intensity Reaction kinetics KW - Mechanical stress types KW - Stress intensity KW - Reaction kinetics Y1 - 2025 U6 - https://doi.org/10.1016/j.powtec.2025.121449 VL - 466 PB - Elsevier ER - TY - JOUR A1 - Peppersack, Christoph A1 - Kwade, Arno A1 - Breitung-Faes, Sandra T1 - Selective Agglomeration and Separation from Heterogeneous Suspensions of Submicron Particles by Controlling Electrostatic Particle Interactions JF - Powders N2 - As part of the so-called interfacial separation techniques, selective particle ag- glomeration is one of the few options that are suitable for the separation of heterogeneous, multicomponent systems of particles smaller than 1 μm. In this regard, the component to be separated is exclusively transferred into a coarser size range, so that a material selective size separation by traditional mechanical methods can be achieved. In the presented study, this is demonstrated using heterogeneous suspensions of ceramic and organic particles, from which the separation of the inorganic material is pursued subsequent to the targeted control of the material-specific, electrostatic particle–particle interaction. Resulting from theoretical considerations on these interactions, favorable conditions for the selective agglomeration can be predicted. Experimental data reveal that for suitable param- eters, resulting from variations in interfacial particle properties, particle size, and the composition of the dispersions, a separation efficiency of up to 97% can be obtained. Thereby, the importance of the particle-number fraction as an adjustable parameter needs to be clearly emphasized. Since a separation of the agglomerates can be achieved by simply using centrifugal forces, the shown technique is easy to apply and valuable for various industrial fields such as chemical and pharmaceutical engineering or recycling processes. In addition, no external additives are required for selective agglomeration, eliminating the risk of secondary contamination. KW - selective agglomeration; particle interactions; separation; heterogeneous suspensions; DLVO theory Y1 - 2025 U6 - https://doi.org/10.3390/powders4010008 IS - 1 ET - 4 ER - TY - JOUR A1 - Prziwara, Paul A1 - Breitung, Sandra A1 - Kwade, Arno T1 - Investigation of stress conditions and energy efficiency in dry stirred media milling by DEM simulation JF - Chemical Engineering Research and Design N2 - Dry operated stirred media mills are gaining increasing relevance in fine grinding applications due to their high energy densities and process flexibility. Nevertheless, the interrelation between operating parameters and stress conditions remains insufficiently understood compared to wet milling systems. In this work, the grinding media motion within a vertically oriented batch stirred media mill was investigated using Discrete Element Method (DEM) simulations, experimentally calibrated to incorporate the influence of powder flowability as a function of grinding aid formulation and applied to dry milling experiments of calcium carbonate. The results reveal that, analogous to wet operation, an optimum stress intensity exists at which the specific energy demand to achieve a target fineness is minimized. For dry milling, however, the stress intensity must be defined as the ratio of stress energy to the stressed product mass, since the captured product fraction which varies with powder properties is decisive for the stress intensity value. DEM analysis further indicates that the tip speed alone does not adequately represent the effective bead velocity distribution under dry conditions. The study demonstrates that both operating parameters and product formulation significantly affect the stress environment and comminution efficiency, implying that individual optimization strategies are required for each product system. KW - Discrete Element Method (DEM) Dry stirred media mill Milling energy efficiency Grinding aids Grinding media motion Stress intensity Y1 - 2026 VL - 2026 IS - 226 PB - Elsevier ER - TY - JOUR A1 - Punt, Franziska A1 - Doose, Stefan A1 - Böttcher, Ann‐Christin A1 - Breitung‐Faes, Sandra A1 - Kwade, Arno T1 - Modeling and Flow Sheet Simulation of Selected Mechanical Recycling Processes for Li‐Ion Batteries JF - Chemie Ingenieur Technik N2 - To investigate the mechanical processes of Li‐ion battery recycling in more detail, models for the different unit processes are to be developed. Here, model approaches for the cutting mill and the zig‐zag‐sifter are presented. These models are to be used in dynamic flow sheet simulations, with which the individual unit processes as well as the combination to a small process chain were simulated. Thereby, the dynamic interactions between the process steps were investigated, which can be used later for optimization and regulation of the processes. The particle sizes after the cutting mill process as well as the mass flow between the processes influence the separation behavior of the sifter. These changes in the separation function due to an increasing mass flow out of the mill are shown. KW - Battery recycling KW - Cutting mills KW - Flow sheet simulations KW - Modeling KW - Zig-zag-sifters Y1 - 2022 U6 - https://doi.org/10.1002/cite.202200156 SN - 0009-286X VL - 95 IS - 1-2 SP - 59 EP - 67 PB - Wiley ER -