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In this study beta-lactoglobulin solutions were processed with glass beads in an orbital shaker at high temperatures and low pH value to identify the effect of mechanical stressing and surfaces on amyloid aggregation kinetics. The information will provide a better understanding on how specific mechanical factors provide a nucleation supporting effect on the assembling of building blocks for a more efficient production of functional amyloid aggregates. Because aggregate morphologies vary at pH 2 (semiflexible) or pH 3.5 (worm-like), examination at both pH values gives information about their specific formation and stability characteristics. Different diameters of glass beads (20–1000 μm), and different shaking frequencies (0 - 280 min−1) were used to vary mechanical stress energy, which was quantified by CFD-DEM simulations. To investigate surface effects, the hydrophobicity and surface roughness of glass beads was altered by modification with stearic acid. Amyloid aggregates and bead surfaces were analysed by ThT-assay, AFM and ATR-FTIR. Hydrophobic beads with high surface roughness affected the aggregation negatively. The use of non-hydrophobic beads increased the formation kinetics of fibrils but not of worm-like aggregates, although, both morphologies had a reduced mean length.

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 classiers for particle separation within the process chain, from the raw material to the nal 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 dierent stages. The natural graphite, increasingly used as anode material, has to be designed in mills and classiers 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.

The increasing significance of products consisting of elongated particles or fibres along with a lack of understanding flow properties of fibrous bulk solids in processes urge for appropriate test procedures. Therefore, a tensile tester was designed with respect to the special needs in terms of test techniques of those bulk solids. The procedure of tensile strength determination was tested with regard to several possible influencing factors. Following from that, the manner of filling and filling height were identified to have the greatest influence on results. Furthermore, it is shown that the developed load system is capable of improving the repeatability of test results for fibrous bulk solids. Based on the derived standard procedure, systematic tests were carried out on beech and spruce chips in three different fractions each as well as model materials such as polypropylene fibres and differently sized bunches of glass fibres. The biomass materials have been characterised by dynamic image analysis prior to and after experiments resulting in particle size and shape factor distributions. It is found that tensile strength is affected by particle shape, size, roughness and interparticle contact area.

The first part of this review revealed a complex relation between the grinding aid molecules, their influence of the particle and powder properties, as well as the particle stressing inside the mill, which is why grinding aids are still only poorly understood already during lab-scale grinding. The second part of the review presents how additive-induced changes of the powder properties do not only affect the grinding, but also the transport and classification behavior of the particles in open as well as closed grinding circuits. The complexity of these effects is underpinned by reviewing several industrial grinding aid applications. Furthermore, an overview on possible impacts of such additives on the final product properties is given. Finally, the current gaps of understanding are identified and critically discussed with a special regard towards a more efficient selection and application of grinding aid additives for future industrial dry fine grinding processes.

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.

A bi-directional coupling between the Discrete Element Method (DEM) and Population Balance Modelling (PBM) is suggested to model the failure of pharmaceutical tablets under abrasive conditions such as bulk flow of impact. DEM provides the description of kinetics and permits the extraction of collision energy distributions. Representation of the primary shape of the tablets is achieved by using the multi-sphere approach, a rigid assembly of systematically connected spheres to resemble non-spherical shape. Based on the collision energy distribution and the abrasion characteristics of the tablets by solving the PBM equations, the mass loss of tablets according to their mechanical resistance, as well as the fragment size distribution progeny can be computed. For the description of the abrasive failure characteristics, a multi-stage calibration procedure for the empirical breakage kernels of Vogel and Peukert as well as of Ghadiri and Zhang is also applied. The novelty of the presented approach is the bi-directional coupling: tablet and fragment distribution masses are dynamically updated for subsequent time steps in DEM by the particle replacement method according to the stress history of the system. The outcome of this methodology helps to get a deeper understanding of the process-property relationships, to evaluate the effect of any process or geometry modifications in processing operations, such as drum coating, and to reduce the requirements of experimental investigations.

For production of electrodes for lithium-ion batteries, conductive carbon black (CB) has to be dispersed within the anode and cathode slurry. A sufficient dispersing degree has to be reached in order to ensure the formation of an adequate conductive network within the electrodes. As intermediate product, CB is dispersed in binder solution, prior to addition of active materials. As binder system on anode side carboxymethylcellulose in water is used, whereas on cathode side polyvinylidene fluoride in N-Methyl-2-pyrrolidone is applied. The conductive carbon slurry facilitates the characterization of the slurry properties, based on changes of CB. The structure and amount of conductive carbon black influences the slurry properties decisively. Viscosity increases with increasing CB content, which affects the shear stress within the mixing process. Rheological properties and particle size distributions are investigated over time while dispersing CB with various tip speeds in a dissolver. Dispersion kinetics are described on behalf of an existing model for tip speed variations. Based on the investigations of rheological changes due to varying amount of CB, an extended model enclosing the CB concentration as variable was developed. Using the extended model, particle sizes for new process parameters can be predicted.

Fractionation through Deterministic Lateral Displacement (DLD) is a promising microfluidic method, able to address several particle characteristics. The influence of particle density on the fractionation however appears to be negligible at low Stokes numbers. In the present study, we investigate the trajectories of neutrally and negatively buoyant particles in standard DLD channels at different Reynolds numbers through coupled DEM-LBM simulations. The results show that the influence of particle density increases with Reynolds number, which enables fractionation by size and density. To facilitate the further use of our study, the results are combined in a correlation describing the influence of row shift fraction, Reynolds number and particle density on the critical diameter. Additionally, we investigate the influence of the Reynolds number on periods of neutrally buoyant particles and show that they can be predicted by simple fluid simulations through the introduced concept of fluidic periodicity.

Fine grinding based on compression stresses is an important industrial process step, which is often applied in mineral, chemical and pharmaceutical industries, for example by using stirred media mills. For this stress mechanism, several studies investigate how to predict the breakage behavior depending on process and formulation conditions by population balance modelling. Breakage rate and breakage function are essential to describe the evolution in particle size distribution over time. Hereby, the division in a mill and a material model has already been shown to be a successful approach for different mills. Especially for fine particles the determination of the breakage function is a particular challenge. In order to predictively model breakage characteristics of materials, such as the breakage function for different energies applied to break the material, it is required to develop a new method, which is easy, fast, and inexpensive to carry out. For this purpose, we present a newly designed breakage tester consisting of a rigidly-mounted two-roll mill. First, a recommendation for the use of a breakage tester is developed. In this step, the investigated machine parameters include the gap size, feed rate, and roller velocity. Furthermore, the influence of feed particle size on the resulting particle size distribution was researched. All tests have been conducted with soda-lime glass as a model material. Second, the applicability of different models for the breakage function, focusing on the tnt10-model, is demonstrated. The breakage can be predicted for new energy values and is in very good agreement with the experimental data. This new breakage tester allows the fast characterization of particle breakage in lower micron range.

Mechanochemical syntheses have a high potential as environmentally friendly and scalable processes. However, especially in case of solid electrolytes, these syntheses are reported as very time consuming with process times up to several days. In this study, the sulfide solid electrolyte Li3PS4 was successfully synthesized in less than 5h after a systematic variation and subsequently optimization of the process parameters in a high energy ball mill. The synthesized electrolyte samples were characterized according to their composition, morphology, particle size distribution and ionic conductivity. Therefore, a better understanding of the process-structure-property relations and process efficiency was achieved. Thus, the results allow a correlation between the stressing conditions and kinetic rates. The stressing conditions are mainly affected by process parameters such as rotational speed, grinding media size and grinding media filling ratio. The kinetic of the mechanochemical process is highly dependent on the normal power input by head-on collisions, leading to a reduction of conversion time with increasing specific power input. The different sets of investigated process parameters also exhibit systematic effects on the crystallinity and particle size distribution of the solid electrolytes. As a result, a highly enhanced process with lowest specific energy demand was achieved by using the largest grinding media with highest rotational speeds at medium grinding media filling ratio.

Fine grinding in stirred media mills is an important process in mineral, chemical and pharmaceutical industry. The stressing mechanism in these mills is grinding through compression and shearing by grinding beads. A few studies have examined grinding bead transport in stirred media mills. Radiometric methods detect the local filling degree, but little is known about the experimental motion of the grinding beads in the mill. This study aims to investigate the position, velocity and radial circulation of individual grinding beads at different operation parameters (viscosity and tip speed) by a fast and inexpensive measurement technique. Additional information about stresses in the mill were derived, such as a relation between axial grinding media distribution and grinding bead velocity. As a result, the two investigated operation parameter (viscosity and tip speed) effect the grinding bead velocity and grinding bead transport in the mill. The mentioned results can be used to validate DEM simulation results.

The micro-processes inside comminution machines are decisive for the grinding result and the overall process efficiency. Especially the estimation of the amount of particles which is captured and stressed between colliding grinding media is of great interest in order to model and optimize the mill operation for dry fine grinding processes. This study investigates the capturing of fine dry particles by means of simplified experiments using a drop-weight tester: While an increase of both the powder flowability and the material fineness were shown to enhance the displacement of the particles out of the zone between a static plate and a falling ball, higher impact velocities and larger media sizes increase the particle capturing. Additionally, the capturing becomes more dependent on the above-mentioned parameters for finer feed materials. Finally, an extension of the active-volume-model, originally developed by Schonert, was proposed to describe the impact of those parameters more adequately.

Processability of powders in high load compaction constitutes a challenge due to particle rearrangement, compression and breakage occurring simultaneously. Although tableting is a central operation in pharmaceutical technology, a better understanding of the link between the macroscopic powder behaviour and its micro-mechanical properties is still required. In the present study, a dual focus on the powder compaction behaviour and the quality properties of final tablets using a compaction simulator is presented. Tableting has been performed for a wide size range of limestone powders from 10 to 400 MPa, in order to understand and compare the powder compaction behaviour at both low and high confining stresses. Compactibility of limestone, the relation between porosity and stress, has been assessed with both the classical (logarithmic) Heckel model and the newly proposed (double logarithmic) Wunsch model, confirming the improvement of the latter to enhance the description of the porosity change during compaction, as well as the model robustness towards non-pharmaceutical powders. The qualitative effect of particle size and thus cohesion on the bulk density at high pressure compaction is found to be very similar to the low pressure regime. However, the geometrical interlocking influence of large size powders found in a previous study becomes irrelevant at such high pressures. For d 50 10 μm, the tablet tensile strength remains almost insensitive to the size variation. However, for the coarsest grades, the tensile strength decreases with increasing d 50 at all compaction stresses. In addition, the tablet tensile strength is found to follow a non-monotonic trend with median particle size.

X-ray computed tomography (XCT) has seen significant development in scan time and spatial resolution over the last decades. It is now increasingly used in the field of particle technology including ex-situ and in-situ applications to study time-lapse processes. This is due to its non-destructive principle giving 3D information on the inner structure and composition of specimens. This article shortly summarizes the field of XCT focusing on terms relevant for particle technology. It also gives a brief outlook on promising directions of development, which may significantly improve XCT. Using different examples from bulk solids handling, flow in porous structures and filtration, the monitoring of concentration differences and the fracture of particles, the application of XCT in particle technology is shown and its perspective is discussed.

The generation of grinding media wear during wet stirred media milling of organic particles was studied in dependence of product formulation parameters. It was shown that targeted product formulation leads to the reduction of ceramic grinding media wear for a certain product quality. Solids concentration and agglomerate size of product particles were identified as key parameters. Both influence the effective stress intensity of grinding media which has a significant impact on the generation of grinding media wear. Moreover, the reduction of grinding media wear can be attributed to the damping properties of comparatively soft organic particles. Their potential to protect ceramic grinding media from abrasion can be increased by tailoring formulation properties. Therefore, especially the increase of solids concentration was identified as most practical formulation variable which affects also grinding efficiency and production capacity.

Fibrous plant-based materials are characterized by inhomogeneous structure and composition, which further evolve during wet grinding processes and affect the surface functionality of micronized particles. Therefore, the performance of aqueous microgrinding operations in stirred media mills can be optimized by investigating the interaction between process conditions and material properties of heterogeneous fibrous plant materials. In this experimental study it is shown how particle size reduction, tendency of re-agglomeration and stability of the suspension of micronized particles are driven by the specific energy input, residence time, temperature and presence of surfactants during the milling process. A structured experimental approach is described to optimize the achievable particle size reduction, expressed by the top cut diameter d90,3. It was found that the applied wet milling process determines the stability of particle suspensions throughout further downstream processing, making the grinding process the core unit operation with respect to the performance and formulation of food products containing micronized particles.

The production of drug nanoparticles is a promising method to enhance dissolution behavior and, by that, bioavailability of poorly soluble drugs. In this study, fenofibrate nanoparticles were produced via high-pressure antisolvent precipitation (HPAP) using a customized microsystem. The benefit of microfluidic systems is the defined streaming behavior inside the microchannels resulting in homogeneous products produced via a continuous process. Formulation strategies (e.g. fenofibrate mass fraction) as well as process parameters (e.g. pressure) were studied to evaluate their influence on particle size and size distribution. Furthermore, the streaming and mixing behavior in the microchannels were visualized via micro particle image velocimetry (µPIV) and laser induced fluorescence (LIF) in order to elucidate the mechanisms inside the microchannels as well as to support the results obtained from HPAP experiments.

Stirred media milling is frequently used to generate nanoparticles for industrial applications such as paints, inks, and food or for the life sciences. Each product suspension has different requirements and therefore different material and formulation parameters. The first attempts to set up a new process are experimental in nature, especially the determination of a suitable composition. To adapt a process to the production scale, more experimental work is often needed to determine suitable operation parameters with regard to energy consumption, throughput, and investment cost. The energy consumption is influenced by operation parameters such as the size of the grinding media or the stirrer tip speed, whereas the investment costs are influenced by the mill geometry and size and the type of grinding media used. Therefore, it is challenging to transfer or scale up processes because lab-scale mills are smaller and may have different geometries than production-scale mills. Moreover, it is well known that the lab-scale operation parameters cannot be easily adapted to the production scale. In this study, the stress model developed by Kwade was improved by introducing parameters corresponding to the mill and the material in addition to the process parameters. Using this model, the optimum operating conditions for stirred media milling processes can be determined with a reduced amount of experimental work, even for geometrically unequal mills.

Calendering is a key process step in the production chain of lithium ion battery electrodes since it strongly affects the microstructure and micromechanics of the electrodes and hence, the performance and life of the battery. A comprehensive understanding is therefore necessary to find optimal levels of calendering which can help to enhance conductive and mechanical properties. Within this context, this study proposes a novel discrete element method (DEM) approach which can capture the mechanical properties of single Li [Ni1/3 Mn1/3 Co1/3]O2 (NMC) particles with an appropriate elasto-plastic contact model, as well as the mechanical behavior of the additive-binder matrix via an additional bond model [1]. With the support of real produced cathodes, the simulations were able to reproduce the calendering process while providing detailed information about the changes in electrode structural and mechanical parameters. In particular, the investigated features comprise the electrode porosity and thickness along with the specific free surface area, the contact area between NMC particles and current collector, the coordination number of NMC particles, the number of broken bonds and the directionality of the contacts together with the generated stress within the electrode. Moreover, the simulations are able to capture the viscoelastic response of the electrode, showing that the relative elastic recovery can be almost up to 17%, an important piece of information that cannot be obtained experimentally to date. Having established the fundamentals and simulation feedback, an upcoming publication is meant to complete this research by providing a numerical overview of the relations between the electrode structure and its properties affected by the calendering process and during the first electrochemical cycles.

Because of a remarkably high theoretical energy density, the lithium–sulfur (Li–S) battery has attracted significant attention as a candidate for next-generation batteries. While employing solid el...

Nanoparticle reinforced fibre composites promise enhanced product properties demanded for many fields of application. However, the targeted production of nanoparticle resin suspensions is demanding and requires detailed knowledge about the fundamental mechanisms acting during the process. In order to obtain this knowledge, the dispersing process of nanoparticle-suspensions with high viscosities is investigated by the example of epoxy resin — alumina suspensions which are used as a matrix material for fiber reinforced plastics. The performance of several dispersing machines with differing stress mechanisms is compared and dependencies on process parameters are characterized. Laminar shear flow dispersing was performed in a three roller mill as well as in a kneader. In a pin-counter-pin stirred media mill and a basket mill dispersing between grinding media surfaces was investigated. The effect of process parameters on the stress energy/intensity and its effect on the product quality was studied for the respective stress mechanisms with special focus on the impact of suspension viscosity. An existing model to quantify the stress acting in laminar shear flow is extended to account for the influence of solids content utilizing the concept of shear stress equivalent shear rates. Deviations from commonly known dependencies of dispersing processes with grinding media are found and explained by a change in the governing stress mechanism which depends on the viscosity and particle size of the suspension. Process maps for the dispersing in highly viscous media are derived regarding desired particle size, energy efficiency and required solids content for the respective machines.

In order to model predictively the breakage kinetics in stirred media mills, it is required to determine the effect of operating conditions on the breakage rate. In this study specific breakage rates are measured for grinding experiments in wet-operated stirred media mills for various operating parameters. The experimental specific breakage rates are compared against two different models using yeast cells and limestone as test materials. A simple stressing energy model is able to predict the effect of changes in grinding bead size, grinding bead material, stirrer speed and mass concentration on the specific breakage rate. A more detailed model, which takes stressing energy distributions achieved by mill simulations and material breakage energy distributions from material tests as input, shows promising results. However, the latter is less robust and needs precise input data. Yeast cells prove to be a good test material for the purpose of model validation because of its well described breakage behaviour.

Electrode structural stability and mechanical integrity is of major importance regarding not only lithium-ion battery performance but also safety aspects. The goal of this study is to design a simulation procedure to reproduce the microstructural and mechanical properties of such lithium-ion battery electrodes. Taking into consideration the particulate state of these electrodes, a discrete element method (DEM) approach is proposed, which comprises a procedure to reproduce real electrode structures and the application of a proper contact model to capture the bulk mechanics. This is accomplished by considering particle interactions as well as the performance of the binder. Three different electrodes are manufactured with the aim of calibrating and validating the Hertzian-bond contact model. Experimental nanoindentation measurements prove to be in good agreement with the simulation outcome, concluding that the method constitutes a valuable physical and mechanical basis for further applications.

The demand on minerals with increasing product fineness is currently rising in many industrial applications. Especially in dry grinding processes, fine powders are difficult to produce and to handle. Particle-particle attractive forces, which become more decisive with decreasing particle size, lead to a higher extent of agglomeration, material adherences and a more cohesive flow behavior. As a consequence, dry fine grinding processes demand large quantities of energy due to the amount of applied energy that is dissipated into heat. Current approaches for improving the energy efficiency mainly cover the improvement of a) machine equipment and b) the material behavior. The main focus of this study was to investigate both aspects within one single study: On the one hand, dry fine grinding of limestone was investigated in a dry operated stirred media mill, which is a promising and emerging option for dry fine grinding applications. On the other hand, the impact of the particle stabilization by liquid grinding aids on the grinding performance was evaluated. It was demonstrated that the grinding mechanism inside the mill depends on both the mill parameters as well as the powder flow behavior. Therefore, it is of crucial importance to adjust the mill parameters to the applied grinding aid when it comes to dry fine grinding in media mills.

The present study focuses on model based parameter optimization of nanosuspension preparation via wet stirred media milling. Based on experimental data of nanomilling a crystalline organic material, two different approaches for process optimization were evaluated: The stress model for stirred media mills, introduced by Kwade, was compared to the microhydrodynamic approach modified by Bilgili and Afolabi. The different approaches to describe influences of operating parameters were discussed with respect to their applicability on process optimization of nanosuspension preparation. Both approaches yield characteristic values which are derived from proportionalities to process parameters. Despite of different physical assumptions, the milling process can be optimized by both approaches. A more detailed insight into physical interactions can be only generated by numerical procedures. Limitations of the applied procedures were observed especially with respect to the accessibility of parameters required for calculation.

Finishing and transport operations of pharmaceutical tablets such as coating and conveying processes can qualitatively be improved with a better understanding of the interplay of process parameters and product quality attributes. This study provides a first step towards the simulation of these processes with the calibration of the motion modelling of uniaxial-compressed cylindrical tablets using the multi-sphere approach (MS) within the Discrete Element Method (DEM). Only high accuracy in the representation of cylindrical tablet shape, especially regarding edges, yields a good agreement between simulated and experimental packing fraction. Sensitivity regarding model parameter calibration was evaluated based on tumbling drum tests which are of wide occurrence in the industry and the so-called pouring experiment extracting static and dynamic angles of repose, identified sliding and rolling friction as the most sensitive parameters. These were successfully calibrated by an iterative crossed analysis in tumbling drum and pouring tests. Additionally, a complete determination and subsequent calibration strategy is provided for Coefficient of Restitution and Young's modulus. Results of the final numerical modelling are qualitative and quantitative in agreement with experimental test case experiments. A final validation is performed through the simulation of an attrition tester with a single baffle, highlighting one of the main limitations of DEM: the problem-targeted nature of the operation of calibration.

Wet grinding is an important unit operation in many industrial fine grinding and dispersing processes. The main aim of this study was the development of a multi-scale modelling method to predict and improve grinding and dispersing processes in wet operated stirred media mills. In the first part of the study “Multiscale simulation of fine grinding and dispersing processes” macro and process scale, e.g. stressing probability, stressing energy and resultant breakage rate, were discussed. To describe those scales in sufficient manner information of the micro and meso scale which affect the macro and process scale are important. In this second part, numerical studies on the micro scale were carried out regarding the effect of different particle sizes and morphologies on the drag coefficient and the mechanical stressing during grinding and dispersing processes in stirred media mills. The fracture processes during compression between two surfaces or grinding beads on the micro scale were investigated numerically as function of the aggregate structure and solid bond properties for aggregates with a linear gradient in fractal dimension using DEM-CFD simulations. Beside the fractal dimension, the inertia tensor was introduced as another decisive aggregate characteristic which has to be taken into account. In the first part of this study the meso and macro scale simulation will be discussed taken the acting forces, stressing probability, grinding media motion and the stress energy distribution of the stirred media mill into account.

Wet grinding is an important unit operation in many industrial fine grinding and dispersing processes. The main aim of this study is the development of a multiscale modelling method to predict and optimize grinding and dispersing processes in wet operated stirred media mills. In the first part of this paper, numerical CFD-DEM studies on the meso and macro scale were carried out with the focus on the acting forces, stressing probability, grinding media motion and the stressing energy distribution of a stirred media mill. The stressing probability of product particles between the grinding media was investigated at varying relative velocities in normal direction as well as at different conditions of grinding bead rotation. The determination of the stressing energy distribution on the macro scale is discussed exemplarily for a disc stirrer at three different rotational velocities. Thus, the increase in stressing frequency and energy at higher rotational speed was quantified. Moreover, the transfer of the results on an overall process simulation using population balance equations was studied. In the second part of this study the effect of the drag coefficient and the fracture processes of aggregates with various fractal dimension and solid bond properties are discussed numerically.

The bulk properties of powders depend on material characteristics and size of the primary particles. During storage and transportation processes in the powder processing industry, the material undergoes various modes of deformation and stress conditions, e.g., due to compression or shear. In many applications, it is important to know when powders are yielding, i.e. when they start to flow under shear; in other cases it is necessary to know how much stress is needed to keep them flowing. The measurement of powder yield and flow properties is still a challenge and will be addressed in this study. In the framework of the collaborative project T-MAPPP, a large set of shear experiments using different shear devices, namely the Jenike shear tester, the ELE direct shear tester, the Schulze ring shear tester and the FT4 powder rheometer, have been carried out on eight chemically-identical limestone powders of different particle sizes in a wide range of confining stresses. These experiments serve two goals: i) to test the reproducibility/consistency among different shear devices and testing protocols; ii) to relate the bulk behaviour to microscopic particle properties, focusing on the effect of particle size and thus inter-particle cohesion. The experiments show high repeatability for all shear devices, though some of them show more fluctuations than others. All devices provide consistent results, where the FT4 powder rheometer gives lower yield/steady state stress values, due to a different pre-shearing protocol. As expected, the bulk cohesion decreases with increasing particle size (up to 150 μm), due to the decrease of inter-particle cohesion. The bulk friction, characterized in different ways, is following a similar decreasing trend, whereas the bulk density increases with particle size in this range. Interestingly, for samples with particle sizes larger than 150 μm, the bulk cohesion increases slightly, while the bulk friction increases considerably—presumably due to particle interlocking effects—up to magnitudes comparable to those of the finest powders. Furthermore, removing the fines from the coarse powder samples reduces the bulk cohesion and bulk density, but has a negligible effect on the bulk friction. In addition to providing useful insights into the role of microscopically attractive, van der Waals, gravitational and/or compressive forces for the macroscopic bulk powder flow behaviour, the experimental data provide a robust database of cohesive and frictional fine powders for industrially relevant designs such as silos, as well as for calibration and validation of models and computer simulations.

Planetary ball mills at laboratory scale are widely used for grinding and alloying processes. However, in contrast to other mill types, no applicable mechanistic model exists to describe the stressing conditions and their effect on particle breakage, so that processes are empirically evaluated so far. Within this study, the stressing conditions are determined by simulations based on the discrete element method including the contact model of Hertz and Mindlin. The contact model parameters are carefully calibrated by a series of experiments, so that it is finally possible to validate the simulation results by comparison of measured and calculated power values. The correlation of stressing conditions and breakage rates of alumina powder demonstrates the effect of stressing on breakage kinetics and breakage mechanism. It allows calculating the active mass in dependence on process parameters by an extension of Schonert’s active mass model. Altogether, the presented stressing model features analytical functions for the mill-related stressing conditions and highlights the importance of stressing intensity as process determining parameter, which defines the required number of material-related stressing events and the specific energy.

Dual-ion or dual-graphite batteries based on the mechanism of electrochemical anion intercalation into a graphite cathode have become attractive as an alternative storage technology in recent years. Due to large volume changes of the graphite particles during electrochemical anion intercalation, an appropriate electrode binder is required to sustain the mechanical integrity of the composite electrode and a stable and highly reversible charge/discharge cycling. Therefore, the expansion and contraction behavior of graphite positive electrodes containing different binders, including Na-carboxymethyl cellulose (CMC), poly(vinylidene)difluoride (PVdF) and a CMC/styrene butadiene rubber (SBR) mixture, during anion intercalation/de-intercalation was investigated by in situ electrochemical dilatometry (ECD). These measurements give insights into reversible and irreversible relative height changes at different cycling conditions and, thus, into the long-term cycling stability of the composite electrodes. Long-term cycling measurements reveal that the maximum and minimum electrode thicknesses of PVdF-based electrodes remain constant during anion intercalation/de-intercalation, while the CMC-containing electrodes exhibit a thickness increase in the first cycles and subsequent decrease after reaching a maximum electrode thickness. This instability can most likely be correlated with the mechanical instability of the electrode due to the high stiffness of the CMC binder compared to PVdF and an active material contact loss during cycling. If CMC is applied as binder mixture in combination with SBR, which shows a high flexibility, the thickness decay can be decreased. Our results give new insights into the optimization potentials of composite electrodes for carbon-based cathodes in dual-ion cells that experience large volume expansion during cycling.

The interplay between structure and mechanical properties of fine and cohesive granular matter is of wide interest and far from being well understood. In order to study this relationship experimentally, it is desirable to record as much information on the particles and their motion behavior as possible during a shear experiment – ideally, the trajectory of every single particle. Observing the particle movements offers deep insights into changes in the mechanical behavior of the bulk (e.g., densification, loosening or formation of failure areas) and into the behavior of single particles. However, obtaining particle-level information on the dynamics of an entire shear-tester experiment remains a great challenge. In this paper we present an experiment and analysis methods which allow the extraction of the trajectories of almost all particles within a shear-tester. A fully functional micro shear-tester was developed and implemented into an X-ray microtomography device. With this combination we can visualize all particles within small bulk volumes of the order of a few μl under well-defined mechanical manipulation. The processing of time-resolved tomographic data makes it possible to localize and track particles despite large angle increments of up to 5° between tomographic measurements. We apply our methods to a torsional shear experiment with spherical micron-sized particles (∼30 μm) and analyze the structural evolution of the sample. In addition, particle tracks provide detailed insights into the formation and evolution of the shear band.

This study presents an approach to scale up wet fine grinding processes of organic particles using stirred media mills. The process transfer is based on the calculation of grinding-relevant energy, which is transferred to the product by a model theory derived from mill-related values, especially geometric aspects. Its application was demonstrated by experimental work with two organic products, which were ground with different sizes and geometries of mills reaching from 20 to 900 mL grinding chamber volume under variation of process parameters.

The application of orodispersible films (ODFs) as carrier for drug nanoparticles was discovered a few years ago. Poorly water-soluble drugs are milled to nanosuspensions to improve their bioavailability. During the manufacturing process they are embedded into a polymer matrix or loaded on the surface of drug-free ODF templates. The particle size of the particles released from the ODF was measured when redispersed in water. A preservation of the drug particle sizes could be achieved for both investigated ODF types when an adequate amount of matrix material is added to prevent agglomeration during the drying process.

The yeast Saccharomyces cerevisiae and the microalga Chlorella vulgaris were mechanically characterized using single-cell compression experiments. Micromechanical cell characteristics could be calculated directly from the force displacement data. The mechanical properties of the cell wall were determined with different analytical models because the intrinsic parameters of the cell wall cannot be measured directly. As expected, the Young's moduli obtained from the cellular model and the cell wall model differ by two orders of magnitude. Although yeast and algal cells need similar forces to get disrupted, the bursting deformation and bursting energy of the algal cells are about two times smaller. Based on the dry biomass, the energy for cell breakage of C. vulgaris is about six times higher than that of S. cerevisiae. Finally, the tensile strength of the cell wall was calculated.

A method to determine the agglomerate and aggregate sizes of carbon black (CB), commonly used in anode and cathode suspensions for lithium-ion battery electrodes, is presented. An analysis via light diffraction and scattering was evaluated, and measuring parameters and the development of sample preparation are described in detail. Within this work, different dispersing additives were tested with regard to their ability to stabilize the CB agglomerates and aggregates after dispersing. Furthermore, a sample preparation routine was set up which enables the determination of CB particle sizes in about 10 min. This includes the separation of active material particles and the particle size analysis itself. Furthermore, the method was tested with discontinuously and continuously processed suspensions using a laboratory dissolver and a pilot-scale extruder. In these experiments, the progress of CB deagglomeration in the dispersing step could be proven. For this reason, the method represents a suitable instrument f...

Composites consisting of graphite and silicon have been considered as potential high-capacity anode materials for the next-generation Li-ion batteries (LIBs). The synthesis method is critical for determining the microstructure, which is directly related to the material performance and the cost-efficiency for making commercial electrode materials. Herein, we report the fabrication of silicon-on-graphite (Si@Gr) composites by fluidized bed granulation (FBG) for the first time. The FBG process is shown to produce composite powders comprising a uniform layer of nano-sized Si particles lodged onto the surface of micron-sized graphite particles to possess a core-shell microstructure. Adopting a suitable binder during the FBG process enables a firm adhesion of the Si nanoparticles on graphite surface during subsequent carbon-coating, where the composite particles are coated with pitch and then carbonised to form a highly electronically conductive and mechanical stabilizing layer of amorphous carbon. These carbon-coated composites exhibit a high capacity reaching over 600 mAh g−1, high rate capability and illustrates the potential of long-cycle stability in Si@Gr || Li metal cells, showing more than 70% capacity retention after 400 charge-discharge cycles even without electrolyte optimization. Furthermore, a significantly improved cycling stability is found for the carbon-coated Si@Gr materials in LiNi0.6Co0.2Mn0.2O2 (NCM-622) || Si@Gr full-cells.