Planetary ball mills are well known and used for particle size reduction on laboratory and pilot scales for decades while during the last few years the application of planetary ball mills has extended to mechanochemical approaches. Processes inside planetary ball mills are complex and strongly depend on the processed material and synthesis and, thus, the optimum milling conditions have to be assessed for each individual system. The present review focuses on the insight into several parameters like properties of grinding balls, the filling ratio or revolution speed. It gives examples of the aspects of grinding and illustrates some general guidelines to follow for modelling processes in planetary ball mills in terms of refinement, synthesis' yield and contamination from wear. The amount of energy transferred from the milling tools to the powder is significant and hardly measurable for processes in planetary ball mills. Thus numerical simulations based on a discrete-element-method are used to describe the energy transfer to give an adequate description of the process by correlation with experiments. The simulations illustrate the effect of the geometry of planetary ball mills on the energy entry. In addition the imaging of motion patterns inside a planetary ball mill from simulations and video recordings is shown.

Commercialization of solid‐state batteries requires the upscaling of the material syntheses as well as the mixing of electrode composites containing the solid electrolyte, cathode active materials, binders, and conductive additives. Inspired by recent literature about the tremendous influence of the employed milling and dispersing procedure on the resulting ionic transport properties of solid ionic conductors and the general performance of all solid‐state batteries, in this review, the underlying physical and mechanochemical processes that influence this processing are discussed. By discussing and combining the theoretical backgrounds of mechanical milling with regard to mechanochemical synthesis and dispersing of particles together with a wide range of examples, a better understanding of the critical parameters attached to mechanical milling of solid electrolytes and solid‐state battery components is provided.

The influence of crucial reaction parameters on Knoevenagel condensation in planetary ball mills was investigated. Rotation frequency (ν rot ), milling ball diameter (d MB ), milling ball filling degree (Φ MB ), and beaker size had obvious influences on yield. It was found that higher ν rot , lower d MB , milling beakers with larger diameter, and a Φ MB of ∼0.3 are advantageous for the reaction. Furthermore, the influence of the type of mill was investigated, including reactions performed in different planetary and mixer ball mills, in a stirred media mill, and with a mortar mill. Comparisons with the other solvent-free synthetic routes showed that ball milling is an effective way of performing the reaction with low energy intensity. ■ INTRODUCTIONThe use of mechanical stress for the accomplishment of mechanochemical reactions is now an established field of research represented by a huge number of reactions in different fields of organic, inorganic, and organometallic chemistry and materials science. 1 In all cases, mechanical stress is provided to the reactants, whereby the energy input can be realized in different ways. The easiest but imprecise way is to use a mortar and pestle. 2 Results that are more reliable can be obtained with different types of ball mills, such as planetary (PBMs) or mixer ball mills (MBMs). The results of organic reactions in ball mills are subject to several influencing parameters, especially the influence of rotation frequency (ν rot ), milling time (t), and number of milling balls (n MB ). 3 Although a large number of synthesis protocols have been published, parameters such as the milling ball diameter (d MB ) 3c,d,4 and beaker size 5 have received less attention. Furthermore, comparative studies on reactions in different types of mills are rare. 2,6 However, the kind of mill utilized can strongly influence the outcome of a reaction. For example, Schneider et al. investigated the Suzuki−Miyaura reaction in two types of PBMs and one MBM. 2 The reaction proceeded well in the PBMs at 300 min −1 , whereas in the MBM at the same frequency only low yields were observed. Wang and co-workers investigated pinacol couplings in an MBM and a mortar mill (MM). 6a Although mechanical energy is supplied in both mill types, higher yields of the pinacol coupling product were obtained in an MM.We have recently investigated the influence of several reaction parameters on the yield of a Knoevenagel condensation of vanillin (1a) and barbituric acid (2a) (Scheme 1) in a planetary ball mill aiming to close this knowledge gap, 5 including questions regarding the influence of beaker size, geometry, and the way the mechanical energy is provided. To this end, Knoevenagel condensation was performed using various tools for allocating mechanical stress.To investigate the influence of different milling and grinding apparatuses, three different types of PBMs, an MBM, a stirred media mill (SMM), an MM, and a mortar and pestle were used. The main differences between the PBMs are the diameter of the main disc (d MD ),...

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The influence of several process parameters like milling time, ball‐to‐beaker volume ratio, diameter of milling balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary ball mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.