Mechanochemical Reactions from Individual Impacts to Global Transformation Kinetics

Abstract

Typically induced by the mechanical processing of powders in ball mills, mechanochemical transformations are considered to result from the application of mechanical force to solid reactants. However, the undeniable deep connection between the dynamic compaction of powders during impacts and the overall transformation degree has yet to be disclosed. In the present work, we show that the square planar bis(dibenzoylmethanato)NiII coordination compound undergoes trimerization when its powder experiences even a single ball impact. Based on systematic experiments with individual ball impacts and analysis by Raman spectroscopy, we provide here quantitative mapping of the transformation in the powder compact and deduce bulk reaction kinetics from multiple individual impacts.

Kinetics of primary mechanochemical covalent-bond-forming reactions

“…It is increasingly clear that the rates of mechanochemical reactions in macroscopic reactorsball mills, planetary mills, and extrudersare dependent on the rates of both primary and secondary processes. While some kinetic models have been developed, [171][172][173][174] models that consider both processes have not yet been successfully applied to describe the kinetics of mechanochemical reactions. While selectivity can now be explained, until new kinetic models emerge that combine primary and secondary processes, the rates and energetics of mechanochemical reaction kinetics cannot be anticipated.…”

Modeling Mechanochemical Depolymerization of PET in Ball-Mill Reactors Using DEM Simulations

“…The kinetics of most of the reactions are dictated by their energy descriptor, i.e., temperature or potential in thermochemical and electrochemical reactions, respectively. For the case of mechanochemical reactions, it has been demonstrated that the critical energetic descriptor is the kinetic energy of the moving balls. , In other words, the reaction rate is expected to be proportional to the milling intensity, via a kinetic parameter a , and consequently to the kinetic energy of the ball and collision frequency. Measuring parameters such as velocities, however, often requires sophisticated experimental setups to record the milling process, while the estimated kinetic parameters will still be dependent on the system specifics.…”

Deriving kinetic insights from mechanochemically synthesized compounds using multivariate analysis (MCR-ALS) of powder X-ray diffraction data

“…8–11 The collection of such data may be also used for obtaining a kinetic profile: along with the information on the evolution time of the reaction, it would also represent a further step in the understanding of the mechanochemical reactions and their following scale-up at the industrial level. 12 By finding the best fitting of kinetic equations with the experimental data, it is possible to gain insight into the microscopic features of mechanical activation. 13 When dealing with crystalline materials, the most powerful method for obtaining kinetic data is the Quantitative Phase Analysis (QPA) via Rietveld refinement.…”