RSC Mechanochemistry最新文献

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Ball-milling of addition polymers such as polyolefins, polystyrene and polyacrylates can be used for depolymerization to obtain the respective monomers. However, absolute yields are typically low, especially from polyolefins which are notoriously difficult to depolymerize. To increase the viability of ball milling as a recycling technique, the effect of milling parameters on small hydrocarbon and monomer yields has to be understood. Herein, we systematically investigate the influence of sphere material, milling frequency, plastic filling degree, and milling temperature. Heavy spheres and high milling frequencies boost hydrocarbon yields by maximizing mechanical forces and frequency of collisions. While the dose of kinetic energy is commonly used to describe mechano-chemical processes, we found that it does not capture the mechano-chemical depolymerization of polyolefins. Instead, we rationalized the results based on the Zhurkov equation, a model developed for the thermo-mechanical scission of polymers under stress. In addition, low plastic filling degrees allow for high percentage yields, but cause significant wear on the grinding tools, prohibiting sustained milling. Milling below 40 °C is beneficial for brittle chain cleavage and depolymerization. This study provides a new approach to rationalize the influence of individual milling parameters and their interplay and serves as a starting point to derive design principles for larger-scale mechano-chemical depolymerization processes.

Na₂CaSnS₄ was prepared by mechanochemical synthesis from a mixture of Na₂S, CaS, and SnS₂. The crystal structure was determined from X-ray powder diffraction data. The chemical composition was confirmed by energy dispersive X-ray spectroscopy, and the ionic conductivity was measured using electrochemical impedance spectroscopy. Na₂CaSnS₄ crystallizes with a rock salt-type structure, space group Fmm, a = 5.6842 (3) Å, V = 183.66 (2) ų, and Z = 1. All the cations are statistically disordered over a unique crystallographic site and are octahedrally coordinated to the sulfur atoms. The ionic conductivity of Na₂CaSnS₄ is 4.2 × 10⁻⁸ S cm⁻¹ (E_a = 0.6 eV) at 33 °C.

This study presents the mechanochemical synthesis of the two K₂Ca(CO₃)₂ polymorphs, fairchildite and buetschliite, from CaCO₃ and K₂CO₃ using a shaker mill. Unlike previous methods requiring high temperatures and prolonged heating, fairchildite, a high-temperature polymorph, is formed initially in all experiments, adhering to Ostwald's rule of stages. Notably, the transformation to the stable buetschliite phase can be achieved by varying milling parameters, particularly frequency and moisture content. The results suggest that pressure, rather than temperature, plays a significant role in this phase transition, with moisture further accelerating the transformation. These findings offer a new, efficient route for the synthesis of these polymorphs, highlighting the critical influence of milling conditions on the reaction pathway.

Efficient treatment of persistent pollutants in wastewater is crucial for sustainable water management and environmental protection. This study addresses this challenge by investigating the mechanochemical synthesis and photocatalytic performance of ZIF-9, a cobalt-based zeolitic imidazolate framework. Using synchrotron-based powder X-ray diffraction, we provide real-time insights into the formation dynamics of ZIF-9 during mechanosynthesis. Our results show that mechanochemically synthesised ZIF-9 exhibits superior photocatalytic activity compared to its solvothermally prepared counterpart, achieving a 2-fold increase in methylene blue degradation rate. This research not only advances our understanding of the synthesis and properties of ZIF-9, but also demonstrates the potential of mechanochemical approaches in the development of high-performance, sustainably produced materials for water treatment and other environmental applications.

The dynamics of cargo transport by two coupled kinesin monomers, such as kinesin-1, kinesin-2 and kinesin-3, is studied theoretically and is compared with that by the corresponding single dimer on the basis of our proposed model for the mechanochemical coupling of the two coupled monomers and that of the single dimer. It is shown that if the stalk, which connects the monomer and cargo, has a short length L_S (e.g., L_S < 5 nm) the cargo transport by the two monomers can be efficient with an unloaded velocity that can be similar to that by the corresponding single dimer, whereas the cargo transport by the two monomers with a long L_S can only be inefficient with an unloaded velocity and a stall force much smaller than those with the short L_S. Although the unloaded velocity for the two coupled kinesin-1 monomers with a short L_S can be similar to that for the single kinesin-1 dimer, the stall force for the former is reduced by about 2 times relative to that for the latter. The dynamics of the two coupled kinesin-3 KIF1A monomers relative to the single kinesin-3 dimer is similar to that of the two coupled kinesin-1 monomers relative to the single kinesin-1 dimer. By contrast, the stall force for the two kinesin-2 KIF3A monomers with a short L_S can be similar to that for the single kinesin-2 KIF3AA, KIF3BB or KIF3AB dimer. The theoretical results agree well with the available experimental evidence. The underlying mechanism of the two coupled kinesin-1 or kinesin-3 monomers with the short L_S having an evidently smaller stall force than the corresponding single dimer and the two coupled kinesin-2 KIF3A monomers with the short L_S having a stall force similar to that of the corresponding single dimer is explained.

We prepared a ternary sulfide with a stoichiometry close to Pb₆Bi₂S₉ from PbS, Bi, and S precursors using mechanochemical synthesis. After 5 min of high-energy milling, conversion of the precursors to Pb_5.95Bi_2.02S_9.03 was confirmed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). Further milling (up to 120 min) led to the metal-enriched and sulfur-deficient composition Pb_6.40Bi_2.24S_8.36. Values of the specific surface area of the produced powder samples were used as an indicator of the transition from the mechanical activation mode to the mechanochemical synthesis mode. The products crystallized in the galena structure, with the crystallite size ranging from 5 to 15 nm, as determined by X-ray diffractometry (XRD) with Rietveld refinement and transmission electron microscopy (TEM). The dissolution of Bi from the synthesized nanocrystals corresponds to changes in the specific surface area. Spark plasma sintering (SPS) densified ingots in the temperature range of 300–525 K exhibit semiconducting properties and a low thermal conductivity of 0.38–0.5 W m⁻¹ K⁻¹, making them promising for thermoelectric applications. The possibility of modifying the properties of a ternary Pb–Bi–S system by mechanochemistry paves the way for the synthesis of more sophisticated ternary and multinary structures suitable for energy applications.

Herein, we developed the mechanosynthesis of ruthenium trisbipyridyl complexes. Such complexes can be difficult to prepare in solution, with long reaction times and average yields. With ball-milling, less than 3.5 hours of milling were sufficient to obtain the complexes in high yield. Such complexes were then evaluated as catalysts in the light-promoted mechanochemical reductive dehalogenation reaction. In addition to working under solvent-less conditions, the use of a Hantzsch amide instead of the classical ester allowed drastic simplification of the purification of the final compounds.

Ball mill mechanosynthesis provides a method for direct C–H activation to prepare NC palladacycle precatalysts via liquid-assisted grinding (LAG). Methanol and dimethylsulfoxide were used as non-innocent LAG reagents, coordinating to the Pd center and producing more reactive intermediates to speed reactions. Kinetic modelling results are consistent with a mechanism of nucleation and autocatalytic growth in these processes.

A series of trifluoromethylated pyrrolo[3,4-c]pyrazoles was obtained via mechanochemical (3 + 2)-cycloaddition of in situ generated trifluoroacetonitrile imines with maleimide and its N-aliphatic/aromatic analogues. The presented work demonstrated that the aforementioned 1,3-dipoles can be efficiently trapped with electron-deficient dipolarophiles under solvent-free ball-milling conditions.