A novel macrokinetic approach for mechanochemical reactions (original) (raw)
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Processing and Investigation Methods in Mechanochemical Kinetics
ACS Omega
The present work focuses on the challenges that emerge in connection with the kinetics of mechanically activated transformations. This is an important topics to comprehend to enable the full exploitation of mechanical processing in a broad spectrum of areas related to chemistry and materials science and engineering. Emerging challenges involve a number of facets regarding materials and material properties, working principles of ball mills and milling conditions, and local changes occurring in series in processed materials. Within this context, it is highly desirable to relate the nature and rate of observed mechanochemical transformations to individual collisions and then to the processes induced by mechanical stresses on the molecular scale. Hence, it is necessary to characterize the milling regimes that can establish in ball mills regarding frequency and energy of collisions, map the relationship between milling dynamics and transformation kinetics, and obtain mechanistic information through proper time-resolved investigations in situ. A few specific hints are provided in this respect.
Some kinetic features of mechanical alloying transformation processes
Journal of Non-Crystalline Solids, 1998
The development of a methodological approach and experimental protocols have permitted the accurate evaluation of some of the key parameters of a ball milling process, such as the impact energy and the number of impacts. Thus, a detailed description of the milling regime in terms of energy transfer to the powders has been possible. On this basis, the crystal to amorphous state reaction of Cu±Ti mixture has been studied for widely diering milling conditions. The analysis of X-ray diraction data has shown correlations between the parameters of the milling treatment which relate to energy and the structural evolution of the amorphous phase. An attempt has been made to relate the observed kinetic features to a rate law involving microscopic pulse energy and structural factors.
Application of Ball Milling for Highly Selective Mechanochemical Polymorph Transformations
Organic Process Research & Development, 2018
Milling is an important secondary processing technique in the manufacture of pharmaceuticals, primarily used as a particle size reduction process. Para-, meta-and ortho-aminobenzoic acid (PABA, MABA, OABA) and carbamazepine (CBZ) are pharmaceutically relevant compounds that can exist in different polymorphic forms with distinct packing motifs and thus different physicochemical properties. A comprehensive study of the effect of milling on the polymorphism of PABA, MABA, OABA and CBZ was carried out. Milling PABA in the presence of catalytic amounts of valeric acid or methanol yielded the -polymorph which is otherwise difficult to obtain in bulk quantities. Milling also proved to be a more convenient method for producing MABA form IV compared to previously reported procedures. Principal component analysis of the pair distribution function transformed X-ray powder diffraction spectra of ball-milled CBZ samples showed that the milling-induced polymorphic transformation strongly depends on the ball-to-powder ratio. Elusive CBZ form IV could be obtained in pure form by optimizing the milling conditions.
Title Application of ball milling for highly selectivemechanochemical polymorph transformations
2019
Milling is an important secondary processing technique in the manufacture of pharmaceuticals, primarily used as a particle size reduction process. Para-, meta-and ortho-aminobenzoic acid (PABA, MABA, OABA) and carbamazepine (CBZ) are pharmaceutically relevant compounds that can exist in different polymorphic forms with distinct packing motifs and thus different physicochemical properties. A comprehensive study of the effect of milling on the polymorphism of PABA, MABA, OABA and CBZ was carried out. Milling PABA in the presence of catalytic amounts of valeric acid or methanol yielded the -polymorph which is otherwise difficult to obtain in bulk quantities. Milling also proved to be a more convenient method for producing MABA form IV compared to previously reported procedures. Principal component analysis of the pair distribution function transformed X-ray powder diffraction spectra of ball-milled CBZ samples showed that the milling-induced polymorphic transformation strongly depends on the ball-to-powder ratio. Elusive CBZ form IV could be obtained in pure form by optimizing the milling conditions.
Fine milling in applied mechanochemistry
Minerals Engineering, 2009
This review paper is devoted to application of mechanochemistry in extractive metallurgy, crystal engineering, materials engineering, coal industry, building industry, agriculture, pharmacy and waste treatment. In extractive metallurgy the most commercially attractive potential applications using fine milling (Activox, Melt) will be illustrated. Mechanochemical approach in crystal and materials engineering will focus on the non-equilibrium processing of materials and their current and potential applications. In agriculture the technological advantages of mechanochemical methods over traditional methods for improving the solubility of natural phosphates will be documented. In pharmacy, the selected examples of fine milling application will show the improved bioavailability of drugs. The examples of fine milling utilization in coal industry, building industry and waste treatment are also given. Simplification of the processes, ecological safety and the product extraordinariness characterize the application of fine milling in mechanochemistry.
Nanomaterials, 2021
Throughout human history, any society’s capacity to fabricate and refine new materials to satisfy its demands has resulted in advances to its performance and worldwide standing. Life in the twenty-first century cannot be predicated on tiny groupings of materials; rather, it must be predicated on huge families of novel elements dubbed “advanced materials”. While there are several approaches and strategies for fabricating advanced materials, mechanical milling (MM) and mechanochemistry have garnered much interest and consideration as novel ways for synthesizing a diverse range of new materials that cannot be synthesized by conventional means. Equilibrium, nonequilibrium, and nanocomposite materials can be easily obtained by MM. This review article has been addressed in part to present a brief history of ball milling’s application in the manufacture of a diverse variety of complex and innovative materials during the last 50 years. Furthermore, the mechanism of the MM process will be di...
Acta Materialia, 1998
AbstractÐA Fe±40Al (at.%) alloy powder having a B2 ordered structure was milled in a high energy planetary ball-mill. The microstructural evolution of the alloy was followed by analysing powder specimens milled for dierent times by X-ray diraction, MoÈ ssbauer spectroscopy and magnetisation measurements. Grain re®nement and chemical disordering were the main transformations resulting from milling. A complete destruction of the long-range order under the adopted conditions of milling was not achieved. From diraction analyses it was possible to see how the concentrations of such defects as dislocations, planar faults, antiphase domain boundaries, etc., were modi®ed by the heavy deformations involved with milling. Starting from the specimens milled for the longest time, considered in this study, isothermal annealing experiments were carried out to monitor the reverse transformations. The annealing temperatures were selected on the basis of dierential scanning calorimetric and thermogravimetric magnetic measurements, which revealed that several transformations occur when treating the deformed powders. Recovery and reordering take place at temperatures ranging from 100 up to 2508C. A complete reordering is possible only at higher temperatures, i.e. 7008C, when recrystallisation is fully accomplished. # 1998 Acta Metallurgica Inc.
Mechanosynthesis of nanophase materials
Nanostructured Materials, 1993
Among the synthesis methods of nanocrystalline materials, high energy milling is promising at production scale. The mec hanoc hemical synthesis ( M echanosynthesis ) of nanophase materials can be realized by direct synthesis of compounds from the elemental powders or by several exchange, transfer and mixing reactions such as for: 1) most metal carbides; 2) intermetallic compounds (silicides, aluminides ) ; 3) semiconducting III-V compounds ( GaAs and AlAs); 4) metal-oxide M-RO composites by reduction of a metal M oxide with a suitable reductant R; 5) metal-sulphide M-RS composites by reduction of a metal M sulphide with R; 6)fluorides and nitrides by exchange reactions. Reactions are driven in a ball mill at almost room temperature. 218 P IV~TrEA~J, D BASSET, F MIANI AND G LE CAI~R synthesis of compounds (7-14) and composite materials , which are, in general, nanophased. Among the processing methods used to obtain nanophase materials, high energy milling (and therefore mechanosynthesis) appear attractive for its potential of large scale economic production required for the development of their technological application (20). This paper presents the results obtained by the authors in the mechanosynthesis of nanophase materials.