Mechanochemistry and the Other Branches of Chemistry: Similarities and Differences

Takács, László

doi:10.12693/aphyspola.121.711

Cited by 24 publications

(22 citation statements)

References 26 publications

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“…There are many examples that show that application of shear reduces PT pressure by a factor of 2 to 10 for some PTs [6,85,90,93,95,96,97,98,99,103], including PTs to superhard phases of BN [90,95], PTs in Si and Ge [85,96], and Zr and Zr-Nb alloys [97,98]. An important point is that some of these discoveries at relatively low pressure can be scaled up using high pressure torsion [97,98,100,101,102,99,103] and ball milling [104,105,106,107,108,109,110].…”

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

“…Despite the simplicity and effective 1D treatment, this model explained many experimental results on PTs in DAC and RDAC and developed our intuition on the interaction between PTs and plasticity at the nanoscale. Due to the generic character of the model, qualitative conclusions from its application have been used by other groups to interpret their experimental findings in high pressure torsion [99,103], mechanochemistry and ball milling [108,109,110] and shock-induced amorphization in Si [111].…”

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

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Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing phase field approach (PFA).The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using finite element method (FEM). The nucleation pressure for high pressure phase (HPP) under hydrostatic condition near single dislocation was determined to be 15.9 GPa. Under shear, a dislocations pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP.When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing the applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect stationary solution and nanostructure. Consequently, there are multiple stationary solutions under the same applied load and PT and deformation processes are path dependent. With an increase in the size of the sample by a factor of two, 2 no effect was found on the average pressure and shear stress and HPP nanostructure, despite the different number of dislocations in a pile-up. Obtained results represent a nanoscale basis for understanding and description of PTs under compression and shear in rotational diamond anvil cell and high pressure torsion.

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Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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“…Automatisiertes Kugelmahlen ist unter den verschiedenen Arten der Anwendung von mechanischer Energie zu einer Standardtechnik geworden, um mechanochemische Reaktionen in verschieden Gebieten, wie der organischen [6] und der anorganischen Chemie, [7] der Metallorganik, [8] der Biokatalyse oder Polymerchemie, [9,10] um nur einige zu nennen, durchzuführen. [11] Abgesehen davon, dass sie als nachhaltigere Alternative zur Einleitung chemischer Umwandlungen anerkannt wurde, [12] hat Mechanochemie durch Kugelmahlen die Synthese von Substanzen ermçglicht, die schwer oder gar nicht durch klassische Synthese zugänglich sind. [11] Abgesehen davon, dass sie als nachhaltigere Alternative zur Einleitung chemischer Umwandlungen anerkannt wurde, [12] hat Mechanochemie durch Kugelmahlen die Synthese von Substanzen ermçglicht, die schwer oder gar nicht durch klassische Synthese zugänglich sind.…”

Section: Introductionunclassified

Mechanochemie gasförmiger Reaktanten

Bolm

Hernández

2019

Angewandte Chemie

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In den letzten Jahren hat sich die Anwendung von mechanischer Energie auf chemische Systeme wiederholt als vorteilhaft erwiesen, um chemische Umwandlungen in verschiedenen Gebieten der Chemie zu erleichtern. Eine Vielzahl von systematischen Studien belegt heute, dass die Mechanochemie vielversprechende Möglichkeiten eröffnet, die chemische Synthese zu verändern. Nicht nur allein die Fähigkeit, die Herstellung von Produkten zu ermöglichen, die durch bestehende Methoden, wie der reinen thermischen Aktivierung, unzugänglich sind, haben zu einer Anerkennung der Mechanochemie geführt. Man hat auch gemerkt, dass mechanochemische Reaktionen ihre nasschemischen Gegenstücke oft hinsichtlich der Nachhaltigkeit übertreffen. Intuitiv sind die meisten mechanochemischen Reaktionen, die durch Kugelmahlen ausgeführt werden, mit der Umwandlung von Festkörpern und Flüssigkeiten verknüpft. In den letzten Jahren hat allerdings die Anzahl mechanochemischer Reaktionen mit gasförmigen Reaktanten zugenommen. Das Ziel dieses Kurzaufsatzes ist es daher, einerseits einen Überblick über chemische Reaktionen zu geben, die den Gebrauch von gasförmigen Proben in Kugelmühlen beinhalten, und andererseits die Fortschritte der Technologien und Aufbauten der Kugelmühlen aufzuzeigen, die den sicheren Umgang mit gasförmigen Reagenzien unter mechanochemischen Bedingungen ermöglicht haben. Darüber hinaus werden Beispiele für Reaktionen aufgezeigt, die an der Grenzfläche Feststoff/Flüssigkeit/Gas–Gas stattfinden und zu einer signifikanten Verbesserung der Reaktivität oder Selektivität geführt haben. Letztendlich hoffen wir zukünftige Arbeiten anzuregen, um verbleibende Herausforderungen auf dem Gebiet der Mechanochemie anzugehen.

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“…The rate of bond breaking can be described by an Arrhenius equation, modied with a term for the mechanical tension applied to the bond [7,8]:…”

Section: Introductionmentioning

confidence: 99%

What Is Unique About Mechanochemical Reactions?

Takács

2014

Acta Phys. Pol. A

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Mechanochemical reactions can provide compounds, phases, and microstructures that are essentially dierent from the products of ordinary reactions. In this paper, the origin of this uniqueness is discussed in light of the recent advances of the eld. It is claimed that the local availability of large batches of energy, well above kT , is the key feature of mechanochemical reactions. As a consequence, reactions that cannot occur thermally become possible, similarly to the reactions induced by the energy of photons in photochemistry. However, the situation is more complex, as macroscopic deformation aects many defect sites simultaneously. The direction of the mechanical load relative to the orientation of a molecule or the crystallographic axes of a solid can be important. Many mechanochemical reactions of organic compounds take place at low milling energy that is not sucient to break primary bonds, but the gentle mechanical grinding can inuence the relative position of macromolecules, leading to the formation of unique cocrystals and compounds. In inorganic systems, unusual products form due to forced mixing and the high defect density generated by intense milling.

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Mechanochemistry and the Other Branches of Chemistry: Similarities and Differences

Cited by 24 publications

References 26 publications

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Mechanochemie gasförmiger Reaktanten

What Is Unique About Mechanochemical Reactions?

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