scholarly journals Tribochemistry, Mechanical Alloying, Mechanochemistry: What is in a Name?

2021 ◽  
Vol 9 ◽  
Author(s):  
Adam A. L. Michalchuk ◽  
Elena V. Boldyreva ◽  
Ana M. Belenguer ◽  
Franziska Emmerling ◽  
Vladimir V. Boldyrev
Keyword(s):  
Mechanical Alloying ◽  
Chemical Reactions ◽  
Mechanical Force ◽  
Experimental Conditions ◽  
Meaningful Comparison ◽  
Constructive Discussion

Over the decades, the application of mechanical force to influence chemical reactions has been called by various names: mechanochemistry, tribochemistry, mechanical alloying, to name but a few. The evolution of these terms has largely mirrored the understanding of the field. But what is meant by these terms, why have they evolved, and does it really matter how a process is called? Which parameters should be defined to describe unambiguously the experimental conditions such that others can reproduce the results, or to allow a meaningful comparison between processes explored under different conditions? Can the information on the process be encoded in a clear, concise, and self-explanatory way? We address these questions in this Opinion contribution, which we hope will spark timely and constructive discussion across the international mechanochemical community.

scholarly journals Synthesis of Pure NiTiSn by Mechanical Alloying: An Investigation of the Optimal Experimental Conditions Supported by First Principles Calculations

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 835 ◽  
Author(s):  
Monique Tillard ◽  
Alexandre Berche ◽  
Philippe Jund
Keyword(s):  
Mechanical Alloying ◽  
Density Functional ◽  
Annealing Temperature ◽  
Theoretical Calculations ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Functional Theory ◽  
X Ray ◽  
Careful Investigation

Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful investigation of the phases present in the samples by systematic X-ray diffraction (after mechanical alloying and after annealing) and selected microscopy analyses, a reaction mechanism is proposed supported by theoretical calculations at the DFT (Density Functional Theory) level. An energy window to prepare directly NiTiSn has been evidenced. Highly pure NiTiSn has also been obtained by conversion from a multicomponent precursor obtained by low energy mechanical alloying.

scholarly journals Comprehensive Analysis of Applicability Domains of QSPR Models for Chemical Reactions

2020 ◽  
Vol 21 (15) ◽  
pp. 5542
Author(s):  
Assima Rakhimbekova ◽  
Timur I. Madzhidov ◽  
Ramil I. Nugmanov ◽  
Timur R. Gimadiev ◽  
Igor I. Baskin ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Model Performance ◽  
Comprehensive Analysis ◽  
Complex Object ◽  
Kinetic Characteristics ◽  
Individual Molecule ◽  
Experimental Conditions ◽  
Structure Activity ◽  
Reaction Characteristics ◽  
Active Research

Nowadays, the problem of the model’s applicability domain (AD) definition is an active research topic in chemoinformatics. Although many various AD definitions for the models predicting properties of molecules (Quantitative Structure-Activity/Property Relationship (QSAR/QSPR) models) were described in the literature, no one for chemical reactions (Quantitative Reaction-Property Relationships (QRPR)) has been reported to date. The point is that a chemical reaction is a much more complex object than an individual molecule, and its yield, thermodynamic and kinetic characteristics depend not only on the structures of reactants and products but also on experimental conditions. The QRPR models’ performance largely depends on the way that chemical transformation is encoded. In this study, various AD definition methods extensively used in QSAR/QSPR studies of individual molecules, as well as several novel approaches suggested in this work for reactions, were benchmarked on several reaction datasets. The ability to exclude wrong reaction types, increase coverage, improve the model performance and detect Y-outliers were tested. As a result, several “best” AD definitions for the QRPR models predicting reaction characteristics have been revealed and tested on a previously published external dataset with a clear AD definition problem.

Redox chemical processes of iodine species with inorganic compounds in ice

2020 ◽  
Author(s):  
Kitae Kim
Keyword(s):  
Chemical Reactions ◽  
Inorganic Compounds ◽  
Molecular Iodine ◽  
Chemical Processes ◽  
High Concentration ◽  
Experimental Conditions ◽  
Austral Spring ◽  
Iodine Species ◽  
Halogen Compounds ◽  
Reaction Media

<p>Ice is ubiquitous and one of the most important environmental reaction media on earth. Generally, chemical reactions take place slowly when temperature decreases according to Arrhenius Equation(k=A·e<sup>-E</sup><sup>A</sup><sup>/RT</sup>). Recently, it has been found that several chemical processes are accelerated by freezing compared to those in aqueous phase. Reactive iodine species (I, I<sub>2</sub>, IO, OIO, HOI) in atmosphere are related to ozone depletion event (ODE) and new particle formation (NPF) in polar troposphere, and finally affect climate change. It was reported that the high concentration of halogen compounds(IO, BrO) in austral spring in Antarctica but the exact mechanism and sources are not fully understood. The biological production of halogens are regarded as the major source of organic and I2. However, the (photo)chemical reactions to produce reactive iodine species are also regarded as possible mechanism to explain the high atmospheric iodine budget. In this presentation, I want to introduce enhanced chemical reaction with laboratory experimental results such as 1)accelerated oxidation of iodide(I<sup>-</sup>) in ice to produce molecular iodine(I<sub>2</sub>) and tri-iodide(I<sub>3</sub><sup>-</sup>), 2)nitrite-induced activation of iodate(IO<sub>3</sub><sup>-</sup>) into molecular iodine in frozen solution. The detailed experimental conditions and mechanism will be discussed in the presentation.</p>

scholarly journals Modeling Chemical Reactivity at the Interfaces of Emulsions: Effects of Partitioning and Temperature

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4703
Author(s):  
Marlene Costa ◽  
Fátima Paiva-Martins ◽  
Sonia Losada-Barreiro ◽  
Carlos Bravo-Díaz
Keyword(s):  
Chemical Reactions ◽  
Rate Constant ◽  
Dynamic Equilibrium ◽  
Chemical Reactivity ◽  
Bulk Solution ◽  
Interfacial Region ◽  
Redox Potentials ◽  
Experimental Conditions ◽  
Phase Chemistry ◽  
Reaction Media

Bulk phase chemistry is hardly ever a reasonable approximation to interpret chemical reactivity in compartmentalized systems, because multiphasic systems may alter the course of chemical reactions by modifying the local concentrations and orientations of reactants and by modifying their physical properties (acid-base equilibria, redox potentials, etc.), making them—or inducing them—to react in a selective manner. Exploiting multiphasic systems as beneficial reaction media requires an understanding of their effects on chemical reactivity. Chemical reactions in multiphasic systems follow the same laws as in bulk solution, and the measured or observed rate constant of bimolecular reactions can be expressed, under dynamic equilibrium conditions, in terms of the product of the rate constant and of the concentrations of reactants. In emulsions, reactants distribute between the oil, water, and interfacial regions according to their polarity. However, determining the distributions of reactive components in intact emulsions is arduous because it is physically impossible to separate the interfacial region from the oil and aqueous ones without disrupting the existing equilibria and, therefore, need to be determined in the intact emulsions. The challenge is, thus, to develop models to correctly interpret chemical reactivity. Here, we will review the application of the pseudophase kinetic model to emulsions, which allows us to model chemical reactivity under a variety of experimental conditions and, by carrying out an appropriate kinetic analysis, will provide important kineticparameters.

Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Site of Lysosome Production During Hepatic Injury

1969 ◽  
Vol 27 ◽  
pp. 348-349
Author(s):  
Nalin J. Unakar
Keyword(s):  
Electron Microscopy ◽  
Golgi Apparatus ◽  
Mouse Liver ◽  
Hepatic Injury ◽  
Close Approximation ◽  
Experimental Conditions ◽  
Toxic Injury

The increased number of lysosomes as well as the close approximation of lysosomes to the Golgi apparatus in tissue under variety of experimental conditions is commonly observed. These observations suggest Golgi involvement in lysosomal production. The role of the Golgi apparatus in the production of lysosomes in mouse liver was studied by electron microscopy of liver following toxic injury by CCI4.

Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 548-549 ◽  
Author(s):  
N. J. Zaluzec
Keyword(s):  
Solid Angle ◽  
Analytical Electron Microscopy ◽  
Incident Beam ◽  
Thin Foil ◽  
Experimental Conditions ◽  
X Ray ◽  
Microchemical Analysis ◽  
Analytical Electron ◽  
Image Position ◽  
Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

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