F. Kh. Urakaev

Mechanism and kinetics of mechanochemical processes in comminuting devices: 1. Theory

For the models built up on the basis of the nonlinear elastoplastic theory describing the collisions of solids, parameters of impact interaction between the working bodies and the material to be treated have been calculated for a series of comminuting devices, i.e., different types of ball mills, disintegrator, etc. Pressure and temperature impulses at the contacts of the treated particles have been calculated. Generalised equations have been deduced for the kinetics rate constants of mechanochemical reactions and for the mechanical activation of the substances in comminuting devices.

Mechanism and kinetics of mechanochemical processes in comminuting devices: 2. Applications of the theory. Experiment

Abstract The equations describing the kinetics of contact melting and crystallization of the substances have been deduced on the basis of the obtained distributions of temperature and pressure impulses during impact–friction interaction of the particles treated in comminuting devices. Possible mechanisms of the formation of nanocrystal particles and of chemical reactions during the crystallization of thin films of a melt at high rates of local temperature changes in the near-contact regions have been studied. Various examples are presented that deal with the application of the generalized kinetic equation to the calculations of ab initio rate constants of specific mechanochemical processes in comminuting devices. The obtained theoretical values have been compared with experimental results.

A study of the mechanochemical synthesis of TlCl nanoparticles by the method of dilution with the final product

The kinetics of the solid-state mechanochemical synthesis of the nanosized product (TlCl) in the reaction 2NaCl + Tl2SO4 + zNa2SO4 = (z + 1)Na2SO4 + 2TlCl was studied experimentlaly. The method used was based on the dilution of the initial mixture of powdered reagents (2NaCl + Tl2SO4) with another exchange reaction product (Na2SO4) at the optimum theoretically estimated z value, z = z* = 11.25. Several special features of the development of this reaction were established. The parameters of the kinetic curve obtained for the mechanochemical synthesis of the desired product were compared with those of the kinetic curve determined theoretically for the model reaction KBr + TlCl + zKCl = (z + 1)KCl + TlBr with z = z1* = 13.5. This allowed us to experimentally estimate the mass transfer coefficient in a mechanochemical reactor by mobile milling bodies. This estimate was obtained for the first time. The dynamics of changes in the size of desired product nanoparticles depending on the time of mechanochemical activation in an AGO-2 ball planetary mill was studied.

Character of change in the work of nucleation of β-quartz, diamond, and aluminum hydride (α-AlH3) crystals in homogeneous media

Abstract The model for homogeneous nucleation of covalent crystals has been developed, which considers the nuclei ranging from n to n×102 atoms and uses the noncontinuous calculations. The critical size of a nucleus depends stepwisely on the supersaturation. The mass crystallization processes are to yield product of stable condition in the wide ranges of supersaturation. The process and product change drastically on the borders of the ranges. The local minimums in the relationship between the free energy of nucleus and its size are evidently observed. Such stable nuclei are the building units which can condense to form the new phase.

Application of Mechanically Stimulated Combustion Reactions in Processing of Geological Materials

Based on the literature review, the use of methods for metallothermy and self-propagating high-temperature synthesis is considered for processing different geological materials. Combination of mechanochemistry and these methods allows to avoid agglomeration of the products due to high temperature. Mechanically stimulated exothermic processes proceed both in combustion regime and at lower temperature, which makes it possible to combine opening and processing of mineral and technogenic raw material with production of highly dispersed materials.

Mechanochemical synthesis of colloidal silver chloride particles in the NH4Cl–AgNO3–NH4NO3 system

Silver chloride nanoparticles prepared by exchange mechanochemical reaction NH4Cl + AgNO3 + zNH4NO3 = (z + 1)NH4NO3 + AgCl in ammonium nitrate matrix (diluent and side reaction product) at dilution parameters z = 7.22 and 3.64 are studied by X-ray diffraction and thermal analysis, electron microscopy, and dynamic light scattering. It is shown that free-form AgCl nanoparticles can be obtained after removal of ammonium nitrate by washing-out with water or thermal annealing at 300°C.

Combustion of mechanically activated quartz-aluminum mixtures

Explored was the effect of mechanical activation of quartz (separate and jointly with aluminum) and abrasive-reactive wear of milling bodies on the induction period and temperature of a thermit-type process for sintering quartz-based materials.

Influence of mechanical activation on the properties of the charge for growing NaBi(WO4)2 and ScBaNa(BO3)2 single crystals

A comparative study was performed on the influence of “pollution-free” mechanical activation (without abrasive-reactive wear of the milling tools of mechanochemical reactors) in oxide-carbonate-acid systems on synthesis and the properties of the charge for growing of bulk crystals.

Energy fluctuations and particle emission in a crack mouth

Numerical estimates of the energy balance in a region lying in front of a main crack are made using classical mechanics and statistical physics and are illustrated through the example of cleavage of alkali halide crystals. It is found theoretically that emission of nanoparticles can occur in the course of dynamic fracture.

Prediction of structural–chemical change in minerals under mechanical impact during milling

There is sufficient experimental database thus far collected on structural and chemical changes in minerals with different types of chemical bonding under activation milling. The research has shown the possibility to predict specifics of grinding and defect formation in minerals with different types of chemical bonding. The article shows that type and number of defects formed on the surface of minerals govern important processing properties of the minerals such as capacities to be hydrated, dissolved, floated etc.