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

doi:10.1016/S0032-5910(99)00200-4

Powder Technology

Volume 107, Issue 3, 1 February 2000, Pages 197-206

https://doi.org/10.1016/S0032-5910(99)00200-4 Get rights and content

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.

Introduction

In the previous communication [1], we have reported the calculations of t–P–T conditions in local regions (in some vicinity x of an impact–friction contact) of the particles under treatment and deduced the generalized equations to describe the kinetics and to calculate the rate constants of mechanochemical processes in comminuting devices. In the present paper, we consider the application of results obtained earlier and confirmed experimentally 2, 3, 4, both to describe some general mechanisms of activation and chemical transformations of substances (these mechanisms being based on numerical evaluations and deduced from the local character Δx∼10⁻⁶ cm and short-time scale τ∼10⁻⁸ s of the existence of pressure σ∼10¹⁰–10¹¹ dyn/cm² and temperature ΔT∼10³ K impulses), and to calculate numerically the rate constants of activation and mechanochemical reactions in ball planetary mills in the impact regime of their operation.

Section snippets

Mechanism of mechanochemical processes

The general questions concerning the effect of local character and short time scale (kinetic factors) on the mechanism of mechanochemical processes and specific character of their course had been discussed qualitatively earlier 5, 6. The quantitative aspect of this problem includes numerical estimates of heat and mass transfer in the local regions of the particles under some given t–P–T conditions aimed at the description of the possibilities and mechanisms of different physicochemical

The use of kinetic equations

In the previous communication [1], we obtained the generalized kinetic equations to describe the transformation degree of mechanochemical processes. The equation for the degree of mechanical activation, without taking account of the changes in particle size, is: $α_{f} (τ)=α*Ψτ≈10ζηψωΦ*(V*/V)τ=K′τ.$ Here, the geometric probability of the impact treatment of particles for unlined balls (see also below) is $ψ = s /π(2R)^{2} =2^{−4} (10π)^{0.4} ρ^{0.4} (θ+ θ)^{0.4} W^{0.8}$ and the product of dimensionless functions ζη is $ζ(N)η(N,R/l_{m})≈N$

Conclusions

On the basis of the obtained theoretical results, it can be stated that the effect of short-time contact fusion of particles treated in various comminuting devices can play the key role in the mechanism of activation and chemical reactions for wide range of mechanochemical processes. This role involves several aspects, i.e., the very fact of contact fusion transforms the solid-phase process into another qualitative level, judging from the mass transfer coefficients. Spatial and time

List of symbols²

m′ and m_s′	The rate and stationary rate of melting
h and f(y,h)	Dimensionless parameters of melting
H_m	Latent heat of melting
μ	Viscosity of the melting zone
τ_c and A	Time and constant of the crystallization process
r_cr and σ_s	Linear dimension of the new phase formed and the crystal–melt surface tension
∇	Diffusion coefficient (diffusivity)
k, χ and K_r0	The Boltzmann, structural and pre-exponential factors
n, n₀, n*	The current, total, reacted number of molecules (atoms)
K_r	The reaction rate constant in the

Urakaev Farit Khisamutdynovich is a Doctor of Chemistry, the Chief of the Mass Crystallization Laboratory of the United Institute of Geology, Geophysics and Mineralogy of the Siberian Branch of the Russian Academy of Sciences, Acad. Koptyug Prosp. 3, Novosibirsk 630090, Russia.Boldyrev Vladimir Vyacheslavovich is a member of the Russian Academy of Sciences, he is also a Doctor of Sciences in Chemistry, Professor of Chemistry, and past Director of the Institute of Solid State Chemistry of the

References (58)

J. Strazisar et al.
Int. J. Miner. Process.
(1996)
V.V. Boldyrev et al.
Int. J. Miner. Process.
(1996)
F.Kh. Urakaev, V.V. Boldyrev, Powder Technol., Part 1 107 (2000) pp....
F. Dachille, R. Roy, Nature, 186 (1960) 34 and...
K. Tanno
Kona: Powder and Particle
(1990)
F.P. Bowden et al.
Proc. R. Soc. London, Ser. A
(1961)
V.V. Boldyrev
Kinet. Katal.
(1972)
G. Heinicke, Tribochemistry, Akademie-Verlag, Berlin,...
E.G. Avvakumov et al.
Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk
(1978)
D.D. Saratovkin et al.
Dokl. Akad. Nauk SSSR
(1947)

P.A. Savincev et al.

Izv. VUZOV, Phys.

(1960)

L.K. Savitskaya

Izv. VUZOV, Phys.

(1960)

K.B. Gerasimov et al.

Int. J. Mechanochem. Mech. Alloying

(1994)

R.F. Strickland-Constable, Kinetics and Mechanism of Crystallization from the Fluid Phase and of the Condensation and...

A.R. Ubellohde, Melting and Crystal Structure, Clarendon Press, Oxford,...

N.I. Galperin, G.A. Nosov, Foundations of melt crystallization technique, Khimiya (Moscow) (1975), in...

H.G. Landau

Q. Appl. Math.

(1950)

I.K. Kikoin (Ed.), Tables of Physical Constants. A Handbook, Atomizdat, Moscow, 1976, in...

H. Shlichting

Z. Angew. Math. Mech.

(1951)

P.M. Heertijes et al.

Chem. Process. Eng.

(1972)

B.Ya. Lyubov, A.L. Roytburd, in: N.N. Syrota (Ed.), Crystallization and Phase Transitions, Akad. Nauk BSSR, Minsk,...

B. Chalmers, Principles of Solidification, Wiley, New York,...

M.C. Flemings, Solidification Processing, McGraw-Hill, New York,...

U. Schneider

Aufbereit.-Tech.

(1968)

E.G. Avvakumov, Mechanical methods of the activation of chemical processes, Nauka (Novosibirsk) (1986), in...

V.L. Shapkin et al.

Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk

(1989)

V.V. Boldyrev et al.

Russ. Chem. Rev. (Usp. Khim.)

(1971)

K. Suzuki et al.

Mater. Trans., JIM

(1995)

C.C. Koch

Mater. Trans., JIM

(1995)

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

Abstract

Introduction

Section snippets

Mechanism of mechanochemical processes

The use of kinetic equations

Conclusions

List of symbols2

Int. J. Miner. Process.

Int. J. Miner. Process.

Kona: Powder and Particle

Proc. R. Soc. London, Ser. A

Kinet. Katal.

Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk

Dokl. Akad. Nauk SSSR

Izv. VUZOV, Phys.

Izv. VUZOV, Phys.

Int. J. Mechanochem. Mech. Alloying

Q. Appl. Math.

Z. Angew. Math. Mech.

Chem. Process. Eng.

Aufbereit.-Tech.

Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk

Russ. Chem. Rev. (Usp. Khim.)

Mater. Trans., JIM

Mater. Trans., JIM

List of symbols²