Enormous free surface area, unique magnetic and optical properties of nanoparticles provide great opportunities for their application. One of the easiest and most efficient methods for getting nanoparticles is mechanical milling of larger-particle powders. Solving specific process tasks often requires nanoparticles of fixed composition and dimensions, but the existing models of obtaining them are rather experimental data integration and can hardly help in selecting powder processing conditions for new tasks.
The Ekaterinburg researchers at the Institute of Chemistry of Solids, Ural Branch, Russian Academy of Sciences, have for the first time suggested a model that is capable to reliably forecast dimensions of obtained nanoparticles. Numerical experiment outcomes coincided with experimental data on getting tungsten carbide (WC). The researchers have managed to find out that particles dimensions decrease as milling time grows and, on the contrary, increase if original particle size and shot mass grow up. The findings of research carried out by Ural and Siberian Branches of the Russian Academy of Sciences with support by the Russian Foundation for Basic Research were published at “Journal of Applied Physics”.
Mechanical milling of powders takes place in a planetary-type mill, filled by rotating spheres. Spheres motion analysis earlier performed by the researchers proved direct relation between consumed energy and time of milling under fixed rotation velocity of the mill. Energy is consumed for bond opening and significant increase of particles free surface.
The formula deduced by Alexander Gusev and Alexy Kurlov describes dimensions of obtained particles as the milling time, shot mass and original particle dimensions function. Shear and compression moduli, crystal framework parameters and some others are used as physical characteristics of the substance. According to the formula, increasing the shot mass, original particle dimensions or decreasing milling time results in expansion of obtained particles.
The data of experiment on coarse-grained tungsten carbide (10 mcm) powder milling up to nanoscale particles (10 nm) coincided well with the deduced formula dependence. For this reason, the suggested model, as the researchers point out, “will enable to pass from empirical fit of milling conditions towards theoretical assessment of milling parameters based on physical characteristics of original substance.”
Source of information:
A.S. Kurlov, A.I. Gusev “Powder milling model”. Journal of Applied Physics (Zhurnal Tekhnicheskoi Fiziki), 2011, Vol. 81, issue 7.
Mikhail Petrov, published by STRF.ru