Kinetics of hydrogen reduction of a-Fe nanopowder 2<sup>O</sup>3under energy-mechanical treatment in an electromagnetic field
Kinetics of the hydrogen reduction of a-Fe2<sup>O</sup>3 nanopowder in an electromagnetic ield and during energy-mechanical treatment (EMT) in an eddy layer of ferromagnetic particles has been investigated. Initial a-Fe2<sup>O</sup>3 nanopowder was produced by chemical precipitation of iron (III) hydroxide a-FeOOH prepared from a 10% aqueous solution of Fe(NO3<sup>)</sup>3 by adding of NaOH 10% solution at pH = 11, followed by thermal decomposition at 250°C for 2 h. Experiments were carried out on the apparatus of eddy layer modiied with a heating module and a low reactor. Calculation of the kinetic parameters under the conditions of linear heating and in isotherm condition was carried out according to the Freeman-Carroll and McKewan models respectively. It is established that the electromagnetic ield reduces the reduction rate of a-Fe2<sup>O</sup>3 nanopowder to 19% at 400°C, and the EMT in the eddy layer intensiies the reduction process up to 4 times. Properties of the original material and the reduction products were examined using the methods of thermogravimetric, X-ray difraction, electron microscopic analyses. Values of the speciic surface area of the products were determined by low-temperature nitrogen adsorption method. It is shown that the reduction of samples in the electromagnetic ield allow to obtain the high dispersion metallic iron nanoparticles. EMT in the eddy layer leads to an intensive aggregation of the particles obtained.