Abstract
The oxidation of mechanically activated ultrafine iron powders was studied using X- ray powder diffraction and thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electric explosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. It was shown that a certain amount of FeO phase is formed during mechanical activation of ultrafine iron powders. According to thermogravimetric analysis, the oxidation process of non-milled ultrafine iron powders is a complex process and occurs in three stages. The preliminary mechanical activation of powders considerably changes the nature of the iron powders oxidation, leads to increasing in the temperature of oxidation onset and shifts the reaction to higher temperatures. For the milled powders, the oxidation is more simple process and occurs in a single step.
Highlights
Iron powders are widely used in powder metallurgy for catalysts and other magnetic fluids producing [1]
According to XRD-data shown in Table 1, a monoxide of iron (FeO) is produced as a result of oxidation of iron powder during mechanical activation; and the concentration of FeO increases with the increase of the milling time
The processes of oxidation of ultrafine iron powders mechanically activated in a planetary ball mill for 15 and 40 minutes were investigated
Summary
Iron powders are widely used in powder metallurgy for catalysts and other magnetic fluids producing [1]. In the works [5,6,7,8], the strongly influence of the structure and particle size on the oxidation rate of ultrafine iron powders was shown, that leads to decrease in temperature and an increase in initial rate of the oxidation process. It was shown that the oxidation of the iron powder is a complicated mechanism; the oxidation occurs through the formation of intermediate products [9], and depends on particle size, temperature, and partial pressure of oxygen in the gas phase, the rate of heating of the powder.
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