Complete Oxidation of Zinc Powder. Validation of Kinetics Models

Abstract

The kinetics of complete oxidation of different samples of zinc powder by air has been investigated by thermogravimetric measurements under isothermal conditions in the range 973-1,173 K. Particles size was in the 63-80 lm range. We succeeded in carrying out the full oxidation of the powders far above the zinc-metal melting point (692.6 K). This phenomenon is linked to the presence of a thin ZnO layer which confines the liquid metal during the oxidation process. Two kinetics models have been verified. The apparent activation energies obtained from the Arrhenius law were 128 kJ mol -1 and 129 kJ mol -1 , respectively.

Kinetics Model of the Thermal Oxidation of Indium Powder

“…The oxidation rate decreased with time and it was strongly influenced by temperature. The complete oxidation of indium power at 858 K required more than 100 h whereas the oxidation progress at 1173 K was completed in about 1 h. This behaviour is similar to that found in previous works on the complete oxidation of cobalt [4], zinc [5] and bismuth [6], powders. Moreover, it is observed that the oxidation rate is increased with the diminution of the particle size and therefore the increase of their surface (Fig.…”

“…Isothermal experiments conducted with zinc and bismuth show that the kinetic model of the parabolic diffusion of oxygen through an oxide layer can be expressed by the expression [4][5][6]: The validity of the model was checked in the present case without any success. The extra-growth of indium at the surface of the particles observed by SEM show that the kinetic of indium is rather more complex.…”

“…The mass of the original metal sample weighted (accuracy up to 1/10 of a mg) was around 50 mg. These conditions allow the formation of a monolayer of particles on the container [4,5].…”

Oxidation of Micro-Sized Aluminium Particles: Hollow Alumina Spheres

“…Another possibility is a mechanical damage during cooling: smaller particles will lead to thinner scales that are not able to withstand mechanical stresses due to temperature drop during cooling. At this oxidation temperature (950°C), it has not been possible to fit typical oxidation kinetics (pseudoparabolic, asymptotic, logarithmic) or others used for powders at high temperatures [7,8]. This can be related to the polymorphic transformations taken place at this temperature.…”

“…There are, however, models regarding the thermal oxidation of two metal powders above their melting temperature: zinc [7] and indium [8].…”