Impact of gamma-radiation exposure on activity parameters of aluminium micropowders

The relevance of the research. One of the leaders in production of aluminum powders in Russia OOO «SUAL-PM» has passed from production of coarse powders to production of micron powders with higher reactivity. Aluminium micropowders are used in many branches of industry: powder metallurgy, self-propagating high-temperature synthesis of new materials, hydrogen energy, pyrotechnics and rocket fuels. Increase of aluminium powders reactivity in various processes leads to reduction in energy consumption and resource saving. The main aim of the research was to obtain and explain experimental data on changes in activity parameters of aluminium micropowders after radiation exposure, depending on the γ-radiation dose. Objects: micron-scaled aluminium powders ASD-6, ASD-6M. Methods: differential thermal analysis, X-ray diffraction analysis, method of aluminium micropowders exposure with γ-radiation, method of calculation of the activity parameters of aluminium powders. Results. Quantitative indicators of the reactivity of aluminium micropowders ASD-6 and ASD-6M before and after exposure with ?-radiation were obtained. The radiation source was the Co60 isotope with the energy of 1,17 and 1,33 MeV, i. e. the energy substantially below the threshold of photonuclear reactions. The doses to the powder samples exposure were 1, 2, 4, 8, and 10 Mrad. After γ-radiation exposure the micropowders oxidation start temperature has maximally decreased on 90 and 85 °C; maximal oxidation rate increased by 83 and 36 %; the degree of oxidation (at heating up to 1250 °C) increased by 5,1 %, and minimally decreased by 1,3 % for the ASD-6 and the ASD-6M micropowders, accordingly. The specific thermal effect of oxidation after γ-radiation exposure with all doses was greater than for non-exposed powders; the maximum values of the specific thermal effect was on 199,5 kJ/mol for ASD-6, and 134,8 kJ/mol for ASD-6M higher than thermal effects for non-exposed powders, which significantly exceeds the standard heat of aluminium melting (10,8 kJ/mol). Consequently, such a state of the «aluminium - aluminium oxide» system is characterized by the stored energy, 9 times higher than the standard heat of aluminium melting, which is impossible according to thermodynamics. At the same time, it is known that energy is stored in nanopowders due to the formation of a double electric layer in aluminium particles.