Isotope Exchange between ¹⁸O₂ Gas and Mechanoactivated Oxide NdMnO_3+δ

Abstract

sotope exchange of oxygen 18О2 with oxides NdMnO3+δ was investigated. The oxide was obtained from oxides Nd2O3 and Mn2O3 using a ceramic technology with annealing in air at 1400°C for 90 hours followed by cooling in a furnace. A planetary mill AGO-2 with a centrifugal factor of g = 60 was used for mechanical treatment of oxides. The study of isotope exchange was carried out by nuclear microanalysis. The concentration of the isotopes 18O and 16O in oxides was determined using a Van de Graaff accelerator and 18O(p, α)15N and 16O(d, p)17O* reactions at the energies of incident beams 762 and 900 keV. Isothermal annealing of powders was carried out in oxygen, enriched to 80% by the isotope 18O. It was established that the concentration of the isotope 18O in mechanically activated powders was several times higher than in the initial micropowder under the same conditions of annealing. The effect increased with increasing of mechanical activation time (30 - 300 s). The isotope exchange parameters connected with the processes at the boundaries of the particles of mechano-activated powder and within their volume were analyzed.

Structural Properties of Mechanically Activated Rare-Earth Manganites

“…17 are processed using the isotope exchange model, in which only oxygen ions from the external atomic layer of the oxide particle participate. In this case we have "relaxation" type dependences C(t) for powders [24][25][26][27]…”

“…The OIE results at 500°С [26] were described in the model allowing for diffusion of oxygen atoms in oxide particles (see Fig. 19).…”

Isotope Exchange between ¹⁸O₂ Gas and Mechanoactivated Oxides of the Family Rare Earth – Manganese – Oxygen

“…In this regard, the present study deals with the bulk diffusion of tracer oxygen in undoped manganites of rare earth metals RMnO 3+δ (LaMnO 3+δ , NdMnO 3+δ , SmMnO 3+δ ) at low temperatures. The procedure described in the works [6,7] has been used to measure the low values of the diffusion coefficients. It is based on the study of the kinetics of oxygen isotope exchange between gaseous oxygen 18 O 2 and micro-and nanopowder oxides.…”