Synthesis of Nanostructured Iron Oxide(III) Powders by Rapid Expansion of Supercritical Fluid Solutions

摘要

Nanostructured a-Fe_2O_3 powders were generated by rapid expansion of supercritical fluid solutions (RESS, T=773 K, P=100 MPa) and by rapid thermal decomposition of precursors in solution (RTDS, T-623 K, P=100MPa) on lab RESS-setup from 0,040 M and 0,10 M aqueous solutions of Fe(NO_3)_3. The size of subcrystallites is about 22-29 nm. Comparison of reactivity of #alpha#-Fe_2O_3 powders in a model solid state reaction between a-Fe_2O_3 powders (generated by rESS from 0,040 M solution) and Li_2CO_3 (mole ratio 1:1) with literature data on a-Fe_2O_3 powders produced by other methods shows that its reactivity is markedly higher. A basic essence possibility of zinc ferrite ZnFe_2O_4 formation immediately at the stage of the rapid expansion (T=773K; P=100 MPa) of a supercritical aqueous solution of zinc and iron nitrates (molar ratio Zn:Fe=1:2; C=0.1 M) was shown.