Preparation of nanosized rhenium oxide and rhenium-based metal particles by thermal decomposition of organic precursors

The thermal decomposition of the organic derivatives of rhenium Re4O2(OMe)(16) (I), ReMoO2(OMe)(7) (II), Re4-xWxO2(OMe)(16) (III) (x less than or equal to 0.25) and Re2O5(acac)(2) (IV) in air at temperatures below 400 degrees C leads in case of I, III and IV to oxide powders where fine crystalline particles (the size in the range 40-60 Angstrom) are included into amorphous matrix. The crystalline phase has ReO3 type structure. In case of II a mixture of ReO3 and MoO3 phases was obtained. In an inert atmosphere (N-2, Ar) and at 300-400 degrees C Re4O2(OMe)(16) (I) decomposes to ReO3 phase; II and III to a tetragonal phase with Re1-xMxO2 composition (M=Mo, x less than or equal to 0.5; M=W, x less than or equal to 0.25); while IV yields spherical amorphous particles (approximate to 1 mu m size) of rhenium metal. The reduction of I-III in hydrogen atmosphere leads to formation of Re or a Re-alloy (with the sigma-phase type of structure) in the temperature range 300-400 degrees C.