THERMAL-DECOMPOSITION OF THE IRON(III) HYDROXIDE AND MAGNETITE COMPOSITES OF POLY(VINYL ALCOHOL) - PREPARATION OF MAGNETITE AND METALLIC IRON PARTICLES

Upon the precipitation of iron(III) hydroxide (Fe(OH)3) and magnetite in the presence of poly(vinyl alcohol) (PVA) at R<3, PVA is bound to the precipitates in very high yields, where R=[PVA polymer residue]/[Fe ion]. The thermal decomposition of the Fe(OH)3-PVA composite at R=1.0 by heating at ca. 700-degrees-C iii nitrogen for 10 min or more affords almost pure iron metal particles of ca. 200 angstrom in diameter: almost no residues originating from the PVA remain. Before formation of the metallic iron, magnetite particles are produced as its precursor in the 250-650-degrees-C temperature range, where the particle size increases with increasing temperature from ca. 80 up to ca. 350 angstrom in diameter, although these iron and magnetite products are not uniform, but are agglomerate or sintered particles. In these processes, the initially bound PVA effectively functions as a reducing agent during its own decomposition.