A Solution Synthetic Route to Nanophase Cobalt Film and Sponge

An efficient, low-cost solution-chemical route to nanophase cobalt as dense films and sponges has been developed. Co(NO 3 ) 2 ·6H 2 O and Co(OAc) 2 ·4H 2 O were mixed with triethanolamine in methanol, and the solution was evaporated in air to a viscous liquid. Heating at 10 °C min - 1 to 470 and 500 °C yielded highly porous sponges consisting of 3−6 and 9−11 nm sized face centered cubic (fcc) cobalt crystallites, respectively. Spin-coating on alumina and aluminum substrates with a 1 M Co-precursor solution and subsequent heating at 10 °C min - 1 to 500 °C yielded dense films of <20 nm sized fcc cobalt crystallites. The microstructural and compositional evolution process on heating to form the cobalt metal was studied by TGA, DTA, and FT-IR spectroscopy, powder X-ray diffraction, TEM-EDS, and SEM-EDS. The C, N, and O contents could be kept low, 0.5, 0.02, and 0.2 wt %, respectively, at 700 °C, but the carbon content could also reproducibly be adjusted to up to 13 wt % C in excess, by varying the precursor composition.