PREPARATION AND CHARACTERIZATION OF UNIFORM PARTICLES OF PURE AND COATED METALLIC COPPER

Colloidal copper of narrow size distribution in the micrometre size range was prepared by two different methods. The first procedure involved the reduction of uniform spherical particles of copper(II) basic carbonate with hydrogen at 150-200-degrees-C. The improved method consisted of a two-step process in which the copper(II) basic carbonate was converted to copper(II) oxide and then treated with hydrogen. In order to preserve particle integrity, the precusor powders were coated with small (approximately 10 nm) silica particles (Ludox HS or 130M) before reduction with hydrogen. In the second method, cubic metallic copper particles were generated in situ in solutions containing Cu(NO3)2, urea and NH2OH.HCl. The uniformity of the dispersion was achieved by controlled growth of the particles on performed nuclei.