| 摘要 |
<p>The invention relates to a process for obtaining hollow metallic micro particles which, due to their reduced density and high specific surface, have a multitude of applications in the preparation of electrically- and thermally-conductive paints and pastes, coatings for protection against electromagnetic fields, powders for producing light pieces by powder metallurgy, moulding paste for making low-cost jewelry, micro containers for biologically active substances, catalysts, chromatographic fillers and the like. According to the invention, the process employs an aqueous suspension of unicellular microorganisms such as yeasts or bacteria or other unicellular biogenous formations, such as erythrocytes, pollen or spores, which are treated, in the first stage, while stirring, at solar or ultraviolet light, at the ambient temperature and pressure and a neutral pH ranging between 4.5...8.5, with a metal compound for surface activation by forming nucleation germs on the cellular membrane, these being intended to catalyze the subsequent deposition and the growth of the metal layer by the reduction of a metallic compound within the solution with a suitable reducing agent, separation of the metallized micro particles by filtration and washing, followed by removal of the biogenous core by alkaline hydrolysis, namely by refluxing for 4...6 h with an aqueous solution of 2...25% NaOH and repeatedly washing with water and organic solvents up to a neutral pH value or by mixing, in a wet phase, with a 2...4 times higher amount of sodium carbonate as powder, followed by drying and calcination of the resulting paste at a temperature of 400...650°C, washing with water up to a neutral pH and drying.</p> |
