Smart Nanocomposites Based on Fe–Ag and Fe–Cu Nanopowders for Biodegradable High-Strength Implants with Slow Drug Release

The present paper deals with the development ofdense Fe–Ag and Fe–Cu high-strength nanocomposites from blends ofnanocomposite powders employing cold sintering (high-pressureconsolidation). Nanocomposite powders were obtained by high-energyattrition milling of micron-scale powder of carbonyl iron (Fe) andnanosized silver oxide powder (Ag2O) as well as ofnanopowders of Fe and cuprous oxide (Cu2O). Phaseidentification was done by X-ray diffraction. Microstructure was viewedin a high-resolution scanning electron microscope. Compacts with ~70%theoretical density were annealed in hydrogen to reduce silver andcuprous oxides to metals and to remove oxide layers from the powderparticle surface. This was followed by cold sintering, i.e.consolidation in a high-pressure gradient at ambient temperature. Theobtained data on the specimen density were analyzed depending on theapplied pressure in the range 0.25–3.00 GPa. At the pressure 3.00 GPa,all the nanocomposites are sintered to more than 95% theoreticaldensity. The compositions demonstrate high mechanical properties inthree-point bending and compression. The nanocomposites were found tohave substantially higher mechanical properties as compared tocomposites with micron-scale grains. It was revealed that Fe–Ag andFe–Cu nanocomposites have a higher ductility as compared tonanostructured Fe, which is due to more plastic Ag and Cu phases in thenanocomposites as compared to the Fe phase. It was shown that loading ofantibiotic Vancomycin into the interconnected nanopore system ofcold-sintered nanocomposites results in nanoencapsulation of the drugand its slow release from the nanocomposite.