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

Abstract

The present paper deals with the development of dense Fe–Ag and Fe–Cu high-strength nanocomposites from blends of nanocomposite powders employing cold sintering (high-pressure consolidation). Nanocomposite powders were obtained by high-energy attrition milling of micron-scale powder of carbonyl iron (Fe) and nanosized silver oxide powder (Ag2O) as well as of nanopowders of Fe and cuprous oxide (Cu2O). Phase identification was done by X-ray diffraction. Microstructure was viewed in a high-resolution scanning electron microscope. Compacts with ~70% theoretical density were annealed in hydrogen to reduce silver and cuprous oxides to metals and to remove oxide layers from the powder particle surface. This was followed by cold sintering, i.e. consolidation in a high-pressure gradient at ambient temperature. The obtained data on the specimen density were analyzed depending on the applied pressure in the range 0.25–3.00 GPa. At the pressure 3.00 GPa, all the nanocomposites are sintered to more than 95% theoretical density. The compositions demonstrate high mechanical properties in three-point bending and compression. The nanocomposites were found to have substantially higher mechanical properties as compared to composites with micron-scale grains. It was revealed that Fe–Ag and Fe–Cu nanocomposites have a higher ductility as compared to nanostructured Fe, which is due to more plastic Ag and Cu phases in the nanocomposites as compared to the Fe phase. It was shown that loading of antibiotic Vancomycin into the interconnected nanopore system of cold-sintered nanocomposites results in nanoencapsulation of the drug and its slow release from the nanocomposite.