Bottom-up and new compaction processes: A way to tunable properties of nanostructured cobalt ferrite ceramics

In this work we describe a novel bottom-up strategy to process cobalt ferrite CoFe2O4 nanostructured bulk material. This strategy offers the possibility to drive their magnetic and mechanical properties in a wide range of different behaviors. In particular, we show how to tune the blocking temperature along with optimized mechanical strength. This method combines forced hydrolysis in polyol, a soft chemistry route, and Spark Plasma Sintering (SPS) for consolidation. To highlight this method, we also performed compaction by a standard Hot Isostatic Pressing (HIP) process. Thus we compare the nanostructured bulk microstructures (for both compaction techniques) and magnetic static properties to those of several CoFe2O4 nanopowder samples showing particle size and annealing temperatures comparable to those of the nanostructured bulk samples. Microstructure, radio-crystallographic and magnetic studies have been carried out in order to show the optimization of the processing strategy in this work.

► A novel bottom-up strategy combing soft chemistry and Spark plasma sintering was employed to process bulk nanostructured spinel CoFe2O4 with limited particle growth ► Bulk nanostructured spinel CoFe2O4 show superparamagnetic behavior with a blocking temperature significantly higher than room temperature ► Hardness of bulk nanostructured spinel can be varied from that of metal to that of hard ceramic