Net Shape Nanostructured Aluminum Oxide Structures Fabricated by Plasma Spray Forming

The plasma spray technique has been used by several researchers to deposit nanostructured ceramic coatings, but there is no available literature discussing how to fabricate a bulk, freestanding nanostructured component by such a technique. In the current study, net shape nanostructured Al2O3 structures have been fabricated using the plasma spray technique. A detailed characterization of the spray-formed Al2O3 structure has been performed using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microhardness measurements. This study validates the feasibility of rapid fabrication of freestanding, near net shape nanostructured Al2O3 components of larger size by plasma spray forming technique. Plasma spray parameters were controlled with a proprietary cooling technique to retain a large fraction of nanosize Al2O3 powder particles in the spray deposit. Partially melted nanosize Al2O3 particles were trapped between the fully melted coarser, micrometer size Al2O3 grains. It was found that densification of the spray deposit has been dominated by both solidification and solid-state sintering. This study proves that a variety of nanostructured materials and their combinations can be fabricated to near net shapes by espousing a similar processing approach.