High Energy Density Processing of a Free Form Nickel–Alumina Nanocomposite

Abstract

The development of a free form bulk Nickel reinforced Alumina matrix nano composites using Air Plasma Spray and laser processing has been presented. The process consumes less time and requires further minimal machining and therefore is cost effective. The relative differences in using APS over laser processing in development of bulk metal-ceramic nanocomposites have been discussed. The process intricacies involved during processing such as material specific mandrel selection, plasma-particle interaction are highlighted. Electroless coating has been used to uniformly disperse Nickel in alumina matrix as a source material. The electroless Ni coated alumina particles are subjected to both laser processing and Air Plasma Spraying with optimized parameters. Consolidation by laser processing could not be achieved as the laser beam was reflective to Nickel. On the other hand, APS Ni–alumina nanocomposite with a cylindrical shape of 1.2″ OD × 1″ ID × 1.5″ length has been fabricated with minimum or no surface defects. HRTEM pictures revealed the nanostructure retention thereby corroborating the fact that bulk nanostructures can be made using Air Plasma Spray. XRD analysis confirmed the phase transformation from alpha alumina to gamma alumina and oxidation of Ni to NiO. Subsequent reduction of NiO to metallic nickel using hydrogen atmosphere has also been demonstrated. Mechanical properties such as, hardness (1025 HV) and fracture toughness (5 MPa m1/2) for the nanocomposite are presented herein.