Exothermic behavior and microstructure control of porous Ni-Al compounds synthesized by ultrafast self-exothermic reaction

Abstract

Porous Ni-Al compounds exhibiting distinct reaction behaviors and pore structure characteristics were fabricated via an instantaneous and synchronous self-exothermic reaction. As the heating rate increased from 2 to 20 °C/min, the porosity decreased significantly from 62.8% to 29.4%. The intensity of the self-exothermic reaction increased with increasing heating rate, and when the heating rate exceeded 5 °C/min, noticeable sample deformation occurred. Cyclic oxidation tests revealed that the oxide layer remained relatively continuous and dense, and adhered well to the product matrix. This layer was identified as an Al2O3, formed because the outward diffusion of Al is kinetically favored over that of Ni, which was strongly influenced by both the diffusion rate and oxidation temperature.