Exothermic behavior and thermodynamic analysis for the formation of porous TiAl3 intermetallics sintering with different heating rates

Abstract

Abstract Porous TiAl3 intermetallcis are of great interest due to its excellent properties and widely applied in filtering apparatus, separation material and catalyst carrier. In this study, interconnected pore-structures have been synthesized by diffusion or thermal explosion (TE) reaction sintering with different heating rates. The thermal characteristics such as temperature-time curves, exothermic change and visual images indicate that the sample experienced a significant TE reaction at higher heating rates. Results shown that the sample was ignited at 672\u202f°C and then rapidly increased to combustion temperature of 1169, 1110 and 933\u202f°C in tens of seconds with the heating rate of 15, 10 and 5\u202f°C∙min−1 respectively. Meanwhile, TE represented the uniformity of volume combustion, instantaneous reaction and rapid cooling to furnace temperature, the amount of heat released during TE reaction dropped from 1303 to 963\u202fJ\u202fg−1. This indicates that the entire sintering process was controlled by TE and the pre-diffusion reaction before the melting temperature of Al atom, which would affect the subsequent combustion reaction. Thermodynamic data explained that the reaction mechanism is mainly step-controlled diffusion reaction at a low heating rate (1\u202f°C∙min−1), while the energy gradually accumulated and thermal explosion (TE) reaction become obvious with the increasing of heating rate (from 2 to 15\u202f°C∙min−1).