Porous CoAl 3 intermetallics have great catalytic potential. However, its high porosity and controllable preparation are still incipient. In this paper, the effect of isothermal treatment on the near-net formation process of porous CoAl 3 material is studied, and the phase transformation process and diffusion kinetics of the Co/Al diffusion couple in the solid-phase diffusion stage are described. The results show that isothermal treatments in the range of 510–550 °C reduce the exothermic intensity of the thermal explosion (TE) reaction. The holding time of 30 min at 530 °C facilitates the near-net formation of porous CoAl 3 . The isothermal treatment does not affect the phase composition of the final product. Still, it causes changes in the phase and depth of the diffusion, affecting the exothermic strength and skeleton morphology. Based on the phase transition and thermodynamic analysis , the CoAl phase formation is the key to reducing the exothermic intensity. The diffusion kinetics indicates that the low diffusion activation energy of the CoAl phase (Q 1 = 1.66 kJ mol −1 ) is the main reason for the preferential formation. And the exponential kinetic factor of the second diffusion layer (n 2 = 0.75) explains its high diffusion depth.
Porous CoAl 3 is a candidate material in the field of catalytic due to its high porosity, good thermostability and quasicrystal structure. However, its rapid preparation are still a challenge, and the oxidation resistance need to be further investigated. In this work, we have rapidly prepared porous CoAl 3 by thermal explosion (TE) reaction and studied its oxidation process . The results show that two exothermic peaks at 616 °C and 646 °C, corresponding to the solid-phase diffusion and TE reaction, respectively. The heat released from the two reactions led to the expansion of the compact, which reached a maximum of 104% at 800 °C, and the corresponding open porosity reached at 53%. The pore sources include the original pores during the green compact pressing process, the Kirkendall pores generated by the solid-phase diffusion process and the in-situ pores generated by the Al consumption after the TE occurs. The cyclic oxidation of porous CoAl 3 at 700 °C for 130 h only increased the weight by 1.52%, forming a continuous protective oxide film on the surface of the skeleton. It has been found that porous CoAl 3 can combine the oxidation resistance of Co–Al monoliths alloys and the high porosity of porous materials, which have potential applications in the field of catalysis such as methanation at 600–700 °C.
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