• A fully vapor-phase route was proposed to fabricate porous alloys via VPA-VPD. • Porous Cu 95 Ti 5 , Cu 50 Ti 50 , and Ti 95 Cu 5 were fabricated by VPA-VPD. • Formation of porous Cu 50 Ti 50 was discussed from thermodynamic and kinetic prospects. Porous Cu-Ti alloys are promising for advanced applications but remain challenging to fabricate through conventional dealloying due to the refractory nature of Ti and its susceptibility to passivation. Herein, we report a fully gaseous approach that seamlessly integrates vapor phase alloying (VPA) with subsequent vapor phase dealloying (VPD) for the synthesis of porous Cu-Ti alloys. This study demonstrates that the VPA process effectively incorporates Zn into various pristine alloys (Cu 95 Ti 5 , Cu 50 Ti 50 , and Ti 95 Cu 5 ), forming Cu-Ti-Zn intermediate phases. Subsequent VPD, through the selective sublimation of Zn, yields a bicontinuous ligament-pore structure. Notably, the initial alloy composition dictates the final microstructure: a uniform porous framework forms from Cu 95 Ti 5 , a regularly aligned, comb-like architecture with secondary pores emerges from Ti 95 Cu 5 , and a unique composite structure with surface-enriched Cu develops from Cu 50 Ti 50 . Specially, the formation of the composite structure in porous Cu 50 Ti 50 is discussed based upon the Gibbs free energy of formation of Ti-Zn and Cu-Zn, the diffusion and saturated vapor pressure of Ti and Cu, which results in different alloying scenarios of Ti and Cu with Zn during VPA. This work not only establishes the VPA-VPD method as a versatile and damage-free route for creating porous alloys from challenging systems, but also provides fundamental insights into the solid-state diffusion mechanisms governing structure evolution.
Yu et al. (Sun,) studied this question.