Multifunctional 3D‐Printed Cellular MAX‐Phase Architectures

Abstract

MAX phases are a family of materials that could replace in the near future some of the most advanced materials employed in distinct technological applications, which could be widened through the development of highly porous MAX structures. Here we present for the first time the additive manufacturing of 3D patterned cellular Cr2AlC MAX-phase architectures using a direct ink writing technique. These architectures exhibit multifunctional properties, in particular, high strength, excellent electrical conductivity, tailored heat dissipation and good thermal cycling resistance.The reported findings will spark, through a versatile and feasible manufacturing approach, to open new research fields of porous MAX phases on advanced demanding applications in the energy and catalysis fields, or in less explored uses such as vibration and sound damping materials.

Processing of MAX phases: From synthesis to applications

“…20 The thermal response is the sum of the electron (Ƙ e ) and phonon (Ƙ ph ) conductivities, where each contribution depends on several factors such as temperature, composition (mostly the "A" element), grain size, secondary phases/impurities, and defect concentration. 20,126,127 Overall, MAX phases are good phonon conductors because of the M-X bonds, and particularly composition containing Al due to the lower scattering since it is light and mobile. Furthermore, phonon contribution is sensitive to the "n" value, where the distribution is wider as follows 211 > 312 > 413.…”

“…236 Regarding the 3D porous Cr 2 AlC architectures, MAX phase powders were mixed with polyethylenimine as dispersant, hydroxypropyl methylcellulose as thickening agent, and ammonium polyacrylate as flocculant. 126 The resulting ink was extruded by robocasting, followed by a drying process and consolidation by SPS under pressureless conditions. The 3D structures present a porosity between 60% and 64% ( Figure 9), with excellent mechanical performance, high electrical conductivity, tailored heat dissipation and good thermal cycling resistance.…”

“…Robocasting and direct ink writing-based on the same principle -have been used to produce complex 3D structures based on Cr 2 AlC ( Figure 9) and Ti 2 AlC, respectively. 126,236 The processing was described above in Section 4.3 (porous architectures).…”

“…As with the electrical response, some MAX phases exhibit larger thermal conductivities than their corresponding transition metals 20 . The thermal response is the sum of the electron (Ƙ e ) and phonon (Ƙ ph ) conductivities, where each contribution depends on several factors such as temperature, composition (mostly the “A” element), grain size, secondary phases/impurities, and defect concentration 20,126,127 . Overall, MAX phases are good phonon conductors because of the M‐X bonds, and particularly composition containing Al due to the lower scattering since it is light and mobile.…”

“…This approach can produce bimodal porosity, which is based on millimeter range channels between struts, and micro‐porosity within struts due to incomplete densification. Well‐defined, complex structures have been recently reported for Ti 2 AlC and Cr 2 AlC, 126,236 . As with the replica method and direct foaming, control of rheological properties is crucial.…”