Exploring material chemistry for direct ink writing of reactively formed conductors

Abstract

<p>Rational design of a reactive material for 3D printing robust electrical conductors which can be integrated into parts or systems.</p>

Multifunctional Reactive Nanocomposites via Direct Ink Writing

“…In instances when the reaction did not go to completion, such as due to excessive heat losses, the intermetallic phases Al 3 Zr and Al 2 Zr are also formed (Figure 3a). Our observations are consistent with previous reports [13,23] of phase formation in the Al-Zr-C system: that the reaction progresses from the exothermic mixing of Al/Zr in the solid phase into Al melting, which enhances further mixing of both Zr and C, promoting the formation of ZrC. When the reaction is retarded due to heat losses, some Al x Zr intermetallics and Al x Zr y C z ternary phases are formed alongside ZrC.…”

“…Similar to analogous PVD materials, [ 13 ] the full SHS reaction of printed Al/Zr/C nanocomposite powders results in complete conversion to ZrC and Al producing a coherent multiphase microstructure which is electrically conductive (Figure 2g,h). In instances when the reaction did not go to completion, such as due to excessive heat losses, the intermetallic phases Al 3 Zr and Al 2 Zr are also formed ( Figure ).…”

“…In a recent publication, [ 13 ] we presented the rational design of a reactive material system for direct ink write 3D printing which forms a functional product: a mechanically robust electrically conductive cermet formed via self‐propagating high temperature synthesis (SHS). Following a method taught [ 14 ] by several of the co‐authors, this material system is composed of a pair of elements which react to form a low‐resistivity carbide, ZrC, releasing sufficient heat to melt and reflow a low‐resistivity matrix phase, Al, thereby producing a mechanically and electrically robust cermet ( Figure ).…”

“…The resulting particles have a median equivalent diameter of 4.4 µm (Figure S1, Supporting Information) and a mean aspect ratio of 0.72 ( n = 80 883). The particles exhibit an ignition temperature of 427 ± 20 °C (see Experimental Section), indicating a highly refined microstructure (analogous PVD films with a trilayer spacing of 183 nm have an ignition temperature of 365 °C [ 13 ] ). This is a significant advance compared to other studies employing ball‐milled powders of Al/Zr/C, which did not exihibit substantive reaction during slow heating until Al melts at 660 °C, and had unreported sizes and ignition temperatures.…”

“…In contrast, Ag inks are conductive as‐printed and can be made more conductive by annealing, but they can be susceptible to electromigration. [ 24 ] The Al/ZrC cermet product is expected [ 13 ] to be more electromigration‐resistant, which could be useful in high‐current density applications. However, it is challenging to directly assess the product's electromigration‐resistance, as standard test apparatus are designed for significantly lower resistivity materials.…”