Materials Science Research Lecture
Abstract: To create metallic scaffolds or microlattices with defined sub-millimeter strut architectures, we develop a new method, Extrusion 3D-Printing, consisting of two simple steps. First, metal oxide particle suspension (inks) are extruded, in air and at ambient temperature, into linear struts creating self-supporting 3D cellular structures. Second, the oxides are hydrogen-reduced to metal and sintered into dense metallic struts.
We describe here micro-lattices made of three metals - iron, nickel and tungsten - created from inks consisting of the respective metal oxides. In all cases, thermochemical reduction and sintering of the 3D-printed oxide scaffolds results in large shrinkages (up to 80% by volume) but without cracking or distortion, as investigated via in-situ tomography. For tungsten micro-lattices created from WO3 particle inks, reduction and partial sintering creates micro-pores within the W struts (advantageous if high surface area is needed). Full sintering of the W struts (desirable for mechanical performance) can be achieved through the addition of 0.5 wt% NiO to the slurry, which, once reduced to Ni, accelerates the sintering of the reduced submicron W particles.
We also demonstrate micro-lattices made from pure metallic powder inks (Fe, Ni and Cu) as well as blends of metallic powders: (i) Ni+Mn+Ga, resulting in lattices with microporous Ni-Mn-Ga alloy struts showing twinning and (ii) Nb+NiTi, leading to microporous struts consisting of liquid-phase-sintered NiTi-Nb.
Biography: David Dunand received a BS/MS degree at the Swiss Federal Institute of Technology (ETH, Zurich) in materials engineering in 1986 and a Ph.D. in materials science and engineering from the Massachusetts Institute of Technology (MIT) in 1991. After serving on the MIT faculty until 1997, he joined Northwestern University (NU). His research focuses on processing, structure and mechanical properties of metallic alloys, composites and foams. Examples range from freeze-casts iron foams for batteries to selective-laser-melted aluminum scaffolds for light-weight structures, to creep- and oxidation-resistant Al-, Ni-, Co- and Fe-based alloys for engines and gas turbines. Dunand is a fellow of ASM International (the Materials Information Society) and a fellow of TMS (the Minerals, Metals and Materials Society). His awards include the 2012 Materials Science & Engineering A Journal Prize, the Distinguished Scientist/Engineering Award Structural Materials Division of TMS and two departmental "Teacher of the Year" Awards at NU. Dunand is co-Founder and co-Chief Scientist of NanoAl, LLC, a start-up company based in Skokie (IL) developing high-strength, high-temperature aluminum alloys in cast, wrought and additively-manufactured form.
Refreshments served at 3:30pm in the Spalding Laboratory Lobby.