Additive Manufacturing: Novel Metal Particle Technology

Abstract

In this program we developed a novel method for making metal thin films, particularly Ni, but likely to work for all base metals. The method consists of creating a paste consisting of a physical mixture of urea and metal in an oxide state, either metal oxide particles or molecular species such as chloride and nitrides, spreading on a surface, and heating in an inert atmosphere. The successful development of this technique is the first step in the larger goal: apply a form of Reduction Expansion Synthesis (RES), a technique developed by an NPS team, to improve Metal Additive Manufacturing (M-AM). This goal was based on an analysis of the current fundamental problems with M-AM technology. These can be distilled to the following: i) The large size and high temperature (>1500 C) of the laser heated zone currently employed to sinter metal particles together, and ii) the size of the metal particles available to create metal objects. This leads to the production of objects in which the ‘roughness’ is of the order of particle/melting method size, ca. 50 micron. The ability demonstrated in the present work to create metallic films using a modified RES process in which crystallite size and thickness is of the order of 1 micron indicates a path forward for solution to the fundamental problems with current M-AD technology. Proposition: Deploy the modified RES process in existing ‘writing’ style plastic AM devices. The pastes, for example a physical mixture of urea and NiCl, should be ‘drop in’ replacements for plastic precursor pastes currently used. Heat the resulting written pattern with either a laser, or in an inert atmosphere furnace. Metal layers, of a micron scale, will form that reliably follows deposited pattern. Repeat for additional layers, as per standard AM protocols.