ERI: Digital Alloying with Metal Precursor Inks

This Engineering Research Initiation (ERI) grant supports fundamental research on digital alloying which uses metal precursor inks and additive manufacturing to fabricate parts with desired alloy composition. Controlling the alloy composition, and thus the microstructure, influences the properties of the final product. The current approach to controlling the alloy composition during the 3D printing of a part is to use individual metal powders and melt them together using a high-power laser beam. Laser melting can lead to undesirable residual stress, distortion, and cracking in the manufactured part, however, and digital printing with metal precursor inks can avoid these issues. This process uses chemical reactions and modest heat to form metal alloy structures. The research focuses understanding the how the process of fabricating metal alloy structures with different elemental ratios by dispensing individual metal precursor inks using an inkjet printer affects the properties and performance of resulting parts. This work has the potential to substantially reduce the cost associated with metal additive manufacturing, by moving way from expensive Laser 3D printing machines and toward Inkjet printers that use metal precursor inks. These Inkjet printers could be used in small-scale industries, teaching institutions, and workshop activities. Additive manufacturing by digital alloying can open the door to new applications in many industrial sectors which benefits the U.S. economy. The project provides training opportunities in engineering for female and under-represented minority students, encourages presentations at conferences, and stimulates interest in STEM among K-12 students. This project aims to involve research that gains insight into the digital printing of alloy structures of desired composition by ex-situ mixing of individual metal precursor inks in appropriate proportions. The mixing is done on a substrate after jetting the inks. Printing with metal precursor inks uses a bottom-up chemical/modest heat route to form the metal alloy structures as opposed to top-down physical/high temperature route used by laser 3D printers. Despite the large body of work on printing metallic inks, mixing two or more metal precursor inks to form an alloy has not been thoroughly explored. This project develops an understanding of thermally induced reduction of multi-metal precursor inks and decomposition of the metal complexes along with the nucleation and growth processes. The reduction temperatures are determined by thermogravimetric analysis. By obtaining a better understanding of the degree of mixing after jetting and how multi-metal precursor inks are reduced, researchers can more effectively predict and manufacture multi-metal functional metal alloy parts with desired microstructures. The project has the potential to create a library of metal precursor inks with different compositions and properties, which can be used to print and sinter a variety of multi-functional components. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.