Article: Hassani-Gangaraj, M; Veysset, D; Nelson, KA; Schuh, CA; “Impact-Bonding with Aluminum, Silver, and Gold Microparticles: Toward understanding the role of native oxide layer”, Applied Surface Science, 476: 528-532
Abstract: Bonding during cold spray has been phenomenologically associated with the breakup of the native surface oxide layer to produce intimate metallic contacts. Here, we resolve the instant of bonding for metals both with and without a significant native oxide, through direct in-situ observation of individual microparticles. We show that fracture of the native oxide layer is not the only physical barrier to impact adhesion; even noble gold must exhibit unstable jetting upon impact in order to attain bonding. However, surface oxide certainly presents an additional barrier to bonding and can increase the critical velocity by a large factor.
Funding Text: This research was accomplished through a cooperative research agreement with the U.S. Army Research Laboratory, Contract: W911NF-15-2-0034, “Development of Additive Manufacturing and Advanced Materials Processing for the DOD”. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0018091. Support was provided in part by the U.S. Army Research Office through the Institute for Soldier Nanotechnologies, under Cooperative Agreement Number W911NF-18-2-0048. Support for equipment was also provided through the Office of Naval Research DURIP Grant No. N00014-13-1-0676. The authors have no competing interests to declare.