title: Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.
abstract: Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.
authors.affiliation: Department of Materials Science &Engineering, Iowa State University, Ames, IA 50011 USA.
authors.forename: Simge
authors.initials: S
authors.lastname: Çınar
authors.affiliation: Department of Materials Science &Engineering, Iowa State University, Ames, IA 50011 USA.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Tevis
authors.affiliation: Department of Materials Science &Engineering, Iowa State University, Ames, IA 50011 USA.|Micro-electronics Research Center, Iowa State University, Ames, IA 50011 USA.
authors.forename: Jiahao
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Materials Science &Engineering, Iowa State University, Ames, IA 50011 USA.|Micro-electronics Research Center, Iowa State University, Ames, IA 50011 USA.|Center for bio-plastics and bio-renewables, Iowa State University, Ames, IA 50011 USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Thuo