title: Synthesis of Nanostructured/Macroscopic Low-Density Copper Foams Based on Metal-Coated Polymer Core-Shell Particles.
abstract: A robust, millimeter-sized low-density Cu foam with ∼90% (v/v) porosity, ∼30 nm thick walls, and ∼1 μm diameter spherical pores is prepared by the slip-casting of metal-coated polymer core-shell particles followed by a thermal removal of the polymer. In this paper, we report our key findings that enable the development of the low-density Cu foams. First, we need to synthesize polystyrene (PS) particles coated with a very thin Cu layer (in the range of tens of nanometers). A simple reduction in the amount of Cu deposited onto the PS was not sufficient to form such a low-density Cu foams due to issues related to foam collapse and densification upon the subsequent polymer removal step. Precise control over the morphology of the Cu coating on the particles is essential for the synthesis of a lower density of foams. Second, improving the dispersion of PS-Cu particles in a suspension used for the casting as well as careful optimization of a baking condition minimize the formation of irregular large voids, leading to Cu foams with a more uniform packing and a better connectivity of neighboring Cu hollow shells. Finally, we analyzed mechanical properties of the Cu foams with a depth-sensing indentation test. The uniform Cu foams show a significant improvement in mechanical properties (∼1.5× modulus and ∼3× hardness) compared to those of uncontrolled foam samples with a similar foam density but irregular large voids. Higher surface areas and a good electric conductivity of the Cu foams present a great potential to future applications.
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Sung Ho
authors.identifier: http://orcid.org/0000-0002-0994-8098
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Atomic Weapons Establishment , Aldermaston, Reading RG7 4PR, United Kingdom.
authors.forename: Nick
authors.initials: N
authors.lastname: Bazin
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Jessica I
authors.initials: JI
authors.lastname: Shaw
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Jae-Hyuck
authors.initials: JH
authors.lastname: Yoo
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Worsley
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Joe H
authors.initials: JH
authors.lastname: Satcher
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: John D
authors.initials: JD
authors.lastname: Sain
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Kuntz
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Sergei O
authors.initials: SO
authors.lastname: Kucheyev
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Theodore F
authors.initials: TF
authors.lastname: Baumann
authors.affiliation: Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States.
authors.forename: Alex V
authors.initials: AV
authors.lastname: Hamza
keywords: copper; core−shell particles; electroless deposition; metal foam; porous materials