Low-density interconnected metal foams and methods of manufacture

Patent metadata

Field	Value
Publication number	US-2018311737-A1
Application number	US-201815956993-A
Country	US
Kind code	A1
Filing date	Apr 19, 2018
Priority date	Nov 30, 2015
Publication date	Nov 1, 2018
Grant date	—

Abstract

Ultralow density pure metal foams, with density approaching 0.1% of the bulk density, and synthesis methods using interconnected metallic nanowires are provided. Nanowires of various sizes and metals are synthesized by electrodeposition into nanoporous templates such as anodized aluminum oxide or polycarbonate. The templates are etched away and the nanowires are dispersed into water through a suitable fluid exchange. Surface treatments ensure that nanowires remain sufficiently metallic and physically separated. Wire-water solutions can be dropped directly into liquid nitrogen in the form of droplets or placed into molds of various shapes. A freeze drying technique is employed to turn the resulting ice-wire mixture into a freestanding, low-density foam composed of interlocked nanowires. Finally, sintering or oxidation and reduction treatment of the foam material at elevated temperatures is used to connect the nanowires into an interconnected metallic foam, greatly improving the strength of the structure.

First claim

What is claimed is:

1 . A method for fabricating low density and ultralow density nanostructured metal foams, the method comprising:
(a) forming a liquid dispersion of metal nanowires in a freezable fluid; (b) freezing the liquid dispersion to form an ice-nanowire structure; (c) sublimating the ice-nanowire structure to expose a free standing nanowire foam structure; and (d) binding the nanowire foam structure at points of contact to form an interconnected metal foam monolith.

2 . The method of claim 1 , further comprising:
treating nanowire surfaces with an acid to remove oxide contaminants; and dispersing treated nanowires in a freezable liquid.

3 . The method of claim 1 , further comprising:
treating nanowire surfaces with a surfactant to separate nanowires from each other; and dispersing treated nanowires in a freezable liquid.

4 . The method of claim 1 , wherein said metal nanowires are formed from a metal selected from the group of metals consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.

5 . The method of claim 1 , wherein said metal nanowires have an aspect ratio of length vs. diameter within the range of 2 to 1,000,000.

6 . The method of claim 1 , wherein said dispersion contains wires diluted in volume by a factor of 2 to 10,000.

7 . The method of claim 1 , further comprising:
depositing the liquid dispersion in one or more molds; and freezing the liquid dispersion in the molds.

8 . The method of claim 1 , wherein said binding of points of contact of the ice-nanowire structure is performed by sintering.

9 . The method of claim 1 , wherein said binding of points of contact of the ice-nanowire structure is performed by one or more oxidation and reduction cycle(s) performed at elevated temperatures.

10 . A method for fabricating low density and ultralow density nanostructured metal foams, the method comprising:
(a) preparing a nanoporous membrane template; (b) applying an electrode to one side of the nanoporous membrane template: (c) forming nanowires within the nanoporous membrane template by electrodeposition; (d) releasing the formed nanowires from the membrane template; (e) forming a liquid dispersion of metal nanowires in a freezable fluid; (f) freezing the liquid dispersion to form an ice-nanowire structure; (g) sublimating the ice-nanowire structure to expose an interlocked nanowire structure; and (h) binding the interlocked nanowire structure at points of contact between nanowires to form an interconnected metal foam.

11 . The method of claim 10 , wherein said releasing of formed nanowires comprises:
etching the membrane template to remove the electrode; disintegrating the membrane template to release nanowires; dispersing the released nanowires in a freezable fluid; and agitating released nanowires to separate and randomize nanowires in the freezable fluid.

12 . The method of claim 10 , wherein said nanoporous membrane template comprises an anodized aluminum oxide (AAO) membrane, a polycarbonate membrane, a porous mica membrane or a nanochannel glass membrane.

13 . The method of claim 10 , further comprising:
treating nanowire surfaces with an acid to remove oxide contaminants; and dispersing treated nanowires in a freezable liquid.

14 . The method of claim 10 , further comprising:
treating nanowire surfaces with a surfactant to separate nanowires from each other; and dispersing treated nanowires in a freezable liquid.

15 . The method of claim 10 , further comprising:
depositing the liquid dispersion in one or more molds; and freezing the liquid dispersion in the molds.

16 . The method of claim 10 , wherein said metal nanowires are formed from a metal selected from the group of metals consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.

17 . The method of claim 10 , wherein said metal nanowires have an aspect ratio within the range of 2 to 1,000,000.

18 . The method of claim 10 , wherein said liquid dispersion contains wires diluted in volume by a factor of 2 to 10,000.

19 . The method of claim 10 , wherein said binding of points of contact of the interlocked nanowire structure is performed by sintering.

20 . The method of claim 10 , wherein said binding of points of contact of the interlocked nanowire structure is performed by one or more oxidation and reduction cycle(s) performed at elevated temperatures.

21 . A metallic foam structure having a bulk density and comprising:
(a) an interconnected metallic nanowire network structure; (b) wherein the network structure has a density of about 0.1% of the bulk density.

22 . The metallic foam structure of claim 21 , wherein the network structure has a density from about 20 g/cm 3 to about 1 mg/cm 3 .

23 . The metallic foam structure of claim 21 , wherein said metallic nanowire network structure is formed from one or more metals selected from the group of metals consisting of consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.

Assignees

• Univ California
• Lawerence Livermore Nat Security Llc
• Nat Tech & Eng Solutions Sandia Llc

Inventors

• Burks Edward C
• Gilbert Dustin A
• Liu Kai
• Kucheyev Sergei O
• Felter Thomas E
• Colvin Jeffrey D

Classifications

• B22F1/0547

  Nanofibres or nanotubes · CPC title

• B22F2301/10

  Copper · CPC title

• C25D1/04

  Wires; Strips; Foils · CPC title

• C25D1/006

  Nanostructures, e.g. using aluminium anodic oxidation templates [AAO] · CPC title

• B22F3/1121 Primary

  by using decomposable, meltable or sublimatable fillers · CPC title