Abstract
This paper describes a nickel-based cellular material, which has the strength of titanium and the density of water. The material’s strength arises from size-dependent strengthening of load-bearing nickel struts whose diameter is as small as 17 nm and whose 8 GPa yield strength exceeds that of bulk nickel by up to 4X. The mechanical properties of this material can be controlled by varying the nanometer-scale geometry, with strength varying over the range 90–880 MPa, modulus varying over the range 14–116 GPa, and density varying over the range 880–14500 kg/m3. We refer to this material as a “metallic wood,” because it has the high mechanical strength and chemical stability of metal, as well as a density close to that of natural materials such as wood.
Highlights
Cellular materials with spatially organized and repeating pore geometries can have dramatic strength improvements as structural elements shrink to the nanometer scale[1,2,3,4]
When nanocrystalline gold was used in the struts of a nanostructured cellular material, the cellular solid showed dramatic strength enhancement as the strut diameter decreased[3,6], but the conflicting results in nanopillars make it difficult to predict if nanostructured cellular materials made from nanocrystalline metals will exhibit a strength enhancement or reduction
Images of nickel inverse opal material. (b,c) A nickel inverse opal with no coating. (d,e) A nickel inverse opal material with a 21 nm coating of additional electrodeposited nickel. (f) A nickel inverse opal material with a 25 nm coating of additional electrodeposited rhenium-nickel. (g) A closer image of one of the struts in (f). (h) A 2 cm[2] nickel inverse opal material with 500 nm pores and 15 μm thickness grown on a gold/chromium coated glass slide. (i) A nickel inverse opal material with 300 nm pores grown on gold/chromium coated 20 μm thick polyimide
Summary
Cellular materials with spatially organized and repeating pore geometries can have dramatic strength improvements as structural elements shrink to the nanometer scale[1,2,3,4]. Cellular materials with nanometer-scale structural elements exhibit remarkable material properties[5], for example high strength[3,6,7,8,9,10], high energy absorption[4], ultra-low density[1,11,12,13,14], and high specific strength[1,15,16]. Compression tests on nanopillars made from single crystal metals showed that reducing pillar diameter increased pillar strength by up to an order of magnitude more than the bulk material’s strength[17,18,19]. There is a lack of published research on strong nanostructured cellular materials that have enough mass to support loads found in industrial applications
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