| Tikalon Blog is now in archive mode.
An easily printed and saved version of this article, and a link
to a directory of all articles, can be found below: |
|
This article |
| Directory of all articles |
The Incredible Lightness of Being
December 5, 2011
Lighter is usually better. That clunky
laptop computer that you may have owned years ago has been replaced by something smaller and lighter, possibly a
tablet. If you have the function, why do you need the mass? On a fundamental
mechanics level, this is what
carbon nanotubes offer,
strength without the bloat. Another low density functional material is the
aerogel, which I wrote about in a
previous article. (Carbon Nano-Aerogel, March 14, 2011)
A
regular gel, is a
colloid of interconnected particles "floating" in a
liquid. For example, a
gelatin dessert is a gel in which
protein molecules are contained in
water. Gels are interesting materials, since they have
mechanical properties like
solids, but they have a
density similar to that of a liquid.
In an aerogel, the liquid is replaced by a
gas, so aerogels have very low density. They are commonly used as a high-tech
thermal insulators in
aerospace applications for which
weight is an important parameter. It's not surprising that aerogels were used as a thermal insulation material on the
Mars Rovers. They are useful, also, for
vibration damping.
A common aerogel is composed of
silica glass and air, and it has just 0.01% the density of the glass itself.
Carbon is another popular solid phase for aerogel materials, and carbon aerogels are excellent
electrodes for
electric double-layer capacitors (supercapacitors), since they have a high surface area.
A research team of scientists from
HRL Laboratories (Malibu, CA), the
University of California at Irvine, and the
California Institute of Technology have just published a paper on a new, lightweight material in the November 18, 2011, issue of
Science.[2-5] The density of this material, which they term an ultralight metallic microlattice, is just 0.9 mg/cc. This density just breaks the apparent record of 1.0 mg/cc for a silica gel,
as quoted in Wikipedia.
This new material is a
lattice array of hollow tubes produced by
electrolessly nickel plating a
template formed from a
photopolymer.[1] The fabrication process was developed by HRL senior scientist,
Alan Jacobsen,[5] and it's adaptable to metals other than nickel.[3] The interconnected hollow tubes have a wall thickness of just 100
nanometers.[5]
One important property of this material is that its
Young's modulus scales with density (ρ) as ρ
2. Ultralight aerogels and carbon nanotube
foams have a Young's modulus that scales a ρ
3. The ultralight metallic microlattice material shows complete recovery from 50% compressive strain, and it has an energy absorption like that of
elastomers.
A picture is worth a thousand words, but my repeated requests to HRL Laboratories for permission to use a photograph of their microlattice material were ignored.
Click here for the image at their web site)
The unique mechanical properties of this material are a consequence of its
hierarchical architecture that has features at the nanometer,
micrometer and
millimeter scales.[2] Bill Carter, manager of the Architected Materials Group at HRL, makes the analogy to larger structures.
"Modern buildings, exemplified by the Eiffel Tower or the Golden Gate Bridge, are incredibly light and weight-efficient by virtue of their architectures. We are revolutionizing lightweight materials by bringing this concept to the materials level and designing their architectures at the nano and micro scales."[5]
Says
Lorenzo Valdevit, coauthor of the paper, Assistant Professor of
Mechanical and Aerospace Engineering, and also
Chemical Engineering and Materials Science, at the University of California at Irvine,
"Materials actually get stronger as the dimensions are reduced to the nanoscale... Combine this with the possibility of tailoring the architecture of the micro-lattice and you have a unique cellular material."[2]
As reported in the
Los Angeles Times, the material will float in the air for more than ten seconds when dropped from shoulder height.[3] The research was funded by the
DARPA, the Defense Advanced Research Projects Agency.[2,5] HRL Laboratories is a corporate research-and-development laboratory owned by
The Boeing Company and
General Motors.
The Unbearable Lightness of Being is a 1984 novel by Milan Kundera about
Czechoslovakia in 1968. It was made into a 1988 movie.[6]
References:
- T. A. Schaedler, A. J. Jacobsen, A. Torrents, A. E. Sorensen, J. Lian, J. R. Greer, L. Valdevit and W. B. Carter, "Ultralight Metallic Microlattices," Science, vol. 334 no. 6058 (November 18, 2011), pp. 962-965.
- Multidisciplinary team of researchers develop world's lightest material, University of California at Irvine Press Release, November 17, 2011.
- Deborah Netburn, "Scientists invent lightest material on Earth. What now?" LA Times Blog, November 17, 2011.
- PR Web, HRL Researchers Develop World's Lightest Material, HRL Laboratories Press Release, November 18, 2011.
- HRL Researchers Develop World's Lightest Material, HRL Laboratories Press Release, November 18, 2011.
- The Unbearable Lightness of Being (1988, Philip Kaufman, Director) on the Internet Movie Database.
Permanent Link to this article
Linked Keywords: Laptop computer; tablet computer; mechanics; carbon nanotube; strength of materials; aerogel; gel; colloid; liquid; gelatin dessert; protein molecule; water; mechanical properties; solid; density; gas; thermal insulator; aerospace; weight; Mars Rover; vibration damping; silicon dioxide; silica glass; carbon; electrode; electric double-layer capacitors; HRL Laboratories (Malibu, CA); University of California at Irvine; California Institute of Technology; Science; Wikipedia; truss; lattice array; electroless nickel plating; template; photopolymer; Alan Jacobsen; nanometer; Young's modulus; foam; elastomer; Dan Little; HRL Laboratories, LLC; hierarchical; architecture; micrometer; millimeter; Lorenzo Valdevit; Mechanical and Aerospace Engineering; Chemical Engineering and Materials Science; Los Angeles Times; DARPA; The Boeing Company; General Motors; The Unbearable Lightness of Being; Czechoslovakia.