University of Wisconsin - Madison Materials Research Science and Engineering Center Education and Outreach

Available Now! 
The Liquidmetal® "Atomic Trampoline" 
Demonstrations with Amorphous Metal

Here's your chance to buy a very neat amorphous metal demonstration kit which includes:
 
  • a stainless steel base
  • a stainless steel base with a 1/8 inch thick disk of Liquidmetal® (Zr41.2Be22.5Ti13.8Cu12.5Ni10.0) glued to it
  • two clear plastic tubes which slide over the top of the bases
  • two hardened steel ball bearings
  • a booklet complete with pictures and figures  which help explain the behavior of the amorphous metal, as well as some other activities to try with the demonstration set-up
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    Watch a movie of the Liquidmetal® demonstration.


    The price of the kit is about $50.00, and is available through the Institute for Chemical Education (ICE).

    What is the science behind this unique demonstration?
    For more information, see Glassy Metals in the April 2004 issue of Discover.

    The ball bearing is being dropped from the same height,  down identical plastic tubes, onto two different surfaces, one stainless steel, and one an amorphous metal called Liquidmetal®.  Several ways in which the energy of the ball bouncing is dissipated are via sound, random collisions with the sides of the tubes,  and friction with the air.  Assuming that for both bases, these factors are, on average, the same, the difference in the ball bouncing must be due mainly to the difference in energy transfer between the ball and the two surfaces.   The fact that the ball bounces for so much longer on the amorphous metal surface indicates a much different energy transfer interaction than that of the stainless steel base.  In order to understand the different ball-surface interactions, we need to look more carefully at the structures of the two materials,  stainless steel is a crystalline solid and Vitreloy is an amorphous metal.

    What is a crystalline material?

    Most metals, including stainless steel, have a crystalline structure. This means that the atoms in the structure arrange themselves in an ordered manner, in which a small repeat unit called a “unit cell” can be identified. This unit cell, which in some cases contains just several atoms, is repeated in all three directions, and in this way, the entire structure is built up.

    More links about unit cells.

    This unit cell description of a crystalline structure implies the atoms are arranged in perfect order, which is only true in an ideal solid.  All crystalline solid structures contain missing atoms, called defects,  impurity atoms of other elements,  and misaligned planes of atoms called dislocations.  Dislocations are rather common in many systems you encounter everyday. For example, look at the corn cob pictured below. Can you see how one row of kernels has been inserted into the regular arrangement of rows?  This is called a dislocation.  This same type of thing occurs in the arrangement of atoms in a crystalline solid.

    Impurity atoms, defects, and dislocations all have an important impact on the physical and chemical properties of the solid. For example, copper wire is easy to bend because the structure contains planes of atoms which can slip easily past one another.  Watch the movie below to see how a model of the structure of copper metal contains these planes of atoms which  slip easily apart.
     
     

    Key to Understanding the Demonstration

    Under the force of the ball impact, some of this energy is transferred to similar planes of atoms which move past each other. In many cases this atomic motion results in permanent deformation of the solid.   The small pits on the surface of the stainless steel base are evidence of how the ball bearing impacts have deformed the surface.
     
    The small pits in the stainless steel base are evidence of the permanent (or plastic) deformation that ocurrs when the ball bearing is dropped onto the surface. This deformation is a high energy process, accounting for  much of the energy dissipation of the bouncing ball. 
    At 7.5x magnification, the pitting of the stainless steel base is clear. The three pits in this image are from consecutive bounces of the steel ball bearing on the surface of the base. 

    What is an amorphous solid?

    The atoms in an amorphous material are not arranged in any ordered structure, rather they have a tightly-packed, but random arrangement.  Amorphous materials are formed by cooling the liquid material quickly enough to prevent crystallization;  the atoms do not have time to arrange themselves into an ordered structure.  Liquidmetal® is an amorphous alloy (also known as a metallic glass) containing five elements, with the elemental composition is 41.2% zirconium, 22.5% beryllium, 13.8% titanium, 12.5% copper, and 10.0% nickel.

    Because of the varying sizes of these atoms, and their random arrangement in the solid, there are no groups of atoms that can easily move past one another.  Because there are no planes of atoms in an amorphous material, the atoms are gridlocked into the glassy structure, making the movement of groups of atoms very difficult.  One consequence of this atomic gridlock, is that some amorphous metals are very hard.  Liquidmetal® is more than two times harder than stainless steel. However, besides being a very hard material, this amorphous alloy has a low elastic (or Young's) modulus.  The combination of hardness and elasticity of Liquidmetal® is an important factor in its many applications.

     

    Please see www.liquidmetaltechnologies.com for further applications.

    This amorphous alloy was developed by William Johnson at Caltech in 1992.

    The Boston Museum of Science has adapted the "Atomic Trampoline" for a museum display.

    We also tried this experiment with a really tall tube filled with either air or sulfur hexafluoride. Does the gas in the tube make a difference?


    Liquidmetal® alloys are products of Liquidmetal Technologies.

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    100 North Tampa Street Suite 3150
    Tampa, Fl 33606

    Otis Buchanan, Vice President, Media Relations
    813-314-0280 x109


    More Useful Links

      Unit Cells
    introduction to cubic crystal lattices

      Coefficient of Resitution
    Coefficient of Restitution

    Young's Modulus - Elastic Modulus
    Young's Modulus Definition

     

    Exploring the Nanoworld   |   MRSEC Nanostructured Interfaces
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