A solid-solid phase change - from one solid to another type of solid - occurs in other materials too. Tin is a shiny metal at room temperature, but it turns to a gray dust when the temperature drops to 56° Fahrenheit /13° Celsius. This process is called ‘tin pest’. Once tin changes it is hard for it to go back. In old churches, there are organ pipes made out of tin that would disintegrate to dust when the weather got cold. There is a legend that Napoleon’s army failed its campaign to Russia in 1812, because the tin buttons used to keep pants up and coats closed, turned to dust.
If you were designing a new cellphone or other electronics that would have various types of metals in it, what might you consider before making it?
When shape memory wires change from one phase to another, their properties significantly change too. The electrical properties in the wire change when you heat it.
Let’s say you have two pieces of metal that are too small to bend and you cannot tell which one was a shape memory material. What kind of experiment would you set up to test which material is which if you had a hotplate and a multi-meter (which, used to measure electrical resistance)?
NASA uses shape memory wires to make dish-shaped antennas to be used in space. However, the dish shape takes up too much space in the rocket payload. Given what you know about shape memory alloys, how can we reduce that amount of space the dish has during the launch but use it once we reach orbit?
Learn more about other cool materials at:
Material Marvels www.materialmarvels.com
PBS Making Stuff http://www.pbs.org/wgbh/nova/tech/making-stuff.html
Material Marvels: Shape Memory Alloys http://youtu.be/WREwKx0qF7o
Science Xplained: Napoleon’s Buttons http://youtu.be/MuadfLiAKkc
Get Some Shape Memory wire to play with from:
TiNi Company http://www.tinialloy.com/livewire.html
Education Resource www.Teachersource.com