Chapter 4: What Makes Diamonds Hard?

Art Kracke of the ASM Education Committee describes the importance of materials in everyday life. We can do amazing things with materials just by controlling their characteristics.

Engineers and scientists use materials to make new products. We work with Atomic Structure to change the way a material behaves. One way is by using extremes of heating and cooling. Using ball bearings, we can show how atoms take on different patterns depending on temperature.

When you bend a piece of steel over and over, you create atomic dislocation. We can bend a piece of steel rod easily because it’s ductile...but once you add heat and then cool it by quenching in water, the atoms experience a “phase transformation” and change their pattern.

A ceramic implant with calcium added (while the material is the powder stage) can help mend broken bones. A demonstration using the Space Shuttle’s silicon dioxide tiles: Hot enough to melt a penny on one side, yet still cool enough to touch on the other.

A wire is bent into a shape like the letters ISU. Coil up the wire, then put it into boiling water...and it will snap right back into its original shape. It’s a shape memory wire, made of nickel and titanium.

Two balls are made of the same polymer. They are the same weight, but when you drop them, one goes splat. It’s all about the way the atoms are linked together. That’s where “super” balls come from.

Although copper isn’t magnetic, it is a good conductor of electricity. Drop a small magnet through a plastic pipe and it slips right through. But drop it down a copper pipe and it slows down inside - because of an electric current created by the magnet.

Let’s see what a racquetball thinks of liquid nitrogen at around minus 196 degrees Celsius. It was soft and bouncy before, but drop it into liquid nitrogen and throw it against the wall. What do you think happens?

Tempered glass is heat treated like steel to become stronger. But if you apply a certain amount of stress, a simple cut along one corner can cause the entire glass to shatter. Don’t try this at home!