Materials Science and Engineering: Metals
How can we create planes that are so light and have so little drag that one day a flight from New York to Tokyo might take only 5 hours instead of 13? How can we design medical implants that are biocompatible and don't wear out during a patient's lifetime? How can we make mountain bikes that are easier to carry over streams? How can we safely store nuclear waste for 10,000 years or more?
The answer to all of these questions is: use metals more effectively!
From a Samurai sword to a steel I-beam to electrical wiring, metals are part of our past, present and future. Metals are the most common elements in the periodic table and are characterized by malleability, ductility, high electrical and thermal conductivity and a shiny surface that reflects light. Metallic bonding where valence electrons are shared by the entire solid gives rise to the "free" electrons responsible for electrical and thermal conductivity.
Most metals and alloys (combinations of metals) are also highly crystalline, which is the key to their ability deform plastically and to resist failure under repeated mechanical loading—good examples of this are the alloys used in aircraft that can compensate for deformation in high-speed flight, or skyscrapers designed to bend in the wind.
When approaching the nanometer scale, in which electrons behave like waves and surface effects are important, metallic materials acquire intriguing properties. For instance, silver nanoparticles are yellow and gold nanoparticles are burgundy. These new optical properties are interesting for sensing and communication technologies.
How is MSE@UMD Working with Metals?
- Pairs of Silver Nanocubes Enhance Raman Scattering by A Million Times: MSE professor Oded Rabin and his research team use silver cubes 100 nanometers (1/10000000 m) in size to detect molecules. With the cubes, signal can be identified with just ten thousand molecules. Without the nanocubes, ten billion molecules would be needed. More »
- Titanium Can Perform Better: MSE professor S. Ankem has studied the deformation of titanium alloys and other metals that occurs over time, an effect called "creep." Predicting creep or getting it under control with new manufacturing techniques could lead to reduced failure rates and improved performance in everything from golf clubs to aircraft landing gear. More »
Watch a materials video demonstration about metals:
Shape Memory Metal
Shape memory materials display an unusual property of "remembering" the shape they were formed into at high temperature. They experience a solid state phase change, in which atoms are rearranged, but the material remains a solid. If a piece of shape memory metal alloy wire is deformed, for example, it will return to its original state when exposed to the heat of a hair dryer—the heat triggers the "memory" of where the atoms were at the time of its production.
An amorphous metal is an alloy combining elements of differing atomic diameters. The dark grey disk (left) is an amorphous metal formed by combining 5 different atoms together: zirconium, titanium, copper, nickel, and beryllium (Zr41.2Be22.5Ti13.8Cu12.5Ni10.0). The differing atomic diameters and unusual composition prevents the atoms from arranging in a regular crystalline structure. The atoms have no easy way to slip by each other under deformation, resulting in a very hard material. When a steel ball bearing is dropped on the amorphous metal, it does not permanently deform and the ball bounces many times before coming to rest.
For more information online:
- Weird, Weird Science »
John Sizemore offers movies on a variety of topics on his Dailymotion site. His "Zoom Into..." series of videos about materials, includes Zoom Into Steel, Zoom Into Brass, and Zoom Into Aluminium.
- Nobelprize.org: Invar® & Steel Alloys »
On this cooking show, allloys are on the menu and you're the chef. Requires the Flash Player (free).
- Home Science Tools: Learn About Metals
Explains qualities and types of metals, how metals are made from ore, and corrosion.
- The Aluminum Association
Did you know that over one third of the total U.S. aluminum supply is provided through recycling? Learn more here.