Electronic Design

Polymer Eases Quasicrystal Processing And Resists Wear

Innovative composites research is unlocking the key to easily processing quasicrystals. Typically aluminum-rich alloys of specific compositions, quasicrystals possess an unusual combination of properties. They're hard, highly resistant to wear and corrosion, and don't conduct heat well.

While these traits make them ideal for coating automotive and mechanical parts, scientists have longed to understand why they have these characteristics. Manufacturers want to use them, but the difficult processing required has posed an obvious stumbling block.

This may be about to change, thanks to a project at the U.S. Department of Energy's Ames Laboratory, Ames, Iowa. Researchers there are integrating the best of polymer technology with quasicrystals to counteract their processing problems. Polymers, which are long chains of flexible molecules often used to make plastics, are much easier to process than quasicrystals.

The quasicrystal-filled polymer resulting from this combination is very hard and nonabrasive. It also has a low thermal conductivity. In wear-resistance tests, the patent-pending composite outperformed similar materials. Additionally, it may offer a more versatile way to use quasicrystalline powders.

Essentially, the polymer acts as filler in the quasicrystal powder. The polymer causes the quasicrystals to readily disperse. This fact alone surprised researchers, as neither polymers nor quasicrystals have been known to mix well with other materials.

Once mixed, the composite was put through a battery of tests. Half-dollar-sized disks of the material were placed on a turntable that looked like a record player. A small stainless-steel ball was placed in the device's arm, roughly where a record needle would go. A 1- to 2-lb. weight attached to the middle of the arm held the ball in contact with the disk as it spun at 125 rpm.

Examination showed that the quasicrystal-filled polymers were five to 10 times better in resisting wear than any other polymer or polymer composite tested. Also, the steel ball showed little or no wear. While the composite material is extremely hard, it's nonabrasive when scraped against another material.

Now that a unique filler for the quasicrystal has been found, researchers hope the industry can easily produce the new composite. Once they jump the hurdle of the initial scale-up for quasicrystal production, the actual processing will be fairly simple. In the meantime, researchers will continue to investigate the composite's low thermal conductivity, while seeking to understand the composite's basic workings.

For more information, go the facility's web site at www.ameslab.gov.

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