Magazine article Science News

Meddling with Metal: Novel Nanocontrol Yields Chromium Rival

Magazine article Science News

Meddling with Metal: Novel Nanocontrol Yields Chromium Rival

Article excerpt

A legal battle launched in 1993 over toxic chromium metal became the basis for the movie Erin Brockovich, which featured superstar Julia Roberts. Now, materials scientists have quietly taken aim at one common use of that harmful substance by creating a nontoxic alloy with the potential to replace a coating containing chromium.

Costarring in these laboratory developments is a new method for making alloys. With it, scientists can dictate the sizes of nanoscale crystals in an alloy's structure--and therefore the alloy's properties--by manipulating its atomic composition. Christopher A. Schuh of the Massachusetts Institute of Technology (MIT) and his colleagues have applied the method to alloys composed mainly of nickel.

The scientists set out to create nontoxic coatings as hard and corrosion resistant as the chromium layer applied to steel. The so-called hexavalent form of chromium--used in those coatings and also in paints and dyes--poses a cancer risk to more than a half-million U.S. workers.

The Occupational Safety and Health Administration on Feb. 28 slashed the permissible concentration of hexavalent chromium in workplace air by a factor of 10.

To make their nontoxic coatings sturdy, Schuh and his coworkers applied a well-known strategy: creating nanoscale crystalline grains in the materials. To do this, other researchers have rolled and pounded metals to reduce grain size (SN: 8/24/02, p. 117) or heated nanocrystalline powders to weld together smaller structures. …

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