January 27, 2014

Modern Alchemy and the Quest for ‘Cheapium’

Tiffany Trader
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In a move reminiscent of medieval times – when alchemists attempted to synthesize noble metals like gold and silver from base metals such as lead and iron – modern engineers are on the hunt for less expensive alternatives to platinum. The search has Duke University engineers using brute force computing to uncover new materials that have the same chemical, physical and/or structural properties of platinum minus the hefty price tag.

A new study published in the American Physical Society journal Physics describes how researchers from Duke University’s Pratt School of Engineering used computational methods to identify dozens of promising platinum-group alloys. Although previously unknown to science, these compounds could be suitable for a wide-range of applications in the same way that platinum-group metals are used now.

With a unique atomic makeup, platinum is a super-material of sorts. As a catalytic converter, it can transform toxic engine exhaust into carbon dioxide and water. To a lesser extent, this rare metal is also used in the production of high octane gasoline, plastics and synthetic rubbers. It’s helpfulness even extends to medicine where it is effective against certain types of cancer.

The only problem with this super-material is its super-high price tag. Developing a more affordable, knock-off compound would benefit a multitude of industries and would encourage greater adoption of catalytic converter technology as well.

“We’re looking at the properties of ‘expensium’ and trying to develop ‘cheapium,’” said Stefano Curtarolo, director of Duke’s Center for Materials Genomics. “We’re trying to automate the discovery of new materials and use our system to go further faster.”

The research is part of the Materials Genome Initiative launched by President Barack Obama in 2011, “to help businesses discover, develop, and deploy new materials twice as fast.” The initiative sees innovative materials as crucial to achieving global competitiveness in the 21st century.

Curtarolo and his team have spent years laying the groundwork for the identification of the new platinum-group compounds. The databases and algorithms they’ve developed are based on an understanding of how atoms interact with model chemical structures. The researchers screened thousands of potential compounds with a priority given to the most stable candidates. A survey of nearly 40,000 calculations resulted in 37 new binary alloys in the platinum-group metals: osmium, iridium, ruthenium, rhodium, platinum and palladium – all rare and in-demand.

The newfound compounds have a number of desirable traits, e.g., catalytic properties, resistance to chemical corrosion and performance at high-temperature environments. These properties recommend their use in a number of commercial applications, such as electrical components, corrosion-resistance apparatus, fuel cells, chemotherapy and dentistry.

The next step is for experimentalists to continue the development process by creating these materials and identifying their physical properties. Historically, Curtarolo’s methods have turned out stable new compounds, but it’s difficult to know how such compounds will behave in the wild.

“The compounds that we find are almost always possible to create,” said Curtarolo. “However, we don’t always know if they are useful. In other words, there are plenty of needles in the haystack; a few of those needles are gold, but most are worthless iron.”

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