BAM nanocoating on steel substrate. (Credit: Ames Lab)
(Also – see BAM Update here.) What’s almost as hard as diamond, slicker than Teflon and “green” enough to reduce the United States’ industrial energy consumption by trillions of BTUs a year? The answer is BAM – a ceramic alloy created by combining a mix of boron, aluminum and magnesium with titanium diboride. The world’s third hardest material, next to diamond and cubic boron nitride, BAM is as slippery as it is strong. With a 0.02 coefficient of friction, it is substantially slicker than Teflon (0.05) and lubricated steel (0.16). Discovered accidentally in 1999 by two researchers at DOE’s Ames Laboratory, BAM has now grown into the nanocoating superstar of a four-year, $3-million project designed to lower industrial energy usage by reducing machine friction. The project, largely funded by DOE’s Office of Energy Efficiency and Renewable Energy, is led by Bruce Cook, one of BAM’s discoverers and a scientist at the Iowa lab.
Reducing friction and energy
“Friction slows machine parts down, making them work harder, wear out faster and utilize more energy than they really need,” Cook stresses in a recent interview with the Bulletin. According to Cook, government statistics show that using BAM-based nanocoatings on the rotor blades of something as ubiquitous as today’s common pumps, could “reduce U.S. industrial energy usage by 31 trillion BTUs annually by 2030, or a savings of $179 million a year.” Alan Russell, a fellow Ames researcher and BAM’s co-discoverer, agrees. “When used as a coating for machine parts in thicknesses of only two microns, BAM’s properties – extreme toughness and super slickness – have been proven to make parts significantly stronger, function more smoothly, generate less friction and use less energy,” the professor of materials science and engineering at Iowa State University says.
Application and expansion
At Ames, BAM nanocoating is applied to hydraulic pump vanes and tungsten-carbide cutting tools via pulsed laser deposition, Cook and Russell report. But the lab is also working with Eaton Corp., and this large manufacturer of fluid-power equipment applies the coating by magnetron sputtering, a method better scaled to commercial operations. The researchers also are working with Greenleaf Corp., a firm that’s extended the use of BAM beyond pump parts to industrial cutting tools. Russell says the Ames team also is beginning to look at titanium-diboride alloys, with tests taking place at DOE’s Oakridge National Lab, the Missouri University of Science and Technology and the University of Alberta. In a Nov. 21, 2008, interview with the online magazine, NewScientist, Russell says BAM also might be used as a hard coating for drill bits. He admits diamond is more commonly used because it is harder than BAM, but reveals diamond has a negative chemical reaction to steel, causing it to degrade “relatively quickly.” For this reason, tests are currently underway in yet another potential new BAM market.
Properties still a mystery
When asked why BAM is so tough and slippery, Russell says he’s not sure, despite Ames’ ongoing research. He tells NewScientist that diamond and most other extremely tough materials have a “simple, regular and symmetrical crystalline structure.” Yet, BAM is “complex, unsymmetrical, and its lattice contains gaps, none of which would be expected in a hard material.” BAM’s slipperiness also is only partly understood. One hypothesis is that “boron interacts with oxygen to make tiny amounts of boron oxide on its surface. They would attract water molecules from the air, to make a slippery coating,” Russell explains in NewScientist. “It’s almost as if it’s a self-lubricating surface. You don’t need to add oil or other lubricants. It’s inherently slippery,” he says. Cook tells the Bulletin, “We’ve done a lot of basic research in trying to find out the molecular structure of these materials and what gives them their properties. We haven’t answered all the questions yet, and research is still ongoing.” Newtech Ceramics, an Iowa-based start-up firm in Des Moines, has licensed BAM, according to Cook.