After Discovery of Ultra-Tough Material Comes the Hard Part
Contrary to the popular view of science as a process that advances methodically from one point to the next toward a clearly defined goal, some of the best science comes about serendipitously.
No one knows that better than scientists at the Energy Department’s Ames Laboratory, who have discovered an ultra-hard material that could have a profound impact on the manufacturing of items ranging from microprocessors to industrial machinery.
“It was one of those accidental discoveries,†said Alan Russell, associate professor of materials science and engineering at Iowa State University, which manages the lab for the Energy Department.
What Russell and colleagues Bruce Cook and Joel Harringa discovered is a material that is almost as hard as diamond and cubic boron nitride, the two hardest known bulk materials, but far cheaper to produce. It also has characteristics that could vastly widen the application for ultra-hard materials. But that isn’t what the researchers had set out to discover.
“We were looking for what’s called thermal electric materials,†Russell said. “These are materials that will produce a voltage if there’s a temperature gradient across the crystal.â€
So they mixed a little magnesium and aluminum with a lot of boride and pounded it into a fine powder. Then they put it into a vacuum chamber at high temperature and let it sit there for about an hour.
“Then out comes this thing that looks a little like a hockey puck,†Russell said.
But when they tested it to see if it might be useful as a thermal electric material, it flunked.
Then a funny thing happened. They found it extremely difficult to cut despite the availability of some very sophisticated equipment. And it was virtually impossible to polish, suggesting that it was resisting all attempts to erode its surface.
The mystery of the new stuff continued to deepen.
All previous ultra-hard materials shared similar characteristics, such as strongly bonded crystal structures of small cells and high symmetry and no missing “sites,†or atom-sized voids that could cause the material to buckle under pressure.
As they looked closer at the aluminum-magnesium-boride material, they found a very different beast indeed. “It violates most of the rules,†Russell said.
The cells are large, with low symmetry and what Russell called “strange and complex bonding.†It even has missing sites, where an atom that should be there isn’t, thus leaving a void big enough to drive the proverbial truck through in the world of ultra-hard materials.
“If you had shown this to a panel of experts, they would have said there’s no way that could be hard,†Russell said. But it passed every hardness test the scientists could administer.
And there was something else.
The material is also a good conductor of electricity, something that other ultra-hard materials, including diamonds, are not.
Although the lab has produced only tiny quantities of the stuff for research, scientists say there is no reason that the process could not be scaled up to manufacture it in huge quantities.
And in contrast to cubic boron nitride, which costs about $7,000 a pound to produce, and diamond dust, which costs about $2,000, this new material should come in at about $700 a pound.
The lab applied for a patent, which is still pending, and then announced the discovery last November. Nobody paid much attention, except for a few industrial giants that asked the lab for a few pounds of the material so they could run their own tests.
The lab had been geared up for research, not industrial production. “All we need is little things the size of your thumbnail to do all our measurements on,†Russell said.
Ames is negotiating a partnership with two unnamed manufacturers to produce bulk quantities of the material.
The interest shown by industry reflects a wide range of possible applications.
For example, microprocessors are connected by tiny gold wires that have to be welded to contact points. Machines that do that can run through 60 miles of gold wire every day. An electric current has to be run to the gold wire to do the welding.
But even soft gold wire, no more than a third the diameter of a human hair, erodes the electric wires as it slips back and forth at tremendous speeds. Since the new material can carry a current, it could be ideally suited for that application because it would resist the wearing much better than other materials.
Russell said he had not even thought of that application until the lab was contacted by a major manufacturer of microprocessors.
Unlike other ultra-hard materials, the new stuff can be melted and sprayed onto other surfaces like paint. Russell said that caught the attention of the pharmaceutical giant Johnson & Johnson, which is looking at the material for possible use on surgical instruments and sutures.
Scientists at the lab are continuing to experiment with the material while lawyers work out agreements with manufacturers, Russell said. Lab officials expect that within a few months, they will scale up production of the material so that enough of it can be made available to see if it lives up to its promise.
By then, maybe they will start saying that’s what they set out to do in the first place.
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Lee Dye can be reached at [email protected].
