Your next smartphone might be made of cement

A little process known as electron trapping can turn metal into cement.
A little process known as electron trapping can turn metal into cement.
Image: AP Photo/Jae C. Hong
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Straw into goldWater into wineServant into princess. It’s a longstanding obsession of human myth-making: turning one thing into another thing—a lowly thing into a vaunted thing—by way of miracle or magic.

Well, someone get Joseph Campbell. Because science has just found another way to bring the Rumpelstiltskin story to life. And to the life, specifically, of your electronics. A collective of researchers from the U.S., Finland, Germany, and Japan, working with the U.S. Department of Energy, has developed a way to make metal out of the straw of the contemporary world: cement. The process they discovered, published yesterday in Proceedings of the National Academy of Sciences, transforms liquid cement into a kind of glass-metal fusion that is exceptionally good at conducting heat and electricity. The resulting hybrid, the scientists say, can be used as a semiconductor in electronics: it offers good conductivity, low energy loss in magnetic fields, better resistance to corrosion than traditional metal, less brittleness than traditional glass, and fluidity for ease of processing and molding.

Which means that your gadgets—their liquid-crystal displays, their protective coatings, their computer chips—may soon be made, in part, of cement.

So how, exactly, do you turn masonry into metal? The scientists made use of a phenomenon known as electron trapping—a condition that occurs when the free electrons in polycrystalline materials are, yep, “trapped” in the cage-like structures that form around them.

Close-up visualizations of (A) the HOMO and (B) LUMO single-particle electron states in the 64CaO glass. Yellow and magenta stand for different signs of the wave-function nodes. (C) Simulation box and the electron spin-density of the 64CaO glass with one oxygen subtracted at h2–that is, with two additional electrons. (D) Cage structure around the spin-density of one electron cor- responding to the h2 cavity (close-up from C). (DOE/Argonne National Laboratory)

The team, under Chris Benmore, a physicist from the U.S. Department of Energy’s Argonne National Laboratory, studied mayenite, a rare calcium aluminium oxide mineral that features, importantly, cubic symmetry. They melted the mayenite at temperatures of 2,000 degrees Celsius using laser beams composed of carbon dioxide. They then processed the resulting liquid within different atmospheres to control the way oxygen would bond in the resulting glass.

For that—and this was key—Argonne’s Advanced Photon Source, led by a team under Benmore, developed a technique for suspending the material. The group used an aerodynamic levitator to levitate the hot liquid in the air, preventing it from touching container surfaces and forming crystals. The suspension, in turn, let the liquid cool, unimpeded, into a glassy state that could trap electrons in the form necessary for electronic conduction.

And voila! A glassy semi-conductor. Cement, made metallic. The scientists, from there, used a supercomputer to determine the best conditions for creating glass that could optimally conduct electricity at room temperature.

The process may not be limited to glass, however. There could be other materials capable of transforming themselves into semiconductors through magic finely honed scientific techniques. ”This phenomenon of trapping electrons and turning liquid cement into liquid metal was found recently, but not explained in detail until now,” Benmore put it. “Now that we know the conditions needed to create trapped electrons in materials, we can develop and test other materials to find out if we can make them conduct electricity in this way.”

Megan Garber is a staff writer at The Atlantic. She was formerly an assistant editor at the Nieman Journalism Lab, where she wrote about innovations in the media.

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