Liquid Benzene Squeezed to Form Diamond Nanothreads - possible future space elevator material

[link to www.scientificamerican.com]

The classic Beatles song “Lucy in the Sky with Diamonds” may have a new meaning. Scientists announced they have likely discovered the strongest, stiffest diamond-based nanomaterial to date. Its properties suggest it could have important industrial applications, such as in transportation or aerospace manufacturing, and it might revive the idea of building elevators to space.

A team led by chemist John Badding of Pennsylvania State University took an approach reminiscent of the way Superman squeezed coal into diamond in comic books. The researchers found that isolated, liquid-state benzene molecules, which consist of rings of carbon atoms, assemble into surprisingly neat and orderly chains after enduring slow, alternating cycles of pressure. The resulting thread, merely three atoms across and thousands of times thinner than a strand of hair, appears to have a zigzagging arrangement of rings of carbon atoms in the shape of a triangular pyramid—a formation similar to diamond’s. Such a structure, which scientists didn’t know was possible until now, could be the strongest and most durable nanomaterial ever made.

Badding says that the team’s discovery was serendipitous: “Honestly, it was just an accident.” Thomas Fitzgibbons, a graduate student in Badding’s lab, wanted to study materials made by the organic chemical compound benzene. When isolated, benzene molecules can react in interesting ways to form unique structures. To study these structures using conventional techniques, however, Fitzgibbons needed large quantities of the product. He brought a sample of liquid benzene to a machine called a Paris-Edinburgh device at Oak Ridge National Laboratory in Tennessee and put the molecules into a high-pressure cell. In general, when a liquid is squeezed under intense pressure, it transforms into a solid. “It essentially freezes,” Badding says. Once frozen, benzene molecules align into predictable patterns of stacked columns.

What happened next is the unusual part. Scientists have generally believed that as compression continues, the benzene molecules eventually yield a sloppy, white powder. “People thought they’d react in a disorganized way and make a mess,” Badding says.

But instead of disarray, Fitzgibbons saw order. “That was a shock to us, to say the least,” Badding confesses. The researchers were so surprised, they deployed a battery of techniques to confirm the finding, including x-ray and neutron diffraction, transmission electron microscopy and vibrational spectroscopy. Their results were consistent: they saw order...50% rule