Diamond Nanothreads: key ingredient for space elevator?

[rhoenix]

Researchers have created the first diamond nanothreads — which are basically like carbon nanotubes, but stronger and stiffer. Mathematically, these diamond nanothreads are possibly the strongest and stiffest material that can be constructed in the known universe. As interest in space elevators and other international megaprojects swell, these diamond nanothreads might be exactly what we need to get crazy seemingly impossible constructions off the whiteboard and into reality.

As you may know, diamond is one of the hardest materials in the known universe. What you might not know is that diamond is very closely related to graphene and carbon nanotubes — two materials that have their own set of remarkable properties. Basically, all three materials are made out of carbon atoms — but the arrangement of the carbon atoms dictates the final properties (these same-but-different materials are called allotropes). Diamond, for example, is exceptionally hard because each carbon atom is bonded to four others to form a tetrahedral (pyramid) structure (this is called sp3 hybridization). Generally, most allotropes of carbon are very strong and exceptionally conductive (both heat and electricity).

In this case, Penn State University researchers have created long threads of tetrahedral carbon — individual molecules of diamond, if you will. “It is as if an incredible jeweler has strung together the smallest possible diamonds into a long miniature necklace,” says John Badding, who led the research. These diamond nanothreads should have even greater strength and stiffness than carbon nanotubes (which are already one of the strongest and lightest materials in the world) and advanced polymers (such as Kevlar or Vectran). It actually sounds like the Penn State researchers haven’t physically tested their diamond nanothreads yet — they probably don’t have enough of them to test — but theoretical maths are pretty solid when it comes to materials science.

Another surprising aspect of this research is that the diamond nanothreads were quite easy to make. The scientists used a machine at the Oak Ridge National Laboratory to compress a sample of benzene – a liquid that consists molecules of six carbon atoms joined in a circle, with one hydrogen atom linked to each carbon. Then, as they slowly reduced the pressure, the carbon atoms shuffled around to create a ribbon of carbon tetrahedrons — diamond nanothread. The scientists aren’t entirely sure why this happened — but it’s probably something to do with the high pressure breaking the benzene rings apart into individual carbon atoms, and then orderly polymerization (long chains) as pressure is released. Importantly, the diamond nanothreads produced in this way are two-dimensional — they’re only one molecule thick, but infinitely long. [Research paper: doi:10.1038/nmat4088 - "Benzene-derived ​carbon nanothreads"]

This new material is exciting for two reasons: a) The apply-extreme-pressure-then-remove-pressure-slowly technique might work with other liquids, creating a whole new range of materials — and b) these diamond nanothreads should be the strongest, stiffest material that’s conceivable within our current understanding of the universe. One of the reasons we haven’t built a space elevator yet is that we don’t really have the right materials for it — but diamond nanothread might be capable of withstanding the almost inconceivable stresses that a 60,000-mile-high structure would have to endure.

The next step, as always with all of the wonder materials we’ve discovered recently, is to work out how to mass produce the diamond nanothreads. In this case, I don’t think it’ll be too difficult — but I wouldn’t put off any immediate purchasing decisions.

I see lots of "might be" type of stuff in there, so it should be obvious that proper tensile testing of these diamond nanothreads haven't really been done yet. With that said, new things like this are at the very least interesting.

[LadyTevar]

The problem with Diamonds is while they are the hardest mineral, they are also prone to breakage along their fracture points. If they didin't, how else would we be able to cut them and polish them?

[Josh]

The biggest question I've seen is how to economically produce materials like this on any sort of actual scale. They keep talking about nanotubes and the prospects for a space elevator (which would fuckin' awesome, no doubts) but it keeps bumping up against limitations like 'we can't produce more than an inch-long string' or whatever.

Obviously we will need lots and lots of inches to reach orbit. Like big lots.