Carbyne: The new world's strongest material?
October 14, 2013
Researchers at Rice University have used a computer simulation to calculate that carbyne, a monodimensional chain of carbon atoms, is twice as strong as carbon nanotubes and three times stiffer than diamond. If their findings are correct and the challenges posed by manufacturing it can be overcome, then carbyne could prove an incredibly useful material for a wide range of applications.
Carbon by any other name
As you may remember from organic chemistry class, one the main factors that makes carbon so special is its ability to easily bond with atoms, including itself, in a number of different forms. Even tinkering with carbon atoms alone can result in different forms (or allotropes) of carbon, ranging from graphite to diamonds and, more recently, artificial forms such as buckyballs, graphene and carbon nanotubes.
These artificial forms can yield surprising results both in terms of their mechanical strength and their possible applications, such as in next-gen electronics. So it should come at no surprise that scientists are looking to uncover new allotropes with similar, perhaps even superior features.
Carbyne, or linear acetylenic carbon, is yet another allotrope of carbon that grows in a single chain with alternating single and triple atomic bonds. As it is a single atom-thick chain and not a sheet (like graphene) or a hollow tube (like carbon nanotubes), it is considered a truly one-dimensional material. Scientists have long believed that this single dimension might give carbyne unparalleled mechanical and electrical properties.
Carbyne and its properties
Rice University theoretical physicist Boris Yakobson and his team set out to describe the properties of carbyne by using the information available from previous research and combining it within a computer simulation to shed a lot more light on the properties of this elusive material.
After confirming that carbyne is stable at room temperature, largely resisting interaction with nearby carbyne atom chains, the researchers went on to find that carbyne has indeed remarkable, unprecedented features of its own.
In terms of mechanical properties its tensile strength, or its ability to withstand stretching, is double that of graphene. According to the computer model, carbyne is also twice as stiff as graphene and three times as stiff as diamonds and, interestingly, carbyne's torsional stiffness can be modified by attaching appropriate molecules at the end of each carbon chain.
According to Yakobson, carbyne also turns out to have some very interesting and unique electrical features. Molecules can be attached to each end of the chain to make it suitable for storing energy, its band gap, an important electric property that determines its electrical conductivity, can be stretched from 3.2 to 4.4 eV just by stretching the material by ten percent and finally, when twisted by 90 degrees, carbyne also turns into a magnetic semiconductor.
If these predictions are true, then the versatility of carbyne could one day lead to important advances in fields ranging from the design of new nanoelectronic and spintronic devices to building very high-performance mechanical parts.
Unfortunately, knowing its properties and being able to harness them are two very distinct problems. While carbyne has been detected in interstellar dust and compressed graphite, it is proving very challenging to recreate in the lab (researchers have only managed to create very small chains of up to 44 atoms). But at the very least, studies such as this might encourage more investment toward solving the practical problems of manufacturing longer carbyne chains.
Yakobson and colleagues now say that they will take a closer look at the conductivity of carbyne, and specifically at the relationship between twisting and its band gap. Their future work will also include finding out whether other elements in the periodic table are also capable of forming similar monodimensional chains.
A paper describing the materials appears in a recent issue of the journal ACS Nano.
Source: Rice University
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