Posted on 07/11/2013 4:03:35 PM PDT by neverdem
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Chinese scientists at Tsinghua University in Beijing have managed to grow a carbon nanotube (CNT) that is just over half a metre long – over double their previous best.
For two hours the group used chemical vapour deposition to grow the long nanotube on a silica substrate. The team managed to improve their technique so much as they discovered that CNT growth is controlled by kinetics and that catalyst activity is the most important factor. If the catalyst has a high probability of failing after 1mm growth, the CNTs grown will be short. Optimising the conditions to reduce the ‘catalyst’s deactivation probability’ meant the CNTs grew longer and, in one instance, over half a metre long.
CNTs are strong and are often suggested as materials for armour and other applications, but the question of how to grow long, controlled CNTs has been a matter of debate. With the latest work from Fei Wei’s group perhaps CNTs will soon break the metre mark.
R Zhang et al, ACS Nano, 2013, DOI: 10.1021/nn401995z
For an nanotube protrusion lasting for more than 4 hours, consult a physician.
Wow!
Space Elevator???
One possibility. Long distance power lines, bridge cables, golf clubs? Who knows?
Weapons. A thin nanotube wire could go through an arm or leg with almost no resistance. Sort of frightening, actually.
Should we call it a macrotube then?
“Variable sword” or “Sinclair molecular chain” applications come to mind.
They could weave long nanotubes into cloth with amazing properties.
Ringworld and Borderlands of Sol? Maybe I was subconsciously influenced...
Nanotube sword- I want one of those!
Nor does it absorb visible light, and is thus transparent. I am not sure what the refractive index is, but because of internal diffusion of light, the powder is a bright white. A powder of such crushed nanotubes would be white. However, it seems pretty obvious that a single long nanotube of BN would be an extremely efficient and lossless light guide, by which a laser beam could be transmitted without being seen, hence a great method of coupling optical computers without the heat loss normally accepted in losses to semiconductor junction resistance.
The two-dimensional crystal sheets are held together by, IIRC, van der Waals forces, thus easily separated. This graphite-analog of BN stoichiometry, but of structural B(3)N(3) six-atom hexagonal rings is one of the slipperiest dry materials I have ever handled.
There is a three-dimensional BN crystal exactly analogous to the diamond structure, but is yet harder than diamond because of the stronger interatomic forces arising from partial sharing of electrons from the superabundant nitrogen with the electron-deficient boron valence orbitals.
I wish I had the resources and knowledge of the technological tricks used to grow these nanotubes, and the time to get reimmersed in this discipline.
Thanks for this very interesting descriptive article for the scientific layman and retired scientist.
You’re welcome. I was a grunt in Vietnam. This stuff keeps me feeling like a kid.
Thanks again for the tips!
This line of inquiry brings to mind the plate-like structures of kaolinite and illite clays, where the interesting effects of these materials has to do with the satisfaction of the charges of the broken bonds at the edge of the plates.
I know this doesn't make sense to you, but kaolinite is a two-dimensional crystal that matches two plates, the one a Si2O5 sheet and the other an Al2(OH)4 sheet, linked by shared oxygen atoms. The faces sharedare closely enough matched to allow the crystal to propagate for a short distance, but ultimately enough mismatch stress makes it impossible for particles to get larger. So the size of the particles is limited and predictable. But some particles actuall form little "nanotubes" so to speak.
Learned this in becoming a ceramic engineer.
Ceramics also pique my curiosity. Thanks for the link.
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