Talk:Carbon nanotube

This technology will greatly reduce the risk of an in-flight failure caused by structural degradation of aircraft.

The current text states that "The Boeing Company has patented the use of carbon nanotubes for structural health monitoring[86] of composites used in aircraft structures. This technology will greatly reduce the risk of an in-flight failure caused by structural degradation of aircraft." The latter claim has no source and seems at least ambiguous if not even implausible given the already low rates of in-flight failure. 140.112.177.67 (talk) 09:58, 20 February 2019 (UTC)

Electronic properties

The current text states that "Single-walled nanotubes are an important variety of carbon nanotube because they exhibit electric properties that are not shared by the multi-walled carbon nanotube (MWNT) variants". However, this statement is not expanded upon or referenced. The Physics World article http://physicsworld.com/cws/article/print/606 suggests that the electric properties such as conductance are in fact very similar between SWNTs and MWNTs. C3lticmatt (talk) 18:36, 27 February 2010 (UTC)

The article is very far from complete, but the electronic properties are very different for MWNT and SWNT - the former are (almost) always metallic, because of high probability of having (at least one) a metallic shell, whereas SWNTs can be semiconducting, which is crucial for electronic applications. Even if not metallic, MWNTs have an almost zero bandgap because of large diameter whereas it is of the order of 1 eV in many SWNTs. Materialscientist (talk) 01:05, 28 February 2010 (UTC)

Drug Delivery Section is WRONG

The section on filling carbon nanotubes with a drug to turn them into a drug delivery device is wrong. The referenced paper is actually talking about nanosized carbon test tubes. They are not carbon nanotubes, but just little tubes made from carbon material. Carbon nanotubes have a single-crystalline structure of their shells and are made with very specific growth processes. Their surfaces are also very hydrophobic and they could never be filled up with a drug. —Preceding unsigned comment added by 128.32.164.220 (talk) 23:55, 4 March 2010 (UTC)

Never say never :-) CNTs are very easy to fill with water and organic molecules (can provide experimental refs on that). The issue is inner diameter (not the walls) which is usually too small for drugs, but this can be tricked by proper CNT growth. That said, the section was indeed poorly referenced and I just deleted it outright. There is much work going on with CNTs for drug delivery, and it should be easier just to rewrite the section. Materialscientist (talk) 00:04, 5 March 2010 (UTC)

Weight of Carbon Nanotube

Is there any information of Carbon Nanotube?
If I want to make a cable of 100km for my project, what will be the weight?
The diameter of the cable must be sufficient to withstand high tension.

See more at: Constructing a Counterweight in Thermosphere

Shivan Raptor (talk) 03:03, 10 March 2010 (UTC)

I have modified space elevator article which might help your project. I don't know how to make a long cable out of nanotubes without sacrificing their strength - about 20 cm seems a current limit. Maybe quartz is a more feasible material. Materialscientist (talk) 04:32, 10 March 2010 (UTC)

Source for "parchment model"?

Does anyone here have a verifiable source for the "parchment model"? Some googling led me only to material that seems to originate from Wikipedia, and there are no obvious hits on Web of Science... Akhuettel (talk) 18:06, 17 May 2010 (UTC)

Never mind, found it. doi:10.1080/10587250008025562 and doi:10.1016/S0008-6223(02)00342-1 for whoever is interested... —Preceding unsigned comment added by Akhuettel (talk • contribs) 18:23, 17 May 2010 (UTC)

electronic properties

while fact that nanotubes can carry much larger current density is interesting, it would be also interesting to know about such basic property as conductivity. 83.18.229.190 (talk) 18:37, 17 December 2011 (UTC)

True. Does anyone know if a four-wire ("Kelvin Connection") electrical resistance measurement has been made on a 'metallic' carbon nanotube? Jamesdbell8 (talk) 21:39, 14 July 2012 (UTC)

See the new text in Carbon_nanotube#Electrical_properties. It's not possible to do a traditional 4-wire measurement on a nanotube because the leads are a significant perturbation on the nanotube. Tls60 (talk) 15:26, 16 July 2012 (UTC)

First reference?

I don't see how it's ~100million : 1 aspect ratio. i see 18 centimeter long and 1 nanometer diameter at one point — Preceding unsigned comment added by 68.126.177.160 (talk) 19:09, 19 March 2012 (UTC)

which is 18/(1×10⁻⁷) = 180,000,000; the article says 132,... because the tube is thicker than 1 nm. Materialscientist (talk) 03:28, 20 March 2012 (UTC)

I think the article's claim that the length/diameter ratio of carbon nanotubes is greater than 'any other material' isn't necessarily correct. Silica optical fibers often have a diameter of 125 microns (0.125 millimeters) and can be drawn to lengths of 1000 kilometers (1,000,000 meters)from a single large preform, which amounts to an L/D ratio of 8,000,000,000. Someone in the fiber-optic manufacturing industry should be able to confirm this. Jamesdbell8 (talk) 21:35, 14 July 2012 (UTC)

Molten Salt Synthesis

Is missing. 131.111.129.252 (talk) 14:53, 15 April 2012 (UTC)

Source needed

Under excessive tensile strain, the tubes will undergo plastic deformation, which means the deformation is permanent. This deformation begins at strains of approximately 5% and can increase the maximum strain the tubes undergo before fracture by releasing strain energy.

Can someone please post a source for this sentence? StainlessSteelScorpion (talk) 12:51, 19 March 2014 (UTC)

Longest carbon nanotube?

Do we have any information on what the longest carbon nanotube is that has been created?--Wyn.junior (talk) 14:35, 7 April 2014 (UTC)

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Removed text about metal or semiconductors

This article is about carbon nanotubes. You can form nanotubes from other materials, but carbon nanotubes cannot contain shells of metal or semiconductor. They're just graphene. Hermanoere (talk) 16:35, 31 October 2016 (UTC)

Merge paragraphs

In 2014, this edit duplicated text from this section into this section. Edits have accumulated since 2014, but for the most part, the former section still duplicates the last half of the latter section. They should be merged. Art LaPella (talk) 03:57, 11 January 2017 (UTC)

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potential use - resistivity or conductivity?

The section on potential used states: "At 300 K, CNT fibers have a resistivity one order of magnitude higher than the best electrical conductors.[91]"

Shouldn't this read either ".. resistivity on order of magnitude lower" or "conductivity one order of magnitude higher..." ? Sven Jense (talk) 10:19, 15 March 2018 (UTC)

In the source, it does in fact say

"At high temperature the results obtained on the raw CNT fibers show a typical metallic behavior and the resistivity levels without postdoping process were found to be only one order of magnitude higher than the best electrical conductors, with the specific conductivity (conductivity per unit weight) comparable to that of pure copper"

- that's at high temperatures. But I agree that including this fact here, without context may be a bit confusing. In the article, the point seems to be that the observed resistivity-temperature dependence implies a 2D mechanism for conduction. CyreJ (talk) 09:12, 16 March 2018 (UTC)

References

"will permit the use of multi-walled nanotubes as main movable arms in coming nanomechanical devices" -- clear example of crystal-balling

The telescopic motion ability of inner shells and their unique mechanical properties will permit the use of multi-walled nanotubes as main movable arms in coming nanomechanical devices. Retraction force that occurs to telescopic motion caused by the Lennard-Jones interaction between shells and its value is about 1.5 nN.

This paragraph is formed around an explicitly prognosticatory assertion. (See "Wikipedia is not a crystal ball".) Perhaps someone can find some way of relating the findings of the cited references in a non-speculative context? Otherwise I'd suggest just deleting the paragraph. I've put in a Speculation-inline template for now. —Undomelin (talk) 18:12, 30 May 2018 (UTC)

References

Possible error in lede

The lede states, in part: "Owing to the material's exceptional strength and stiffness, nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] significantly larger than for any other material." I believe that most common quartz optical fibers (optical waveguides) have a diameter of about 125 micrometers. It's been a few years, but I am under the impression that they can be drawn directly to lengths of at least 1000 kilometers, and possibly substantially longer. 1000 km is about 8 billion times longer than 0.000125 meters. In addition, such quartz fibers can be welded together, using lasers, for even larger lengths. This is a bit difficult to research, because if you do a google search for 'longest optical fiber length', the usual result refers to the maximum data link distance, which might involve many fibers attached with mechanical connectors. 2601:1C2:4E02:3020:75FC:EE91:77A2:647A (talk) 20:44, 7 August 2018 (UTC)

Top image in Android Wikipedia app is not a carbon nanotube

Just to say I'm currently using the Android Wikipedia app and the top image behind the title for some reason is showing a buckyball instead of a CNT... CharlesC (talk) 10:58, 23 December 2018 (UTC)

Symmetry section/article

I started writing the following section about the symmetries of carbon nanotubes. Naturally I assumed infinite length (that is, assumed that the ends are so faraway that their influence on the part of interest is negligible), and a regular graphene-like geometry with all atoms on a cylindrical surface. This seems to be a standard assumption in studies of this kind.
However, I now wonder whether real nanotubes may not be that nice. Given that the bonds are strained compared to graphene, perhaps the atoms find a way to relieve some of the strain by puckering in and out of that ideal cylinder? In that case, the theoretical analysis of the symmetries, below, would not hold. The actual symmetry group could be just as subgroup of the ideal one below. Or there may not even be any symmetry.
Are there emprical or quantum-theoretical papers that have looked into this question?
Anyway, even if this analysis is sound and relevant, maybe it should be a separate article?

---

Symmetry

Ideal (infinitely long) carbon nanotubes are highly symmetrical, and that symmetry influences the physical properties of the tubes, even of actual (finite) ones.

A (three-dimensional) isometry is a mapping from three-space to itself that preserves distances between points (and therefore also angles). They comprise rotations, translations, and reflections, and arbitrary sequences of those. A symmetry of a shape is an isometry that leaves the shape unchanged -- like rotation of an n-sided pyramid about its axis by 1/n of a turn, or mirroring a box across one of its bissecting planes.

The symmetries of a chiral nanotube must preserve its handedness, and therefore can be described as combinations of rotations and translations, with no reflections. For any two atoms A and B of the tube, there is exactly one isometry that takes A to the position of B. if A and B belong to the same class (that is, their bonds point in the same directions in the unrolled diagram) then the isometry is either a rotation of the tube around its axis M, a translation along the direction of M, or a combination of the two (a screw motion). If the atoms belong to opposite classes, the isometry is a rotation by 180 degrees around an axis L that is perpendicular M and to the line segment AB, and goes through the midpoint of the latter.

These isometries imply that all atom positions are equivalent, with respect to the tube's structure. On the other hand, the bonds are not equivalent. They can be divided into three classes, depending on the angle that they make with respect to the direction of M. For any two bonds of the same class, there is an isometry that takes one to the other, in each of the two possible senses; but no isometry can take a bond to another bond of a different class.

The isometries that move the atoms by the smallest amounts are the six screw motions that take any atom to one of the six nearest atoms of the same class. In the unrolled diagram, they correspond to translations by the six vectors u, v, v−u, −u, −v, and u−v.

Let g be the greatest common divisor of the type indices n and m of the tube. If g is greater than 1, then the isometries of the tube include pure rotations of the tube about the axis by multiples of 1/g of a turn. (These symmetries also exist for finite tubes of that type, if properly terminated.) Moreover, for any n and m, there are isometries that are pure translations by multiples of |r| along the direction of M, where r = ((2m n)u - (2n m)v)/g. That is, the tube's structure is periodic along the tube's axis, even without rotation.

Zigzag and armchair nanotubes have all these rotational and translational isometries, but, being achiral, have also many symmetries that involve reflections.

On a zigzag nanotube, for any atom A, there is an "axial" plane of symmetry that contains A and the axis M of the tube. There is also a "transversal" plane of symmetry, perpendicular to M, halfway between any two successive zigzag rings. On an armchair nanotube, for each bond that is directed perpendicularly to M there is a "transversal" plane of symmetry that includes that bond and is perpendicular to M; and an "axial" plane that contains M and bisects that bond.

Thus, a zizgzag tube of type (n,0) and an armchair tube of type (n,n) have n axial planes of symmetry. Their symmetries include pure rotations around the axis M by 1/n of a turn, and pure translations in the direction of M, by the distance |2v − u| for the zigzag types, and |u| for the armchair types.

The mirror symmetries imply that the bonds in achiral tubes are of only two types, not three. In zigzag tubes, one bond out of every atom is parallel to the axis M, and two are directed at 60 degrees from it. In armchair tubes, one bond is directed at 90 degrees to M, and two at 30 degrees from it. The skew bonds are all structurally equivalent, and distinct from the parallel or perpendicular bonds.

---

All the best, --Jorge Stolfi (talk) 07:05, 7 May 2019 (UTC)

They are not the strongest?

The article on linear acetylenic carbon (carbyne, [−C≡C−]_n or [=C=C=]_n) claims that it is stronger and tougher that nanotubes. Can we organize a boxing match between them, to settle the question?
(Unless the nanotubologists agree carbyne IS a degenerate nanotube, of type (1,0)...)
--Jorge Stolfi (talk) 09:10, 8 May 2019 (UTC)

Doubts about terminology

I am referring to the following sentences in the text, just before the box of the content, and reported here in italics: The unique strength of carbon nanotubes (or fullerenes in general) is due to orbital hybridization, which causes the bonds between adjacent carbon atoms to be of the sp2 type. These bonds, which are similar to those of graphene, are stronger than the sp3 bonds in alkanes and diamond. Now, to my knowledge, sp2 or sp3 are symbols referring to the kind of hybridization of an atom, and are not to be employed to designate a kind of bond. Therefore, the covalent homonuclear bonds of the topic should be designed as σ , obtained by overlappind of sp2 hybrid orbitals. This kind of overlapping produces bonds stronger than employing sp3 ones; of course, there is also the π-component to be taken into account. In addition, strictly, the hybridization of carbon atoms in nanotubes is somewhat intermediate between sp2 and sp3, the contribution of the former being however larger than the latter. But perhaps it is preferable not to mention this topic in an introductory article such as Wikipedia's one.Ekisbares (talk) 07:22, 30 September 2019 (UTC)

@Ekisbares: Good catch. I've removed the text. John P. Sadowski (NIOSH) (talk) 02:37, 2 October 2019 (UTC)

In my opinion, removing the whole passage is too much. Perhaps, it could remain, after modification, for instance as follows:

The unique strength of carbon nanotubes (or fullerenes in general) is due to the fact that the σ-bonds between adjacent carbon atoms come out of the overlap of sp2 orbitals. These bonds, which are similar to those of graphene, are stronger than the bonds in alkanes and diamond, which are produced by the overlap of sp3 orbitals. Moreover, the presence of a delocalized π-bond in addition to the σ-ones gives further strength to the bonds in nanotubes (as well as in fullerenes and graphene).

I would point out that also the article of Wikipedia about graphite contains similarly objectionable terminology. As I did for the article about nanotubes, I wrote some remarks in the “Talk” section. If there is agreement, that article could be modified as well.Ekisbares (talk) 16:57, 10 October 2019 (UTC)

@Ekisbares: I'd like to see a reference for that from a peer-reviewed source. My instinct is that it's simplistic to say that material strength is based solely on bond order. There's also the difference between single-molecule and bulk strength, and also different kinds of mechanical stress. You might want to take a look at Mechanical properties of carbon nanotubes, that article could certainly use some improvement. John P. Sadowski (NIOSH) (talk) 03:00, 17 October 2019 (UTC)

I agree with you. I erroneously gave as ascertained the statement about the "unique strength of carbon nanotubes" as depending only on the strength of the chemical bonds, and just wanted to give this statement a more correct form. But your observation has convinced me that it is preferable to remove the whole passage. I would like to know your opinion about my observations regarding the article concerning graphite.Ekisbares (talk) 20:36, 20 October 2019 (UTC)

Article issues and classification

The article is tagged "citation needed" since December 2020 and November 2022. The criteria #1 states; The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited.

• Unsourced content:

The 2nd and 3rd paragraphs of the "Basic details" section, and the last 3 sentences of the last paragraph,

The entire "Types" section as well as the 1st paragraph of the "Narrowest examples" subsection,

The "Variants" section,

The "Properties" section,

The 4th paragraph of the "Electrical" section,

The 1st paragraph in the "Optical" section,

The 2nd paragraph of the "Synthesis" section,

The 2nd paragraph of the "Functionalization" section,

The 1st paragraph of the "Current" section

The article is reasonably well-written. (#4) yet the lead has nine paragraphs. The article is tagged as having "predictions or speculation" and "needing clarification".

• This article fails the B-class criteria. -- Otr500 (talk) 09:57, 27 February 2023 (UTC)