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Length dependent stability of single-walled carbon nanotubes and how it affects their growth
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.ORCID-id: 0000-0003-1542-6170
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.ORCID-id: 0000-0003-3455-2877
Antal upphovsmän: 22017 (Engelska)Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 116, s. 443-447Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Using density-functional theory the stability of armchair and zigzag single-walled carbon nanotubes and graphene nanoribbons was investigated. We found that the stability of armchair and zigzag nanotubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each nanotube series. We explain these dependencies by competing edge and curvature effects. We have found that within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths. These results shed new insights into why (near) armchair nanotubes are the dominant product from catalytic chemical vapor deposition growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable nanotubes.

Ort, förlag, år, upplaga, sidor
Elsevier, 2017. Vol. 116, s. 443-447
Nyckelord [en]
Single-walled carbon nanotubes; Density functional theory; Stability; Selective growth; Chirality
Nationell ämneskategori
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Identifikatorer
URN: urn:nbn:se:ltu:diva-61856DOI: 10.1016/j.carbon.2017.02.007ISI: 000397549300053Scopus ID: 2-s2.0-85012164107OAI: oai:DiVA.org:ltu-61856DiVA, id: diva2:1072207
Anmärkning

Validerad; 2017; Nivå 2; 2017-02-15 (andbra)

Tillgänglig från: 2017-02-07 Skapad: 2017-02-07 Senast uppdaterad: 2018-12-14Bibliografiskt granskad
Ingår i avhandling
1. A Theoretical Study: The Connection between Stability of Single-Walled Carbon Nanotubes and Observed Products
Öppna denna publikation i ny flik eller fönster >>A Theoretical Study: The Connection between Stability of Single-Walled Carbon Nanotubes and Observed Products
2017 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Alternativ titel[sv]
En Teoretisk Studie: Sambandet mellan Stabiliteten for Enkelväggiga Kolnanorör och Observerade Produkter
Abstract [en]

Over the past 20 years’ researchers have tried to utilize the remarkable properties of single-walled carbon nanotubes (SWCNTs) to create new high-tech materials and devices, such as strong light-weight composites, efficient electrical wires and super-fast transistors. But the mass production of these materials and devices are still hampered by the poor uniformity of the produced SWCNTs. These are hollow cylindrical tubes of carbon where the atomic structure of the tube wall consists of just a single atomic layer of carbon atoms arranged in a hexagonal grid. For a SWCNT the orientation of the hexagonal grid making up the tube wall is what determines its properties, this orientation is known as the chirality of a SWCNT. As an example, tubes with certain chiralities will be electrically conductive while others having different chiralities will be semiconducting.

Today’s large scale methods for producing SWCNTs, commonly known as growth of SWCNTs, gives products with a large spread of different chiralities. A mixture of chiralities will give products with a mixture of different properties. This is one of the major problems holding back the use of SWCNTs in future materials and devices. The ultimate goal is to achieve growth where the resulting product is uniform, meaning that all of the SWCNTs have the same chirality, a process termed chirality-specific growth. To achieve chirality-specific growth of SWCNTs requires us to obtain a better fundamental understanding about how they grow, both from an experimental and a theoretical point of view.

This work focuses on theoretical studies of SWCNT properties and how they relate to the growth process, thereby giving us vital new information about how SWCNTs grow and taking us ever closer to achieving the ultimate goal of chirality-specific growth. In this thesis, an introduction to the field is given and the current state of the art experiments focusing on chirality-specific growth of SWCNTs are presented. A brief review of the current theoretical works and computer simulations related to growth of SWCNTs is also presented. The results presented in this thesis are obtained using first principle density functional theory. The first study shows a correlation between the stability of SWCNT-fragments and the observed products from experiments. Calculations confirm that in 84% of the investigated cases the chirality of experimental products matches the chirality of the most stable SWCNT-fragments (within 0.2 eV). Further theoretical calculations also reveal a previously unknown link between the stability of SWCNT-fragments and their length. The calculations show that at specific SWCNT-fragment lengths the most stable chirality changes. Thus, introducing the concept of a switching length for SWCNT stability. How these new results link to the existing understanding of SWCNT growth is discussed at the end of the thesis.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2017
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nyckelord
Single-walled carbon nanotubes, density functional theory, catalytic chemical vapor deposition, chirality-specific growth, stability, length, diameter, edge, chirality
Nationell ämneskategori
Den kondenserade materiens fysik Atom- och molekylfysik och optik
Forskningsämne
Tillämpad fysik
Identifikatorer
urn:nbn:se:ltu:diva-62321 (URN)978-91-7583-837-3 (ISBN)978-91-7583-838-0 (ISBN)
Presentation
2017-05-03, E632, Luleå, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2017-03-09 Skapad: 2017-03-07 Senast uppdaterad: 2017-11-24Bibliografiskt granskad

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