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The importance of strong carbon-metal adhesion for catalytic nucleation of single-walled carbon nanotubes
Fysiska Institutionen, Göteborgs Universitet.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
Tyndall National Institute, Unversity College Cork.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
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2008 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 2, 463-468 p.Article in journal (Refereed) Published
Abstract [en]

Density functional theory is used to show that the adhesion between single-walled carbon nanotubes (SWNTs) and the catalyst particles from which they grow needs to be strong to support nanotube growth. It is found that Fe, Co, and Ni, commonly used to catalyze SWNT growth, have larger adhesion strengths to SWNTs than Cu, Pd, and Au and are therefore likely to be more efficient for supporting growth. The calculations also show that to maintain an open end of the SWNT it is necessary that the SWNT adhesion strength to the metal particle is comparable to the cap formation energy of the SWNT end. This implies that the difference between continued and discontinued SWNT growth to a large extent depends on the carbon-metal binding strength, which we demonstrate by molecular dynamics (MD) simulations. The results highlight that first principles computations are vital for the understanding of the binding strength's role in the SWNT growth mechanism and are needed to get accurate force field parameters for MD.

Place, publisher, year, edition, pages
2008. Vol. 8, no 2, 463-468 p.
National Category
Other Physics Topics
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-108264DOI: 10.1021/nl072431mISI: 000253166200016PubMedID: 18162001OAI: oai:DiVA.org:uu-108264DiVA: diva2:234803
Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
Open this publication in new window or tab >>Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Density functional theory has been used to investigate cathode materials for rechargeable batteries, carbon nanotube interactions with catalyst particles and transition metal catalyzed hydrogen release in magnesium hydride nanoclusters.

An effort has been made to the understand structural and electrochemical properties of lithium iron silicate (Li2FeSiO4) and its manganese-doped analogue. Starting from the X-ray measurements, the crystal structure of Li2FeSiO4 was refined, and several metastable phases of partially delithiated Li2FeSiO4 were identified. There are signs that manganese doping leads to structural instability and that lithium extraction beyond 50% capacity only occurs at impractically high potentials in the new material.

The chemical interaction energies of single-walled carbon nanotubes and nanoclusters were calculated. It is found that the interaction needs to be strong enough to compete with the energy gained by detaching the nanotubes and forming closed ends with carbon caps. This represents a new criterion for determining catalyst metal suitability. The stability of isolated carbon nanotube fragments were also studied, and it is argued that chirality selection during growth is best achieved by exploiting the much wider energy span of open-ended carbon nanotube fragments.

Magnesium hydride nanoclusters were doped with transition metals Ti, V, Fe, and Ni. The resulting changes in hydrogen desorption energies from the surface were calculated, and the associated changes in the cluster structures reveal that the transition metals not only lower the desorption energy of hydrogen, but also seem to work as proposed in the gateway hypothesis of transition metal catalysis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 670
Keyword
Materials science, density functional theory, cathode materials, hydrogen-storage materials, carbon nanotube growth
National Category
Other Physics Topics
Research subject
Physics of Matter; Materials Science
Identifiers
urn:nbn:se:uu:diva-108261 (URN)978-91-554-7603-8 (ISBN)
Public defence
2009-10-23, Polhemsalen, Ångströmlaboratoriet, Uppsala, 13:15 (English)
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Supervisors
Available from: 2009-10-01 Created: 2009-09-10 Last updated: 2009-10-01

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Ahuja, Rajeev

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