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The influence of crystallinity on the properties of carbon nanotubes
Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).ORCID-id: 0000-0002-5627-7637
2021 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Carbon nanotubes have been advertised as a material with quite extraordinary properties, both mechanically and electrically. The truth is that carbon nanotubes is not one material, but several different. Depending on the method used to produce them, and consequently the quality of the atomic structure within their walls, their physical properties can also differ drastically. 

In this doctoral thesis a method was developed for quantifying the degree of order within the tubes' walls, namely their crystallinity, by using transmission electron microscopy. The method enables the characterization of the inherent properties of the tubes such as electrical conductivity and bending stiffness, alongside the determination of crystallinity, making it possible to quantify the influence of tube crystallinity on these critical properties. Furthermore, a model for electrical conduction in the outermost wall of multi-walled carbon nanotubes is suggested, enabling the determination of intrinsic quantities like the sheet resistance of individual crystallite grains within the walls and the boundaries in-between them. 

The studies reveal a profound shift in both mechanical and electrical behavior at a critical crystallite size, with large differences connected to production method, and even between individual tubes from the same production batch. These findings successfully explain previously seen differences and highlight the need for well-defined characterization techniques with protocols and classification systems, in order to successfully exploit the promising properties of carbon nanotubes in the future.

Ort, förlag, år, upplaga, sidor
Karlstad: Karlstads universitet, 2021. , s. 82
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2021:30
Nyckelord [en]
carbon nanotubes, crystallinity, electrical conductivity, transmission electron microscopy
Nationell ämneskategori
Fysik Den kondenserade materiens fysik
Forskningsämne
Fysik
Identifikatorer
URN: urn:nbn:se:kau:diva-86394ISBN: 978-91-7867-235-6 (tryckt)ISBN: 978-91-7867-246-2 (digital)OAI: oai:DiVA.org:kau-86394DiVA, id: diva2:1607203
Disputation
2021-12-17, 21A 342 Eva Eriksson, Karlstads universitet, Karlstad, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2021-11-26 Skapad: 2021-10-29 Senast uppdaterad: 2021-11-26Bibliografiskt granskad
Delarbeten
1. Quantifying crystallinity in carbon nanotubes and its influence on mechanical behaviour
Öppna denna publikation i ny flik eller fönster >>Quantifying crystallinity in carbon nanotubes and its influence on mechanical behaviour
2019 (Engelska)Ingår i: Materials Today Communications, ISSN 2352-4928, Vol. 18, s. 39-45Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The different fabrication methods that have been developed for making carbon nanotubes will provide materials with different levels of crystallinity. As crystallinity is qualitatively known to have a profound influence on material properties, this raises the need for standardised quantitative analysis. Here we show how transmission electron microscopy can be used to provide quantitative information about effective crystallite sizes in individual nanotubes which we link to the mechanical behaviour of the tubes. The method relies on a thorough analysis of diffraction patterns and a careful extraction of instrumental and sample contributions to the peak shapes. We find that arc-discharge grown tubes have crystallite sizes that are comparable to the circumference of the outer tube walls, while commercial catalytically grown tubes have much smaller crystallites implying that each cylindrical nanotube wall can be thought of as a patchwork of small graphene-like grains. The clear differences in crystallite sizes are then compared to known differences in mechanical behaviour, such as a substantial disparity in stiffness and significantly different behaviours under bending stress.

Ort, förlag, år, upplaga, sidor
Elsevier, 2019
Nyckelord
Carbon nanotubes, Crystallite size, High resolution transmission electron microscopy, Transmission electron microscopy, Arc discharge, Bending stress, Crystallinities, Cylindrical nanotube, Fabrication method, Graphene likes, Mechanical behaviour, Quantitative information, Yarn
Nationell ämneskategori
Materialteknik Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-70410 (URN)10.1016/j.mtcomm.2018.11.003 (DOI)000456868200006 ()2-s2.0-85056626896 (Scopus ID)
Tillgänglig från: 2018-12-05 Skapad: 2018-12-05 Senast uppdaterad: 2021-10-29Bibliografiskt granskad
2. Accurate determination of electrical conductance in carbon nanostructures
Öppna denna publikation i ny flik eller fönster >>Accurate determination of electrical conductance in carbon nanostructures
2022 (Engelska)Ingår i: Materials Research Express, E-ISSN 2053-1591, Vol. 9, nr 3, artikel-id 035010Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Electrical characterization of nanostructures, such as nanotubes and wires, is a demanding task that is vital for future applications of nanomaterials. The nanostructures should ideally be analyzed in a free-standing state and also allow for other material characterizations to be made of the same individual nanostructures. Several methods have been used for electrical characterizations of carbon nanotubes in the past. The results are widely spread, both between different characterizations methods and within the same materials. This raises questions regarding the reliability of different methods and their accuracy, and there is a need for a measurement standard and classification scheme for carbon nanotube materials. Here we examine a two-probe method performed inside a transmission electron microscope in detail, addressing specifically the accuracy by which the electrical conductivity of individual carbon nanotubes can be determined. We show that two-probe methods can be very reliable using a suitable thermal cleaning method of the contact points. The linear resistance of the outermost nanotube wall can thus be accurately determined even for the highest crystallinity materials, where the linear resistance is only a few kΩ/µm. The method can thereby by used as a valuable tool for future classification schemes of various nanotube material classes. 

Ort, förlag, år, upplaga, sidor
Institute of Physics Publishing (IOPP), 2022
Nyckelord
carbon nanotubes, electrical conductivity, transmission electron microscopy
Nationell ämneskategori
Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-86393 (URN)10.1088/2053-1591/ac5e21 (DOI)000776456300001 ()2-s2.0-85128666644 (Scopus ID)
Anmärkning

Publicerades som manuscript i avhandlingen The influence of crystallinity on the properties of carbon nanotubes. 

Tillgänglig från: 2021-10-29 Skapad: 2021-10-29 Senast uppdaterad: 2022-06-14Bibliografiskt granskad
3. Influence of crystallinity on the electrical conductivity of individual carbon nanotubes
Öppna denna publikation i ny flik eller fönster >>Influence of crystallinity on the electrical conductivity of individual carbon nanotubes
2021 (Engelska)Ingår i: Carbon Trends, ISSN 2667-0569, Vol. 5, artikel-id 100125Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The material properties of graphene and carbon nanotubes are highly sensitive to defects. Future exploitation of these materials will thereby rely on both a detailed understanding and classification schemes for material quality. Here we have used electron diffraction to measure the mean effective crystallite size of individual multiwalled carbon nanotubes, while also probing their electrical resistance. At room temperature we find a drastic shift in linear resistance of two orders of magnitude at a critical grain size of about 11 nm, which we interpret as an effect from quantum confinement and edge effects in the individual crystallites. For the regions above and below the critical grain size value we suggest a scaling model for the electrical conductivity within a single layer of a multiwalled carbon nanotube which connects its electrical conductivity with the effective crystallite size and tube diameter.

Nyckelord
carbon nanotubes, electrical conductivity, crystallinity, quantum confinement, transmission electron microscopy
Nationell ämneskategori
Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-86392 (URN)10.1016/j.cartre.2021.100125 (DOI)2-s2.0-85119419513 (Scopus ID)
Anmärkning

Datasets related to this article are hosted at Mendeley Data and can be found at https://doi.org/10.17632/wwwb6txc4h.1 

Tillgänglig från: 2021-10-29 Skapad: 2021-10-29 Senast uppdaterad: 2022-03-10Bibliografiskt granskad
4. Effects of high temperature treatment of carbon nanotube arrays on graphite: Increased crystallinity, anchoring and inter-tube bonding
Öppna denna publikation i ny flik eller fönster >>Effects of high temperature treatment of carbon nanotube arrays on graphite: Increased crystallinity, anchoring and inter-tube bonding
Visa övriga...
2020 (Engelska)Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 31, nr 45, artikel-id 455708Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Thermal treatment of carbon nanotubes (CNTs) can significantly improve their mechanical, electrical and thermal properties due to reduced defects and increased crystallinity. In this work we investigate the effect of annealing at 3000 degrees C of vertically aligned CNT arrays synthesized by chemical vapor deposition (CVD) on graphite. Raman measurements show a drastically reduced amount of defects and, together with transmission electron microscope (TEM) diffraction measurements, an increased average crystallite size of around 50%, which corresponds to a 124% increase in Young's modulus. We also find a tendency for CNTs to bond to each other with van der Waals (vdW) forces, which causes individual CNTs to closely align with each other. This bonding causes a densification effect on the entire CNT array, which appears at temperatures >1000 degrees C. The densification onset temperature corresponds to the thermal decomposition of oxygen containing functional groups, which otherwise prevents close enough contact for vdW bonding. Finally, the remaining CVD catalyst on the bottom of the CNT array is evaporated during annealing, enabling direct anchoring of the CNTs to the underlying graphite substrate.

Ort, förlag, år, upplaga, sidor
Institute of Physics Publishing (IOPP), 2020
Nyckelord
carbon nanotubes, heat treatment, annealing, crystallinity
Nationell ämneskategori
Nanoteknik Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-80341 (URN)10.1088/1361-6528/ab9677 (DOI)000565731300001 ()32454479 (PubMedID)2-s2.0-85090079772 (Scopus ID)
Tillgänglig från: 2020-09-24 Skapad: 2020-09-24 Senast uppdaterad: 2022-03-30Bibliografiskt granskad
5. Hierarchical cellulose-derived CNF/CNT composites for electrostatic energy storage
Öppna denna publikation i ny flik eller fönster >>Hierarchical cellulose-derived CNF/CNT composites for electrostatic energy storage
Visa övriga...
2016 (Engelska)Ingår i: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, nr 12, artikel-id 124001Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Today many applications require new effective approaches in energy delivery on demand. Supercapacitors are viewed as essential energy storage devices that can continuously provide quick energy. The performance of supercapacitors is mostly determined by electrode materials that can store energy via electrostatic charge accumulation. This study presents new sustainable cellulose-derived composite electrodes which consist of carbon nanofibrous (CNF) mats covered with vapor-grown carbon nanotubes (CNTs). The CNF/CNT electrodes have high electrical conductivity and surface area: two most important features that are responsible for good electrochemical performance of supercapacitor electrodes. The results show that the composite electrodes have fairly high values of specific capacitance, energy and power density and can retain excellent performance over at least 2 000 cycles. All of that makes us think that sustainable cellulose-derived composites can be extensively used in future as supercapacitor electrodes.

Ort, förlag, år, upplaga, sidor
Institute of Physics (IOP), 2016
Nationell ämneskategori
Fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-45613 (URN)10.1088/0960-1317/26/12/124001 (DOI)000389022900002 ()
Tillgänglig från: 2016-09-01 Skapad: 2016-09-01 Senast uppdaterad: 2021-10-29Bibliografiskt granskad

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