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Analytical Electron Microscopy Studies for Development of New Carbon Based Materials
Stockholm University, Faculty of Science, Department of Physics.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis presents transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) studies of new carbon based materials synthesized with two different techniques. In the first project, nitrogen is incorporated into carbon nanostructures by supersonic cluster beam deposition (SCBD) to favor the formation of curved and cross-linked structures, ultimately aiming at creating a material with high hardness combined with good elasticity. The second project deals with nanoporous carbon derived from various carbides (VC, WB, NbC, TaC, HfC, ZrC and TiC) synthesized at temperatures ranging from 700 to 1200 °C, ultimately aiming at creating a porous material with large surface area and narrow poor size distribution. In both projects, the results of different synthesis conditions are investigated with the help of high resolution TEM and EELS. Structural and chemical information about the samples is extracted and it is found that it is possible to alter the nanostructure depending on the synthesis conditions. The thesis ends with implementation and evaluation of Gold’s iterative deconvolution method for enhanced energy resolution in EEL spectra. Relevant background about the chemical elements, transmission electron microscopy and electron energy loss spectroscopy is included in the introductory chapters.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2010. , 136 p.
Keyword [en]
TEM, EELS, CNx thin films, Carbide derived carbons, Gold deconvolution, Resolution improvement
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-49549ISBN: 978-91-7447-191-5 (print)OAI: oai:DiVA.org:su-49549DiVA: diva2:378421
Public defence
2011-01-21, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2010-12-29 Created: 2010-12-15 Last updated: 2010-12-17Bibliographically approved
List of papers
1. Nanostructured CNx (0 < x < 0.2) films grown by supersonic cluster beam deposition
Open this publication in new window or tab >>Nanostructured CNx (0 < x < 0.2) films grown by supersonic cluster beam deposition
2005 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 43, 1460-1469 p.Article in journal (Refereed) Published
Abstract [en]

Nanostructured CNx thin films were prepared by supersonic cluster beam deposition (SCBD) and systematically characterized by transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The incorporation of nitrogen in the films (0 < x < 0.2) and the nanostructure were controlled by using different synthesis routes. Films containing bundles of well-ordered graphene multilayers, onions and nanotubes embedded in an amorphous matrix were grown alongside purely amorphous films by changing the deposition parameters. Graphitic nanostructures were synthesized without using metallic catalysts. The structural and electronic properties of the films have been studied by EELS. The role played by N in the carbon nanostructures has been deduced from XPS line-shape analysis.

Place, publisher, year, edition, pages
Oxford: Elsevier, 2005
Keyword
Electron energy loss spectroscopy, Electron microscopy, X-ray photoelectron spectrosopy, D. electronic structure, Chemical structure
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-49670 (URN)10:1016/j.carbon.2005.01.022 (DOI)
Note
Authors - beyond those already mentioned at Stockholm University - include: G. Bongiorno, M. Blomqvist, P. Piseri, P. Milani, C. Lenardi, C. Ducati, T. Caruso, P. Rudolf, E. Coronel.Available from: 2010-12-17 Created: 2010-12-17 Last updated: 2017-12-11Bibliographically approved
2. Structural and tribological properties of cluster-assembled CNx films
Open this publication in new window or tab >>Structural and tribological properties of cluster-assembled CNx films
2007 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 87, 767-772 p.Article in journal (Refereed) Published
Abstract [en]

We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence of the depsotion parameters on the chemical composition and structure of the films has been systematically studied by X-ray photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy. Depending on the deposition parameters, the films show a stucture ranging from amorphous to disordered graphitic with interlinked planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties.

Place, publisher, year, edition, pages
Springer Science, 2007
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-49666 (URN)10.1007/s00339-007-3898-8 (DOI)000245964300030 ()
Note
Authors - beyond those already mentioned at Stockholm University - include: M. Blomqvist, G. Bongiorno, A. Podesta, V. Serin, G. Abrasonis, U. Kreissig, W. Möller, E. Coronel, V. Casina, P. Piseri, P. Milani.Available from: 2010-12-17 Created: 2010-12-17 Last updated: 2017-12-11Bibliographically approved
3. EELS studies of carbide derived carbons
Open this publication in new window or tab >>EELS studies of carbide derived carbons
Show others...
2007 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 45, no 10, 2047-2053 p.Article in journal (Refereed) Published
Abstract [en]

Carbide derived carbons (CDCs) have been synthesized from VC, WC, TaC, NbC, HfC and ZrC at T = 1000 °C, and from TiC at T = 700–1200 °C via a chlorination reaction. The CDCs have been studied by means of high resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). These studies show that the structures of CDCs are strongly dependent upon the nature of the starting carbide and the synthesis temperature. The structures range from very disordered nanoporous carbon, consisting of randomly curved graphene layers, to compact spherical entities of compactly packed graphitic layers. EELS studies of carbon core-loss spectra show that the relative sp2 content in these carbons varies between 83% and 98%. The low-loss part of the EEL spectra shows that the positions of the π-plasmons and the bulk plasmons are more dependent on the carbide precursor, than the synthesis temperature. The densities of the CDC particles have been estimated using the bulk plasmon positions as well as the sp3 content determined from the C-K edge spectra. The densities calculated from sp3 are close to the pycnometric ones, while the densities calculated from bulk plasmon positions are lower and reflects the nanostructure of CDCs.

Place, publisher, year, edition, pages
Elsevier, 2007
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-24745 (URN)10.1016/j.carbon.2007.05.022 (DOI)000249540500017 ()
Available from: 2008-03-13 Created: 2008-03-13 Last updated: 2017-12-13Bibliographically approved
4. Implementation of Gold deconvolution for enhanced energy resolution in EEL spectra
Open this publication in new window or tab >>Implementation of Gold deconvolution for enhanced energy resolution in EEL spectra
2011 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 111, no 2, 79-89 p.Article in journal (Refereed) Published
Abstract [en]

Gold’s iterative deconvolution algorithm has been applied to one-dimensional EEL spectra from hexagonal BN. The experimental resolution was varied from 1.1 to 2.25 eV and Gold’s algorithm was able to restore low-loss and core-loss spectra overall well. To estimate the instrument response function, the most convenient method was to extract the zero-loss peak from the low-loss spectrum. It was also found as suggested by Egerton, that by using low-loss spectra as kernel, enhanced energy resolution could be obtained as plural scattering was simultaneously removed. It’s further shown how the FWHM of the p* peak in the boron K‑edge of hexagonal BN is reduced from 1.4 to 0.7 eV with almost no noise-amplification after 500 iterations while resolving the s* doublet. The result was almost identical after a stunning 5 000 - 10 000 iterations, implying that Gold’s method converges and can be stable for a large number of iterations. However, for lower-intensity spectra the number of iterations is limited. The results close to the intense zero-loss peak were uncertain and further testing with better experimental resolution is recommended. It’s also found that to improve the resolution and not just sharpen the spectra, a large number of iterations is required.

Keyword
EELS, Gold deconvolution, Resolution improvement, Hexagonal boron nitride
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-49663 (URN)10.1016/j.ultramic.2010.10.006 (DOI)000286552200001 ()
Available from: 2010-12-17 Created: 2010-12-17 Last updated: 2017-12-11Bibliographically approved

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