Thermal Measurements on Multi-wall Nanotubes #43 TSUN

Thermal Measurements on Multi-wall Nanotubes #43 TSUN -...

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Thermal Measurements on Multi-wall Nanotubes E. Brown, L. Hao, J. C. Gallop, and J. C. Macfarlane* National Physical Laboratory, Queens Road, Teddington, Middlesex, TW11 0LW, UK *University of Strathclyde, Glasgow, G4 0NG, UK Abstract. The electrical and mechanical properties of carbon nanotubes (CNTs) have been studied in depth at a single nanotube level; the same though cannot be said for their thermal properties. We have measured the thermal properties of multi-wall carbon nanotubes (MWNTs) using a temperature sensing scanned microscope probe. An arc-grown MWNT bundle is attached to a thermal probe with several individual MWNTs protruding from the end of the bundle. The system is operated in high vacuum and the temperature of the thermal probe may be controlled anywhere between 300 and 600 K. Then, under piezo displacement, the MWNT is brought into contact with a substrate surface (HOPG, highly oriented pyrolitic graphite). The substrate can be cooled from room temperature to ~100 K. The heat flow down the MWNTs in contact with the substrate can be recorded as a function of the temperature difference across their ends. Simultaneous measurements of the electrical conductance and force applied to the nanotube are taken. The thermal and electrical conductance curves of different MWNTs are presented; the size of the conductance steps observed and the correlation between electrical and thermal conductance steps are discussed together with the effect of oxygen adsorption on the properties of the MWNTs. INTRODUCTION: PROPERTIES OF CARBON NANOTUBES CNTs have been predicted to show extremely high thermal conductivity [1] and are also expected to display a 1-dimensional (1D) phonon density of states.[2] However measurements on individual nanotubes have been very few.[3] We suggested that carbon nanotubes should also be the ideal test beds for the study of ballistic phonon transport and of thermal conductance quantisation.[4] This has been theoretically confirmed in a recent publication by T Yamamoto et al.[5] Thermal conductance quantisation occurs in a dielectric quantum wire at low enough temperatures when its dimensions are smaller than its phonon mean free path.[6,7] The quantum of thermal conductance is G th . The total number of phonon channels available in a CNT is three times the number of atoms in its unit cell: 3N. N can be
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This note was uploaded on 03/18/2012 for the course PHYSICS 303 taught by Professor Ihn during the Spring '12 term at Swiss Federal Institute of Technology Zurich.

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Thermal Measurements on Multi-wall Nanotubes #43 TSUN -...

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