The Fabrication of Thermoelectric Materials Using Functionalised Silicon Nanoparticles

Ashby, Shane (2015) The Fabrication of Thermoelectric Materials Using Functionalised Silicon Nanoparticles. Doctoral thesis, University of East Anglia.

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    Silicon nanoparticles (SiNPs) can be synthesised by a variety of methods. A one-pot synthesis
    based on the chemical reduction of inverse micelles has been used to produce SiNPs with ligands
    of varying alkyl chain length. These particles were characterised to determine how the chain
    length affects the surface functionalities and particle size. The particles produced show optical
    properties typical of SiNPs produced by solution methods.
    Silicon based materials are a potential alternative to current thermoelectric materials (e.g.
    Bi2Te3) due to their abundance and low toxicity. Phenylacetylene functionalised SiNPs have been
    synthesised using a bottom up approach. A cold pressed pellet of this material displays an
    electrical conductivity of 18.1 S m-1, in addition to a high Seebeck coefficient and a low thermal
    conductivity. These properties combine to give a figure of merit (ZT) of 0.6 at 300 K. This ZT value
    is significant for a silicon based material, and comparable to that of other thermoelectric materials
    such as Mg2Si, PbTe and Si-Ge alloy.
    To investigate the effects that the doping of ligands have on the thermoelectric properties of
    such materials, terthiophene functionalised SiNPs were synthesised and subsequently doped using
    varying levels of NOBF4. The electrical resistivity shows a decrease of 7 orders of magnitude
    between the undoped and optimised material although the electrical resistivity is still higher than
    required for application. In addition, the material produced displays a modest ZT of 0.08.
    Top down methods allow control of the carrier concentration of the silicon core, as the
    material is doped prior to being broken down. Phenylacetylene SiNPs were synthesised using
    electrochemical etching followed by functionalisation via a two-step chlorination-alkylation
    process. These particles were characterised and their thermal stability analysed, showing a
    maximum operation temperature of 200oC.

    Item Type: Thesis (Doctoral)
    Faculty \ School: Faculty of Science > School of Chemistry
    Depositing User: Mia Reeves
    Date Deposited: 19 Jun 2015 11:48
    Last Modified: 19 Jun 2015 11:48

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