Rahman, AS;
(2014)
Theoretical and experimental investigations of graphitic and crystalline carbon nitrides.
Doctoral thesis , UCL (University College London).
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Abstract
Solid-state carbon nitride materials are useful in a number of areas in industry, ranging from heat retardation, photocatalysis, electrochemistry, as well as the potential to form a new super hard material to rival diamond. The flexible nature of the chemical bonding and environment of C and N atoms in a carbon nitride system gives rise to wide structural diversity, which present challenges in characterisation of the material. Theoretical modeling for such a versatile system is an essential part of scientific research. Quantum mechanical computational methods are employed to study carbon nitride materials in dense sp3 bonded and planar polymeric graphitic phases. The computer codes used for this study are CRYSTAL and CASTEP, both based on DFT. Synthesis of dense and graphitic carbon nitride materials, using ionothermal and thermal methods were also conducted towards part of this research. The results from each theoretically calculated investigation in this thesis are compared with experimental data, to guide the understanding of the experimental results for the system under study. Experimentally synthesised and recovered carbon nitride material, with defective wurtzite structure and C2N3H stoichiometry, was investigated for its stability over a range of pressures. Three possible C2N3H phases arising from different proton arrangements were modeled to determine the most stable arrangement. A metastable C2N3H phase was detected experimentally; an ab initio structure prediction method was employed, which identified a structure that complied with experimental observations. CASTEP was tested and used to calculate NMR chemical shifts for 13C and 15N atoms for a number of carbon nitride materials. Predictions were focused on determining the atom connectivity and structural topology for thermal synthetic methods that yielded dense and graphitic carbon nitride solid‐state materials. Calculated NMR chemical shifts were also employed in a collaborative study to guide the understanding of planetary tholins, formed in Titan’s atmosphere.
Type: | Thesis (Doctoral) |
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Title: | Theoretical and experimental investigations of graphitic and crystalline carbon nitrides |
Open access status: | An open access version is available from UCL Discovery |
Language: | English |
Additional information: | Third party copyright material has been removed from ethesis. |
UCL classification: | UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
URI: | https://discovery.ucl.ac.uk/id/eprint/1426441 |
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