Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532281
Title: Structural and thermogravimetric studies of group I and II borohydrides
Author: Nickels, Elizabeth Anne
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2010
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Abstract:
This thesis investigates the structure and thermal behaviour of LiBH4, NaBH4, KBH4, LiK(BH4)2, Ca(BH4)2 and Sr(BH4)2. LiK(BH4)2 is the first mixed alkali metal borohydride and was synthesised and characterised during this work. The crystal structures of these borohydrides were studied using variable temperature neutron and synchrotron X-ray diffraction. The synthesis of isotopically enriched samples of 7Li11BD4, Li11BD4, Na11BD4 and K11BD4 allowed high quality neutron diffraction data to be collected. Particular attention was paid to the exact geometry of the borohydride ions which were generally found to be perfect tetrahedra but with orientational disorder. New structures of Ca(BH4)2 were identified and the first crystal structure of Sr(BH4)2 was determined from synchrotron X-ray diffraction data. Solid state 11B NMR and Raman spectroscopy provided further information about the structure of these borohydrides. The thermal behaviour of the borohydrides was investigated using thermogravimetric analysis with mass spectrometry of the decomposition gas products. Hydrogen is the main decomposition gas product from all of these compounds but small amounts of B2H6 and BH3 were also detected during decomposition. Thermogravimetic analyses of Na11BD4 and K11BD4 were completed whilst collecting in-situ neutron diffraction data allowing information about structural changes and mass losses to be combined in order to better understand the decomposition process.
Supervisor: Edwards, Peter P. ; David, William I. F. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.532281  DOI: Not available
Keywords: Chemical crystallography ; Crystallography ; Hydrogen Storage ; Inorganic chemistry ; NMR spectroscopy ; Solid state chemistry ; Borohydrides ; Hydrogen storage ; X-ray and neutron diffraction ; crystal structure ; thermogravimetric
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