Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.766505
Title: In-situ generation and dissolution of nano structures by liquid and dry electron irradiation method
Author: Asghar, Muhamamd Sajid Ali
ISNI:       0000 0004 7655 2063
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Abstract:
Ceria nanostructure synthesis and dissolution has been achieved by using the dry and liquid electron beam irradiation method in transmission electron microscope (TEM). Traditionally used methods for synthesis of ceria nanostructures are chemical precipitation and for dissolution of ceria are based on strong acid with high temperature. Ceria nanoparticles and nanorods immersed in deionised water were irradiated with different intensity of electron beam using special liquid cell holder in TEM. For this purpose, transmission electron microscopes operating at 200 and 300 kV was used. Upon irradiation, various novel, unknown and known phenomena have been observed live such as, chain formation, new phase formation including (1D needle, multiple spiky needle, star shape needle and nanoparticles) and dissolution. Live in-situ observation of fast and giant dissolution of functional ceramic nanostructure at room temperature without external supply of acid is one of the main novel finding which is never observed before. We quantitatively measure and report the ceramic dissolution of ceria nanoparticles and nanorods in this work and our calculated dissolution rate is 5 orders of magnitude higher than the previous ex-situ calculated dissolution. On the other hand, two types of hydrated cerium salt were irradiated using electron beam of different intensity with or without condenser aperture. Upon direct dry irradiation of hydrated cerium precursors we have successfully explored the amorphous to crystalline transformation and formation of ceria and cerium chloride nanoparticles and nanorods in TEM. During the irradiation of cerium nitrate hexahydrate (CNH) in TEM at 200 kV we have explored the redox transformation and observed the internal precipitation of precursor causes the formation of nanoparticles on precursor. Furthermore, we have also explored the synthesis of ceria nanoparticles, nano rods and ceria nano-tubes by using the wet-chemical precipitation method at room temperature with different molar ratios of CNH and sodium hydroxide.
Supervisor: Moebus, Guenter ; Inkson, Beverley Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.766505  DOI: Not available
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