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Multiscale structuring and characterisation of polyvinylidene difluoride based nanodielectrics
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Pickford, Tom (2022) Multiscale structuring and characterisation of polyvinylidene difluoride based nanodielectrics. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3879788
Abstract
In the 21st century, the efficiency and sustainability of devices used for electrical energy storage presents a significant challenge for various technologies and industries. Despite many electrical devices and systems becoming more advanced, the components that power these systems are often based on technologies that have not substantially modernised over the past few decades. Dielectric polymers offer a new route for enhancing pulsed power delivery in electrical systems, offering a plethora of advantages over the industry standard ceramics that dominate the field, resolving both the sustainability and energy efficiency problems simultaneously.
This project explores the potential of electrospun polyvinylidene difluoride (PVDF) nanofibre membranes for use in pulsed power devices. PVDF is notable due to the ferroelectric behaviour of its crystalline β-phase, which leads impressive energy storage properties in the polymer, allowing it to compete with commercial capacitors. This has led to the development of a variety of approaches to producing PVDF with a high β-phase content in recent years, with many endeavours producing near 100% β-phase content. Hence attention is now being paid to the subtleties of the crystalline nanostructure of PVDF, such as crystallite size and the orientation of crystallites to further bolster its energy storage potential.
Here, the crystalline nanostructure of PVDF nanofibres is extensively explored under different processing conditions using materials characterisation techniques such as infrared spectroscopy, X-ray diffraction and scanning electron microscopy, while characterising the energy storage potential of these materials using . Correlations are drawn between processing conditions to crystalline nanostructure, and in turn nanostructure in relation to energy storage performance.
Notably in this work, PVDF is electrospun using an ionic liquid in the electrospinning solution, which seeks to maximise the β-phase crystallinity and optimise the crystalline nanostructure of the nanofibre membranes at minimal additional time or cost investment. The unique morphology of the nanofibres is utilised to construct nanocomposites by coating the nanofibres with nanoparticles – in particular, metal organic frameworks (MOFs) – to further increase the energy storage potential of the nanofibre membranes. Finally, multilayer all-polymer laminate materials are constructed to prevent the high energy losses and low-field electrical breakdown experienced by electrospun PVDF nanofibre membranes when used for capacitive energy storage in isolation, as well as alleviating the mechanical fragility of the membranes. This thesis presents a route to creating highly ferroelectric polymer-based materials with impressive energy storage properties that could shape the future of materials in pulsed power devices.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) T Technology > TK Electrical engineering. Electronics Nuclear engineering |
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Library of Congress Subject Headings (LCSH): | Energy storage, Dielectrics, Vinylpyridine, Polymerization, Crystallization, Nanocomposites (Materials), Metal-organic frameworks | ||||
Official Date: | May 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Warwick Manufacturing Group | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Wan, Chaoying | ||||
Format of File: | |||||
Extent: | xvi, 171 pages : colour illustrations, colour charts | ||||
Language: | eng |
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