Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.742210
Title: Crystallisation at functionalised interfaces
Author: Ravenhill, Emma Rosanna
ISNI:       0000 0004 7227 596X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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Abstract:
Within this thesis, a broad range of microscopic and spectroscopic methods are employed to investigate crystallisation processes initiated at novel functionalised interfaces. This approach combines in situ optical microscopy (OM) with several surface sensitive techniques, including atomic force microscopy (AFM), scanning electron microscopy (SEM) and interferometry, with further structural analysis provided via Raman spectroscopy and X-ray diffraction (XRD). This method allows the key mechanistic phenomena to be elucidated to a high level of detail for crystal growth processes with extreme industrial and biological importance. The main focus of the thesis is around a specific industrial problem, concerning the detrimental growth of inorganic crystalline materials within internal combustion engines. Firstly, the deposit structure is revealed by implementing analytical techniques such as SEM, Raman spectroscopy and XRD to characterise real engine deposits. This in depth analysis demonstrates the high abundance of the calcium sulfate polymorphs bassanite (CaSO4⋅0.5H2O) and anhydrite (CaSO4) within the deposit, providing initial insights into this unfavourable growth process. These deposit growth mechanisms are further studied via in situ OM, monitoring calcium sulfate crystallisation at aqueous-organic liquid-liquid interfaces to mimic real life conditions within the engine environment. As well as providing a wealth of knowledge on the deposit formation process, this approach highlights the unique properties liquid-liquid interfaces offer for crystal growth, revealing via Raman spectroscopy and XRD analysis their applicability for synthesising typically unstable materials under low energy, ambient conditions. This industrial problem is further investigated by studying the surface reactivity of the growing calcium sulfate mineral faces via AFM force spectroscopy. This allows interaction forces between the deposit surface and different additive chemistries to be quantitatively determined in an oil-based environment, opening up methods for preventing deposition on engine surfaces. Unexpected, low adhesion values are obtained between polar additive head groups and the polar crystal deposit surface, a consequence of electrostatic repulsion. Thus, this work reveals key aspects related to the structure of charge in organic environments, an area still under much debate. The last chapter of this thesis switches focus to one of the key minerals responsible for engine deposit growth, calcium carbonate. Charged graphite interfaces are implemented to study their effects on the oriented nucleation and polymorphism of this crystal system, in the absence of defects and chemical functionalities. This highlights the significant role electrostatics play in nucleating high energy crystal planes and polymorphs, which is of huge importance for biomineralisation, and scale-prone, charged industrial surfaces. Overall, this thesis elucidates the unexplored properties of two highly relevant functionalised crystal growth interfaces, demonstrating their importance for preventing deposit growth, as well as their diverse application for the synthesis of high energy crystalline materials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.742210  DOI: Not available
Keywords: QD Chemistry ; TL Motor vehicles. Aeronautics. Astronautics
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