Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.796419
Title: An investigation of halogenated copper phthalocyanine pigments using transmission electron microscopy
Author: McColgan, Paul
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1990
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Abstract:
Halogenated copper phthalocyanines are an important class of organic materials, widely used in pigmentary form in paints, plastics, dyes and printing inks. The properties of these materials are strongly dependent on the size and chemical composition of the individual pigmentary particles. As individual pigmentary particles are typically 50nm, analytical techniques of high spatial resolution are required to investigate them. Electron microscopy is capable of providing structural and compositional information on the required scale and is thus well suited to the investigation of these materials. The industrial preparation of the pigmentary material is described in chapter 1, together with a brief introduction to the analytical techniques available in electron microscopy. The information that can be obtained using electron beam techniques is,however, limited by damage the material suffers during electron irradiation. This results in a loss of crystallinity and mass as the sample is irradiated. Care must therefore be taken when analysing radiation sensitive materials to ensure that the results obtained pertain to the as-prepared and not the damaged material. As radiation damage imposes severe limits on the investigation of organic materials by electron microscopy, chapter 2 gives a review of the major aspects of the damage processes together with particular damage studies of various phthalocyanines. In chapter 3, the theory of diffraction and imaging in the CTEM and STEM instruments used in this work is described. The results obtained from the CTEM diffraction and imaging studies of the pigment are presented in chapter 4. In chapter 5, results obtained using the Differential Phase Contrast (DPC) imaging mode in a STEM are presented. Advantages of this technique include its efficient use of electrons and the simultaneous availability of information on specimen topography and internal structure. Considerations relevant to energy dispersive x-ray (EDX) microanalysis are discussed in chapter 6. However, as discussed above, damage results in the breaking of chemical bonds leading in this case to the loss of peripheral halogen atoms and thus to a reduction in the halogen to copper ratio. As diffusion processes are strongly temperature dependent, cooling the sample should reduce the rate of halogen loss. To investigate this a specially designed low temperature x-ray rod was used. The experimental procedure adopted for EDX microanalysis is described in detail in chapter 7. It involved the acquisition of series of spectra at room and low temperature from the various pigmentary samples. This had two advantages. Firstly it provided accurate information on the halogen to copper ratios through extrapolation of each series to zero dose from which the undamaged composition was recovered. Additionally it allowed a comparison to be made between room and low temperature microanalysis under carefully controlled experimental conditions. This is important in assessing the improvements conferred by low temperature microanalysis. Finally in chapter 8, general conclusions are drawn on the work described in this thesis along with suggestions for possible continuation of the work.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.796419  DOI: Not available
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