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Title: An X-ray Bicrystal Truncation Rod Study of a Si Σ13 Symmetric Tilt Grain Boundary and Design and Commissioning of a Holography Endstation at Beamline I06
Authors: Rhead, Stephen David
Supervisors: Howes, Paul
Award date: 1-Oct-2011
Presented at: University of Leicester
Abstract: Naturally occurring grain boundary interfaces greatly influence important characteristics of many materials including their mechanical, electrical and magnetic properties. The atomic structure of such grain boundaries, while crucial to their behaviour, are inaccessible to most experimental techniques as they are internal to the material. Theoretical studies are complicated by the existence of multiple structures for a given grain boundary. Data from an X-ray diffraction experiment is presented, along with the model used for simulated scattering from Keating energy minimised grain boundary structures. The X-ray diffraction data was measured using a (2+3)-type diffractometer on beamline I07 of the Diamond Light Source. The traditional way to measure the integrated intensity from an X-ray diffraction experiment is to perform a rocking scan. By use of a large 2D area PILATUS detector, an alternative method of measuring diffraction data, where the sample remains fixed, can be implemented. A comparison of the different techniques shows that the stationary scan improves the reliability and shortens the measuring time by almost an order of magnitude. The theory of crystal truncation rod scattering is extended to account for the bicrystallography of the sample, which gives rise to two overlapping rods; one from each crystal. Simulated X-ray scattering from Keating energy minimised grain boundaries is compared with experimental data. The simulated scattering, which has atomic sensitivity, is used to discriminate between potential structures based on the statistical goodness of fit with the data. Finally, a custom designed diffraction chamber was built allowing users to perform lensless Fourier transform holography experiments on the branchline of I06 at the Diamond Light Source. Preliminary data is presented and data analysis techniques discussed. Phase retrieval algorithms do not yield any further high resolution reconstructions due to the noise levels of the hologram.
Type: Thesis
Level: Doctoral
Qualification: PhD
Rights: Copyright © the author, 2011.
Appears in Collections:Theses, Dept. of Physics and Astronomy
Leicester Theses

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