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Title: The application of microwave radiation in materials chemistry
Author: Piña-Sandoval, Flora Marcela
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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We have developed tuned or tunable microwave cavities to be used in conjunction with an X-ray diffractometer working either in transmission mode with a capillary sample, or in reflection mode, with a flat plate. We have also developed further a microwave cavity that enables high-resolution neutron powder diffraction patterns to be taken, and tested it successfully on the High Resolution Powder Diffractometer (HRPD), at the ISIS Facility UK. One application that was planned was the elucidation of synthetic steps in the microwave-assisted formation of the zeolite ZSM-5. We also studied microwave-assisted processing of zeolites Na-Y and H-ZSM-5, accelerating the insertion of nickel, copper of molybdenum ions in the solid-state. Phase transitions in the ferroelectric materials BaTiO3, and KNbO3 were studied by in situ diffraction to determine whether microwave irradiation can influence the transition between phases of different dielectric susceptibility, and evidence for a lower transition temperature in both cases compared to that of conventional heating. In situ neutron diffraction measurements have provided the first direct evidence of a differential heating under microwave irradiation of heterogeneous catalysts in the form of MoS2 or Ni particles dispersed over a high surface area Al2O3 support. Finally, we performed in situ X-ray diffraction on a sample of AgI held in a glass capillary to observe the transformation between the dense β phase, and the more open, fast-ion conducting α phase; this revealed a significant reduction in the transition temperature, possibly arising from a strong interaction between the microwave field and the defects or lattice modes implicated in the transition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available