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Title: Chemical methods for the production of standard non-spherical particulate materials for the calibration of aerosol characterisation equipment
Author: Carpenter, J. D.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Non-spherical homogeneous particles in the 1.0 to 10.0μm size range are required for the calibration of aerosol shape analysis equipment based on light scattering principles (ASAS). A variety of particulate systems are needed, each with a uniform but easily definable morphology. An extensive literature review identified several chemical reactions which could be used for the production of uniform non-spherical particles in the specified size range. Small scale reaction schemes were devised to produce these particulate systems for an initial series of trials to assess their suitability as candidate materials for calibration of the ASAS. It was found that hematite particles produced by the hydrothermal ageing of ferric chloride solutions were highly suited to calibration purposes, as the particles could be prepared with either cuboidal or prolate spheroidal morphologies by slight modification in the reaction conditions. A research programme was then undertaken to establish the reproducibility of the ferric chloride reaction and the effects caused by further modifications and refinements in the reaction conditions. Highly homogeneous particles could be obtained only when reaction volumes of ten litres were used, giving hematite particles of cuboidal, spherical and prolate spheroidal morphologies, with aspect ratios of the prolate spheroids being variable from 1.0 to approximately 3.3. Magnetite and maghemite particles could also be produced by reduction and reduction/oxidation of the hematite particles with no change in the morphology of the particles. X-ray diffraction analyses confirmed the composition of these materials. The ASAS was challenged with these materials, demonstrating that it could recognise and distinguish between differently shaped homogeneous particles of the same material. It could also detect when particle orientation had occurred in the airflow carrying the particles through the laser beam. It was found that different degrees of particle orientation occurred for identical hematite, magnetite and maghemite prolate spheres. As the ASAS provided a measure of the degree of particle orientation, the operator was able to distinguish between these samples even though their size and shape characteristics were identical.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available