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Title: Manganese Based Nanoparticles via Inert Gas Condensation
Author: Ward, Michael Bernard
ISNI:       0000 0001 3563 1994
Awarding Body: University Of Leeds
Current Institution: University of Leeds
Date of Award: 2008
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Manganese nanoparticles have been produced using inert gas condensation. The process involves the evaporation of a metal in an inert gas (helium) at low pressure. The resultant metal vapour is cooled rapidly through collisions with the inert gas, and the resulting supersaturated vapour drives homogenous nucleation and growth of fine particles. These are then carried by convection to be collected at a point away from the evaporation source. Transmission electron microscopy (TEM) has been used as the primary characterisation technique, with X-r~y diffraction (XRD) providing . additional bulk structural data. In the current study, different samples have been produced containing particles between 5 and 200 nm in diameter. The particle size and size distribution has been studied as a function of evaporation temperature and inert gas pressure, with higher temperatures and pressures producing larger particles. The structure of the particles has been found to be p-Mn, which is only usually stable above 973 K in the bulk. Heating experiments have shown that the structure is retained even at high temperatures, and it has been proposed that the structure is ---- -stabilis~d'by the both the reduced dimensions of the partici~~·~~d=the~~~id~ shell that is formed on all particles. Manganese oxides have been identified, with the phase MnO being the first to form on exposure to air but with a slow transformation to Mn304 occurring after prolonged exposure. The magnetic properties of the samples are dominated by the ferrimagnetic phase Mn304. Silver coating experiments have also been performed, by adding a silver evaporation source above the manganese source in the chamber. The idea of the experiments was to first condense the manganese particles, and then pass them through the silver vapour region to coat them. The primary aim of these experiments was to protect the manganese particles against oxidation. Initial experiments are promising, with some coated particles being produced. However, further experiments are needed to gain complete control over the process and produce consistently coated samples.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available