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Nucleation and growth of industrial nanomaterials in a continuous hydrothermal reactor

Denis, CJU; (2017) Nucleation and growth of industrial nanomaterials in a continuous hydrothermal reactor. Doctoral thesis , UCL (University College London).

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Abstract

This thesis focuses on the synthesis and characterisation of nanomaterials produced using a continuous hydrothermal reactor. Cobalt oxide (Co3O4), magnesium hydroxide (Mg(OH)2) and zinc oxide (ZnO) nanomaterials were produced via a continuous hydrothermal flow synthesis (CHFS) process, where solutions of chemical precursors were mixed with hot, pressurised water. Samples were collected as slurries and processed to obtain dry powders. The effect of precursor concentration, mixing conditions and temperature profile on the nucleation and growth of Co3O4 were investigated. The use of a quench mixer to rapidly cool down the nascent feed of nanoparticles was explored. The role of experimental parameters and the extent of their effect on the size of the nanoparticles produced were discussed and ideal synthesis conditions for the synthesis of < 10 nm Co3O4 nanoparticles were sought. The synthesis of Mg(OH)2 nanoparticles with a range of morphologies followed by their conversion to MgO via a heat treatment stage were investigated. The crystal planes and their position within the nanoparticles of magnesium hydroxide and oxide were investigated to unveil preferred morphologies for the preferential exposition of certain crystal planes. Experimental parameters such as concentration, temperature, reaction time and presence of surfactants/additives and their effect on the size and morphology of the produced Mg(OH)2 were investigated. Dispersions of ZnO nanoparticles and their UV attenuation properties were investigated. The use of seeds, dopants and surfactants on the ZnO particle size were discussed. Possible mechanisms for the improvement of the nucleation of ZnO were considered and experiments were carried out to test some hypotheses. The UV attenuation properties of the as prepared dispersions and re-dispersed powders were evaluated and allowed for a better understanding of the factors influencing the UV absorbance profile of ZnO.

Type: Thesis (Doctoral)
Title: Nucleation and growth of industrial nanomaterials in a continuous hydrothermal reactor
Event: University College London
Language: English
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1542325
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