This PhD thesis reports three novel ambient pressure drying (APD) synthesis methods for producing aerogels and characterisation of the resulting products. Motivated by overcoming the disadvantages of the conventional APD method, a novel approach, which utilises sodium bicarbonate solution instead of the organic low-surface-tension (LST) solvent (e.g. hexane, heptane, etc.) usually employed, has been successfully developed to produce silica aerogels. The novel APD method dramatically reduces costs (~70 times) in comparison with conventional approaches, and it solves the problems associated with generation of hydrochloric acid by trimethylchlorosilane. In order to fabricate nickel nanoparticle/silica (NiNP/SiO2) aerogel composites a new process was developed based on conventional APD with an organic LST solvent. A straightforward approach for dispersing the nickel nanoparticles in a silica aerogel matrix was established. The catalytic activity of the NiNP/SiO2 aerogel composites for the hydration reaction of carbon dioxide in water was then investigated. Finally, to develop the first ambient pressure dried zinc oxide aerogels, zinc-based aerogels were fabricated from zinc nitrate salt precursors by conventional APD with organic LST solvents. The microstructure of the resulting zinc-based aerogels was studied, and the macropores were found to have a flower-like multilayered nanoplate structure. After mild heat treatment, zinc oxide aerogels were generated from the zinc-based aerogels. Depending on the phase composition of the zinc-based aerogels and the different synthesis conditions, general routes for ambient pressure drying synthesis of zinc oxide aerogels are suggested. The morphologic characterisations of synthesised aerogels was performed by transmission electron microscope (TEM), scanning electron microscope (SEM), and scanning transmission electron microscope (STEM). The elemental and structural analysis of prepared aerogel materials was investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), respectively. The specific surface area and pore size are analysed by Brunauer–Emmett–Teller (BET) and Barrett-Joyner-Halenda (BJH) methods via nitrogen gas physisorption.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:719776 |
| Date | January 2016 |
| Creators | Han, Xiao |
| Publisher | University of Newcastle upon Tyne |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10443/3489 |
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