Crystallographic Phase Control of Iron Oxide Particles in Liquid Flame Spray and Utilization of Nanoparticles in Applications
Sorvali, Miika (2021)
Tampere University
2021
Tekniikan ja luonnontieteiden tohtoriohjelma - Doctoral Programme in Engineering and Natural Sciences
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Väitöspäivä
2021-11-12
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-03-2178-9
https://urn.fi/URN:ISBN:978-952-03-2178-9
Tiivistelmä
Nanotechnology has become a very important branch of research and industry especially during this millenium, and it keeps growing constantly. Simultaneously, demand for large volumes of quality nanomaterial is increasing. Flame spray pyrolysis (FSP) is one of the most promising fabrication methods for inexpensive and simple large-scale production. However, the details of the synthesis process still remain reasonably poorly understood. Liquid flame spray (LFS), a certain type FSP method, was chosen as the focal point of this dissertation. Because both the knowledge on the synthesis process and utilization of LFS in applications are essential for capitalizing on its the strengths in the long term, half of this dissertation was dedicated to improving the understanding of the process, and the other half for exploring its potential in two distinct applications.
In the first part, factors determining the crystallographic phase composition of iron oxide particles in LFS synthesis was studied. The synthesis yielded maghemite (γ-Fe2O3) and hematite (α-Fe2O3), and the equivalence ratio was found as the best measure for predicting their ratio. However, the correlation between the phase ratio and the equivalence ratio was observed to differ between different experimental setups. Modifying the precursor solution through mixed solvents or additives also had a clear effect on the phase composition, which indicates that the solution chemistry likely has unknown effects on the process.
The first of the two applications was bidisperse magnetorheological (MR) fluids, where LFS-made nanoparticles were added to a more traditional MR fluid to counteract sedimentation. The addition reduced the sedimentation rate considerably without impairing its performance. The second application was a liquid-repellent nanocoating consisting of a nanoparticle layer produced with LFS, an ALD mid layer, and a topmost silane layer. The ultrathin final coating repelled several test liquids effectively, but possessed lower stability than initially hoped.
In the first part, factors determining the crystallographic phase composition of iron oxide particles in LFS synthesis was studied. The synthesis yielded maghemite (γ-Fe2O3) and hematite (α-Fe2O3), and the equivalence ratio was found as the best measure for predicting their ratio. However, the correlation between the phase ratio and the equivalence ratio was observed to differ between different experimental setups. Modifying the precursor solution through mixed solvents or additives also had a clear effect on the phase composition, which indicates that the solution chemistry likely has unknown effects on the process.
The first of the two applications was bidisperse magnetorheological (MR) fluids, where LFS-made nanoparticles were added to a more traditional MR fluid to counteract sedimentation. The addition reduced the sedimentation rate considerably without impairing its performance. The second application was a liquid-repellent nanocoating consisting of a nanoparticle layer produced with LFS, an ALD mid layer, and a topmost silane layer. The ultrathin final coating repelled several test liquids effectively, but possessed lower stability than initially hoped.
Kokoelmat
- Väitöskirjat [4859]