Synthesis of functional iron oxide nanoparticles (Fe2O3) has attracted considerable attention recently due to their potential diverse applications such as catalysis, optical magnetic recording, gas sensors, electronic devices and biomedical applications. This work establishes the science of the synthesis of functional iron oxide nanoparticles from premixed flames. The optimal experimental conditions were conducted at the equivalence ratio of rich condition (ϕ >1), a constant precursor gas flow rate of 0.10 lmp, and 0.2 lpm flow rate of propane with a 4.32 lpm flow rate of air. This thesis has advanced flame-synthesis of particles by achieving nanoparticle sizes of less than 3 nm. In the present work, a detailed overview of the gas phase synthesis of nanoparticles, focusing on the types and natures of nanoparticles, common properties of nanoparticles, current classification and their applications, common methods for producing ferric oxide nanoparticles particularly sol-gel, hydrothermal, co-precipitation and microwave with comparative assessment for these methods, and the combustion synthesis of nanoparticles. Of all the methods, combustion based synthesis method was found to be the most appropriate due to numerous advantages it presents. A brief experimental work to evaluate the efficacy of diffusion burner based ferric oxide nanoparticle synthesis method was undertaken, and it was concluded that diffusion flame burner system was not suitable to achieve functional ferric oxide nanoparticle synthesis instead, an experimental methodology for single gas phase synthesis of nanoparticles using a pre-mixed flame configuration was used and a novel thermophoretic sampling method was developed to capture particle inception and growth in the premixed flame space. A novel discovery was that inception of primary spherical particles and aggregates were taking place within the precursor droplet. The growth of particles after inception takes place by several independent pathways, including hexagonal coalesced particles, hard agglomerates of hexagonal coalesced particles, aggregates of hexagonal coalesced particles, soft agglomerates of hexagonal coalesced particles, aggregates of primary particles formed inside both the inner and outer flame zones. Using these research findings, a new particle growth model has been constructed in the present work. Next, experimental studies were undertaken on the effects of precursor (Fe(CO)5) flow rates on the size and morphology of end particles. It was found that at low rates (0.07 - 0.1 lpm) a large number of functional primary particles were produced in the range 1-10 nm, and at higher rates (0.12 - 0.15 lpm) a cloud of small vapour spheres was produced. The phase purity of the particles was also affected as the maghemite concentration is highest at 0.2 lpm and low at 0.07 lpm. Particle size was found to increase at greater heights above the burner. Different morphologies of the particles were also observed at increasing heights above the burner. Finally, experimental work was undertaken to validate the use of UV-visible spectroscopy in determining the particle sizes of known gold nanoparticles. In this work, the spectra of iron oxide nanoparticles in the size range 5-30 nm were deconvoluted. A ratio of the absorbance of the peak at shortest wavelength divided by the absorbance at 450 nm against particle size showed a linear relationship. The results show that the UV-VIS methodology developed in the present work accurately predicted the particle size and volume concentration of iron oxide particles in the suspension sample. It can be concluded from the present work that the UV-Vis technique can be applied to determine iron oxide nanoparticle size and volume concentration.
|Date of Award||Dec 2019|
|Supervisor||Khizer Saeed (Supervisor) & Simon Busbridge (Supervisor)|