Synthesis and characterisa on of barium hexaferrite nanoplatelets for ferrofluids and composites

Ahmed, Yusra 2025. Synthesis and characterisa on of barium hexaferrite nanoplatelets for ferrofluids and composites. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

A colloidal suspension of magnetic nanoparticles can offer exciting and ever–expanding opportunities for applications requiring hybrid particle/fluid phenomena. Ferrofluids are a classic example of this hybrid behaviour, whereby radical changes in shape and magnetically controlled transport can be easily observed and has potential in a variety of technical and biomedical applications. It has been particularly challenging to make ferrofluids that are ferromagnetic in nature, such that they produce spontaneous, equilibrium magnetic ordering in the absence of an applied field. In contrast to conventional ferrofluids, this thesis focuses on ferrofluids based on barium hexaferrite nanoparticles, which exhibit distinctive magnetic properties due to their anisotropic structure. The primary aim of this thesis is to synthesis barium hexaferrite nanoparticles with optimal structural properties to enable stable dispersion in a non–volatile solvent, thereby producing a stable magnetic ferrofluid. The use of a non–volatile, high boiling point solvent is a deliberate design choice, as it extends the operational temperature range of the ferrofluid and opens the potential for exploration of practical applications that would not be achievable with conventional volatile carrier fluids. Some potential applications include magnetic hyperthermia for cancer treatment, magnetic sealing, magnetically directed drug delivery, sensors, actuators, and heat transfer applications among many others. The first part of this thesis explores the optimal hydrothermal synthesis conditions for producing magnetically applicable barium hexaferrite nanoparticles with a platelet morphology and narrow size distribution. The surface of the nanoparticles is coated with a long – chain surfactant during the hydrothermal process which allows them to disperse in an appropriate carrier fluid. It has been shown that coating the nanoparticles with dodecylbenzenesulfonic acid (DBSA) surfactant allows an extremely successful dispersion in 1-butanol with long – term stability and excellent magnetic properties. However, 1-butanol is an extremely volatile solvent with limited miscibility in water. The experimental observations presented in this thesis show that replacing DBSA with hexadecyltrimethylammonium bromide (CTAB) surfactant allows dispersion of the barium hexaferrite nanoparticles in ethylene glycol which has a much higher boiling point than 1-butanol and is miscible in water. The resulting ethylene glycol ferrofluid shows long – term stability and comparable magnetic properties to DBSA–coated barium hexaferrite nanoparticles. In addition, replacing 1-butanol with ethylene glycol greatly improves the applicability of the ferrofluid. The second part of this thesis utilises the ethylene glycol ferrofluid composing barium hexaferrite nanoparticles by taking advantage of the low volatility and high boiling point of ethylene glycol as a carrier fluid. A condensation polymerisation reaction between the ethylene glycol ferrofluid and succinic acid yields a novel polyethylene succinate (PES) based polymer matrix composite (PMC) with hard magne8c proper8es and a filler content much higher than previous studies.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Engineering
Uncontrolled Keywords:	1. Barium Hexaferrite nanoplatelets 2. Ferrofluids 3. Polymer composites 4. Cetyl Trimethylammonium Bromide (CTAB) 5. Hydrothermal synthesis 6. Ethylene glycol
Date of First Compliant Deposit:	11 September 2026
Last Modified:	11 Sep 2026 11:24
URI:	https://orca.cardiff.ac.uk/id/eprint/188944

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