Novel water-based processing route for producing structured graphene/alumina composites

Menendez Rodriguez, Guillermo 2022. Novel water-based processing route for producing structured graphene/alumina composites. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Graphene/ceramic composites have settled as a promising vehicle for exploiting graphene’s outstanding combination of mechanical, electrical and thermal properties. However, graphene is still not fully established in the industry after many years of thorough research, owing to its processing cost and scalability. Recent works have integrated innovative processing techniques (such as freeze-casting and nanoparticle deposition) to produce highly-structured ceramic-based composites inspired from hierarchical natural materials (e.g. nacre) to achieve mechanical performance beyond current synthetic materials. This thesis explored a novel processing strategy for graphene/ceramic composites, using water-based graphene oxide (GO) suspensions and alumina powder as precursors. Reduced graphene oxide (rGO) aerogels of 1.5 – 4 mg cm-3 were obtained by freeze-casting water-based GO slurries after optimisation of GO concentration, additives content and freezing rate and later carbonisation at 900°C. After thermal annealing, the directional alignment of the aerogels was preserved with channel widths of 15 – 30 µm, verifying the significant elimination of oxidised groups in the GO sheets through chemical and structural characterisation and moderately restoring the electrical conductivity up to 20 S m-1. Using this water-based processing approach, rGO aerogels were successfully decorated with alumina nanoparticles below 20 nm after exploring a scarcely researched gel synthesis route based on aluminium lactate. An amphiphilic triblock copolymer (PF127) was included in the water-based alumina suspensions to enable the infiltration into rGO structures, otherwise prevented by their hydrophobicity. PF127/Al2O3 wt./wt. ratios were adjusted from extensive wettability and infiltration tests. After consolidation via Spark Plasma Sintering (SPS), the structure of embedded rGO scaffolds was preserved within the sintered alumina matrix, exhibiting channel widths of 5 – 15 µm. This work aimed to set the basis for a cost-effective environmentally-friendly approach to produce ordered graphene/ceramic composites through a scaffold and infiltration process, with high potential for obtaining stronger and tougher materials with electrical functionalities.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	Ceramic-based composites, Freeze-casting , Graphene oxide , Materials Processing , Spark Plasma Sintering
Date of First Compliant Deposit:	5 July 2022
Last Modified:	11 Mar 2023 02:19
URI:	https://orca.cardiff.ac.uk/id/eprint/151040

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