Properties of Scalable Atomically Thin Materials on Ultra Permeable Substrates

Abstract

Macroscopic and large-scale two-dimensional materials are now accessible, which opens up the prospect of using them in an increasing number of applications. The properties of high-quality, micron scale graphene flakes, have historically been characterised, however large-scale graphene produced by chemical vapour deposition, has intrinsic defects in the form of point defects and grain boundaries. This MPhil investigated some of the properties of scalable atomically thin materials, CVD graphene, and fluorinated graphene, in which fluorine was incorporated into centimetre-scale CVD graphene. These materials were supported by ultra-permeable polycarbonate track-etch membranes as substrates, which have the benefit of finely and accurately customising the permeability and pore size through the polycarbonate membrane. Properties investigated were the proton conductance and cation selectivity of fluorinated graphene, when compared to CVD graphene. Proton conductance was found to be generally poorer in fluorinated graphene than in CVD graphene, while cation selectivity was comparable. PCTE, monolayer CVD graphene and centimetre-scale fluorinated graphene were all shown to exhibit positive cation selectivity. Additionally, a novel technique for completing fluorinated graphene to PCTE transfers, using spin-coated Nafion as an adhesive and proton conducting layer was developed in this thesis, facilitating further research into centimetre-scale fluorinated graphene. Pressure driven helium permeance of CVD graphene on 0.2μm diameter pore PCTE substrates were compared against CVD graphene on 0.01μm diameter pore PCTE substrates as a precursor to explore the hydrogen isotope separation properties of graphene, focussing on the separation factor of hydrogen from tritium. This was part of a wider research plan to investigate the suitability of atomically thin materials for applications in the nuclear fusion fuel cycle. Helium leak rates measured reduced non-linearly with the reduction of pore size, suggesting the potential for optimising the reduction of leak rates without drastically reducing throughput for hydrogen isotope selectivity.

Date of Award	31 Dec 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Marcelo Lozada Hidalgo (Supervisor) & Ed Pickering (Supervisor)