Imperial College Projects

Following on from previous work on dwell fatigue in Ti-6Al-4V and on RR11, we now identify an opportunity to introduce an alloy that is immune to dwell fatigue and has higher usable fatigue strength, whilst not having an overly strong yield strength, limited ductility and processability. This is achieved by nanoscale microstructure control; generating fine scale secondary alpha and limiting the Al content to avoid alpha2-Ti3Al formation, keeping the alloy solvus low. This leads to questions around partitioning at the nanoscale, sympathetic and autocatalytic nanoscale alpha plate nucleation (in 3D), and the avoidance of slip band formation. These are technical areas well suited to 4DSTEM examination and development, to STEM-EDX and EFTEM, and to atom probe analysis (e.g. Worsnop et al, Nature Comms, 2022; Xu et al, Nature Commun 2020; Joseph et al, Acta Mater., 2022).

Metal-halide perovskite materials have had a transformative impact on the research landscape since they were first demonstrated just over a decade ago. Outstanding improvements in the performance of a variety of electro-optical devices have been demonstrated through structural, compositional, and morphological enhancements of active layers and device interfaces. Compositional variation can be readily achieved through substitutional doping, the objective of which is usually modification of electronic properties i.e. bandgap, but in parallel can influence other structural parameters of intertest, including degree of crystallinity, grain size, orientation, roughness and density. In the MM and NG labs a suite of perovskite compositions, additives and interlayers have been developed resulting in high performing devices across a wide technology space, including photovoltaics, light-emitting diodes, photodetectors, and sensors. [1-4] As is the case often in a university setting these advances have been proven only on the small-scale – to exemplify this a typical 1cm2 substrate may contain up-to 8 devices to be prototyped and tested. To deliver their full potential across these technology realms it is necessary to take the small-scale control demonstrated and expand to significantly larger areas using high-throughput processes such as printing. This presents numerous challenges that will lie at the heart of this project, including i) achieving large-area compositional and microstructural homogeneity, ii) implementing solvents with low/no toxicity, iii) development of process compatible with rigid (current) and flexible (future) substrates, and critically iv) multi-lengthscale correlation of structural, electrical, optical and performance characteristics. The suite of tools available across Imperial College will be key to probing and elucidating local characteristics i.e. nm to mm. The time-resolved microwave conductivity probes developed by JL and available in their lab will allow the spatial mapping of electronic properties to be rapidly obtained with an initial target of demonstration using 100cm2 substrates.

To mitigate climate changes, wider adoption of electric transportation and electricity storage of renewable sources are urgently needed. Li ion batteries (LIBs) are the current battery of choice for these applications, but LIB cathodes use relatively expensive transition metals (TMs), e.g. Co, Ni, some of which have unethical issues, and have limited capacities (≤ 200 mAh g-1).
This project aims to design, synthesise and characterise new cathode materials, Li-rich Li1+xTM1-xOy for LIBs. The new cathode materials will contain multiple earth-abundant TMs, e.g. Mn, Fe, to replace the current expensive and scarce TMs while increasing battery capacities with the excess Li (≥ 300 mAh g-1). This project will also explore the equivalent Na-rich Na1+xTM1-xOy cathode materials for Na ion batteries (NIBs) because Na has higher abundancy than Li to widen materials choices.
Current research challenges of the Li1+xTM1-xOy materials are the low endurance (≤ 100 (dis)charge cycles). The supervisory team has a track record of battery materials research and developing novel multimodal characterisation techniques such as XRD-CT to understand degradation mechanisms [1,2]. This project will focus on the following research questions:
• Chemistry – cations: what is the optimal combination of TMs?
• Chemistry – anions: will anion doping such as Li1+xTM1-xOyF2-y prevent O loss and improve material stability through a combination of more covalent TM-O and more ionic TM-F bonds?
• Structure: what are the effects of the TM types and F doping on the crystal structure and material function?
• Design: what are the material design strategies of improving cycle stability, and can we translate the methodology to Na1+xTM1-xOyF2-y to also improve the capacity and stability of NIBs?
The developments will benefit the energy industry through more sustainable and improved energy storage performance.
[1] C. Huang et al. Advanced Science 2105723, 1-12 (2022)
[2] D. Matras et al. Journal of Power Sources 539, 231589 (2022)

The purpose of this studentship is to use complementary characterisation methods to establish the factors controlling the activity of IrOx-based catalysts for O2 evolution and how they evolve with time.
The increased uptake of renewables is contingent on efficient means to store the energy. Polymer electrolyte membrane (PEM) electrolysers are ideal for this purpose; they split water to form hydrogen, an energy-dense fuel, and their relatively low operating temperature means that they can be started up and shut down quickly and their tolerance to varying electrical power, means they are ideal for coupling with intermittent renewables. The efficiency of these devices is governed by the rate of the oxygen evolution reaction (OER) at the anode. Currently only Ir-based oxides (IrOx) are able to drive this reaction at sufficient rates without excessive dissolution into the acidic electrolyte, but there remains an urgent need to improve their stability as even IrOx dissolves into the electrolyte at a low rate, which is accentuated by potential cycling. Moroever, the scarcity of Ir sets a limit to the long-term scalability of current PEM electrolysis technology without significant thrifting of the Ir loading in PEM systems.
We posit that we will be able to quantitatively describe the catalytic activity a function of experimentally determined binding energies of reactive intermediates, temperature and potential on a number of different catalysts supplied by Johnson Matthey. This would provide us with the ability to relate electrocatalyst kinetics directly to atomistic models of electrocatalysis. We will establish how the performance, structure and composition of the catalyst transforms upon extensive cycling. This will provide us with insight into how to improve the catalyst performance, with a view to decreasing Ir loading and improving the scalability of PEM electrolysis technologies.
1. Rao, R. R., Corby, S., Bucci, A., Garcia-Tecedor, M., Mesa, C. A., Rossmeisl, J., Gimenez, S., Lloret-Fillol, J., Stephens, I. E. L. & Durrant, J. R. Spectroelectrochemical Analysis of the Water Oxidation Mechanism on Doped Nickel Oxides (2022) J. Am. Chem. Soc. 144, 7622-7633.

The main objective of this project is to increase the lifetime of solid oxide cells (SOCs)s by means of decreasing the rate of degradation and managing overpotential to increase cell efficiency. To achieve that, the effect of packing density and porosity of electrodes would be investigated. Varying particle sizes from micro to nano dimension would provide a variable packing density and porosity of the individual electrodes under investigation. This in turn will change the grain distribution and grain boundary framework. Multiscale characterisation techniques including SEM, ToF-SIMS, TEM and Atom Probe Tomography (ATP) would be utilised to understand the effect of particle size and porosity variation in SOC performance.
The performance of SOFC is governed by the oxygen reduction reaction (ORR) and the mechanism can be split into five elemental steps: i) dissociative adsorption of molecular oxygen at the catalyst surface, ii) surface diffusion of oxygen atoms from the catalyst surface to the triple phase boundary (TPB), iii) charge transfer to produce oxygen ions, iv) oxygen ions incorporation into the ionic conductive electrolyte and finally v) diffusion of ionized oxygen atoms in the bulk of the electrolyte. In this project, three-dimensional flow dynamics of oxygen ions and distribution of electrochemical reaction sites in SOFC cathode will be investigated through active sites imaging by oxygen isotope labelling combined with three-dimensional microstructure observation using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations and FIB-SEM.
This work would include very close collaboration with Ceres, with at least 3 months of on-site hand-on-experience. Expert industry guidance will also be provided through best-practice-methodologies, design-of-experiment, and measurement diligence.

The mechanical properties of biological tissues play a key role in diseases from cancer to fibrosis, and can impact the response to treatments from both conventional drugs and immunotherapies. Critically, we are learning that mechanical properties vary rapidly within tissues, hence a micro-mechanical perspective down to scales < 100 m is essential. There is thus a need for new characterization approaches in tissue micromechanics, building on concepts from conventional Materials Science. A vital target for mechanomedicine is lung disease, which excluding the COVID-19 pandemic accounts for c. 20% of all deaths in the UK. Mostly this comprises fibrotic diseases such as COPD, IPF and chronic obstructive pulmonary disease (COPD) and induced pulmonary fibrosis (IPF), with now also unfortunately the potential for new long-term conditions caused by COVID-19. This project will use atomic force microscopy indentation to generate a multiscale mechanical map of lung tissue down to c. 10 m lengthscales. Using both healthy and fibrotic-disease samples, we will determine the micromechanical signature of fibrosis. Importantly, these micromechanical measurements will be correlated to optical images of the same tissues. These will include conventional biomedical histology images, as well as confocal imaging, and advanced non-linear optical methods that reveal fiber-alignment in tissues (second-harmonic generation). The target is for correlated optical and micromechanical imaging to enable micromechanical properties to be inferred directly from optical images. This would empower high-throughput micromechanical tissue analysis, with impact on clinical science.

The proposed project aims to widen the palate of materials that can be processed using laser additive manufacturing (LAM) while increasing its energy and process efficiency. LAM is one of the most mature and promising additive manufacturing technologies. However, it requires materials able to absorb either a near/far-infrared laser beam, which restricts the range of suitable compounds significantly. Recent work by the supervisory team has shown that reduced graphene oxide (rGO) can act as an universal absorbance enhancing additive to enable processing a wide range of compounds and increase the process efficiency of LAM.[1] To reach this goal the project addresses several scientific questions related to development of rGO-enhanced feedstocks for LAM of reflective (e.g. Cu) or transparent (e.g. glasses or ceramics) materials:
-What is the optimum graphene chemistry to enhance laser absorption while retaining flowability of the powder feedstocks?
-What are the fundamental phenomena driving densification or leading to the formation of defects during LAM? Although there is substantial literature on the LAM of metals much less is known in ceramics and glasses.
-How to link in situ analysis of LAM with the design of powder feedstocks, the processing conditions for the practical fabrication of parts, and their final microstructure and properties?
Currently, less than 30 commercial metal powder compositions can be printed reliably using LAM, with ceramics, glasses and more than 5,500 alloys being practically unprocessable. [2] This project will help to increase the energy efficiency of the LAM process and enable the fabrication of parts using a much wider range of materials. It will therefore enable the fabrication of structures for a broad range of product applications, from for healthcare to energy generation.
[1] Leung et al., Applied Materials Today 23, 2101009, 2021.
[2] Martin et al., Nature, 549(7672), pp.365-369, 2019.

The World Health Organisation estimates that exposure to ambient air pollution results in 4.2 million deaths/year. Air pollution particulate matter (PM) is a cocktail of soot aggregate, secondary organic aerosols, nitrates, sulphates, dust, bioaerosols and different redox active trace transition metals. PM from vehicle emissions and abrasive wear contain oxidising, neurotoxic metals such as Fe, Cu and other toxic metals that can lead to increased production of damaging reactive oxygen species (ROS), as well as genotoxicity. There is mounting evidence for a causal link between air pollution exposure and neurodegenerative diseases. PM including Magnetite (Fe3O4) nanoparticles have been found in brains retrieved from adult and child human subjects that lived in extremely polluted cities [10.1177/0192623307313011; 10.1073/pnas.1605941113], together with features of early-stage neurodegenerative Alzheimer’s Disease (AD) including Tau cortical tangles, amyloid-β (Aβ) plaques and abnormal neurovascular units. Furthermore, mice that are exposed to polluted air showed an increased level of Aβ plaques and brain inflammation. Although a causal link between metal-rich pollution PM and neurodegeneration in AD has been made, there is no direct experimental evidence for a link between AD and air pollution exposure or the cellular mechanisms involved. The goal of this project is to directly image the effect of air pollution exposure on cultured cells, in the presence and absence of Aβ. Some redox-active transition metals that are present in PM, notably Fe and Cu, are also prevalent endogenously in the brains of patients with AD, can generate ROS and cause aggregation of Aβ that was shown to play a central role in the pathogenesis of AD. We will directly correlate the presence of PM (via EM) with Aβ and degree of its aggregation (confocal microscopy and antibody-based structural characterisation) and subcellular damage (EM+ML) and test whether PM and Aβ together enhance neurotoxicity.

In the last decade, superspintronics – the superconducting analogue of spin-based electronics (spintronics), emerged as an exciting research field. It represents a striking combination of spin-sensitive phenomena in solid state devices with dissipationless quantum coherence of superconductivity allowing the design of ultra-low power spin-based logic and memory devices with unique functionalities not possible with spintronics alone1,2. However, despite a decade-long intense activity such devices remain elusive.
A major reason is the lack of a systematic materials-based exploration of the structure-property relationship in superconductor/ferromagnet (S/F) hybrids such as, film crystallinity, interface transparency between S and F, and magnetism at the nanoscale.
Here, we will take the first steps towards realizing this goal. We will start with a systematic thin-film growth study of the dependence of superconducting properties of S/F hybrids by tuning F layer properties like film crystallinity, layer thicknesses, composition. Beyond traditional 3d elemental and alloy ferromagnets, we will also investigate rare-earth ferromagnets and their alloys (Ho, Gd, Dy). Using X-ray diffraction, reflectivity and spectroscopy, together with scanning probe microscopy (atomic and magnetic), we will build a comprehensive structure-property relationship in these systems.
Based on the optimised systems identified in the first part, we will nanofabricate a superconducting magnetic memory and logic-type device where the magnetic state encodes the information, and the superconducting part is used for reading and logic processing. An example is a Josephson junction with a spin valve barrier incorporated in a SQUID circuit. Here, a key step will be to use PhotoElectron Emission Microscopy at Diamond to understand the role of the micromagnetic structure in controlling the device response in the superconducting state.
Through this highly interdisciplinary project, the student will gain a comprehensive view of a range of advanced characterisation techniques unified by a common aim: engineering functional materials for ultra-low energy information technology devices.
1 Niladri Banerjee Physics World 32 (4) 31 (2019)
2 J Linder and J. W. A. Robinson Nature Physics 11 307-315 (2015)

In a world facing a global warming crisis due to CO2 emissions, electrochemical reduction of carbon dioxide presents itself as a promising contribution to restoring balance in CO2 levels, and for producing high energy density fuels 1. However, the high cost of CO2 reduction with respect to the energy content in the products it forms makes it economically unfeasible, especially considering its major dependence on Cu-based catalysts, leaving a vast realm of possibilities in other metallic systems. Conventional characterisation techniques cannot resolve some of the important processes happening during the reaction, mainly due to the lack of resolution, and the volatile nature of the reactants and products, leaving our perception of CO2 reduction limited. In this project, we envision the use of cryo-atom probe tomography (APT)2 for the first time since its recent development to “see” the C atoms at the catalytic interfaces during the reaction at the atomic scale. We will be answering unresolved questions regarding the possibility of using other metals such as Ni for CO2 reduction, by tuning its chemical properties through alloy design, electrodeposition and dealloying procedures. Insights from model cryo-APT studies on pure Ni and Cu, in correlation with x-ray absorption studies, will help us design nanoporous Ni-Cu which will be fabricated through selective dissolution (dealloying), and electrodeposition. Structural and chemical characterisation of the developed nanoporous materials will be done using correlative APT and CT techniques.
1. Nitopi, S. et al. Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte. Chem. Rev. 119, 7610–7672 (2019).
2. El-Zoka, A. A. et al. Enabling near-atomic–scale analysis of frozen water. Sci. Adv. 6, eabd6324 (2020).

We have recently demonstrated that graphene oxide works as a sacrificial template, replicating its nano- and two-dimensionality in different metal oxides such as TiO2 and CeO2 [1]. Resulting nanostructured metal oxides consist of <20 nm nanoparticles in a two-dimensional arrangement. These oxides obtain superior results in a wide range of catalytic applications due to their larger surface area. Moreover, their high-aspect ratio restricts their sintering at high temperatures, preserving higher surface areas. This approach is key to preparing materials for solid oxide cells for chemical-to-electrical and electrical-to-chemical energy conversion, where surface area is compromised by high operating temperatures [2]. In this project the student will exploit graphene sacrificial templating and other novel approaches to develop novel doped ceria-based materials with high surface areas and controlled sintering behaviour. These materials will be extensively characterised covering their novel physico-chemical, structural and electrochemical properties for their application in solid oxide cells. These characterisation techniques will be combined to relate the properties of these materials to their best performance, guiding the design of more efficient solid oxide cells for chemical-to-electrical and electrical-to-chemical energy conversion. [1] Rood, S.; Ahmet, H.; Gomez-Ramon, A.; Torrente-Murciano, L.; Reina, T. R.; Eslava, S. Enhanced Ceria Nanoflakes using Graphene Oxide as a Sacrificial Template for CO Oxidation and Dry Reforming of Methane, Appl. Cat. B Environ. 2019, 242, 358–368. [2] S. J. Skinner, Recent advances in the understanding of the evolution of surfaces and interfaces in solid oxide cells, Adv. Mater. Inter. 6 1900580 2019

Lignin is the main component of biomass from plants. It is the second most abundant terrestrial biopolymer following cellulose. Yet, it remains the least utilized biopolymer. The complexity of the lignin structure, which also depends on how lignin is extracted from plant biomass, poses challenges to the utilization of lignin in the chemical and materials industry. In this project, we are looking to develop new strategies to selectively introduce or remove chemical functionalities to Kraft lignin (a side product from pulp and paper production), thus rationally modifying the Kraft lignin properties. Environmentally friendly strategies based on solid-state chemical synthesis are highly desirable in the chemical modification of Kraft lignins (e.g., mechanochemical synthesis). In this endeavor, we want to make Kraft lignin more compatible with synthetic polymers to produce materials suitable for high-end uses. The potential impact of this project will reflect a better understanding of properties-structure relationships that underpin the rational development of high-performance lignin-hybrid materials.