In a rapidly evolving energy & security landscape, a diverse mix of power generation methods is essential to enable our sustainable future.
Higher temperatures in advanced modular reactors (AMRs) improve efficiency and enable deep decarbonisation, opening the door to large-scale carbon-free hydrogen production.
Article by Adam Green, freelance journalist.
The UK has seen great progress toward decarbonisation with 63% of electricity now low-carbon, especially thanks to wind and nuclear, supported by hydro, solar and biomass. However, our electricity grid still requires huge amounts of gas 26.8% [NESO], which is even worse when we consider energy for gas heating of homes & industry process (e.g. steelmaking). We urgently need to further decrease emissions, while increasing the security of our energy system – accounting for the intermittency of renewables, and supply & price volatility of gas.
The Materials for Extreme Environments Group at the University of Birmingham, led by Professor Sandy Knowles, is dedicated to designing, fabricating, and testing novel materials capable of performing under extreme conditions. Their research spans fusion and fission reactors, aerospace gas turbines, and concentrated solar power, which are critical to the future of energy generation and transport. The harsh operating conditions of these technologies requires advanced materials with exceptional properties capable of withstanding the challenges.
“Materials behave very differently in a nuclear environment,” explains Professor Knowles. “As we dial up the heat, they get wobbly and soft, unable to support their own weight, a bit like a chocolate teapot. At the other extreme, they can become brittle like glass when irradiated at low temperatures.” To endure these environments, materials must combine high melting points, strength at high temperatures, environmental resistance, and, in nuclear applications, irradiation tolerance. Increased temperature capabilities are needed to reduce fuel use and improve efficiency, performance, design life and safety, as well as open up new energy applications, such as generating clean hydrogen.
Professor Knowles specialises in the design and development of novel alloys. Alloys are metallic materials composed of two (or more, or many more) elements, engineered to enhance the properties of their base elemental metal. For example, steel is significantly stronger than its primary component, iron. Among alloys, superalloys are specifically designed to perform under extreme conditions, namely high temperatures. “Superalloys can utilise different base elements depending on their intended application,” explains Professor Knowles. “For concentrated solar power, we care about oxidation and corrosion resistance, so we use chromium. In aerospace, we care about low density, so we use titanium. For fusion applications, it’s all about high temperatures, so we use tungsten or other high melting point refractory metals.”
At the atomic level, alloys form tiny metallic crystals – from nanometers to micrometers, and the arrangement or structure of these micro crystals – their ‘microstructure’, strongly influences their properties. Professor Knowles is a world leader in the emerging field of body-centered cubic (bcc) superalloys. In these alloys, atoms are arranged in a body-centered cubic crystal structure (such as for Cr, Ti or W), with a microstructure reinforced by high-strength intermetallic compounds. “We mix different elements together, melt them to form a single-phase liquid of molten metal, and then cast it,” Professor Knowles explains. “After that, we apply different thermal heat treatments, baking the material up to 1600 degrees Celsius, and that heat treatment controls how the microstructure or nano-structure forms.”
This “bcc-superalloy” microstructure concept helps enable higher strength and melting points than traditional superalloys, but designing and producing them is challenging largely due to their low ductility (the ability of a material to deform without cracking). Professor Knowles’ £1.8mil UKRI Future Leaders Fellowship (FLF) funded project, Bcc-superalloys: Engineering Resilience to Extreme Environments, explores multiple strategies to overcome the ductility barrier, aspiring to enable a new class of high temperature-resistant alloys to scale commercially.
The innovative nature of these superalloys requires new scientific approaches. “In some areas of materials science, you can rely heavily on predictions from computers, but with bcc-superalloys, that just isn’t possible: there’s little to no prior data for us to plug into AI or computational models to make reliable predictions,” says Professor Knowles. “A lot of work involves trying to make the best predictions we can by digging into old literature and using state-of-the-art modelling, but ultimately we get our hands dirty to synthesise the alloys and prove what happens – which can then be taken into a revised model. It’s a cycle of prediction, testing, and learning.”
In some areas of materials science, you can rely heavily on predictions from computers, but with bcc-superalloys, that just isn’t possible: there’s little to no prior data for us to plug into AI or computational models to make reliable predictions. A lot of work involves trying to make the best predictions we can by digging into old literature and using state-of-the-art modelling, but ultimately we get our hands dirty to synthesise the alloys and prove what happens – which can then be taken into a revised model. It’s a cycle of prediction, testing, and learning.
The project has four pillars: steel, tungsten, titanium and chromium. That line up with different end applications: fission, fusion, gas turbines, and concentrated solar power. While high temperature capability is key across all of them, these applications have different needs that correspond to different aspects of superalloy research.
“In aerospace, the main driver is engine efficiency. A 50-degree increase in operating temperature could lead to roughly a 2% efficiency gain,” says Professor Knowles. “Each percentage point of efficiency improvement saves hundreds of millions of dollars in fuel a year which creates a huge driver for innovation”. “Further, for hypersonic aircraft, higher temperatures allow for more thrust, and more thrust = more speed.”
A fusion reactor is much hotter than any jet engine environment, with the plasma getting hotter than the sun! Magnets do a lot of the containment, but the plasma facing structure will still be exposed to temperatures hotter than lava. The internals of a fusion power plant can have extreme temperature, being hot plasma facing, or cryogenic cold - for the superconducting magnets. “There’s great need for new materials here because we already have concerns about the limits of the existing ones,” says Professor Knowles. “Tungsten tiles, for example, may last only two years in a reactor before they need replacing at a high cost. What we’re trying to do is devise a new, fusion-specific material that balances high-temperature strength, room-temperature ductility, manufacturability and irradiation resistance.”
In fission Advanced Modular Reactors (AMRs), higher temperatures again provide efficiency gains, but there is also a unique opportunity on deep decarbonisation. If you can run a reactor at higher temperatures, you can use that heat directly for other industrial processes termed ‘co-generation’; this opens the door to producing carbon-free hydrogen generation on an industrial scale or decarbonising steel production. Innovation often emerges along the way, even from research that starts with a specific application in mind. “For me, that’s one of the most exciting aspects of research: it could create entirely new technologies and industries that don’t exist today,” says Professor Knowles.
PANDA (Programme for Accelerating Nuclear Development and Applications) is a £24 million programme to train up to 100 doctoral researchers to help meet the UK’s future nuclear, clean energy and defence needs.
The University’s advanced materials research is spread across a network of close partners who support the translation from concept to scale-up. “We have partners across the aerospace, fusion, and fission sectors: Rolls Royce and TIMET in aerospace, the UK Atomic Energy Agency (UKAEA) fusion research centre, and the UK National Nuclear Laboratory on fission,” says Professor Knowles. “It’s very much a collaborative endeavour, because the industry has end-application & manufacturing knowledge we benefit from at the University.”
The commercial demands of partners like Rolls-Royce create an enabling environment for innovation. “About every ten years, Rolls-Royce produces a new engine that has yet higher performance & efficiency than the previous generation. If they don’t, their competitor will, so research and development staying at the cutting-edge is existential,” says Professor Knowles. Birmingham offers advanced facilities that enable every part of this work. Much of the effort relies on collaboration and knowledge-sharing. The UKRI FLF helped fund key facilities for bcc-superalloys – namely arc melting of high melting temperature materials, and hot rolling thermomechanical processing, but they are also applicable to other projects, and link to other hubs like the Henry Royce Institute and the National Nuclear User Facility that are open to external researchers.
The Materials for Extreme Environments Group’s work is one piece of a larger puzzle for an ideal Rolls-Royce engine. Led by Professors Nick Green and Paul Withey at the University’s High Temperature Research Centre (HTRC) is focused on production-scale materials research for aero engines. “We’re both in the same ecosystem, although they’re much more focused on manufacturing at industry scale and rapid translation,” says Professor Knowles. “If me and my team do our job well, our novel alloys may feed into their scale-up systems in 5-10 years.”
The group’s research also sits within a dynamic ecosystem of fusion energy innovation. The UK is a leader in this field, particularly in the development of tokamaks such from JET, UKAEA STEP, and Tokamak Energy, which are demand entirely new classes of materials, along with rigorous testing regimes tailored to extreme conditions.
Fusion research at Birmingham benefits from the High Flux Accelerator-Driven Neutron Facility, which has created the most intense accelerator-driven neutron source worldwide, supporting the study of materials for fusion and fission technologies by enabling them to simulate the damage done by extreme conditions.
Building on this strength, the University via Professor Knowles was recently awarded a Doctoral Focal Award (DFA) ‘PANDA’ on advanced fission technologies, as well as with Profs Bhattacharya & Knowles a Centre for Doctoral Training in Fusion Engineering supported by UKAEA, which together with their partners will train more than 250 postgraduate researchers in fission & fusion energy technologies. The University of Birmingham has a strong research presence in the field, with the UKAEA NEURONE Steels development programme, a new multi-million pound EPSRC Prosperity Partnership with UK-based fusion company Tokamak Energy to explore tungsten-based materials for fusion reactors, and with the UK Atomic Energy Authority’s Lithium Breeding Tritium Innovation (LIBRTI) programme to advance research into lithium-based materials for future fusion power plants.
For me, that’s one of the most exciting aspects of research: it could create entirely new technologies and industries that don’t exist today.
In terms of impact and next steps, the group is working closely with University of Birmingham Enterprise and Birmingham’s EPSRC Impact Acceleration Accounts for commercialisation funding streams to map out the technology’s future pathway. The next priority is in alloy design and development, moving beyond improvements in a single property at a time to achieving the right balance of many properties under extreme conditions. “Our work fits very well with the Future Leaders Fellowship: you need a five-, maybe ten- or even twenty-year research effort to really push forward a new technology to market,” says Professor Knowles. “There are innovative ideas that can be taken forward and progressed down a development pipeline, but there’s also still exciting fundamental science that needs to be done along the way!”
External recognition has reinforced the team’s momentum. With Professor Knowles receiving the 2025 Harvey Flowers Titanium prize from the Institute of Materials, Minerals and Mining for the success of its titanium research, as well as being awarded a Senior Fellowship from the University of Bayreuth Alexander Von Humboldt Centre of International Excellence in Germany. Visiting and exchange programmes have strengthened international partnerships and provided independent validation of the group’s work. “I’m passionate about curiosity-driven research going into the unknown to push forward human knowledge & find innovation,” he says. “At the same time, I want to do work that can have a real societal benefit. We’ve found that this balance between industry relevance and science leads us to top-tier research.”
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Professor in Nuclear Materials
Staff profile for Dr Alexander (Sandy) Knowles, School of Physics and Astronomy, University of Birmingham.
