Thousands of years ago, the first civilisations started using clay pottery and tiles in their everyday life, turning ceramics into a key component of society. They could hardly imagine that future generations, far away in time, would still be using similar materials but incorporating them into one of the most ambitious projects of modern times: harnessing the power of the Sun on Earth in the form of a fusion power plant.

Materials evolving over time

Ceramics is a term that encompasses a broad range of materials. Those materials are usually associated with “mixed” bonding – a combination of ionic, covalent and even metallic processes. This variety of bonding makes the list of ceramics so long that David Richerson, author of the book “The Magic of Ceramics”, says: “most solid materials that aren’t metal, plastic, or derived from plants are ceramics.”

Throughout the centuries, the use of ceramics evolved according to the needs of the era and the discovery of new technologies. The use of different ceramic materials, as well as multiple manufacturing processes, have made ceramics a constant presence in our lives. It is natural to realise that, for the technological challenges of the future, and in a world which controlled nuclear fusion plays a major role, ceramics will continue to be of particular relevance.

Demonstrating their fusion value

DEMO will be the future demonstration power plant designed to pave the way to the industrial and commercial exploitation of nuclear fusion.

The choice of materials plays a key role in its development. Several ceramics have been selected as candidate materials because their electrical, dielectric, magnetic, optical,
mechanical and thermal properties make them suitable for various applications.

Due to its excellent dielectric properties along a broad range of frequencies, aluminium-oxide (Al2O3) has been proposed as an insulator for diagnostics, for the Neutral Beam Injector high voltage source and possibly for the Ion Cyclotron Resonance Heating and Lower Hybrid Heating systems. Also, due to its optical and mechanical properties, it has been proposed as a candidate material for optical windows, along with silica composites, spinel and diamond. Yes, a Chemical Vapour Deposition Diamond is also considered to be a ceramic!

In DEMO, these ceramic materials will be operated under harsh conditions. They will, in particular, be exposed to considerable levels of neutron irradiation. Therefore, their optimum properties must be tested under relevant neutron irradiation conditions.

European work in progress

Set of different types of ceramic materials currently being studied at CIEMAT. Picture: CIEMAT

Set of different types of ceramic
materials currently being studied
at CIEMAT. Picture: CIEMAT

Scientists at the EUROfusion’s Spanish Research Unit CIEMAT are currently testing and validating the best candidates. This work is part of the Functional Materials group tasks carried out under the umbrella of the Materials Work Package in EUROfusion. Ceramic manufacturing companies are involved in the project, since the manufacturing process plays a crucial role in determining the final properties of the materials.

So far, the results show that the un-irradiated samples exhibit the desired qualities for their intended applications. However, the resulting values vary between samples of the same material. This means that there is a reproducibility issue on the manufacturing side that has to be addressed before the irradiation phase takes place.

Plans for the future

Once the samples can be reproduced with the same quality, irradiation experiments of those ceramics will start. The plan is to use beta and gamma radiation from accelerators and radioactive sources, fission neutrons produced by nuclear reactors and finally fusion neutrons from specialised neutron sources as the Demo Oriented NEutron Source (DONES).

The ultimate goal of the project is to validate a standard manufacturing route that ensures a supply of ceramic material with homogeneous and standardised properties for the forthcoming fusion machines. And in doing so, ceramics will contribute to the future development of society just like they have been doing for so many thousands of years.

Darío Andrés Cruz Malagón. Picture: privateMy background is in both Physics and Energy Engineering. I think that the Fusion community is a very skilled global team that is trying to achieve a scientific and technological breakthrough for the sake of our future generations and I am proud to be able to contribute to that effort. My article is about EUROfusion’s current Research and Development on ceramic materials for DEMO, in which I participate  through my PhD research.

Darío Andrés Cruz Malagón (33) from Colombia is currently based at Madrid, Spain.  (Picture: private)