Neutron imaging is a powerful technique for visualising the minutest structural details of materials and looking at the inner workings of everything, from ancient Antarctic rock samples that are millions of years old, to the latest technological innovations in battery research – which will be at the centre of our increasingly electric future.
Neutrons are a sub-atomic particle found abundantly throughout all matter. The intrinsic properties of these particles make them a powerful tool for scientific research into other materials.
Neutron imaging is the process of making an image of the attenuation of neutrons with the object being investigated – rather than the patterns of its scattering.
A broad range of materials and scientific fields can benefit from the technique thanks to the unique properties of neutrons.
They can be used to study everything from pharmaceutical drugs to aircraft components, revealing the atomic structure and behaviour of the materials that make up our world.
Understanding why concrete explodes
From multiple 2D projections of the object (the radiographies) at different angles, it is possible to reconstruct a 3D image of the field of attenuation of an object, named a tomography. When multiple tomographies are acquired while a process occurs we can even derive a 4D image (3D + time).
This technique has for example been used to help us understand why industrial concrete can explode ‘like popcorn’ when exposed to extremely high temperatures.
Using neutrons, a team from ILL, Empa and the University of Grenoble were able to visualise the processes causing hot moisture within a concrete block to vaporise and become trapped within the material – eventually causing the entire block to break apart.
The experiments were performed at the Institut Laue Langevin (ILL) neutron source, which has the highest neutron flux in the world.
This flux meant the researchers could capture one scan per minute of the concrete as it was heated – providing an unparalleled view of how the moisture distribution leads to such a dramatic, and potentially dangerous, effect.
Revealing the secrets of water uptake in plants
Improving the sustainability of agricultural processes relies on our understanding of the minute processes within plants enabling water and fertiliser to be distributed among crops.
Plants have a dynamic and complex relationship with the soil that they live in. They exchange water, nutrients, and other materials through a range of interactions with the surrounding earth.
Thanks to the high-sensitivity of neutrons to hydrogen, which is the main component of water molecules, neutron tomography can create precise 3D maps of water as it travels between root and soil.
Only recently has neutron tomography been able to capture rapid processes like water update. Previously capture of 3D images has taken over 10 seconds, which could not be used to effectively visualise how water enters the root system.
Using ILL’s super advanced neutron beam, the necessary time was reduced to almost one second.
Thanks to the non-invasive nature of neutrons, and their sensitivity to light elements critical in energy transfer - such as lithium - neutron imaging is fundamental in the ongoing effort towards a greener energy, and most notably for the study of batteries.
Lithium batteries are used widely across consumer electronics, back-up power sources, and aerospace applications, and understanding what goes on at the atomic level while they are in use is important to ensure their safety and efficiency.
A recent study used neutron and X-ray tomography, in combination, to virtually ‘unroll’ a lithium battery, and visualise the internal processes in 3D.
Researchers analysed the fluctuations of elements inside the batteries while they were in use – possible because of neutrons’ high sensitivity to lithium.
Revealing unprecedented insights into the electrochemical and mechanical properties can instruct how to best maximise the efficiency of lithium batteries. This will be crucial for steps towards a more sustainable future.
Neutron tomography has made leaps and bounds in recent years, enabling more detailed imaging and capturing never-before-seen processes.
One important catalyst for this improvement of neutron imaging techniques is the rapidly increasing demand for non-destructive and non-invasive methods for investigating materials and devices that are used for energy supply, such as batteries and fuel cells.
The sensitivity of neutrons to light elements makes them extremely good at looking at energy storage materials.
Mapping dangerous pollutions in rocks
The pollution of soil and ground water poses a serious public health risk. Heavy metals, in particular, can be very dangerous in the environment.
Cadmium is a hazardous heavy metal compound found in many electronic devices, including batteries, and is among the top six pollutants worldwide to be found in soil and groundwater.
Its unique toxicological profile makes it dangerous even at low concentrations, meaning it is important to understand how Cadmium could potentially move from source, to soil, to plants or animals, which might be consumed by humans.
As neutrons are ideal for studying the presence of hydrogen in a structure, neutron imaging is highly suited to looking at fluid flow through geological materials, which almost always contains hydrogen.
Recent advances in neutron tomography allowed scientists to track the contaminant and fluid flow at higher spatial and temporal resolution than ever before – helping them to both understand the risk of Cadmium pollution and consider how to adapt hazardous waste treatment in future.
A quickly advancing field
The Institut Laue-Langevin (ILL) is a world-class neutron source and home of globally significant research.
Here neutron imaging techniques have been steadily advancing for many years, and recent developments have unlocked new insights for academia and industry, across a broad range of scientific fields.
To meet the evolving needs of users, ILL continuously upgrades and advances the resources it has available to its users.
Neutron imaging experts from Institut Laue-Langevin have joined forces with other leading facilities to develop innovative, state-of-the-art imaging techniques to serve researchers from across academia and industry.
Launched in 2016, NeXT-Grenoble (Neutron and X-ray Tomography in Grenoble) is a collaboration between ILL and Universite Grenoble Alpes to develop world-class methods for investigating materials.
This is the latest in a whole host of steps that pushing the boundaries of scientific analysis techniques.
