Carbon materials, especially graphite, exhibit a fascinating, virtually infinite, variety of microstructures.
By understanding the structure of these materials we are able to predict their properties and tailor them for specific applications. For example, graphite is used extensively in next generation nuclear reactors. These reactors are passively safe, meaning they cannot undergo thermal runaway which may lead to a nuclear meltdown. This is because graphite loses its capability to sustain the nuclear reaction as the temperature rises. However, understanding the long term properties of graphite under nuclear irradiation or its behaviour during accident situations such as air ingress, are crucial for designing safe, reliable reactors. Current work in this area is focused on identifying the relevant microstructural features and applying multi-scale modelling to predict their behaviour. In addition, this will then be used to compare different starting materials, such as the mesophase pitch shown here, in order to produce materials with specific qualities.
Graphite, specifically natural graphite, is a layered crystalline material which can be broken down into particles with very high aspect ratios. A single atomic layer of graphite, known as graphene, has demonstrated some remarkable properties, such as excellent thermal conductivity. This makes these particles, also known as graphite nanoplatelets (GNPs), an excellent additive for creating composite materials. If renewable energy such as solar power is to achieve widespread implementation, energy storage will be critical. This will allow the variability of these resources to be mitigated and enable the matching of energy supply and demand. One option is the storage of thermal energy directly using phase change materials (PCMs). These materials store energy during the transition from a solid to a liquid, offering high energy densities due to use of latent heat. The thermal conductivities of these solids tend to be very low, limiting the rate at which energy can be extracted from the store. GNPs can be used to enhance the thermal conductivity of the storage material by several orders of magnitude at comparatively low cost. A remaining challenge is to optimize the composite material structure in order to deliver a constant power output.
The next evolution in energy storage is the use of reversible, chemical reactions to store energy. Metal hydroxides offer a non-toxic, environmentally friendly method for storing energy using water. However, these materials face significant practical challenges such as mass and heat transfer limitations. By using composites and controlling the microstructure of the material, the aim is to develop revolutionary energy storage media for low loss, long term energy storage. Using these novel compounds it may be possible to harvest energy in summer for use in winter or even transport captured solar energy between different regions.