Muons make the most of waste heat

Phenyl acetylene Silicon Nanoparticles

Phenyl acetylene Silicon Nanoparticles
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Approximately 90% of the world’s electricity comes from heat energy generated by fossil fuels. These power stations operate at about 30 – 40% efficiency, with the remaining heat being lost to the environment. One way to improve efficiency is through the use of thermoelectric materials, which convert waste heat directly into electricity. Scientists from the University of East Anglia have been working with the muon group at ISIS to understand a new type of thermoelectric material that could take advantage of waste heat from, for example, furnaces, car exhausts or solar cells, improving overall efficiency and helping in the move towards a low carbon economy.

Thermoelectric materials do exist already, but the power output is modest and the materials that are currently used are running out - so an alternative is needed. Dr Yimin Chao from the University of East Anglia is studying silicon nano particles capped with conductive polymers, which have already been observed to have useful thermoelectric properties. However, all they were able to measure were the bulk properties of groups of nanoparticles. To understand how these properties come about requires an understanding of how they behave on the atomic scale.

Dr Chao says, “The new material we have developed is basically a polymer with silicon quantum dots (SiQDs). We’ve shown that these SiQDs have promising thermal and electrical properties, but we think these can be significantly improved. Muons help understand how the electrons transfer within the material and how this contributes to the thermoelectric behaviour. So far our results have been very promising, and the next step is to try and interpret these to explore the mechanism of performance.”

The research is already seeing interest from industry – Dr Chao has a research student funded by European Thermodynamics Ltd - and the UK government, through the Engineering and Physical Sciences Research Council (EPSRC), who have recently set up a UK Thermoelectric Network to bring together researchers with an interest in the field.

Dr Chao says, “If we can understand the microscopic conduction rates and mechanisms it will allow us to improve these materials by design. The information provided by our muon studies lets us take a strategic approach to building more efficient thermoelectric materials that can be synthesised without relying on already depleted resources and could help the UK reach its commitment to reduce 80% of greenhouse gas emissions by 2050.”

Sara Fletcher

Research date: February 2014

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