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Understanding and Controlling High Temperature Mechanical Properties of Ceramics to Enable the Ultimate Engine

Ceramic materials are unique in their ability to operate in extreme temperatures and are vital to enable devices and systems to function in extreme environments. However, the mechanical properties of ceramics at room temperature are not consistent with those at elevated temperature. In addition, due to the significant thermal insulating properties of most ceramic materials, the temperature experienced by the bulk of a ceramic may be significantly lower than the environmental temperature during operation over shorter time periods, making it challenging to accurately predict mechanical performance in use. Similarly, where ceramic parts are in contact with metal or other ceramic parts their tribological properties at the surface will be extremely important for the performance, and the variation in thermal and mechanical behaviour must be well understood for such materials to be employed in applications. Data for high temperature mechanical and thermal properties of ceramic materials is extremely limited, and even where available is highly dependent on microstructure, geometry, and precise compositional control. This presents a significant challenge for engineers attempting to use ceramics in new applications where the geometry of the ceramic is unlikely to match standard test pieces or those used in previous devices, and the operating temperature may be significantly higher than that typically used for standard measurements. With limited information available for modelling candidate materials in many cases attempts to use ceramics have to be abandoned.

In this PhD project you will investigate how mechanical properties of ceramic materials can be accurately and reliably measured at high temperatures by developing and modifying destructive and non-destructive tests. Mechanical tests both in compression and in flexure will be carried out across a wide range of temperatures, along with fracture toughness measurements, tribological and surface-focused methods such as nano-scratch, and non-destructive tests. These will be correlated with accurate measurement of sample internal and external temperature and along with measurements of thermal conductivity these will be used to generate empirical relationships between temperature and mechanical properties for specific ceramic materials. You will be required to master a range of characterisation techniques to support the mechanical and thermal testing, including electron microscopy, Raman spectroscopy, and X-ray diffraction, to ensure consistency in microstructure and composition is accounted for in the analysis. This will be supported by the training embedded into the Analytical Sciences CDT programme, through taught modules completed in the first year.

Carnot Engines, the sponsor of this project, are a start-up SME whose aim is to build world’s most efficient engine. The research methods developed during this project and the data they produce will tackle this challenge and enable Carnot Engines to progress towards their goal. The PhD student who works on this project will benefit from contact with Carnot Engines staff for supervision and collaboration, and access to their prototype engine for testing materials with promising properties to verify the validity of the lab-based mechanical and thermal tests.

For more information about the project please contact the supervisor Dr Claire Dancer for an informal discussion. More information about Carnot Engines can be found on their website