Tungsten Coatings for Nuclear Fusion Applications (Materials Strand Project)

Supervisor/s: Dr Ying Chen and Dr David Hall (University of Manchester)

The requirements for high resistance against extreme heat flux and sputter erosion caused by the incident particle flux has led to the choice of tungsten as the most promising armour or tile material for future nuclear fusion reactors. Tungsten offers a range of outstanding material properties including high melting point, high thermal conductivity, low thermal expansion and low activation. On the other hand, Tungsten is hard and brittle, which has brought great technological challenges and high cost in manufacturing of tungsten parts.

An alternative material solution to tackle the manufacturing challenges is to apply tungsten coatings on reactor components. However, conventional coating methods such as thermal spray, physical vapour deposition (PVD) or chemical vapour deposition (CVD) have intrinsic problems in manufacturing tungsten coatings. For example, thermally sprayed coatings are usually porous and suffer material loss in the manufacturing process due to oxidation and evaporation. PVD and CVD are costly and cannot deposit thick coatings. As a result, a new coating method is needed to bridge this gap.

This project aims to develop a new method called aerosol deposition to manufacture tungsten coatings for nuclear fusion applications. Aerosol deposition is a novel coating process in which fine powder is mixed with a carrier gas to form an aerosol flow, ejected through a micro-orifice nozzle and deposited onto a substrate in a vacuum chamber. The method can be used to deposit non-metal, metal, thin and thick layers and has several advantages such as room temperature processing, suitability for mass production, direct deposition and low-cost. These features make aerosol deposition a promising method to deposit tungsten coatings for nuclear fusion applications.

The objectives of the project include

    1. Develop an aerosol deposition process to make dense and thick tungsten coatings
    2. Determine the mechanical properties of the tungsten coatings that govern their durability
    3. Understand the structure-property relationship of the tungsten coatings and provide scientific guidance for optimising coating process and microstructural design

The coating process development will be based on the newly established aerosol deposition facility in the Henry Royce Institute at Manchester. We have demonstrated that the facility is capable of depositing dense and thick ceramic coatings at room temperature in an efficient manner. Particle flow and impact modelling will be carried out to accelerate the development of suitable process parameters for tungsten powder. The crystallinity and microstructures of the coatings will studied by XRD, SEM and TEM. The mechanical properties of the coatings (e.g. stiffness, adhesion and fracture toughness) will be determined using the cutting-edge in-situ micromechanical testing suite that comprise a combination of SEM, FIB and nanoindentation in the Henry Royce Institute. The results will be used to develop structure-property relationships for the tungsten coatings deposited by aerosol deposition to optimise microstructural design and process development. The successful development of aerosol deposition of tungsten coatings will provide a potential material solution for plasma facing materials in nuclear fusion reactors.

The project will be mainly based in Manchester, but there is the opportunity for travel to conferences and collaborations with other groups

The project is offered by the University of Manchester. For further information please contact Ying Chen: ying.chen-2@manchester.ac.uk David Hall: david.a.hall@manchester.ac.uk

The project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.

Image above: Left: a dense coating made by aerosol deposition; Right: micromechanical testing of coatings