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Daniel Tejero-Martin

PhD researcher (IMPaCT CDT) in Environmental Barrier Coatings (EBC) from suspension thermal spray

SEM images of two splats of niobium-doped titanium oxide produced using solution precursor HVOF 

The need for more efficient and environmental-friendly gas turbine engines has always been the driving force for the increase of operating gas temperatures. To accommodate such conditions, novel materials that can withstand high temperatures, mechanical stresses and corrosion attach are being explored. A promising group of such materials are ceramic matrix composites (CMCs) which possess the required toughness and creep resistance. To prevent the development of undesired corrosion-related species, environmental barrier coatings (EBC) are being applied. The aim of this project is to develop, characterise and test EBCs produced through the use of novel thermal spraying techniques such as suspension high velocity oxy-fuel (SHVOF) and solution precursor HVOF, gaining a deeper understanding of the foundations.

In order to better understand these novel deposition techniques, single splat experiments are being conducted. Individual splats are formed when solid suspended material is molten, or when the high temperature of the flame induces the pyrolysis of the solution precursor. These splats represent the building blocks of any thermal sprayed coating, determining the physical properties of the coating, such as porosity, hardness or thermal conductivity. Since the shape and morphology of the splats can be controlled through the spraying parameters, the produced coatings can be optimised.

In addition to the understanding of the coating formation process, a suitable technique is required to study the obtained coating. Neutrons and high-energy photons provide an unique probe with which these materials can be studied in depth. Small-angle neutron diffraction (SANS), for instance, provides a reliable method to study the inner structure of the coating, providing information on the pore geometry, size distribution and total content. On the other hand, x-ray tomography allows the creation of a visual framework in which pores can be detected and quantified.