Effect of silica aerogel particles on plasma sprayed yttria-stabilised zirconia coatings

The aim of this study is to assess the effect of incorporating silica aerogel particles on the microstructure and thermal conductivity of plasma sprayed yttria-stabilised zirconia (YSZ) coatings. Aqueous suspensions of YSZ, containing different loads of silica particles ranging from 2 to 98 vol.%, were prepared and spray-dried to obtain free-flowing, agglomerated powders. An optimised dose of a surfactant was used to prepare stable suspensions with aerogel particles. After analysing powder flowability, particle size and morphology, the feedstocks were deposited onto metallic substrates by atmospheric plasma spraying (APS). Different spraying distances and flow rates of plasma gases were tested. The obtained coatings were microstructurally characterised by scanning electron microscopy and X-ray diffraction, and their thermal conductivity was measured by means of a laser flash equipment.

In all the cases, spherical agglomerated powders with excellent flowability were obtained which successfully leaded to coatings of different porosity. In addition, increasing aerogel particles content in the feedstock strongly affects coating microstructure and properties giving rise to more porous coatings of lower thermal conductivity.

This work has been supported by the Research Promotion Plan of Universitat Jaume I (action 1.1, UJI-B2017-77) and by the Spanish Ministry of Science, Innovation and Universities (RTI2018-099033-B-C3, MCIU/AEI/FEDER, UE).