Feasibility of incorporating silica aerogel in atmospheric plasma spraying coatings

This study aims to demonstrate the feasibility of developing zirconia ceramic coatings with the incorporation of silica aerogel particles, which exhibit outstanding insulating properties. Thus, the research aims to find a suitable methodology to disperse aerogel particles, which are strongly hydrophobic, in an aqueous medium. In the study, a double rheological characterisation was carried out, firstly, to adapt the dispersion of the aerogel particles and, secondly, to characterise the different suspensions made up of silica aerogel and zirconia to be atomised. Aerogel additions ranging from 2% to 98% in volume were addressed. Spray-dried powders were characterised in terms of flowability. Finally, coatings microstructure was examined, and their thermal conductivity determined. The results showed that it is possible to disperse aerogel particles in an aqueous medium and to obtain stable suspensions together with the addition of zirconia. Suitable spray-dried powders were then produced in all the cases. On the other hand, coatings obtained by atmospheric plasma spraying showed appreciable microstructural differences with the addition of aerogel particles and their insulating effect is evident in the thermal tests, with their improved (decreased) thermal conductivity.