Reaction-sintered zircon-based nanostructured coatings obtained by suspension plasma spraying.

Zircon (ZrSiO 4) is an inexpensive and widely available material with excellent thermal properties that makes it an ideal candidate for thermal barrier coatings. Previous works have demonstrated the feasibility of obtaining coatings with a high retention of zircon by plasma spraying of ZrSiO 4 and ZrSiO 4 /ZrO 2 suspensions. Suspensions of ZrSiO 4 /Al 2 O 3 and ZrSiO 4 /TiO 2 were produced by dispersing a micrometric zircon powder into alumina and titania colloidal sols, optimising their colloidal stability and rheological behaviour. Optimised slurries were plasma sprayed onto metallic substrates, obtaining coatings with the typical morphologies obtained by suspension plasma spraying (SPS). Nanostructured coatings with nanoparticles embedded in the molten matrix were obtained at higher proportions of sprayed colloidal sol. The high retention of ZrSiO 4 in the final coatings and the formation of new crystallographic phases of mullite and zirconium titanate by reaction of the by-products of zircon decomposition (SiO 2 and ZrO 2) and the Al 2 O 3 and TiO 2 colloids was demonstrated. [ABSTRACT FROM AUTHOR]