Low thermal conductivity Y2Ti2O7 as a candidate material for thermal/environmental barrier coatings

Abstract

Ceramic matrix composites of yttrium titanate (Y2Ti2O7) with nickel (Ni) or silicon carbide (SiC) were synthesized to investigate their potential as candidate materials for thermal/environmental barrier coatings. The composites were sintered by hot-pressing at 25MPa. The mechanical properties of the composites including bulk density, Vickers hardness, and fracture toughness were evaluated. The measurements indicated that the incorporation of Ni or SiC has a positive effect in terms of enhancing the fracture toughness of the composites. Microstructural observations revealed that Y2Ti2O7/Ni is an inter/intra nanocomposite, while Y2Ti2O7/SiC has characteristics of a network microstructure composite. In addition, X-ray diffraction and energy dispersive X-ray spectroscopy analyses confirmed Y2Ti2O7 was chemically stable against Ni, but reacted with SiC to form silicates during the sintering process. The mechanisms for these reactions are also proposed.