In order to cope with the ever-increasing operating temperature of aero gas turbines, new thermal barrier coatings are being investigated. Among the different solutions, erbia-yttria co-doped zirconia coatings made by electron-beam physical vapour deposition (EB-PVD) show promising results in terms of thermal insulation enhancement. Annealing of these coatings was performed at 1100°C in air in order to investigate their stability in comparison with that of standard 8 wt.% yttria-stabilized zirconia (8YSZ). Their thermal transport properties were measured using the laser-flash technique. The results show that the as-deposited co-doped coatings offered lower heat conduction than the standard ones in the studied temperature range (from room temperature to 1100°C). However, the microstructural and phase transformations of the co-doped coatings after annealing were significantly greater than those of the standard coatings, hence strongly modifying their thermal insulation potential.

The syntheses of the ethyltetramethylcyclopentadienyl complexes Ru(r/s-cs Me4 Et)(CO)2 el, Co(//s -C s Me4 Et)(CO)2, and [M(rlS-c5 Mea Et)CI2 ]2 (M = Rh or It) are described; the ruthenium complex reacts with triphenylarsine to give Ru('r/S-cs Me 4 Et)(AsPh3 )(co)el. I H and 13C n.m.r, spectra, i.r. spectra and the physical properties of the compounds are discussed and contrasted with the known Cs Hs and CsMcs analogues.

The impact of the penetration of small quantities of calcium-magnesium-aluminosilicates (CMAS) glassy melt in the porous plasma-sprayed (PS) thermal barrier coatings (TBCs) is often neglected even though it might play a non-negligible role on the sintering and hence on the thermal insulation potential of TBCs. In this study, the sintering potential of small CMAS deposits (from 0.25 to 3 mg.cm-2) on freestanding yttria-stabilized zirconia (YSZ) PS TBCs annealed at 1250°C for 1 h was investigated. The results showed a gradual in-depth sintering with increasing CMAS deposits. This sintering was concomitant with local transformations of the tetragonal YSZ and resulted in an increase in the thermal diffusivity of the coatings that reached a maximum of 110 % for the fully penetrated coating.

We present a normal incidence terahertz reflectivity technique to determine the optical thickness and birefringence of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs). Initial verification of the method was achieved by measurement of a set of fused silica calibration samples with known thicknesses and showed excellent agreement (<1% of refractive index) with the literature. The THz-measured optical thickness and its variation through the depth profile of the YSZ coating are shown to be in good agreement (<4%) with scanning electron microscope cross-sectional thickness measurements. In addition, the position of discontinuities in both the optical thickness and birefringence appear to be correlated to coating failure points observed during accelerated aging trials.

The impact of small deposits of calcium–magnesium–aluminium silicates (CMAS) on the top of thermal barrier coatings (TBCs) made of yttria-stabilised zirconia (YSZ) produced via electron-beam physical vapour deposition (EB-PVD) is shown to play a role in the microstructural and chemical stability of the coatings; hence, it also affects the thermal insulation potential of TBCs. Therefore, the present work investigates the degradation potential of minor CMAS deposits (from 0.25 to 5 mg·cm−2) annealed at 1250 °C for 1 h on a novel Er2O3-Y2O3 co-stabilised ZrO2 (ErYSZ) EB-PVD TBC, which is compared to the standard YSZ coating. Due to the higher reactivity of ErYSZ coatings with CMAS, its penetration is limited in comparison with the standard YSZ coatings, hence resulting in a better thermal insulation of the former after ageing.