Ceramic Thermal Barrier Coatings with a Low Thermal Conductivity - YSZs

Low thermal conductivity (K) values have been observed by an independent study, by the Thermal Spray Team of the National Research Council of Canada (NRC), for coatings manufactured from Innovnano’s 7 wt% Yttria Stabilized Zirconia (YSZ) powder through Air Plasma Spraying (APS) and Suspension Plasma Spraying (SPS).

The powders were developed using Emulsion Detonation Synthesis (EDS) - Innovnano’s proprietary manufacturing process.

EDS converts precursor chemicals into nanostructured powders through a micro-second exposure to high pressures and temperatures through controlled explosions. Temperatures can go beyond 3000 K and pressures are more than 10 GPa. EDS develops nanostructured ceramic powders capable of being customized for unique properties and structures.

Low Thermal Conductivity YSZ Thermal Barrier Coatings

Low thermal conductivity thermal barrier coatings (TBCs) are preferred as they can increase turbine engine efficiency, lower costs, reduce emissions and increase durability.

A 30% reduction in thermal conductivity translates into an approximately 100 °C increase in temperature difference across a 200 µm thick coating. Alternatively, a 30% reduction in thermal conductivity would need 30% less coating thickness in order to produce the same surface temperature.

The Thermal Spray Team of the NRC produced YSZ coatings and thermal conductivity measurements. The various as-sprayed coatings produced at the NRC are displayed in Figures 1a, 1b and 1c.

APS Benchmark.

Figure 1a. APS Benchmark.

Innovnano APS.

Figure 1b. Innovnano APS.

Innovnano SPS.

Figure 1c. Innovnano SPS.

The benchmark APS coating is shown in Figure 1a. Figure 1b reveals the Innovnano APS coating with regions of partially melted YSZ particles where the nanostructure is retained (dark-grey phase). Figure 1c shows the micro-porosity of the Innovnano SPS coating. These coating features lead directly to the lower thermal conductivity values provided in Figure 2.

The as-sprayed YSZ TBCs were also heat-treated for 10 hours at 1300 °C prior to measuring in order to provide more representative thermal conductivity values. At 1300 °C, Innovnano SPS and APS TBCs show a ~30% and ~20% reduction in thermal conductivity when compared to the APS Benchmark. It is possible to produce low K YSZ coatings though defect driven, micro-porous coating structures, without the use of rare earth oxide additions.

Future studies will explore other important properties of YSZ coatings including: thermal cycle durability, erosion resistance, structural stability and phase stability.

Thermal Conductivity Values of the Different YSZ TBCs.

Figure 2. Thermal Conductivity Values of the Different YSZ TBCs.

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This information has been sourced, reviewed and adapted from materials provided by Innovnano.

For more information on this source, please visit Innovnano.

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