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Guide to Thermal Barriers

To protect a vulnerable substrate from the effects of an external heat source it is necessary to reduced the flow of heat into the surface. This requires a coating with a low thermal conductivity, typically a ceramic. The thicker the coating, then the greater the temperature drop from the surface to the substrate. The insulation can be further improved by introducing porosity into the coating, since the thermal conductivity of air very low (when there is no convection in the confined space of each pore).

Temperature drop across a thermal barrier coating

The best thermal barriers are zirconia (stabilised with ittria) or alumina