Article with a diffuse reflective barrier coating and a low-emissity coating thereon, and its preparation

A coating composition for making diffuse reflective barrier coatings, the composition comprising:

• first alumina particles having a number average diameter of between 3.0 and 6.0 micrometers, the first alumina particles being present at a level of from 10 to 60 percent by weight based on the total weight of the composition,
• second alumina particles having a number average diameter of between 0.05 and 0.8 micrometers, the second alumina particles being present at a level of from 10 to 50 percent by weight based on the total weight of the composition,
• a silicone present at a level of from 5 to 35 percent by weight based on the total weight of the composition, and
• a carrier liquid present at a level of from 10 to 50 percent by weight based on the total weight of the composition.

A method for producing a coated article having a diffuse reflective barrier coating, the method comprising:

• providing a substrate made from a material selected from a metal and a ceramic,
• spraying a diffuse reflective barrier coating composition onto the substrate to provide an as-sprayed diffuse reflective barrier coating layer having a thickness of from 0.0005 to 0.007 inch, the diffuse reflective barrier coating composition comprising,
• (i) first alumina particles having a number average diameter of between 3.0 and 6.0 micrometers, the first alumina particles being present at a level of from 10 to 60 percent by weight based on the total weight of the composition,
• (ii) second alumina particles having a number average diameter of between 0.05 and 0.8 micrometers, the second alumina particles being present at a level of 5 to 85 percent by weight based on the total weight of the composition,
• (iii) a silicone present at a level of from 1 to 55 percent by weight based on the total weight of the composition, and
• (iv) a carrier liquid present at a level of from 10 to 80 percent by weight based on the total weight of the composition,
• drying the as-sprayed diffuse reflective barrier layer coating to produce a dried coating layer,
• firing the dried coating layer to produce a diffuse reflective barrier coating, and
• applying a low-emissivity coating composition to the diffuse reflective thermal barrier coating.

A coated article suitable for use at elevated temperature comprising:

• a substrate made from a material selected from the group consisting of a metal and a ceramic;
• a diffuse reflective barrier coating overlying the substrate, the diffuse reflective barrier coating comprising
• a transmissive medium having a transmissive-medium index of refraction, and
• a plurality of radiation-scattering centers distributed in the transmissive medium, the radiation-scattering centers having a scattering-center index of refraction different from the transmissive-medium index of refraction;
• and
• a low-emissivity top coat covering the diffuse reflective barrier coating.