Aqueous slurry for the production of thermal and environmental barrier coatings and processes for making and applying the same

A slurry composition for the production of a thermal or environmental barrier coating comprising:

• a first ceramic material comprising oxide-based particles having a first median particle size ranging from about 5 microns to about 60 microns, the particles being temperature resistant and substantially impermeable to gas and liquid;
• a second ceramic material comprising oxide-based particles that are substantially solid, the substantially solid particles having a second median particle size ranging from about 0.1 to about 5 microns;
• and
• a binder in combination with at least a portion of the first and the second materials in relative proportions to form a bimodal particle distribution therein;
• wherein in a cured state the closed porosity of the first ceramic material provides a non-degrading, high temperature stable porous structure to the produced thermal barrier coating

A thermal or environmental barrier coating comprising:

• a glass-ceramic matrix, said matrix is formed by a binder and a fine fraction of powder particles, said particles having a first median particle size;
• and
• a plurality of particles having a closed porosity that is non-collapsing at elevated temperatures of at least about 1000° C., and substantially impermeable to gas and liquid, the plurality of closed porosity containing particles having a second median particle size that is substantially non-overlapping with the first median particle size to form a bimodal particle distribution, the second median particle size being at least about five times larger than the first median particle size,
• wherein the plurality of closed porosity containing particles are dispersed in the glass-ceramic matrix in an effective amount to lower a thermal conductivity of the coating to about 2 W/m K or lower.

A method for the production of an aqueous slurry comprising:

• introducing into an aqueous binder a first powder and a second powder, wherein each of the first and the second powders comprise oxide materials, with a thermal conductivity of not higher than about 5 W/m K, further wherein the first powder is composed of a first plurality of particles comprising closed porosity with a median particle size in the range of about 10 micron to about 60 micron and the second powder is composed of a second plurality of dense particles with a median particle size in the range of about 0.1 micron to about 5.0 micron;
• forming a bimodal particle size distribution comprising the first plurality of particles and the second plurality of particles,
• introducing elemental Boron;
• mixing the first and the second powders and the elemental Boron with the aqueous, mostly inorganic binder to form a particle suspension in the aqueous binder.

A method for applying a thermal or a environmental barrier coating with an aqueous slurry comprising:

• providing an aqueous slurry comprising:
• a first ceramic powder comprising particles having closed porosity and having a first median particle size between about 10 micron to about 60 micron;
• a second ceramic powder comprising dense particles having a second median particle size between about 0.1 micron to about 5 micron, whereby the first and the second powders form a bimodal particle size distribution;
• elemental Boron;
• an aqueous, substantially inorganic binder;
• applying the aqueous slurry onto a surface of a substrate;
• and
• curing the slurry into the coating.