Slurry-based methods for forming a bond coat and articles formed by the methods

A method comprising:

• applying a bond coat slurry on a silicon-based substrate, wherein the bond coat slurry comprises:
• a bond coat patching material in a bond coat fluid carrier, wherein the bond coat patching material comprises a silicon-based powder,
• a bond coat binder, and
• a bond coat sintering aid, wherein the bond coat sintering aid is boron;
• wherein the silicon-based powder comprises a plurality of small particles with a median particle size less than 1 micron, a plurality of medium particles with median particle size in a range from 1 micron to 6 microns, and a plurality of large particles with median particle size greater than 6 microns, and wherein the plurality of small particles is present in an amount in a range from about 60 volume % to about 80 volume %, the plurality of medium particles is present in an amount in a range from about 10 volume % to about 30 volume %, and the plurality of large particles is present in an amount in a range from about 10 volume % to about 30 volume % of the volume of the silicon-based powder;
• drying the bond coat slurry on the silicon-based substrate to form a dried bond coat;
• and
• sintering the silicon-based powder in the dried bond coat in an oxidizing atmosphere to form a sintered bond coat on the silicon-based substrate, wherein the sintered bond coat comprises a silicon-based phase and an oxide of the silicon-based phase, and the silicon-based phase comprises silicon, a silicon alloy, a metal silicide, or a combination thereof, wherein the oxide of the silicon-based phase in the sintered bond coat is present in an amount in a range of 25 volume % to 55 volume %.