Preparation method of calcium hexaluminate foamed ceramic with multilayer structure

The invention discloses a preparation method of a calcium hexaluminate foamed ceramic with a multilayer structure. The preparation method comprises the following steps: completely immersing a pretreated polyurethane sponge template in slurry I, extruding redundant slurry by rolling, then carrying out high-pressure blast or centrifugal slurry throwing, and drying at 100-120 DEG C for 16-24 hours; then putting the mixture into a muffle furnace at 700-900 DEG C, keeping the temperature for 2-4 hours, and naturally cooling; and completely immersing a calcium hexaluminate foamed ceramic preform in the slurry II, keeping for 3-7 minutes under a vacuum condition, carrying out high-pressure air blowing or centrifugal slurry throwing and natural drying to obtain a calcium hexaluminate foamed ceramic green body, drying for 16-24 hours at 100-120 DEG C, then putting the green body into a high-temperature furnace, carrying out heat preservation for 2-5 hours at 1500-1600 DEG C, and then cooling along with the furnace to