Method for preparing bulk C—AlN composite aerogel with high strength and high temperature resistance

A method for preparing a bulk C—AlN composite aerogel with high strength and high temperature resistance, the method comprising the following steps:

• (1) evenly stirring aluminum chloride crystals, distilled water, anhydrous ethanol and epoxy propane, to obtain a clear aluminum oxide sol solution;
• (2) adding formaldehyde (referred to as F for short) and resorcinol (referred to as R for short) to the aluminum oxide sol solution obtained in Step (1) and performing even stirring, to obtain an RF/Al2O3 composite aerogel sol solution;
• (3) pouring the RF/Al2O3 composite aerogel sol solution in Step (2) into a mold for reaction to form a gel;
• (4) adding at least one of anhydrous ethanol and deionized water to the gel obtained in Step (3) for aging replacement;
• (5) placing the wet gel after aging replacement in Step (4) in an oven at 60° C. to 75° C., aging the wet gel for 5 to 10 d, and then drying the wet gel using a supercritical CO2 drying method;
• and
• (6) heat-treating the sample after drying in Step (5) under the condition of nitrogen, to obtain the bulk C—AlN composite aerogel with high strength and high temperature resistance;
• wherein:
• in Step (1), a molar ratio of aluminum chloride crystals, distilled water, anhydrous ethanol and epoxy propane is 1:(50 to 70):(20 to 30):(8 to 13);
• in Step (2), a molar ratio of aluminum chloride crystals:resorcinol:formaldehyde is (1 to 5):1:2;
• in the supercritical CO2 drying method of Step (5), CO2 is used for protection, a reaction temperature is 45° C. to 50° C., pressure of a high pressure reactor is controlled at 8 to 12 MPa, and reaction time is 2 to 3 d;
• and
• in Step (6), a heat treatment temperature ranges from 1500° C. to 1700° C., and heat treatment time is 1 h to 10 h.