Application of polysilazane in coatings

Example 1: ceramic coating

The coating is prepared by dispersing silicon carbide, silicon tetrachloride or their mixture in a solution composed of polysilazane and aromatic solvent. The coating can provide protective ceramic coating for carbon / carbon composites, graphite and other carbon containing materials. For example, grind the graphite test piece with the size of 3.8 cm × 2.5 cm × 0.5 cm to a smooth surface, clean and dry in vacuum, brush and dry it with the paint fully, dry it for 5 min at 100 ℃, heat it to 150 ℃ at the rate of about 10 ℃ / min, keep it at 150 ℃ for 15-30 min, and then let it cool to room temperature. Then brush another layer of the coating on the test piece, heat it to about 175-186 ℃, keep it at this temperature for at least 15 minutes, cool it, and the thickness of the coating is about 0.08-0.10 mm. The coating sample was heated to 650-700 ℃ and kept at this temperature for 15-30 minutes, then cooled to room temperature, so that the coating could be pyrolyzed into ceramic coating. The effectiveness of the ceramic coating in protecting the graphite surface from thermal degradation can be proved by the following tests: heating the painted specimen in air to 600 ℃ for 1 h, and calculating the number of dents on the surface. The average number of dents per square inch of three painted specimens is only 8-86, but the unpainted graphite test The average number of dents per square inch is 590 ~ 630.