The ceramic coating
Coatings are made by dispersing silicon carbide, tri-silicon tetranitride or their mixtures in a solution consisting of polysilazane and aromatic solvents. This coating provides a protective ceramic coating for carbon/carbon composites, graphite and other carbon containing materials. For example, the graphite specimen with the size of 3.8cm × 2.5cm × 0.5cm was polished into a smooth surface, cleaned, vacuum dried, fully brushed with this coating, dried, dried at 100℃ for 5 min, heated to 150℃ at a rate of about 10℃ /min, and kept at 150℃ for 15~30 min. Let cool to room temperature. Then, another coating was brushed on the specimen, heated to about 175~186℃, kept at this temperature for at least 15 min, cooled, and the coating thickness was about 0.08~0.10 mm. The painted specimen was heated to 650~700℃, and kept at this temperature for 15~30 min before cooling to room temperature, so that the coating was pyrolyzed into ceramic coating. When the painted samples were heated to 850℃ and held for 5~10 min, the effectiveness of the resulting ceramic coating in protecting the graphite surface from thermal degradation can be demonstrated by the following tests: The lacquered specimens were heated in the air to 600℃ for 1 h, and the number of dents on the surface was calculated. The average number of dents per square inch of the three lacquered specimens was only 8~86, while the average number of dents per square inch of the unpainted graphite specimens was 590~630.