溶胶-凝胶法制备无机涂层及热防护性能研究

Preparation of Inorganic Coating by Sol-Gel Method and Its Thermal Protection Performance

为实现铝合金结构材料在高温环境下的热防护,采用溶胶-凝胶法在铝合金表面制备无机锆溶胶涂层。采用正丙醇锆和冰醋酸制备了稳定性良好的锆溶胶,研究了聚乙烯基吡咯烷酮(PVP)含量对锆溶胶粒子大小和黏度的影响规律,并分析了PVP对溶胶粒子的作用机制。添加60%(质量分数,下同)SiO2填料制备无机涂层,并对涂层进行烧蚀考核,对比研究了不同胶粘剂对涂层结构和热防护性能的影响。根据涂层在烧蚀考核中的宏微观响应,分析了无机涂层在高温下的热防护机制。结果表明:冰醋酸添加量为2.6 g时,锆溶胶稳定性最好;添加质量分数为7%PVP优化后,锆溶胶粒子大小均匀并且具有最好的涂覆性;3种不同胶黏剂基涂层在1300℃火焰烧蚀30 s后基体均未发生破坏,水玻璃基涂层烧蚀后发生剥落;较其它胶黏剂涂层,锆溶胶基涂层具有最好的热防护效果。烧蚀过程中,锆溶胶粒子在高温下发生脱水缩合形成纳米氧化锆粒子,弥散分布在填料周围,与填料产生良好的协同隔热作用,使涂层整体具有良好的高温热防护性能。

In order to realize the thermal protection of aluminum alloy structural materials in high temperature environment,an inorganic zirconium sol coating was prepared on the surface of aluminum alloy by sol-gel method.The zirconium sol with good stability was prepared using n-propanol zirconium and glacial acetic acid.The effect of PVP content on the size and viscosity of zirconium sol particles was studied.The mechanism of PVP on sol particles was analyzed.The inorganic coating was prepared by adding 60%(mass fraction)SiO2,and the coating was ablated.The effects of different adhesives on the coating structure and thermal protection performance were compared.According to the macroscopic response and microscopic morphology of the coating in the ablation test,the thermal protection mechanism of the inorganic coating at high temperature was analyzed.The results show that the stability of zirconium sol is the best when the content of glacial acetic acid is 2.6 g.After optimization of 7 wt%PVP,the zirconium sol particles are uniform in size and have the best coating property.The silica sol-based coating has the best moldability.After the three kinds of adhesive coatings are ablated at 1300℃for 30 s,the substrate is not broken,and the water glass-based coating peels off after ablation;compared with other adhesive coatings,the zirconium sol-based coating has the best thermal protective ability.During the ablation process,the zirconium sol particles dehydrate and condense at high temperature to form nano-zirconia particles,which are dispersed around the filler and produce good synergistic heat insulation with the filler,so that the coating has good high-temperature thermal protection performance.