新型MoSi_2-Al_2O_3-SiO_2系耐高温高发射涂层的热膨胀系数调控

Preparation and Thermal Expansion Coefficient Control of MoSi_2-Al_2O_3-SiO_2 Coating with High Temperature Resistance and Emissivity

采用料浆喷涂法在陶瓷纤维瓦表面制备了一种新型MoSi2-Al2O3-SiO_2耐高温高发射涂层,通过控制Al2O3-SiO_2体系中SiO_2含量,对涂层热膨胀系数进行调控;通过高温灼烧实验考察涂层的耐高温性能。使用XRD、SEM和热膨胀系数测试仪对涂层物相组成、微观形貌和热膨胀系数进行表征。结果表明,本实验所制备的MoSi2-Al2O3-SiO_2涂层主要由MoSi_2、少量MoSi_2氧化产物、方石英晶相以及硅铝玻璃相构成,涂层表面致密、平整并且与多孔陶瓷纤维基体形成了紧密的结合;经过1500℃,1 h高温热处理后,涂层宏观和微观结构均没有发生明显变化;涂层的热膨胀系数可通过Al2O3-SiO_2体系中SiO_2的含量在一定范围内进行调节,当SiO_2含量由70%增加到85%(质量分数)时,涂层热膨胀系数由4.49×10^(-6) K^(-1)降低至3.45×10^(-6) K^(-1)。

New type coatings of MoSi_2-Al_2O_3-SiO_2 system with high temperature resistance and emissivity were prepared on porous ceramic fibrous substrate by a slurry spraying method. Thermal resistance of coating samples was studied. The effects of SiO_2 amount on the coefficient of thermal expansion, crystallization and micromorphology of coatings were investigated. The result shows that the coating is consisted of MoSi_2, small amount of MoSi_2 oxides, cristobalite and glass. Surface of the coating is smooth, dense and crackless. A fastness association between the coating and the substrate is formed. There are no obvious changes observed on the coating samples after a heat treatment at 1500 ℃ for 1 h. The coefficient of thermal expansion decreases from 4.49×10^(-6) K^(-1) to 3.45×10^(-6) K^(-1) as the amount of SiO_2 increases from 70% to 85%, while the oxidation of MoSi_2 is restrained.