Production and thermal behaviour of rare earth elements silicate ceramics for environmental barrier coating application

In order to improve the performance of gas turbine engines, more durable materials are needed in the areas exposed to high temperatures than the metallic materials used today. Parts manufactured from superalloys used in areas exposed to high temperatures of motors are used by applying ceramic-based thermal barrier coatings with high temperature resistance and low thermal conductivity. At high temperatures, metallic parts are damaged by time and lose their high temperature insulation properties and cannot be protected from the high temperature effects of metallic parts. Being lighter than the metallic materials used today, it provides higher propulsion power with less fuel for gas turbine engines and enables the production of more powerful engines with high temperature resistance. In order to prevent this situation, the so-called peripheral barrier coating is applied on SiC based ceramic matrix composites. The formation of silicon hydroxide in the gas phase as a result of silicon carbide based composites reacting with water vapor in high speed combustion environments and at high temperatures limits the use of these materials without coating. In order to prevent this situation, the so-called peripheral barrier coating is applied on SiC based ceramic matrix composites. In this study, 60% Rare Earth Elements (La, Y, Yb, Sm, Gd) - 40% Silicate Pellets were produced which are likely to be used as coating material on SiC / SiC ceramic matrix composite materials. The microstructure, phase and thermal properties of the pellets were investigated. The characteristics of the obtained results showed that dense and less hollow microstructure was formed in the pellets. However, it was observed that the dense microstructure of Y2O3-SiO2 powder mixture was formed and the pellet density was not deteriorated. It was observed that monosilicate and disilicate phases formed in the pellets formed in X-ray diffraction obtained. It was observed that monosilicate and disilicate phases started to form after 1350 ºC in thermal characterization reactions with DTA-TG. Yb2O3-SiO2 materials formed as a result of thermal conductivity measurements when Gd and Sm additions were observed to cause a decrease in thermal conductivity values. The use of materials with lower thermal conductivity as the peripheral barrier coating material will allow to extend the life of the substrate material and the lower coating layers.