Microstructure and Thermal Analysis Kinetics of Y2Hf2O7/Y3Al5O12 Composites Prepared by Solution Combustion Synthesis

With the development of high-speed and high-temperature equipment, thermal barrier materials are facing increasingly harsh service environments. The addition of YAG to Y2Hf2O7 has been proposed in order to improve its long-term high-temperature performance. In this work, Y2Hf2O7/Y3Al5O12 composite powders were synthesized by combustion synthesis with urea, glycine, EDTA, citric acid, and glucose as fuels, while hafnium tetrachloride, yttrium nitrate hexahydrate, and aluminum nitrate nonahydrate were used as raw materials. The effects of fuels on the morphology and phase composition of synthetic powders were studied. Chemical reaction kinetic parameters were established by the Kissinger, Augis and Bennett, and Mahadevan methods. Y2Hf2O7 and Y3Al5O12 are the main components in the powders synthesized with urea as fuel, while YAlO3 and Y2Hf2O7 are the main phases with the other fuels. SEM and TEM analysis reveal that the powders prepared by the solution combustion method exhibit a typical porous morphology. When urea is used as fuel, the powders show a uniform elemental distribution, distinct ceramic grain crystallization, clear grain boundaries, and a uniform distribution of alternating grains. Compared to several other fuels, urea is more suitable for the preparation of Y2Hf2O7/Y3Al5O12 composite powders. In the process of preparing powders with urea, the activation energies for the combustion reaction calculated using the three methods are 100.579, 104.864, and 109.148 kJ·mol−1, while the activation energies related to crystal formation are 120.397, 125.001, and 129.600 kJ·mol−1, respectively.