Method for preparing low-thermal-conductivity high-temperature thermal barrier ceramic CaWTa2O9 by solid-phase method

Abstract

The invention relates to the technical field of high-temperature ceramic coatings, and particularly discloses a method for preparing low-thermal-conductivity high-temperature thermal barrier ceramic CaWTa2O9 by a solid-phase method, which comprises the following steps: proportioning Ta2O5 and CaWO4 according to a molar ratio of 1: 1, mixing with a ball milling medium, carrying out ball milling, drying, and screening to obtain powder; carrying out compression molding on the powder in a mold, and carrying out pressure-maintaining sintering at 1400-1600 DEG C for 5-10 hours to obtain the thermalbarrier ceramic CaWTa2O9. The thermal conductivity of the thermal barrier ceramic CaWTa2O9 prepared by the method at 800 DEG C reaches 1.25 W.m<-1>.K<-1> at minimum, the thermal expansion coefficientreaches 8.6 K<-1> at 1100 DEG C, the requirements of a high-temperature thermal barrier coating on low thermal conductivity and high thermal expansion coefficient of a ceramic material are met, and the thermal conductivity of the obtained pure CaWTa2O9 ceramic is far lower than that of the existing rare earth tantalate ceramic.

Description

technical field [0001] The invention relates to the technical field of high-temperature ceramic coatings, in particular to a solid phase method for preparing low thermal conductivity high temperature thermal barrier ceramics CaWTa 2 o 9 Methods. Background technique [0002] Yttria-stabilized zirconia (YSZ) is currently the most widely used TBCs material in gas turbines and turbine engines. The research of NASA~Lewis shows that in the YSZ system, Y 2 o 3 The optimal content of YSZ is 6-8wt%, but YSZ materials also have some disadvantages, first of all, the problem of phase stability, 6-8wt% of YSZ actually exists in a metastable t' phase, when the temperature is higher than 1200 ℃, the t' phase will be decomposed into a tetragonal phase (t) and a cubic phase (c), and the tetragonal phase will be transformed into a monoclinic phase (m) during the cooling process. Cracks or even peeling of the coating occur in the coating, so the use temperature of YSZ is often limited to...

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Problems solved by technology

The research of NASA~Lewis shows that in the YSZ system, Y 2 o 3 The optimal content of YSZ is 6-8wt%, but YSZ materials also have some disadvantages, first of all, the problem of phase stability, 6-8wt% of YSZ actually exists in a metastable t' phase, when the temperature is higher than 1200 ℃, the t' phase will be decomposed into a tetragonal phase (t) and a cubic phase (c), and the tetragonal phase will be transformed into a monoclinic phase (m) during the cooling process. Cracks or even peeling of the coating occur in the coating, so the use temperature of YSZ is often limited below 1200 °C

[0003] The rare earth tantalate thermal barrier ceramic coating system developed by Feng Jing's team at Kunming University of Science and Technology studied divalent ions (Ca 2+ , Mg 2+ , Cu 2+ ,), trivalent ions (Fe 3+ , Al 3+ , rare earth oxide RE 2 o 3 ), tetravalent ions (Si 4+ , Ti 4+ , Zr 4+ ), pentavalent ions (V 5+ , Nb 5+ ) doped or double-doped tantalum oxide to obtain a variety of rare earth tantalates, among which the thermal conductivity of rare earth tantalates is low at 1200 ° C, ranging from 1.38 to 1.94 W m -1 ·K -1 range, making it the most potential thermal barrier ceramic material, but to make the rare earth tantalate coating have lower thermal conductivity, it can only be designed and improved from the structure or composition gradient of the coating, such The design improvement effect is largely limited by the current coating process. Although the thermal conductivity can be further reduced, the coating preparation process is very complicated.

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