Preparation, microstructure, and thermophysical properties of Cr3+ - modified cordierite high emissivity ceramic for metal thermal protection

The Cr3+-modified alpha-cordierite ceramics Mg2Al4-xCrxSi5O18 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1, named MAS, MASCr(0.2) , MASCr(0.4) , MASCr(0.6) , MASCr(0.8) , and MASCr(1) , respectively) have been synthesized via the sol-gel process followed by cold isostatic pressing and sintering. The effects of trivalent chromium ion content in alpha cordierite ceramic on microstructure and thermophysical properties were investigated. The MASCr(0.2) ceramic exhibits the highest average emissivity value of 0.87 across the whole infrared range of 3-20 mu m at 500 degrees C, especially at the vital infrared wavelength of 3-5 mu m, the value can reach 0.92. The emissivity will decrease with the increase of doping amount owing to the growing precipitation of cristobalite and MgAl2O4 spinel phases. The lowest thermal conductivity 2.077 W/m K is discovered in MASCr(0.2) , a decrease of 23% compared to MAS. The MASCr(0.4) ceramic with a close emissivity value compared to MASCr(0.2) exhibits the TEC of 7.8 x 10(-6) K-1 due to the multiphase structure. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The Cr3+-modified alpha-cordierite ceramics were synthesized via the sol-gel process and their effects on microstructure and thermophysical properties were investigated. MASCr(0.2) ceramic exhibited the highest emissivity and lowest thermal conductivity, while MASCr(0.4) ceramic showed a higher coefficient of thermal expansion due to its multiphase structure.