Catalytic Effect of CeO₂‐Stabilized ZrO₂ Ceramics with Strong Shock‐Heated Mono‐ and Di‐Atomic Gases

Abstract

The reducibility of synthesized ceria‐stabilized zirconia (CSZ) with strong shock‐heated test gases is investigated. Free piston‐driven shock tube operating at hypersonic speed at Mach number of 6–8 has been used to heat the ultrahigh pure test gases like Ar to ~12800 K, N2 to ~7960 K, and O2 to ~5500 K at a medium reflected shock pressure (5.0–7.4 MPa) for a short duration of 1–2 ms test time. Under this extreme thermodynamic condition, test gases undergo real gas effects. The structural and spectroscopic investigations of CSZ (Ce2Zr2O8) after interaction with shock‐heated argon gas show pyrochlore structure of Ce2Zr2O7−δ which is observed to be black in color. In presence of shock‐heated N2 gas, CSZ remains in fluorite structure by changing its color to pale green as nitrogen atoms fill oxygen vacancies. After O2 interaction with the shock wave, CSZ remains pale yellow but the X‐ray diffraction pattern shows the presence of monoclinic ZrO2 due to phase separation. During reduction process, Ce4+ has been reduced to Ce3+ which is an unusual effect. In this study, the catalytic and surface recombination effects of CSZ due to shock‐induced compression in millisecond timescale are presented.

Shock wave‐material interaction in ZrB2–SiC based ultra high temperature ceramics for hypersonic applications

“…17 But, this aspect is not captured through conjugate heat transfer analysis, owing to surface and shock radiation effects. Concomitantly, the ultra-fast heating and quenching of the test gas at 10 6 K/s, may possibly result in localized melting and solidification.…”

“…[16][17][18][19][20][21][22] For example, Jayaram et al performed FPST experiments on hot pressed ZrB 2 -SiC-MoSi 2 ceramic for hypersonic re-entry applications in argon-oxygen environment and reported surface oxidation. [16][17][18][19][20][21][22] For example, Jayaram et al performed FPST experiments on hot pressed ZrB 2 -SiC-MoSi 2 ceramic for hypersonic re-entry applications in argon-oxygen environment and reported surface oxidation.…”

“…[16][17][18][19][20][21][22] For example, Jayaram et al performed FPST experiments on hot pressed ZrB 2 -SiC-MoSi 2 ceramic for hypersonic re-entry applications in argon-oxygen environment and reported surface oxidation. 17 In the same way, Reddy et al conducted shock tube tests on graphitic carbon nanoparticles for thermal protection of aerospace applications, which exhibited weight loss and growth of second order nanostructure. 17 In the same way, Reddy et al conducted shock tube tests on graphitic carbon nanoparticles for thermal protection of aerospace applications, which exhibited weight loss and growth of second order nanostructure.…”

“…Shock tubes are employed in the area of material science for synthesis and testing of materials at elevated loading conditions. [16][17][18][19][20][21][22] For example, Jayaram et al performed FPST experiments on hot pressed ZrB 2 -SiC-MoSi 2 ceramic for hypersonic re-entry applications in argon-oxygen environment and reported surface oxidation. 16 Also, Vishakantaiah and Reddy studied the catalytic effect of CeO 2 stabilized ZrO 2 using FPST, and showed the occurrence of phase transformation.…”

“…16 Also, Vishakantaiah and Reddy studied the catalytic effect of CeO 2 stabilized ZrO 2 using FPST, and showed the occurrence of phase transformation. 17 In the same way, Reddy et al conducted shock tube tests on graphitic carbon nanoparticles for thermal protection of aerospace applications, which exhibited weight loss and growth of second order nanostructure. 18 Analogously, shock compression testing by Vasu et al on metal chalcogenides (MoS 2 , WS 2 and MoSe 2 ) exhibited changes in structure and vibrational spectra, along with reduction in interplanar spacing.…”