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Catalytic Effect of CeO 2 ‐Stabilized ZrO 2 Ceramics with Strong Shock‐Heated Mono‐ and Di‐Atomic Gases
Author(s) -
Vishakantaiah Jayaram,
Reddy Kalidevapura Polareddy Jagannatha
Publication year - 2016
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14454
Subject(s) - pyrochlore , materials science , cubic zirconia , shock tube , monoclinic crystal system , shock (circulatory) , analytical chemistry (journal) , oxygen , shock wave , phase (matter) , ceramic , thermodynamics , crystallography , composite material , chemistry , crystal structure , medicine , physics , organic chemistry , chromatography
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, N 2 to ~7960 K, and O 2 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 (Ce 2 Zr 2 O 8 ) after interaction with shock‐heated argon gas show pyrochlore structure of Ce 2 Zr 2 O 7−δ which is observed to be black in color. In presence of shock‐heated N 2 gas, CSZ remains in fluorite structure by changing its color to pale green as nitrogen atoms fill oxygen vacancies. After O 2 interaction with the shock wave, CSZ remains pale yellow but the X‐ray diffraction pattern shows the presence of monoclinic ZrO 2 due to phase separation. During reduction process, Ce 4+ has been reduced to Ce 3+ 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.