Investigation of strong shock wave interactions with CeO2 ceramic

Strong shock wave interactions with ceramic material ceria (CeO2) in presence of O-2 and N-2 gases were investigated using free piston driven shock tube (FPST). FPST is used to heat the test gas to very high temperature of about 6800-7700 K (estimated) at pressure of about 6.8-7.2 MPa for short duration (2-4 ms) behind the reflected shock wave. Ceria is subjected to super heating and cooling at the rate of about 10(6) K/s. Characterization of CeO2 sample was done before and after exposure to shock heated test gases (O-2 and N-2). The surface composition, crystal structure, electronic structure and surface morphology of CeO2 ceramic were examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Results obtained from the experimental investigations show that CeO2 can withstand high pressure accompanied by thermal shock without changing its crystal structure. Reducible CeO2 releases lattice oxygen making it possible to shift between reduced and oxidized states upon the interaction with shock heated gas. Due to such reaction mechanism, CeO2 ceramic undergoes nitrogen doping with decrease in lattice parameter. Investigations reveal that CeO2 retains its crystal structure during strong shock interaction, even at elevated pressure.