Abstract: Systems and techniques are disclosed for removing contaminants from a surface of a thermal barrier coating (TBC) and, optionally, estimating the remaining lifetime of the TBC. Laser induced breakdown spectroscopy (LIBS) is one method that may be used to remove contaminants from a surface the TBC prior to performing photo luminescence piezo spectroscopy (PLPS) or another spectroscopic technique on a thermally grown oxide (TGO). LIBS may facilitate monitoring substantially in real-time the chemical composition of the material removed. LIBS may be used to remove substantially only the contaminants with minimal effects on the underlying TBC. One technique for determining when to stop removal of material from the TBC is cross-correlation between a spectrum collected from the ablated material and a reference spectrum collected from a reference substrate. In some embodiments, the same system may be used to perform LIBS to remove impurities and PLPS to measure stress in the TGO.

Abstract: Systems and techniques are disclosed for removing contaminants from a surface of a thermal barrier coating (TBC) and, optionally, estimating the remaining lifetime of the TBC. Laser induced breakdown spectroscopy (LIBS) is one method that may be used to remove contaminants from a surface the TBC prior to performing photo luminescence piezo spectroscopy (PLPS) or another spectroscopic technique on a thermally grown oxide (TGO). LIBS may facilitate monitoring substantially in real-time the chemical composition of the material removed. LIBS may be used to remove substantially only the contaminants with minimal effects on the underlying TBC. One technique for determining when to stop removal of material from the TBC is cross-correlation between a spectrum collected from the ablated material and a reference spectrum collected from a reference substrate. In some embodiments, the same system may be used to perform LIBS to remove impurities and PLPS to measure stress in the TGO.

Abstract: The present disclosure relates to in-situ, line-of-sight measurements of partial pressure and temperature associated with at least one flow channel of a fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) is employed for measurements for which water transition states sensitive to temperature and partial pressure are utilized. Measurements are achievable for a fuel cell operating under both steady-state and time-varying load conditions. For steady-state operation, the water partial pressure increases with increasing current density on a cathode side of the fuel cell due to production of water by electrochemical reaction. Temperature in a gas phase remains relatively constant since the fuel cell housing temperature is controlled externally. For non-steady-state operation of the fuel cell through a time-varying current profile, the water partial pressure responds to the load changes rapidly and follows a current profile.

Abstract: The present disclosure relates to in-situ, line-of-sight measurements of partial pressure and temperature associated with at least one flow channel of a fuel cell. Tunable diode laser absorption spectroscopy (TDLAS) is employed for measurements for which water transition states sensitive to temperature and partial pressure are utilized. Measurements are achievable for a fuel cell operating under both steady-state and time-varying load conditions. For steady-state operation, the water partial pressure increases with increasing current density on a cathode side of the fuel cell due to production of water by electrochemical reaction. Temperature in a gas phase remains relatively constant since the fuel cell housing temperature is controlled externally. For non-steady-state operation of the fuel cell through a time-varying current profile, the water partial pressure responds to the load changes rapidly and follows a current profile.