Experimental study of laser irradiated graphite oxidation using IFTS

Graphite oxidation is investigated at varying porosity and laser irradiance, resulting in surface temperatures of 1500-3100 K. Samples are irradiated using a 1.07 µm fiber laser at irradiances of 1000 and 3600 W/cm2 in dry air environment (20% O2,  < 1% H2O) at atmospheric pressure, producing a buoyant flow. Combustion plumes are analyzed using a midwave (MW) imaging Fourier transform spectrometer (IFTS) at 2 cm−1 spectral resolution, 0.5 mm/pixel spatial resolution, and data cube rates of 1 Hz. Spectral signatures from CO and CO2 are predominant in the 1800-2500 cm−1 spectral region. A radiative transfer model is used to infer species concentration and temperature from the hyperspectral data, resulting in 2D characterization of the reacting boundary layer. Plume temperatures of up to 2500 K are observed. CO and CO2 populations are correlated with surface temperature, with a general trend of [CO]/[CO2]=10exp(−5,200/Ts). A simplified model incorporating diffusion transport and surface kinetics is presented to assess the relative strengths of the S1) 2C+O2⇒2CO, S2) C+CO2⇒2CO, and S3) C+O2⇒CO2 surface oxidation mechanisms. The role of kinetic and transport mechanisms is discussed.