Mullite Coatings on SiC and C/C-Si-SiC Substrates Characterized by Infrared Spectroscopy
Mullite (3Al2O3·2SiO2) coatings on SiC substrates and SiC precoated carbon/carbon composite (C/C-Si-SiC) substrates were produced by pulsed laser deposition (PLD) using pressed mullite powder targets. The layers can be characterized efficiently by IR reflection spectroscopy in the spectral range between 650 and 5000 cm−1. The deposited coatings turn into mullite upon oxidation in air at temperatures between 1400° and 1600°C. Fabry-Perot interferences indicate a high quality and homogeneity of the mullite coating/SiC substrate interface. Amorphous SiO2 gradually forms during prolonged heating or at higher temperatures.
Basing on coal and the oxygen evolving complex theory, the method of study on the spontaneous combustion by analysis the microporous in coal has been established in this article. By the electron microscope, the process of microporous volume changeing with the temperature gradually increased is observed. It is believe that the process of spontaneous combustion reaction should be carried out in the microporous. Finally, under the help with finite element analysis , the temperature field surrounding microporous has been analyzed and the distribution regularity of the temperature field has been obtain. It make the conclusion that coal surface microporous can be used as evidence of coal spontaneous combustion reaction.