ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
The oxidation of BN composite interphases was examined with a series of model materials. Oxidation was examined in both low-water-vapor (∼20 ppm H2O/O2) environments at 900°C and high-water-vapor (1% and 10% H2O/O2) environments at 700° and 800°C. The low-water-vapor case was explored with layered BN/SiC materials. This case was dominated by borosilicate glass formation, and the 20 ppm water vapor gradually removed the boron from the glass, leaving a larger amount of SiO2 than would be expected from simple SiC oxidation. Layered SiC/BN/SiC materials were also used to study low-water-vapor oxidation effects within the composite. The high-water-vapor case was explored with SiC/BN/SiC minicomposites, and it was dominated by volatilization of BN as HBO2(g), H3BO3(g), and H3B3O6(g). A model for recession of the BN fiber coating was developed based on the gas-phase diffusion of these species out of the annular region around the SiC fiber and concurrent sealing of this annular region by oxidation.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1151-2916.1999.tb01944.x
