Oriented microchannel membranes were fabricated by the selective oxidation of carbon-fiberreinforced Pyrex glass composites. The oxidation behavior of two PAN-based fibers (T-300R and IM-7) was studied in the as-received condition, and after incorporation into the glass matrix, in order to elucidate differences in oxidation behavior controlled by differences in fiber structure and catalysis by matrix constituents. As-received T-300R fibers oxidized preferentially in an axial fashion from the fiber ends, whereas IM-7 fibers oxidized uniformly on all fiber surfaces. The oxidation rate for the as-received T-300R fiber decreased steadily throughout the oxidation process as a result of a loss of fiber mass, without an increase in the concentration of exposed fiber surface area. The oxidation behavior of the as-received IM-7 fiber was dramatically different than the T-300R fiber. The oxidation rate of the IM-7 fiber increased through 35% burn-off and then steadily decreased, corresponding to the decrease in fiber mass. Incorporation of both fibers in a glass matrix resulted in composites which exhibited similar oxidation behavior. However, the initial oxidation rates for the IM-7 and T-300R fibers in the composite were greater than the initial oxidation rates for the as-received fibers. Interrupted oxidation tests revealed possible catalytic effects of minor constituents in the glass (most notably, sodium) on the oxidation behavior of these fibers embedded in a Pyrex matrix.
All Science Journal Classification (ASJC) codes
- Materials Science(all)