Effect of boron on carbon-fiber microstructure and reactivity
A mesophase pitch P55 and a PAN T-300 carbon filter were substitutionally doped with boron at concentration levels ranging from 4 x 10/sup -5/ to 0.05 B/C atom ratio. Boron enhanced graphitization in these fibers at concentrations greater than 2 x 10/sup -4/ B/C. Below this concentration level, the microstructure of the pitch P55 fiber was unaffected. High concentrations of boron were found to modulate the (001) diffraction profiles in both fibers. This indicated the presence of two separate graphite fractions in the same fiber (one fraction was much more turbostratic than the other). The presence of boron was also found to increase the L/sub c/ and decrease the L/sub a/ dimensions of the more graphitic fractions of the fiber structure. The decrease in the L/sub a/ is the result of an increase in tilt boundaries along the a direction, parallel to the fiber axis. The presence of boron inhibits fiber gasification. The cause of gasification inhibition at high boron concentrations is related to changes in the fiber microstructure; however, there is a pronounced effect of specific-site blockage by an oxide of boron that develops on the surface during gasification. At relatively low boron concentrations, decrease in the reactivity of the fiber was correlated to changes in fiber electronic structure which, in turn, influences the chemistry of the active surface sites.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 7160850
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BORON ADDITIONS
CARBON FIBERS
ACTIVATION ENERGY
MICROSTRUCTURE
DOPED MATERIALS
ELECTRONIC STRUCTURE
GASIFICATION
GRAPHITIZATION
SURFACES
ALLOYS
BORON ALLOYS
CRYSTAL STRUCTURE
ENERGY
FIBERS
MATERIALS
THERMOCHEMICAL PROCESSES
360602* - Other Materials- Structure & Phase Studies
360603 - Materials- Properties