The role of substitutional boron in carbon oxidation: Inhibitor and catalyst!
- Penn State Univ., University Park, PA (United States)
Boron is considered to be one of the very few promising candidates for chemical protection of carbon/carbon composite materials against oxidation. The conventional wisdom is that boron inhibits carbon oxidation. Its inhibiting effect can be manifested in three different ways: (1) Substitutional boron enhances the graphitization of carbon. (2) As the surface carbon atoms are consumed, substitutional boron forms an oxide surface film, which acts as an O{sub 2} diffusion harrier and an active site blocker. (3) Substitutional boron redistributes the {pi} electrons in the basal plane (graphene layer), lowers the Fermi level of carbon, and hence presumably inhibits the desorption of CO and CO{sub 2}. This last mode of inhibition is of great fundamental interest; it had not been verified in the past. Upon closer examination of some early studies, its closer scrutiny is wan-anted. We provide such a scrutiny in the present communication. Three widely differing carbon materials were used: a heat-treated ({open_quote}graphitized{close_quote}) carbon black (Graphon), Saran char and a glassy carbon. Boron was introduced substitutionally into the quasi-graphitic lattice by heating these carbons, physically mixed with boron powder. Isothermal carbon oxidation experiments were performed. In selected cases, the reactive surface area of the carbons was determined.
- OSTI ID:
- 370338
- Report Number(s):
- CONF-960376-; TRN: 96:003805-0390
- Resource Relation:
- Conference: Spring national meeting of the American Chemical Society (ACS), New Orleans, LA (United States), 24-28 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of 211th ACS national meeting; PB: 2284 p.
- Country of Publication:
- United States
- Language:
- English
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