Methods of producing continuous (or discontinuous) boron carbide fibers. The method comprises reacting a continuous or discontinuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Articles including such partially or fully converted fibers may be provided, including such reinforcing fibers in a matrix of ceramic (a CMC), in metal (a MMC), or other matrix (e.g., polymer, etc.).
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under Contract Number DE-AC07-05ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.