Boron migration in boron-doped carbon/carbon composites

Boron in the form of a carborane compound has been shown to be an effective means of accelerating the graphitization of thermosetting-resin-derived matrices within C/C composites. However, diffusion of B into the fiber can be detrimental to the tensile strength of the composites. Such diffusion must be controlled to achieve the positive attributes of a graphitizable matrix without the deleterious effects of fiber strength degradation. The type of fiber used (e.g. T50, E35 and E130) has been shown to be a major factor in affecting additional fiber graphitization. Well-graphitized fibers, such as the E130, are more resistant to substitutional B and, therefore, to further graphitization, with its concomitant strength reduction. Poorly graphitized fibers, such as those derived from PAN, are much more readily altered in structure by the B dopant.