Deposition of refractory coatings on carbon fibers from volatile Hf-containing precursors

The possibility to modify the carbon fiber surface by refractory hafnium compounds via chemical vapor deposition of volatile metal-organic complexes is studied. Thermodynamic modeling is applied to calculate the CVD diagram of the Hf-C-O-F-H system within a 25–1200°C temperature range, 10⁻¹–10 Torr pressure range, and 0–2000 hydrogen/precursor vapor ratio. It is demonstrated that the deposition should be carried out at the maximum hydrogen flow and the minimum total pressure in the system. SEM and AFM techniques are used to examine the morphology and topography of the coatings on the fibers. Continuous coatings that are uniform in length and diameter of monofilaments and are tightly bound to them are obtained.