Comparative Study of the Structure and Properties of Composite Materials Produced From Hydroxyapatite Glass Ceramics and Carbon Fibers of Different Types

A comparative study of the structure and properties of composite materials produced from biogenic hydroxyapatite/glass/carbon fibers, depending on the type of carbon fibers (activated carbon nanostructured fibers or cellulose fibers), was conducted employing scanning electron microscopy, X-ray diffraction, infrared spectroscopy, Brunauer–Emmett–Teller method, helium pycnometry, and in vitro experiments. The potential to produce a biogenic hydroxyapatite/glass/carbon fiber composite by sintering at 800°C, involving the simultaneous formation of carbon nanostructures during thermal destruction and carbonization of cellulose fibers, was ascertained. This method allows preserving the hydroxyapatite phase in the newly formed biogenic hydroxyapatite/glass/carbon fiber composite and ensures the presence of carbon nanostructures. The microstructure of the composites produced with activated carbon nanostructured fibers is characterized by the presence of these fibers, contrastingly to the composite produced with cellulose fibers, which has more homogeneous microstructure. Moreover, as opposed to cellulose fibers, activated carbon nanostructured fibers in the composite significantly increase (by more than three times) the specific surface area of the material and significantly reduce the particle size. Regardless of the carbon fibers used, the biogenic hydroxyapatite/glass/carbon fiber composites are nanostructured and microporous (pores < 2 nm). The resorption rate of the biogenic hydroxyapatite/glass/carbon (activated nanostructured or hydrated cellulose) fiber composites in the physiological solution within the first two days is significantly higher than that of the starting biogenic hydroxyapatite/glass composites because of changes in the porous structure.