In order to prepare HA coatings on the carbon fibers,chemical modification and biomineralization processes were applied.The phase components,morphologies,and possible growth mechanism of calcium phosphate were studied by infrared spectroscopy(IR),X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The results show that calcium phosphate coating on carbon fibers can be obtained by biomineralization.But the phase components and morphologies of calcium phosphate coatings are different due to different modification methods.Plate-like CaHPO4.2H2O(DCPD)crystals grow from one site of the active centre by HNO3 treatment.While on the para-aminobenzoic acid treated fibers,the coating is composed of nano-structural HA crystal homogeneously.This is because the -COOH functional groups of para-aminobenzoic acid graft on fibers,with negative charge and arranged structure,accelerating the HA crystal nucleation and crystallization on the carbon fibers.
Composite felts reinforced by both SiC nano-fibers(SiC-NFs)and carbon fibers were prepared at 1 273 K using Ni granules as catalyzers with different deposition time.SiC-NFs were deposited on the surface of the carbon fibers in situ by catalytic chemical vapor deposition(CCVD).The phase,microstructure and morphology of the fibers after electroplating and deposition were characterized by XRD,SEM and TEM.The results show that the SiC-NFs produced by CCVD are composed of single crystal of β-SiC.It is found that smaller nano-granules are more active as catalyzers.The resulting SiC-NFs appear more spindle-like and have a more homogeneous dispersion.The mass change of the samples before and after deposition shows that using more Ni granules results in a faster growth velocity of SiC-NFs.With the same electroplating time,the growth velocity of the SiC-NFs first increases and then decreases.At around 4 h,it reaches the maximum growth velocity,and it becomes nearly constant at around 8 h.After 8 h, the stable growth velocity of the electroplated Ni samples is faster than that of the conventional sample produced without catalyzers, because the SiC-NFs can improve the specific surface area and the activity of the surface.
