Calcium phosphate biocements reinforced with graphene oxide

In order to improve the strength of calcium phosphate cements(CPCs), graphene oxide(GO) in nano-sheet form was composited with CPCs. CPCs whose amount ratio of substance for α-Ca₃(PO₄)₂, CaHPO₄ and CaCO₄ was 1:1:1 were used as solid phase, the aqueous dispersions of GO with different concentrations were used as solidification liquids, both of them were mixed according to certain powder/liquid ratio, set and solidified, thus the GO/CPCs were prepared firstly. Then, the effect of GO additive amount on the mechanical strength of GO/CPCs was discussed. The setting time, degradation rate after immersion in simulated body fluid and pH of extract liquids were measured, the phase was tested by XRD, and the micromorphology was observed by SEM. The results show that GO additive amount has remarkable effect on compressive strength of CPCs, the optimum additive amount is 0.0500wt%. With the aging time increasing, all of the compressive strength of CPCs with different GO additive amounts improves significantly, especially in the earlier stage. Comparing to the control group without the addition of GO, after aging for 2 h and 24 h, the compressive strength of 0.0500wt% GO/CPCs increase by 200% and 67%, respectively. The degradation rate of GO/CPCs in simulated body fluid increases, and pH of extract liquid decreases. GO/CPCs can obtain more hydroxyapatite phase in the corresponding period of hydration reaction, and the grains are well-aligned, regular and fine. The conclusions obtained indicate that the addition of GO can improve the compressive strength of CPCs significantly.