Preparation of silicon coated-carbon fiber reinforced HA bio-ceramics for application of load-bearing bone

Abstract

To facilitate the optimal application of carbon fiber (CF) reinforced hydroxyapatite (HA) bio-ceramics as load-bearing bone substitutes, we adopted the magnetron sputtering method to prepare a Si coating on CF surface and then prepared Si-coated CF (Si-CF) with controllable alignment reinforced HA composites via pressureless and hot-press sintering. CFs were evenly distributed in the HA matrix according to the designed layers and alignment states using a special mold and technology. The results showed that uniform and continuous Si coatings with a thickness of approximately 0.2 μm covered the surface of CF. The bending strength of three-layer Si-CF reinforced HA (3Si-CF/HA) bio-ceramics fabricated by pressureless sintering was 33 MPa, which is 45% higher than that of three-layer CF reinforced HA (3CF/HA) bio-ceramics. Three-layer Si-CF reinforced HA bio-composites fabricated by hot-press sintering (H/Si-CF/HA) had a bending strength of 80.9 MPa, which is more than five times that of 3CF/HA bio-ceramics. The corresponding fracture toughness of H/Si-CF/HA was 2.53 MPa m1/2, which is 27.14% higher than that of 3Si-CF/HA composites. Compared with CF reinforced by HA, Si-coated CF could reduce the contact between CF and the O2 produced by the decomposition of HA. The chemical reaction between Si and O2 produces SiO2. The barrier layer provided by the Si and SiO2 coatings can prevent oxidative damage of CF during sintering and maintain the original reinforcing and toughening effects of CF. Axial pressure strengthened the bond between CF and the HA matrix in the H/Si-CF/HA composites sintered at high temperature. The pores and activated grain boundaries of the composites were reduced, and their degree of densification was improved. Therefore, the bending strength and fracture toughness of H/Si-CF/HA composites were improved and are able to satisfy the requirements of load-bearing bones.