Fabrication And Characterization Of HAP/SiO₂ Bioceramic Composites

Hydroxyapatite (HAP) is the main inorganic component of human and animal teeth, bones, bone collagen protein fibers arranged around inorganic components in regularly. Hydroxyapatite is about 65% mass fraction in human bone, and more than 95% mass fraction in human enamel, hydroxyapatite without toxicity and possess good biocompatibility, can be formed a strong chemical combination at the interface after implantation of living tissue, it was the best bioactive material compatibility with the organization, have been widely used as biological tissue repair and replacement materials.In this experiment, HAP materials were prepared with Ca(NO3)2·4H2O and NH4H2PO4 as a calcium source and phosphorus source, and then compound it with SiO2, prepared a new HAP/SiO2 complex system, also discussed the impact of SiO2 content on the composite ceramics physical and mechanical properties, biological properties and induced mechanism of carbonated hydroxyapatite on surface of the HAP/SiO2 composite system were studied.The results show that under the conditions of concentration 0.3M, pH value of 10, reaction temperature is 70℃,24h aging time rod HAP were prepared; DTA-TG, XRD, SEM analysis showed that, in the compound and sintering process, SiO2 did not enter the crystal structure of HAP.By testing the hardness of the composite ceramics, the effect of SiO2 content on the hardness of composite were discussed, the hardness of sample increases first and then decreases with the increase of SiO2 content, the hardness in the range of 4.23GPa to 4.90GPa; bending strength of samples have been greatly improved with the addition of SiO2, the maximum 147MPa were reached in the SiO2 content of 30wt.%, and compared with samples without adding SiO2, almost twice as much; fracture toughness of the samples also has been improved with the addition of SiO2, the maximum fracture toughness of 2.4MPa·m1/2 when SiO2 content of 30wt.%,3 times of the sample before adding SiO2. A layer of material deposited on the surface after samples soaked in simulated body fluid. XRD detection showed apatite crystal phase, but the diffraction peak distribution wider than that before immersion, indicating that grain shape were not good enough, but still maintained a similar structure with bone apatite. Infrared analysis showed that after immersion, bone-like apatite crystals obtained on the surface were carbonated apatite. From the trends quality change of the sample, the higher SiO2 content in the samples, the faster HAP dissolution, precipitation, and the larger increase in the final quality of the sample, which is due to the sample in the deposition of SiO2 can be played on the apatite promotion.