Influence Of Stress On Apatite Deposition On Titanium Surface After Immersion In SBF

This paper mainly deals with apatite on the surface of commercial pure titanium, through alkaline and heat treatment and biological immersion in SBF, especially in terms of the microstructure, phases composition and features under the effects of stresses. Bending method was used to simulate the stress condition in the human body. HA coatings were researched by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), field emission scanning electron microscope (FE-SEM) and metallographic microscope.The results of the experiment showed that the thicknesses of apatite on the surface of titanium would regularly change with different stress conditions. The compressive stress would make the apatite coatings thicker than the common ones, while the thicknesses of them hardly changed when stress was stronger. Otherwise, the thicknesses of apatite were larger under tensile stress than those of coatings without stress and increased with the improving of stress. It is because compressive stress forced pores on the surface of sodium titanate hydrogel layer to close, which led to slowing down of apatite degradation. However, tensile stress made pores open, which accelerated the degradation.When the surface of the specimens were observed, it was found the apatite coatings were full of cracks, the angle of which was almost120°. Under stresses, the apatite layers were divided into rectangle plates. And the plates were lengthened with tensile stress and compressed with compressive stress. It was because pores on the surface enhanced the degradation of apatite, and the effect of stresses would open or close the cracks vertical the direction of stress, which resulted in the orientation of apatite growth. In the process of apatite growth, it was more possible to produce cracks along the direction where apatite coatings tended to be thinner and weaker. Stronger stresses intensified this phenomenon of orientation and the extension of cracks which eventually led to the orientation of cracks.This paper focused on the influence stress made on the original degradation of apatite when the biomaterial was implanted into the human bodies. By SBF immersion, it was simulated that titanium was putting into the effect of both body fluid and stress.This paper hopes to illustrate the differential growth of apatite may lead to the defects of biomaterials and reactions in the interface in the process of design and use of biomaterials, by the research of stress effect on apatite growth. And it may also be proved that stress can be a very important factor in biomaterial researches, and even a indispensible one in the vitro simulating experiments.