Tudies On Si-HA/gelatin Coating On C/C Composites Surface Prepared By Ultrasonic Electrodeposition/Hydrothermal Methods

Hydroxyapatite-carbon/carbon composites(HA-C/C)is an ideal novel bone repair material as it combines the excellent mechanical properties of C/C composites and the good biological activity of HA.The inorganic component of human bones and teeth contains not only HA,but also sodium ion,silicon ion,etc,which influence mechanical properties and biological activity of bone apatite.To satisfy the needs of clinical applications,these ions are often incorperated to HA to improve its properties.In this paper,based on related reviews about the HA coating preparation technologies and its properties,we tried to prepare gelatin/Si-HA coating by ultrasonic electrodeposition /hydrothermal.The main contents are as follows:Firstly,the hydrophilic modifications of the C/C surface with H2O2 and(NH4)2S2O8 as oxidants were studied.Secondly,Gelatin/CaP coating was deposited on C/C composite material by the ultrasonic electrodeposition method.Finally,the Gelatin/CaP coating was futher transformed to HA by a two-step hydrothermal treatment to get a Gelatin/Si-HA coating.The composition,structure,morphology,adhesive performance and biological activity of the coatings were investigated by X-ray diffraction(XRD),scanning electron microscope and energy spectrometer(SEM&EDS),infrared spectrometer(FTIR),thermo-gravimetric analyzer(TGA),X-ray photoelectron spectroscopy(XPS),transmission electron microscope(TEM)and scratch test,and in the meantime,the biological activity in vitro of the coatings was evaluated by SBF tests.The optimal experiments of the C/C surface modifications showed that the best parameters of the hydrothermal treatments are the(NH4)2S2O8 concentration of 1 M and the hydrothermal temperature of 160 ?.The Gelatin/CaP coatings experiments prepared by ultrasonic electrodeposition presented that the brushite crystals growed along the(002)crystal plane.The coatings were mainly composed of flakey grains.The density of the coatings decreased and the cracks increasedwith increasing the current densities,which resulting in decreasing the critical load of the coatings.shear tests of the coatings obtained at 3 m A/cm2 demonstrated the maximum value of 42.4 MPa.The higher the applied electric field intensity was,the higher the critical load of the coatings were.Scratch tests showed that when the electric field intensity increased from3.5 V/cm to7.0 V/cm,the shear strength of coating increasing from 33.4 MPa to 43.1 MPa.The Gelatin/CaP coating was transformed into Gelatin/HA and Gelatin/Si-HA coating by a hydrothermal process in ammonia and sodium silicate solution,respectively.After hydrothermal treatment in ammonia,the density of the coatings decreased,which futher treament sodium silicate solution,that of the coatings increased.Scratch tests disclosed that the shear stress was 42.4 MPa for theprecursor Gelatin/CaP coating,33.1 MPa for the Gelatin/HA coating and 47 MP afor the Gelatin/Si-HA coating is.The in vitro SBF tests showed that the Gelatin/Si-HA coatings were capable of inducing bone-like apatite,exhibiting its good biological activity.