| β-Tricalcium phosphate(β-TCP)has a strong ability to induce bone tissue regeneration.It degrades rapidly in physiological medium environment and is easy to bioabsorb.It is a bioactive ceramic for bone conduction and bone induction with good development prospect.However,massive β-TCP ceramics have high brittleness and low bearing capacity,so they can not be directly used in the preparation of artificial bearing bone.β-TCP and its composite film prepared on metal base surface by surface modification technology can be used for bone tissue repair and replacement of human body bearing site with good mechanical properties of metal material and good biological activity of β-TCP.In this experiment,β-TCP/ZrO2 composite films were prepared on the surface of titanium alloy by pulsed laser deposition technology,and the performance of β-TCP films was improved by the toughening effect of ZrO2.The effects of laser fluence,substrate temperature,deposition frequency,deposition time and other process parameters on the surface microstructure,phase composition,atomic groups and mechanical properties of the composite films were investigated by SEM,EDS,XRD,FTIR and nano-indentation tests.The effects of target composition changes on the microstructure and properties of composite films were studied by adding Nanohydroxyapatite(n-HA)with different mass ratios to β-TCP/ZrO2 mixed targets;the amorphous films prepared at low substrate temperatures were subjected to subsequent heat treatment,and the changes in microstructure and properties of the composite films before and after heat treatment were analyzed.The high laser fluence can promote laser ablation of the target material and spray more particles to gather on the substrate to form large spherical particles,causing an increase in film roughness.With the increase of laser fluence,the grain size,crystallinity,nanohardness and elastic modulus of β-TCP/ZrO2 composite films increased.The composite film prepared by high laser fluence preferentially underwent dissolution and precipitation behavior when immersed in simulated body fluid.Ca2+and(PO4)3-in the film dissolved and diffused into the body fluid,and when the solution was supersaturated,they precipitated onto the substrate to form a new calcium phosphorus phase.The increase of substrate temperature was beneficial to the increase of density and the decrease of surface roughness of β-TCP/ZrO2 composite films,and the increase of crystallinity,nanohardness and elastic modulus of the composite films.The deposition frequency had little effect on the phase composition and atomic groups of the composite film,but high deposition frequency can improve the density,crystallinity,and mechanical properties of the film.The elastic modulus and nanohardness of the composite film prepared at a deposition frequency of 10 Hz are 181.28 ± 2.54 GPa and 5.72 ± 0.32 GPa,respectively.With the extension of deposition time,the thickness of the composite film increased,but the elastic modulus and nanohardness increased first and then decreased.The β-TCP/ZrO2 composite film with n-HA was mainly composed of HA,β-TCP and ZrO2 phases.The increase of n-HA addition had little effect on the surface morphology,phase composition and group characteristics of the composite film,but can improve the elastic modulus and nanohardness of the film,and leaded to the increase of the Ca/P atomic ratio in the composite film.The addition of n-HA can slow down the degradation rate of the films in body fluids,so as to effectively regulate the dissolution process of β-TCP/ZrO2 composite films.When the addition of n-HA was 35wt.%,the prepared films showed better biological activity.After heat treatment at 600℃ for 2 hours,the surface roughness of the composite film increased,the elastic modulus increased by 63%,and the nanohardness increased by 22%.The composite film exhibited good biological activity.Composite films with good mechanical properties and high crystallinity can be obtained by selecting a substrate temperature of 600℃for deposition or by depositing at 25℃ followed by heat treatment at 600℃.However,the surface roughness of the composite film after heat treatment increased,which was more conducive to cell adhesion on its surface and promoted its binding to bone tissue after implantation into the human body. |
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