Preparation And Properties Of Gradient Porous Ag Doped Hydroxyapatite Based Composite Ceramic

Hydroxyapatite?HA?has excellent biological activity and bone inductance.Its chemical composition and structure are very similar to the hard tissue of human body which makes it as a very valuable substitute for bone tissue.However,because of easy adsorption of proteins,amino acids and other organic matters,HA material causes the growth of bacteria.HA material has insufficient mechanical properties,which greatly limits its use.In this study,Ag-HA powder was synthesized by hydrothermal method.At the same time,gradient porous Ag-HA ceramic and gradient porous Ag-HA/TiO₂ composite ceramic were prepared by adding pore-making agent method.The effects of hydrothermal reaction temperature and Ag loading content on the phase composition and microstructure of Ag-HA powder were studied.The antibacterial properties of Ag-HA powder were studied.In addition,the effects of pore-making agent distribution,pressing pressure,sintering temperature and TiO₂ contents on the porosity and sintering shrinkage of the two gradient porous ceramics were studied.The phase composition and microstructure of the sintered products were analyzed,the compression and antibacterial properties of sintered gradient porous ceramics were measured.The experimental results show that the Ag-HA powder prepared by hydrothermal method has the same crystal structure as HA,and the addition of Ag ions makes the diffraction peak in the XRD pattern deflected to a small Angle.After hydrothermal synthesis at 180?,the 2Ag-HA powder has a good crystallinity,a fine stick shape and a good aspect ratio.The antibacterial experiments of Ag-HA powder show that the diameter of the antibacterial ring of Ag-HA powder increase with the increase of Ag ions,and the minimum inhibitory concentration decreases with the increase of Ag ions.The pure HA powder has little inhibitory effect on the growth of bacteria.The porosity of gradient porous Ag-HA ceramics increase with the increase of the contents of interlayer pore-making agent,but the sintering shrinkage and compressive strength all decrease.With the increase of pressing pressure and sintering temperature,the porosity of gradient porous Ag-HA ceramics decrease,but the sintering shrinkage and compressive strength all increase.When the distribution of pore-making agent of 20wt%-10wt%-20wt%,the pressing pressure of 100 MPa,the sintering temperature of 1150?,Ag content of 2%,the porosity,sintering shrinkage,compressive strength of the sintered gradient porous 2Ag-HA ceramics are 24.7%,13.7%,12.6MPa,respectively.The antibacterial experiments of gradient porous Ag-HA ceramics show that with the increase of Ag loading and porosity,the antibacterial ring diameter of gradient porous Ag-HA ceramics against escherichia coli and staphylococcus aureus increase while pure HA ceramic shows no antibacterial properties.With the increase of TiO₂ contents,the porosity of the gradient porous 2Ag-HA/TiO₂ complex ceramics decrease first and then increase slightly,while the sintering shrinkage and compressive strength increase first and then decrease slightly.The compressive strength of the gradient porous 2Ag-HA/TiO₂ composite ceramics with 7wt% TiO₂ increased by 33.3%,compared with the gradient porous 2Ag-HA ceramic prepared at the same process conditions.SEM observation shows that with the increase of TiO₂ contents,the number of white particles dispersed in the pore wall of composite ceramic increase,the number of micropores in the pore wall decrease,and the pore wall becomes compactly.Antimicrobial properties of gradient porous Ag-HA/TiO₂ composite ceramic shows that with the increase of TiO₂ contents,the antibacterial circle diameter of gradient porous Ag-HA/TiO₂ composite ceramic for escherichia coli and staphylococcus aureus increase.When the content of TiO₂ is 7wt%,the antibacterial circle diameter of gradient porous composite ceramic for escherichia coli and staphylococcus aureus increase by 8.7% and 8.8%,respectively,which indicates that the joint action of TiO₂ and Ag ions has better antibacterial effect.The fungicidal rates of gradient porous Ag-HA ceramic and Ag-HA/TiO₂ composite ceramic reach over 99.9% after 1h,and reach 100% after 5h,9h,18 h and 24 h,and the antibacterial effect had certain persistence.