Preparation And Properties Of Sr-doped Porous TiO₂ Coatings By Pulse Electrodeposition

Titanium and titanium alloys have good mechanical properties and excellent biological properties,and are widely used in biomedical applications,especially dental implants in the field of stomatology.In addition,it is often used as a substitute for human tissues and organs.Although widely used in the clinic,the biocompatibility of titanium and titanium alloys still needs improvement.As an implant,pure titanium has an inert oxide film on its surface,which affects the fusion with the organism after implantation into the body,and the implanting fails in severe cases.The surface modification process can increase the specific surface area of the material and thereby improving the biological properties of the implant material.In addition,the addition of some bioactive elements to the surface of the implant material also benefits to increase the surface activity.Therefore,in this study the micro-arc oxidation and pulse electrodeposition composite process were used to prepare erbium-doped TiO₂ coating,and the cerium element was doped into the surface of the coating prepared by micro-arc oxidation and pulse electrodeposition process,and adjusting the process parameters.The current density was set to 13 A/dm²,20A/dm²,27 A/dm²,and the duty cycle was set to 10%,30%,50%;the frequency was set to 500Hz,1000 Hz,2000 Hz;the deposition time was set to 5 min,10 min,and 15 min.Under these conditions,the deposition products with different morphologies were prepared,and the optimal parameters were determined,and finally the coating with better comprehensive performance was obtained.The morphology of the coating prepared under different parameters was observed by scanning electron microscope.The composition and phase analysis of the coating were carried out by energy spectrometer,X-ray diffractometer and Fourier transform near-infrared spectroscopy.The plasma emission spectrometer was used to detect the normal saline.The concentration of cesium ions released by the coating after soaking for 24 h,72 h,120 h,and 168 h.The hydrophilicity of the coatings with different topographical deposition products and the hydrophilicity of the coatings produced at different deposition times were determined by a high speed video optical contact angle meter.The results showed that the morphology of the deposited products tended to be"needle-like",the number increased,and the size increased when the pulse current density reached from 13 A/dm² to 27 A/dm²;the pulse duty cycle hardly changed the morphology of the deposited products,however the size of the deposited product was increased when the duty cycle was increased from 10%to 50%;the pulse frequency was increased from 500 Hz to 2000 Hz,and the obtained deposition product was also slender;the deposition time was 5min.During the process of increasing to 15 min,the morphology of the deposited product changed from a short"rice-like"shape to a slender"needle-like shape",which increased the number and size,comparing with unidirectional pulse electrodeposition.A"long grained"deposition product was prepared by means of bidirectional pulses,which were doped with a small amount of"short clusters".The coating prepared by micro-arc oxidation and pulse electrodeposition had the presence of rutile phase and anatase phase and SrCO₃.The concentration of strontium ions were detected after soaking for 24 h in physiological saline.When the immersion time was increased to 120 h and 168 h,the released concentration of cesium ions remained to be unchanged,indicating that the cerium ions in the coating was quickly and stably released.After deposited to 5 min at the conditions of 13 A/dm² pulse current density,2000 Hz pulse frequency and 10%duty cycle,the finest deposition products with the smallest contact angle were obtained,which possessed the most hydrophilic coating.