Research On The Preparation And Properties Of Mg/TCP Biodegradable Composite

Magnesium and its alloys are characterized by the density and Young's modulus close to human bone, non-toxicity and good biocompatibility, thus they are considered a novel promising biodegradable biomaterial. However, due to its high corrosion rate, poor bioactivity and insufficient mechanical strength, magnesium and its alloys are not used in clinics up to now. The composition of tricalcium phosphate (Ca3(PO4)2,TCP) is similar to that of the mineral in human bone. It is excellent biocompatible, biodegradable, osteoconductive and non-toxic. But TCP is unsuitablefor load-bearing implants due to its low fatigue resistance, brittleness, insufficient flexural strength and impact resistance. In this work, a magnesium/TCP composite was prepared by powder metallurgy process in order to develop a new biodegradable hard tissue substituent possessing the advantages of the both components. The mechanical properties and corrosion behavior of the Mg/TCP composite were discussed.Mg/TCP composite with various TCP contents (0-20 wt%) were prepared using pure magnesium and TCP powder as raw materials. Compression yield strength and compressive strength of the Mg/TCP composite was measured by universal material tester. In order to investigate the corrosion behavior of Mg/TCP in vitro, the composite samples were immersed in Hank's simulated body fluid (SBF) at 37℃. The released hydrogen volume, weight loss and pH of SBF were recorded at different time. Also, electrochemical tests were conducted under the same condition. The samples were charaterised by scanning electronic microscope (SEM), optical microscope and X-ray diffraction (XRD). The effect TCP content on the corrosion mechanical properties was studied. The main conclusions were as the follow.1 TCP improved the yield strength and Vickers hardness of the Mg/TCP composite. The yield strength of the Mg/TCP composites was similar to that of human bones.2 TCP increased corrosion resistance of the Mg/TCP composite. But the effect of TCP content on the corrosion resistance was non-linear.3 Mg(OH)2 and HA deposited on the surface of as-immersed Mg/TCP samples, but no HA was found on the surface of the as-immersed pure magnesium. The HA deposition inhibited the corrosion of the composites to some extent, leading to the decrease of the corrosion.4 In this work, the Mg-5wt% TCP composite was of the optimal mechanical properties, corrosion resistance and biological activity.5 Porous TCP skeleton was prepared by organic foam dipping method. The porosity was around 80% and the pore size ranged from 50μm to 500μm.