Research On Powder Sintering Preparation And Properties Of Porous Titanium

Recently, biomedical metallic materials become the widely used implant materials for hard tissues like dental roots. Porous titanium has become the research focus because of its combinations of good biocompatibility and unique pore structure. Porous structure contributes to ingrowth of tissues and transportation of body fluid. Additionally, as a bioinert material, the surface bioactivity of titanium can be improved by surface modification. In this paper, porous titanium was prepared by powder sintering. Furthermore, hydroxyapatite (HA) coating on its surface was deposited by chemical method.Porous titanium with different porosity was prepared by using powder sintering, i.e. sintering by adding pore forming agent (NH4HCO3) into titanium hydride powers in this paper. Mechanical property of porous titanium is related to its porosity. Therefore, the mechanical property can be adjusted by different addition content of pore forming agent. The research results indicate that the content of pore forming agent has a great effect on the compressive strength and pore characteristics of porous titanium. As the content of pore forming agent increases, the compressive strength decreases gradually while the porosity of porous titanium increases in proportion basically under the conditions of constant pressing and sintering parameters. The focus of this paper is to prepare porous titanium with suitable porosity and mechanical performances matching with bone. The sintered porous titanium was featured by porosity of 41.61-56.74% , pore size of 346-427μm, compressive strength of 100-200MPa, elastic modulus of 7.9-17.5GPa.The pore characteristics and mechanical property of the sintered porous titanium meet the basic pore characteristic and mechanical property requirements of compact bones. In this paper, the surface of the sintered porous titanium was modified by chemical method, the HA coating was deposited on its surface. There were some pits after modification by acid. And these pits increase the internal surface areas of the pores. The sodium titanate gel layer was formed after modification by sodium hydroxide. HA coating was deposited on the surface of porous titanium after immersion in simulated body fluid (SBF). The alkali concentration and immersion time have great influences on the deposition of HA coating. The research results indicate that ideal HA coating can be obtained after acid (32.5% HNO3) and alkali (1.5M NaOH ) treatments in succession at 60°C for 24h, respectively followed by immersion in SBF at 37.5°C. Under the same acid-alkali treatment conditions of modification, the pre-calcified process contributes to accelerate the deposition rate of HA coating of porous titanium sample.